FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/pmap.c

     /*-
      * SPDX-License-Identifier: BSD-4-Clause
      *
      * Copyright (c) 1991 Regents of the University of California.
      * All rights reserved.
      * Copyright (c) 1994 John S. Dyson
      * All rights reserved.
      * Copyright (c) 1994 David Greenman
      * All rights reserved.
     * Copyright (c) 2003 Peter Wemm
     * All rights reserved.
     * Copyright (c) 2005-2010 Alan L. Cox <alc@cs.rice.edu>
     * All rights reserved.
     *
     * This code is derived from software contributed to Berkeley by
     * the Systems Programming Group of the University of Utah Computer
     * Science Department and William Jolitz of UUNET Technologies Inc.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from:   @(#)pmap.c      7.7 (Berkeley)  5/12/91
     */
    /*-
     * Copyright (c) 2003 Networks Associates Technology, Inc.
     * Copyright (c) 2014-2019 The FreeBSD Foundation
     * All rights reserved.
     *
     * This software was developed for the FreeBSD Project by Jake Burkholder,
     * Safeport Network Services, and Network Associates Laboratories, the
     * Security Research Division of Network Associates, Inc. under
     * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA
     * CHATS research program.
     *
     * Portions of this software were developed by
     * Konstantin Belousov <kib@FreeBSD.org> under sponsorship from
     * the FreeBSD Foundation.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #define AMD64_NPT_AWARE
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: head/sys/amd64/amd64/pmap.c 345382 2019-03-21 19:52:50Z markj $");
    
    /*
     *      Manages physical address maps.
     *
     *      Since the information managed by this module is
     *      also stored by the logical address mapping module,
     *      this module may throw away valid virtual-to-physical
     *      mappings at almost any time.  However, invalidations
     *      of virtual-to-physical mappings must be done as
     *      requested.
    *
    *      In order to cope with hardware architectures which
    *      make virtual-to-physical map invalidates expensive,
    *      this module may delay invalidate or reduced protection
    *      operations until such time as they are actually
    *      necessary.  This module is given full information as
    *      to which processors are currently using which maps,
    *      and to when physical maps must be made correct.
    */
   
   #include "opt_pmap.h"
   #include "opt_vm.h"
   
   #include <sys/param.h>
   #include <sys/bitstring.h>
   #include <sys/bus.h>
   #include <sys/systm.h>
   #include <sys/kernel.h>
   #include <sys/ktr.h>
   #include <sys/lock.h>
   #include <sys/malloc.h>
   #include <sys/mman.h>
   #include <sys/mutex.h>
   #include <sys/proc.h>
   #include <sys/rangeset.h>
   #include <sys/rwlock.h>
   #include <sys/sx.h>
   #include <sys/turnstile.h>
   #include <sys/vmem.h>
   #include <sys/vmmeter.h>
   #include <sys/sched.h>
   #include <sys/sysctl.h>
   #include <sys/smp.h>
   
   #include <vm/vm.h>
   #include <vm/vm_param.h>
   #include <vm/vm_kern.h>
   #include <vm/vm_page.h>
   #include <vm/vm_map.h>
   #include <vm/vm_object.h>
   #include <vm/vm_extern.h>
   #include <vm/vm_pageout.h>
   #include <vm/vm_pager.h>
   #include <vm/vm_phys.h>
   #include <vm/vm_radix.h>
   #include <vm/vm_reserv.h>
   #include <vm/uma.h>
   
   #include <machine/intr_machdep.h>
   #include <x86/apicvar.h>
   #include <x86/ifunc.h>
   #include <machine/cpu.h>
   #include <machine/cputypes.h>
   #include <machine/md_var.h>
   #include <machine/pcb.h>
   #include <machine/specialreg.h>
   #ifdef SMP
   #include <machine/smp.h>
   #endif
   #include <machine/sysarch.h>
   #include <machine/tss.h>
   
   static __inline boolean_t
   pmap_type_guest(pmap_t pmap)
   {
   
           return ((pmap->pm_type == PT_EPT) || (pmap->pm_type == PT_RVI));
   }
   
   static __inline boolean_t
   pmap_emulate_ad_bits(pmap_t pmap)
   {
   
           return ((pmap->pm_flags & PMAP_EMULATE_AD_BITS) != 0);
   }
   
   static __inline pt_entry_t
   pmap_valid_bit(pmap_t pmap)
   {
           pt_entry_t mask;
   
           switch (pmap->pm_type) {
           case PT_X86:
           case PT_RVI:
                   mask = X86_PG_V;
                   break;
           case PT_EPT:
                   if (pmap_emulate_ad_bits(pmap))
                           mask = EPT_PG_EMUL_V;
                   else
                           mask = EPT_PG_READ;
                   break;
           default:
                   panic("pmap_valid_bit: invalid pm_type %d", pmap->pm_type);
           }
   
           return (mask);
   }
   
   static __inline pt_entry_t
   pmap_rw_bit(pmap_t pmap)
   {
           pt_entry_t mask;
   
           switch (pmap->pm_type) {
           case PT_X86:
           case PT_RVI:
                   mask = X86_PG_RW;
                   break;
           case PT_EPT:
                   if (pmap_emulate_ad_bits(pmap))
                           mask = EPT_PG_EMUL_RW;
                   else
                           mask = EPT_PG_WRITE;
                   break;
           default:
                   panic("pmap_rw_bit: invalid pm_type %d", pmap->pm_type);
           }
   
           return (mask);
   }
   
   static pt_entry_t pg_g;
   
   static __inline pt_entry_t
   pmap_global_bit(pmap_t pmap)
   {
           pt_entry_t mask;
   
           switch (pmap->pm_type) {
           case PT_X86:
                   mask = pg_g;
                   break;
           case PT_RVI:
           case PT_EPT:
                   mask = 0;
                   break;
           default:
                   panic("pmap_global_bit: invalid pm_type %d", pmap->pm_type);
           }
   
           return (mask);
   }
   
   static __inline pt_entry_t
   pmap_accessed_bit(pmap_t pmap)
   {
           pt_entry_t mask;
   
           switch (pmap->pm_type) {
           case PT_X86:
           case PT_RVI:
                   mask = X86_PG_A;
                   break;
           case PT_EPT:
                   if (pmap_emulate_ad_bits(pmap))
                           mask = EPT_PG_READ;
                   else
                           mask = EPT_PG_A;
                   break;
           default:
                   panic("pmap_accessed_bit: invalid pm_type %d", pmap->pm_type);
           }
   
           return (mask);
   }
   
   static __inline pt_entry_t
   pmap_modified_bit(pmap_t pmap)
   {
           pt_entry_t mask;
   
           switch (pmap->pm_type) {
           case PT_X86:
           case PT_RVI:
                   mask = X86_PG_M;
                   break;
           case PT_EPT:
                   if (pmap_emulate_ad_bits(pmap))
                           mask = EPT_PG_WRITE;
                   else
                           mask = EPT_PG_M;
                   break;
           default:
                   panic("pmap_modified_bit: invalid pm_type %d", pmap->pm_type);
           }
   
           return (mask);
   }
   
   static __inline pt_entry_t
   pmap_pku_mask_bit(pmap_t pmap)
   {
   
           return (pmap->pm_type == PT_X86 ? X86_PG_PKU_MASK : 0);
   }
   
   #if !defined(DIAGNOSTIC)
   #ifdef __GNUC_GNU_INLINE__
   #define PMAP_INLINE     __attribute__((__gnu_inline__)) inline
   #else
   #define PMAP_INLINE     extern inline
   #endif
   #else
   #define PMAP_INLINE
   #endif
   
   #ifdef PV_STATS
   #define PV_STAT(x)      do { x ; } while (0)
   #else
   #define PV_STAT(x)      do { } while (0)
   #endif
   
   #define pa_index(pa)    ((pa) >> PDRSHIFT)
   #define pa_to_pvh(pa)   (&pv_table[pa_index(pa)])
   
   #define NPV_LIST_LOCKS  MAXCPU
   
   #define PHYS_TO_PV_LIST_LOCK(pa)        \
                           (&pv_list_locks[pa_index(pa) % NPV_LIST_LOCKS])
   
   #define CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa)  do {    \
           struct rwlock **_lockp = (lockp);               \
           struct rwlock *_new_lock;                       \
                                                           \
           _new_lock = PHYS_TO_PV_LIST_LOCK(pa);           \
           if (_new_lock != *_lockp) {                     \
                   if (*_lockp != NULL)                    \
                           rw_wunlock(*_lockp);            \
                   *_lockp = _new_lock;                    \
                   rw_wlock(*_lockp);                      \
           }                                               \
   } while (0)
   
   #define CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m)        \
                           CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, VM_PAGE_TO_PHYS(m))
   
   #define RELEASE_PV_LIST_LOCK(lockp)             do {    \
           struct rwlock **_lockp = (lockp);               \
                                                           \
           if (*_lockp != NULL) {                          \
                   rw_wunlock(*_lockp);                    \
                   *_lockp = NULL;                         \
           }                                               \
   } while (0)
   
   #define VM_PAGE_TO_PV_LIST_LOCK(m)      \
                           PHYS_TO_PV_LIST_LOCK(VM_PAGE_TO_PHYS(m))
   
   struct pmap kernel_pmap_store;
   
   vm_offset_t virtual_avail;      /* VA of first avail page (after kernel bss) */
   vm_offset_t virtual_end;        /* VA of last avail page (end of kernel AS) */
   
   int nkpt;
   SYSCTL_INT(_machdep, OID_AUTO, nkpt, CTLFLAG_RD, &nkpt, 0,
       "Number of kernel page table pages allocated on bootup");
   
   static int ndmpdp;
   vm_paddr_t dmaplimit;
   vm_offset_t kernel_vm_end = VM_MIN_KERNEL_ADDRESS;
   pt_entry_t pg_nx;
   
   static SYSCTL_NODE(_vm, OID_AUTO, pmap, CTLFLAG_RD, 0, "VM/pmap parameters");
   
   static int pg_ps_enabled = 1;
   SYSCTL_INT(_vm_pmap, OID_AUTO, pg_ps_enabled, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
       &pg_ps_enabled, 0, "Are large page mappings enabled?");
   
   #define PAT_INDEX_SIZE  8
   static int pat_index[PAT_INDEX_SIZE];   /* cache mode to PAT index conversion */
   
   static u_int64_t        KPTphys;        /* phys addr of kernel level 1 */
   static u_int64_t        KPDphys;        /* phys addr of kernel level 2 */
   u_int64_t               KPDPphys;       /* phys addr of kernel level 3 */
   u_int64_t               KPML4phys;      /* phys addr of kernel level 4 */
   
   static u_int64_t        DMPDphys;       /* phys addr of direct mapped level 2 */
   static u_int64_t        DMPDPphys;      /* phys addr of direct mapped level 3 */
   static int              ndmpdpphys;     /* number of DMPDPphys pages */
   
   static vm_paddr_t       KERNend;        /* phys addr of end of bootstrap data */
   
   /*
    * pmap_mapdev support pre initialization (i.e. console)
    */
   #define PMAP_PREINIT_MAPPING_COUNT      8
   static struct pmap_preinit_mapping {
           vm_paddr_t      pa;
           vm_offset_t     va;
           vm_size_t       sz;
           int             mode;
   } pmap_preinit_mapping[PMAP_PREINIT_MAPPING_COUNT];
   static int pmap_initialized;
   
   /*
    * Data for the pv entry allocation mechanism.
    * Updates to pv_invl_gen are protected by the pv_list_locks[]
    * elements, but reads are not.
    */
   static TAILQ_HEAD(pch, pv_chunk) pv_chunks = TAILQ_HEAD_INITIALIZER(pv_chunks);
   static struct mtx __exclusive_cache_line pv_chunks_mutex;
   static struct rwlock __exclusive_cache_line pv_list_locks[NPV_LIST_LOCKS];
   static u_long pv_invl_gen[NPV_LIST_LOCKS];
   static struct md_page *pv_table;
   static struct md_page pv_dummy;
   
   /*
    * All those kernel PT submaps that BSD is so fond of
    */
   pt_entry_t *CMAP1 = NULL;
   caddr_t CADDR1 = 0;
   static vm_offset_t qframe = 0;
   static struct mtx qframe_mtx;
   
   static int pmap_flags = PMAP_PDE_SUPERPAGE;     /* flags for x86 pmaps */
   
   static vmem_t *large_vmem;
   static u_int lm_ents;
   
   int pmap_pcid_enabled = 1;
   SYSCTL_INT(_vm_pmap, OID_AUTO, pcid_enabled, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
       &pmap_pcid_enabled, 0, "Is TLB Context ID enabled ?");
   int invpcid_works = 0;
   SYSCTL_INT(_vm_pmap, OID_AUTO, invpcid_works, CTLFLAG_RD, &invpcid_works, 0,
       "Is the invpcid instruction available ?");
   
   int __read_frequently pti = 0;
   SYSCTL_INT(_vm_pmap, OID_AUTO, pti, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
       &pti, 0,
       "Page Table Isolation enabled");
   static vm_object_t pti_obj;
   static pml4_entry_t *pti_pml4;
   static vm_pindex_t pti_pg_idx;
   static bool pti_finalized;
   
   struct pmap_pkru_range {
           struct rs_el    pkru_rs_el;
           u_int           pkru_keyidx;
           int             pkru_flags;
   };
   
   static uma_zone_t pmap_pkru_ranges_zone;
   static bool pmap_pkru_same(pmap_t pmap, vm_offset_t sva, vm_offset_t eva);
   static pt_entry_t pmap_pkru_get(pmap_t pmap, vm_offset_t va);
   static void pmap_pkru_on_remove(pmap_t pmap, vm_offset_t sva, vm_offset_t eva);
   static void *pkru_dup_range(void *ctx, void *data);
   static void pkru_free_range(void *ctx, void *node);
   static int pmap_pkru_copy(pmap_t dst_pmap, pmap_t src_pmap);
   static int pmap_pkru_deassign(pmap_t pmap, vm_offset_t sva, vm_offset_t eva);
   static void pmap_pkru_deassign_all(pmap_t pmap);
   
   static int
   pmap_pcid_save_cnt_proc(SYSCTL_HANDLER_ARGS)
   {
           int i;
           uint64_t res;
   
           res = 0;
           CPU_FOREACH(i) {
                   res += cpuid_to_pcpu[i]->pc_pm_save_cnt;
           }
           return (sysctl_handle_64(oidp, &res, 0, req));
   }
   SYSCTL_PROC(_vm_pmap, OID_AUTO, pcid_save_cnt, CTLTYPE_U64 | CTLFLAG_RW |
       CTLFLAG_MPSAFE, NULL, 0, pmap_pcid_save_cnt_proc, "QU",
       "Count of saved TLB context on switch");
   
   static LIST_HEAD(, pmap_invl_gen) pmap_invl_gen_tracker =
       LIST_HEAD_INITIALIZER(&pmap_invl_gen_tracker);
   static struct mtx invl_gen_mtx;
   static u_long pmap_invl_gen = 0;
   /* Fake lock object to satisfy turnstiles interface. */
   static struct lock_object invl_gen_ts = {
           .lo_name = "invlts",
   };
   
   static bool
   pmap_not_in_di(void)
   {
   
           return (curthread->td_md.md_invl_gen.gen == 0);
   }
   
   #define PMAP_ASSERT_NOT_IN_DI() \
       KASSERT(pmap_not_in_di(), ("DI already started"))
   
   /*
    * Start a new Delayed Invalidation (DI) block of code, executed by
    * the current thread.  Within a DI block, the current thread may
    * destroy both the page table and PV list entries for a mapping and
    * then release the corresponding PV list lock before ensuring that
    * the mapping is flushed from the TLBs of any processors with the
    * pmap active.
    */
   static void
   pmap_delayed_invl_started(void)
   {
           struct pmap_invl_gen *invl_gen;
           u_long currgen;
   
           invl_gen = &curthread->td_md.md_invl_gen;
           PMAP_ASSERT_NOT_IN_DI();
           mtx_lock(&invl_gen_mtx);
           if (LIST_EMPTY(&pmap_invl_gen_tracker))
                   currgen = pmap_invl_gen;
           else
                   currgen = LIST_FIRST(&pmap_invl_gen_tracker)->gen;
           invl_gen->gen = currgen + 1;
           LIST_INSERT_HEAD(&pmap_invl_gen_tracker, invl_gen, link);
           mtx_unlock(&invl_gen_mtx);
   }
   
   /*
    * Finish the DI block, previously started by the current thread.  All
    * required TLB flushes for the pages marked by
    * pmap_delayed_invl_page() must be finished before this function is
    * called.
    *
    * This function works by bumping the global DI generation number to
    * the generation number of the current thread's DI, unless there is a
    * pending DI that started earlier.  In the latter case, bumping the
    * global DI generation number would incorrectly signal that the
    * earlier DI had finished.  Instead, this function bumps the earlier
    * DI's generation number to match the generation number of the
    * current thread's DI.
    */
   static void
   pmap_delayed_invl_finished(void)
   {
           struct pmap_invl_gen *invl_gen, *next;
           struct turnstile *ts;
   
           invl_gen = &curthread->td_md.md_invl_gen;
           KASSERT(invl_gen->gen != 0, ("missed invl_started"));
           mtx_lock(&invl_gen_mtx);
           next = LIST_NEXT(invl_gen, link);
           if (next == NULL) {
                   turnstile_chain_lock(&invl_gen_ts);
                   ts = turnstile_lookup(&invl_gen_ts);
                   pmap_invl_gen = invl_gen->gen;
                   if (ts != NULL) {
                           turnstile_broadcast(ts, TS_SHARED_QUEUE);
                           turnstile_unpend(ts);
                   }
                   turnstile_chain_unlock(&invl_gen_ts);
           } else {
                   next->gen = invl_gen->gen;
           }
           LIST_REMOVE(invl_gen, link);
           mtx_unlock(&invl_gen_mtx);
           invl_gen->gen = 0;
   }
   
   #ifdef PV_STATS
   static long invl_wait;
   SYSCTL_LONG(_vm_pmap, OID_AUTO, invl_wait, CTLFLAG_RD, &invl_wait, 0,
       "Number of times DI invalidation blocked pmap_remove_all/write");
   #endif
   
   static u_long *
   pmap_delayed_invl_genp(vm_page_t m)
   {
   
           return (&pv_invl_gen[pa_index(VM_PAGE_TO_PHYS(m)) % NPV_LIST_LOCKS]);
   }
   
   /*
    * Ensure that all currently executing DI blocks, that need to flush
    * TLB for the given page m, actually flushed the TLB at the time the
    * function returned.  If the page m has an empty PV list and we call
    * pmap_delayed_invl_wait(), upon its return we know that no CPU has a
    * valid mapping for the page m in either its page table or TLB.
    *
    * This function works by blocking until the global DI generation
    * number catches up with the generation number associated with the
    * given page m and its PV list.  Since this function's callers
    * typically own an object lock and sometimes own a page lock, it
    * cannot sleep.  Instead, it blocks on a turnstile to relinquish the
    * processor.
    */
   static void
   pmap_delayed_invl_wait(vm_page_t m)
   {
           struct turnstile *ts;
           u_long *m_gen;
   #ifdef PV_STATS
           bool accounted = false;
   #endif
   
           m_gen = pmap_delayed_invl_genp(m);
           while (*m_gen > pmap_invl_gen) {
   #ifdef PV_STATS
                   if (!accounted) {
                           atomic_add_long(&invl_wait, 1);
                           accounted = true;
                   }
   #endif
                   ts = turnstile_trywait(&invl_gen_ts);
                   if (*m_gen > pmap_invl_gen)
                           turnstile_wait(ts, NULL, TS_SHARED_QUEUE);
                   else
                           turnstile_cancel(ts);
           }
   }
   
   /*
    * Mark the page m's PV list as participating in the current thread's
    * DI block.  Any threads concurrently using m's PV list to remove or
    * restrict all mappings to m will wait for the current thread's DI
    * block to complete before proceeding.
    *
    * The function works by setting the DI generation number for m's PV
    * list to at least the DI generation number of the current thread.
    * This forces a caller of pmap_delayed_invl_wait() to block until
    * current thread calls pmap_delayed_invl_finished().
    */
   static void
   pmap_delayed_invl_page(vm_page_t m)
   {
           u_long gen, *m_gen;
   
           rw_assert(VM_PAGE_TO_PV_LIST_LOCK(m), RA_WLOCKED);
           gen = curthread->td_md.md_invl_gen.gen;
           if (gen == 0)
                   return;
           m_gen = pmap_delayed_invl_genp(m);
           if (*m_gen < gen)
                   *m_gen = gen;
   }
   
   /*
    * Crashdump maps.
    */
   static caddr_t crashdumpmap;
   
   /*
    * Internal flags for pmap_enter()'s helper functions.
    */
   #define PMAP_ENTER_NORECLAIM    0x1000000       /* Don't reclaim PV entries. */
   #define PMAP_ENTER_NOREPLACE    0x2000000       /* Don't replace mappings. */
   
   static void     free_pv_chunk(struct pv_chunk *pc);
   static void     free_pv_entry(pmap_t pmap, pv_entry_t pv);
   static pv_entry_t get_pv_entry(pmap_t pmap, struct rwlock **lockp);
   static int      popcnt_pc_map_pq(uint64_t *map);
   static vm_page_t reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp);
   static void     reserve_pv_entries(pmap_t pmap, int needed,
                       struct rwlock **lockp);
   static void     pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
                       struct rwlock **lockp);
   static bool     pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, pd_entry_t pde,
                       u_int flags, struct rwlock **lockp);
   #if VM_NRESERVLEVEL > 0
   static void     pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
                       struct rwlock **lockp);
   #endif
   static void     pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va);
   static pv_entry_t pmap_pvh_remove(struct md_page *pvh, pmap_t pmap,
                       vm_offset_t va);
   
   static int pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode,
       bool noflush);
   static boolean_t pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va);
   static boolean_t pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde,
       vm_offset_t va, struct rwlock **lockp);
   static boolean_t pmap_demote_pdpe(pmap_t pmap, pdp_entry_t *pdpe,
       vm_offset_t va);
   static bool     pmap_enter_2mpage(pmap_t pmap, vm_offset_t va, vm_page_t m,
                       vm_prot_t prot, struct rwlock **lockp);
   static int      pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t newpde,
                       u_int flags, vm_page_t m, struct rwlock **lockp);
   static vm_page_t pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va,
       vm_page_t m, vm_prot_t prot, vm_page_t mpte, struct rwlock **lockp);
   static void pmap_fill_ptp(pt_entry_t *firstpte, pt_entry_t newpte);
   static int pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte);
   static void pmap_invalidate_cache_range_selfsnoop(vm_offset_t sva,
       vm_offset_t eva);
   static void pmap_invalidate_cache_range_all(vm_offset_t sva,
       vm_offset_t eva);
   static void pmap_invalidate_pde_page(pmap_t pmap, vm_offset_t va,
                       pd_entry_t pde);
   static void pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int mode);
   static vm_page_t pmap_large_map_getptp_unlocked(void);
   static void pmap_pde_attr(pd_entry_t *pde, int cache_bits, int mask);
   #if VM_NRESERVLEVEL > 0
   static void pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
       struct rwlock **lockp);
   #endif
   static boolean_t pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva,
       vm_prot_t prot);
   static void pmap_pte_attr(pt_entry_t *pte, int cache_bits, int mask);
   static void pmap_pti_add_kva_locked(vm_offset_t sva, vm_offset_t eva,
       bool exec);
   static pdp_entry_t *pmap_pti_pdpe(vm_offset_t va);
   static pd_entry_t *pmap_pti_pde(vm_offset_t va);
   static void pmap_pti_wire_pte(void *pte);
   static int pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
       struct spglist *free, struct rwlock **lockp);
   static int pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t sva,
       pd_entry_t ptepde, struct spglist *free, struct rwlock **lockp);
   static vm_page_t pmap_remove_pt_page(pmap_t pmap, vm_offset_t va);
   static void pmap_remove_page(pmap_t pmap, vm_offset_t va, pd_entry_t *pde,
       struct spglist *free);
   static bool     pmap_remove_ptes(pmap_t pmap, vm_offset_t sva, vm_offset_t eva,
                       pd_entry_t *pde, struct spglist *free,
                       struct rwlock **lockp);
   static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va,
       vm_page_t m, struct rwlock **lockp);
   static void pmap_update_pde(pmap_t pmap, vm_offset_t va, pd_entry_t *pde,
       pd_entry_t newpde);
   static void pmap_update_pde_invalidate(pmap_t, vm_offset_t va, pd_entry_t pde);
   
   static vm_page_t _pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex,
                   struct rwlock **lockp);
   static vm_page_t pmap_allocpde(pmap_t pmap, vm_offset_t va,
                   struct rwlock **lockp);
   static vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va,
                   struct rwlock **lockp);
   
   static void _pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m,
       struct spglist *free);
   static int pmap_unuse_pt(pmap_t, vm_offset_t, pd_entry_t, struct spglist *);
   
   /********************/
   /* Inline functions */
   /********************/
   
   /* Return a non-clipped PD index for a given VA */
   static __inline vm_pindex_t
   pmap_pde_pindex(vm_offset_t va)
   {
           return (va >> PDRSHIFT);
   }
   
   
   /* Return a pointer to the PML4 slot that corresponds to a VA */
   static __inline pml4_entry_t *
   pmap_pml4e(pmap_t pmap, vm_offset_t va)
   {
   
           return (&pmap->pm_pml4[pmap_pml4e_index(va)]);
   }
   
   /* Return a pointer to the PDP slot that corresponds to a VA */
   static __inline pdp_entry_t *
   pmap_pml4e_to_pdpe(pml4_entry_t *pml4e, vm_offset_t va)
   {
           pdp_entry_t *pdpe;
   
           pdpe = (pdp_entry_t *)PHYS_TO_DMAP(*pml4e & PG_FRAME);
           return (&pdpe[pmap_pdpe_index(va)]);
   }
   
   /* Return a pointer to the PDP slot that corresponds to a VA */
   static __inline pdp_entry_t *
   pmap_pdpe(pmap_t pmap, vm_offset_t va)
   {
           pml4_entry_t *pml4e;
           pt_entry_t PG_V;
   
           PG_V = pmap_valid_bit(pmap);
           pml4e = pmap_pml4e(pmap, va);
           if ((*pml4e & PG_V) == 0)
                   return (NULL);
           return (pmap_pml4e_to_pdpe(pml4e, va));
   }
   
   /* Return a pointer to the PD slot that corresponds to a VA */
   static __inline pd_entry_t *
   pmap_pdpe_to_pde(pdp_entry_t *pdpe, vm_offset_t va)
   {
           pd_entry_t *pde;
   
           pde = (pd_entry_t *)PHYS_TO_DMAP(*pdpe & PG_FRAME);
           return (&pde[pmap_pde_index(va)]);
   }
   
   /* Return a pointer to the PD slot that corresponds to a VA */
   static __inline pd_entry_t *
   pmap_pde(pmap_t pmap, vm_offset_t va)
   {
           pdp_entry_t *pdpe;
           pt_entry_t PG_V;
   
           PG_V = pmap_valid_bit(pmap);
           pdpe = pmap_pdpe(pmap, va);
           if (pdpe == NULL || (*pdpe & PG_V) == 0)
                   return (NULL);
           return (pmap_pdpe_to_pde(pdpe, va));
   }
   
   /* Return a pointer to the PT slot that corresponds to a VA */
   static __inline pt_entry_t *
   pmap_pde_to_pte(pd_entry_t *pde, vm_offset_t va)
   {
           pt_entry_t *pte;
   
           pte = (pt_entry_t *)PHYS_TO_DMAP(*pde & PG_FRAME);
           return (&pte[pmap_pte_index(va)]);
   }
   
   /* Return a pointer to the PT slot that corresponds to a VA */
   static __inline pt_entry_t *
   pmap_pte(pmap_t pmap, vm_offset_t va)
   {
           pd_entry_t *pde;
           pt_entry_t PG_V;
   
           PG_V = pmap_valid_bit(pmap);
           pde = pmap_pde(pmap, va);
           if (pde == NULL || (*pde & PG_V) == 0)
                   return (NULL);
           if ((*pde & PG_PS) != 0)        /* compat with i386 pmap_pte() */
                   return ((pt_entry_t *)pde);
           return (pmap_pde_to_pte(pde, va));
   }
   
   static __inline void
   pmap_resident_count_inc(pmap_t pmap, int count)
   {
   
           PMAP_LOCK_ASSERT(pmap, MA_OWNED);
           pmap->pm_stats.resident_count += count;
   }
   
   static __inline void
   pmap_resident_count_dec(pmap_t pmap, int count)
   {
   
           PMAP_LOCK_ASSERT(pmap, MA_OWNED);
           KASSERT(pmap->pm_stats.resident_count >= count,
               ("pmap %p resident count underflow %ld %d", pmap,
               pmap->pm_stats.resident_count, count));
           pmap->pm_stats.resident_count -= count;
   }
   
   PMAP_INLINE pt_entry_t *
   vtopte(vm_offset_t va)
   {
           u_int64_t mask = ((1ul << (NPTEPGSHIFT + NPDEPGSHIFT + NPDPEPGSHIFT + NPML4EPGSHIFT)) - 1);
   
           KASSERT(va >= VM_MAXUSER_ADDRESS, ("vtopte on a uva/gpa 0x%0lx", va));
   
           return (PTmap + ((va >> PAGE_SHIFT) & mask));
   }
   
   static __inline pd_entry_t *
   vtopde(vm_offset_t va)
   {
           u_int64_t mask = ((1ul << (NPDEPGSHIFT + NPDPEPGSHIFT + NPML4EPGSHIFT)) - 1);
   
           KASSERT(va >= VM_MAXUSER_ADDRESS, ("vtopde on a uva/gpa 0x%0lx", va));
   
           return (PDmap + ((va >> PDRSHIFT) & mask));
   }
   
   static u_int64_t
   allocpages(vm_paddr_t *firstaddr, int n)
   {
           u_int64_t ret;
   
           ret = *firstaddr;
           bzero((void *)ret, n * PAGE_SIZE);
           *firstaddr += n * PAGE_SIZE;
           return (ret);
   }
   
   CTASSERT(powerof2(NDMPML4E));
   
   /* number of kernel PDP slots */
   #define NKPDPE(ptpgs)           howmany(ptpgs, NPDEPG)
   
   static void
   nkpt_init(vm_paddr_t addr)
   {
           int pt_pages;
           
   #ifdef NKPT
           pt_pages = NKPT;
   #else
           pt_pages = howmany(addr, 1 << PDRSHIFT);
           pt_pages += NKPDPE(pt_pages);
   
           /*
            * Add some slop beyond the bare minimum required for bootstrapping
            * the kernel.
            *
            * This is quite important when allocating KVA for kernel modules.
            * The modules are required to be linked in the negative 2GB of
            * the address space.  If we run out of KVA in this region then
            * pmap_growkernel() will need to allocate page table pages to map
            * the entire 512GB of KVA space which is an unnecessary tax on
            * physical memory.
            *
            * Secondly, device memory mapped as part of setting up the low-
            * level console(s) is taken from KVA, starting at virtual_avail.
            * This is because cninit() is called after pmap_bootstrap() but
            * before vm_init() and pmap_init(). 20MB for a frame buffer is
            * not uncommon.
            */
           pt_pages += 32;         /* 64MB additional slop. */
   #endif
           nkpt = pt_pages;
   }
   
   /*
    * Returns the proper write/execute permission for a physical page that is
    * part of the initial boot allocations.
    *
    * If the page has kernel text, it is marked as read-only. If the page has
    * kernel read-only data, it is marked as read-only/not-executable. If the
    * page has only read-write data, it is marked as read-write/not-executable.
    * If the page is below/above the kernel range, it is marked as read-write.
    *
    * This function operates on 2M pages, since we map the kernel space that
    * way.
    *
    * Note that this doesn't currently provide any protection for modules.
    */
   static inline pt_entry_t
   bootaddr_rwx(vm_paddr_t pa)
   {
   
           /*
            * Everything in the same 2M page as the start of the kernel
            * should be static. On the other hand, things in the same 2M
            * page as the end of the kernel could be read-write/executable,
            * as the kernel image is not guaranteed to end on a 2M boundary.
            */
           if (pa < trunc_2mpage(btext - KERNBASE) ||
              pa >= trunc_2mpage(_end - KERNBASE))
                   return (X86_PG_RW);
           /*
            * The linker should ensure that the read-only and read-write
            * portions don't share the same 2M page, so this shouldn't
            * impact read-only data. However, in any case, any page with
            * read-write data needs to be read-write.
            */
           if (pa >= trunc_2mpage(brwsection - KERNBASE))
                   return (X86_PG_RW | pg_nx);
           /*
            * Mark any 2M page containing kernel text as read-only. Mark
            * other pages with read-only data as read-only and not executable.
            * (It is likely a small portion of the read-only data section will
            * be marked as read-only, but executable. This should be acceptable
            * since the read-only protection will keep the data from changing.)
            * Note that fixups to the .text section will still work until we
            * set CR0.WP.
            */
           if (pa < round_2mpage(etext - KERNBASE))
                   return (0);
           return (pg_nx);
   }
   
   static void
   create_pagetables(vm_paddr_t *firstaddr)
   {
           int i, j, ndm1g, nkpdpe, nkdmpde;
           pt_entry_t *pt_p;
           pd_entry_t *pd_p;
           pdp_entry_t *pdp_p;
           pml4_entry_t *p4_p;
           uint64_t DMPDkernphys;
   
           /* Allocate page table pages for the direct map */
           ndmpdp = howmany(ptoa(Maxmem), NBPDP);
           if (ndmpdp < 4)         /* Minimum 4GB of dirmap */
                   ndmpdp = 4;
           ndmpdpphys = howmany(ndmpdp, NPDPEPG);
           if (ndmpdpphys > NDMPML4E) {
                   /*
                    * Each NDMPML4E allows 512 GB, so limit to that,
                    * and then readjust ndmpdp and ndmpdpphys.
                    */
                   printf("NDMPML4E limits system to %d GB\n", NDMPML4E * 512);
                   Maxmem = atop(NDMPML4E * NBPML4);
                   ndmpdpphys = NDMPML4E;
                   ndmpdp = NDMPML4E * NPDEPG;
           }
           DMPDPphys = allocpages(firstaddr, ndmpdpphys);
           ndm1g = 0;
           if ((amd_feature & AMDID_PAGE1GB) != 0) {
                   /*
                    * Calculate the number of 1G pages that will fully fit in
                    * Maxmem.
                    */
                   ndm1g = ptoa(Maxmem) >> PDPSHIFT;
   
                   /*
                    * Allocate 2M pages for the kernel. These will be used in
                    * place of the first one or more 1G pages from ndm1g.
                    */
                   nkdmpde = howmany((vm_offset_t)(brwsection - KERNBASE), NBPDP);
                   DMPDkernphys = allocpages(firstaddr, nkdmpde);
           }
           if (ndm1g < ndmpdp)
                   DMPDphys = allocpages(firstaddr, ndmpdp - ndm1g);
           dmaplimit = (vm_paddr_t)ndmpdp << PDPSHIFT;
   
          /* Allocate pages */
          KPML4phys = allocpages(firstaddr, 1);
          KPDPphys = allocpages(firstaddr, NKPML4E);
  
          /*
           * Allocate the initial number of kernel page table pages required to
           * bootstrap.  We defer this until after all memory-size dependent
           * allocations are done (e.g. direct map), so that we don't have to
           * build in too much slop in our estimate.
           *
           * Note that when NKPML4E > 1, we have an empty page underneath
           * all but the KPML4I'th one, so we need NKPML4E-1 extra (zeroed)
           * pages.  (pmap_enter requires a PD page to exist for each KPML4E.)
           */
          nkpt_init(*firstaddr);
          nkpdpe = NKPDPE(nkpt);
  
          KPTphys = allocpages(firstaddr, nkpt);
          KPDphys = allocpages(firstaddr, nkpdpe);
  
          /* Fill in the underlying page table pages */
          /* XXX not fully used, underneath 2M pages */
          pt_p = (pt_entry_t *)KPTphys;
          for (i = 0; ptoa(i) < *firstaddr; i++)
                  pt_p[i] = ptoa(i) | X86_PG_V | pg_g | bootaddr_rwx(ptoa(i));
  
          /* Now map the page tables at their location within PTmap */
          pd_p = (pd_entry_t *)KPDphys;
          for (i = 0; i < nkpt; i++)
                  pd_p[i] = (KPTphys + ptoa(i)) | X86_PG_RW | X86_PG_V;
  
          /* Map from zero to end of allocations under 2M pages */
          /* This replaces some of the KPTphys entries above */
          for (i = 0; (i << PDRSHIFT) < *firstaddr; i++)
                  /* Preset PG_M and PG_A because demotion expects it. */
                  pd_p[i] = (i << PDRSHIFT) | X86_PG_V | PG_PS | pg_g |
                      X86_PG_M | X86_PG_A | bootaddr_rwx(i << PDRSHIFT);
  
          /*
           * Because we map the physical blocks in 2M pages, adjust firstaddr
           * to record the physical blocks we've actually mapped into kernel
           * virtual address space.
           */
          *firstaddr = round_2mpage(*firstaddr);
  
          /* And connect up the PD to the PDP (leaving room for L4 pages) */
          pdp_p = (pdp_entry_t *)(KPDPphys + ptoa(KPML4I - KPML4BASE));
          for (i = 0; i < nkpdpe; i++)
                  pdp_p[i + KPDPI] = (KPDphys + ptoa(i)) | X86_PG_RW | X86_PG_V;
  
          /*
           * Now, set up the direct map region using 2MB and/or 1GB pages.  If
           * the end of physical memory is not aligned to a 1GB page boundary,
           * then the residual physical memory is mapped with 2MB pages.  Later,
           * if pmap_mapdev{_attr}() uses the direct map for non-write-back
           * memory, pmap_change_attr() will demote any 2MB or 1GB page mappings
           * that are partially used. 
           */
          pd_p = (pd_entry_t *)DMPDphys;
          for (i = NPDEPG * ndm1g, j = 0; i < NPDEPG * ndmpdp; i++, j++) {
                  pd_p[j] = (vm_paddr_t)i << PDRSHIFT;
                  /* Preset PG_M and PG_A because demotion expects it. */
                  pd_p[j] |= X86_PG_RW | X86_PG_V | PG_PS | pg_g |
                      X86_PG_M | X86_PG_A | pg_nx;
          }
          pdp_p = (pdp_entry_t *)DMPDPphys;
          for (i = 0; i < ndm1g; i++) {
                  pdp_p[i] = (vm_paddr_t)i << PDPSHIFT;
                  /* Preset PG_M and PG_A because demotion expects it. */
                  pdp_p[i] |= X86_PG_RW | X86_PG_V | PG_PS | pg_g |
                      X86_PG_M | X86_PG_A | pg_nx;
          }
          for (j = 0; i < ndmpdp; i++, j++) {
                  pdp_p[i] = DMPDphys + ptoa(j);
                  pdp_p[i] |= X86_PG_RW | X86_PG_V;
          }
  
          /*
           * Instead of using a 1G page for the memory containing the kernel,
           * use 2M pages with appropriate permissions. (If using 1G pages,
           * this will partially overwrite the PDPEs above.)
           */
          if (ndm1g) {
                  pd_p = (pd_entry_t *)DMPDkernphys;
                  for (i = 0; i < (NPDEPG * nkdmpde); i++)
                          pd_p[i] = (i << PDRSHIFT) | X86_PG_V | PG_PS | pg_g |
                              X86_PG_M | X86_PG_A | pg_nx |
                              bootaddr_rwx(i << PDRSHIFT);
                  for (i = 0; i < nkdmpde; i++)
                          pdp_p[i] = (DMPDkernphys + ptoa(i)) | X86_PG_RW |
                              X86_PG_V;
          }
  
          /* And recursively map PML4 to itself in order to get PTmap */
          p4_p = (pml4_entry_t *)KPML4phys;
          p4_p[PML4PML4I] = KPML4phys;
          p4_p[PML4PML4I] |= X86_PG_RW | X86_PG_V | pg_nx;
  
          /* Connect the Direct Map slot(s) up to the PML4. */
          for (i = 0; i < ndmpdpphys; i++) {
                  p4_p[DMPML4I + i] = DMPDPphys + ptoa(i);
                  p4_p[DMPML4I + i] |= X86_PG_RW | X86_PG_V;
          }
  
          /* Connect the KVA slots up to the PML4 */
          for (i = 0; i < NKPML4E; i++) {
                  p4_p[KPML4BASE + i] = KPDPphys + ptoa(i);
                  p4_p[KPML4BASE + i] |= X86_PG_RW | X86_PG_V;
          }
  }
  
  /*
   *      Bootstrap the system enough to run with virtual memory.
   *
   *      On amd64 this is called after mapping has already been enabled
   *      and just syncs the pmap module with what has already been done.
   *      [We can't call it easily with mapping off since the kernel is not
   *      mapped with PA == VA, hence we would have to relocate every address
   *      from the linked base (virtual) address "KERNBASE" to the actual
   *      (physical) address starting relative to 0]
   */
  void
  pmap_bootstrap(vm_paddr_t *firstaddr)
  {
          vm_offset_t va;
          pt_entry_t *pte;
          uint64_t cr4;
          u_long res;
          int i;
  
          KERNend = *firstaddr;
          res = atop(KERNend - (vm_paddr_t)kernphys);
  
          if (!pti)
                  pg_g = X86_PG_G;
  
          /*
           * Create an initial set of page tables to run the kernel in.
           */
          create_pagetables(firstaddr);
  
          /*
           * Add a physical memory segment (vm_phys_seg) corresponding to the
           * preallocated kernel page table pages so that vm_page structures
           * representing these pages will be created.  The vm_page structures
           * are required for promotion of the corresponding kernel virtual
           * addresses to superpage mappings.
           */
          vm_phys_add_seg(KPTphys, KPTphys + ptoa(nkpt));
  
          virtual_avail = (vm_offset_t) KERNBASE + *firstaddr;
          virtual_end = VM_MAX_KERNEL_ADDRESS;
  
          /*
           * Enable PG_G global pages, then switch to the kernel page
           * table from the bootstrap page table.  After the switch, it
           * is possible to enable SMEP and SMAP since PG_U bits are
           * correct now.
           */
          cr4 = rcr4();
          cr4 |= CR4_PGE;
          load_cr4(cr4);
          load_cr3(KPML4phys);
          if (cpu_stdext_feature & CPUID_STDEXT_SMEP)
                  cr4 |= CR4_SMEP;
          if (cpu_stdext_feature & CPUID_STDEXT_SMAP)
                  cr4 |= CR4_SMAP;
          load_cr4(cr4);
  
          /*
           * Initialize the kernel pmap (which is statically allocated).
           * Count bootstrap data as being resident in case any of this data is
           * later unmapped (using pmap_remove()) and freed.
           */
          PMAP_LOCK_INIT(kernel_pmap);
          kernel_pmap->pm_pml4 = (pdp_entry_t *)PHYS_TO_DMAP(KPML4phys);
          kernel_pmap->pm_cr3 = KPML4phys;
          kernel_pmap->pm_ucr3 = PMAP_NO_CR3;
          CPU_FILL(&kernel_pmap->pm_active);      /* don't allow deactivation */
          TAILQ_INIT(&kernel_pmap->pm_pvchunk);
          kernel_pmap->pm_stats.resident_count = res;
          kernel_pmap->pm_flags = pmap_flags;
  
          /*
           * Initialize the TLB invalidations generation number lock.
           */
          mtx_init(&invl_gen_mtx, "invlgn", NULL, MTX_DEF);
  
          /*
           * Reserve some special page table entries/VA space for temporary
           * mapping of pages.
           */
  #define SYSMAP(c, p, v, n)      \
          v = (c)va; va += ((n)*PAGE_SIZE); p = pte; pte += (n);
  
          va = virtual_avail;
          pte = vtopte(va);
  
          /*
           * Crashdump maps.  The first page is reused as CMAP1 for the
           * memory test.
           */
          SYSMAP(caddr_t, CMAP1, crashdumpmap, MAXDUMPPGS)
          CADDR1 = crashdumpmap;
  
          virtual_avail = va;
  
          /*
           * Initialize the PAT MSR.
           * pmap_init_pat() clears and sets CR4_PGE, which, as a
           * side-effect, invalidates stale PG_G TLB entries that might
           * have been created in our pre-boot environment.
           */
          pmap_init_pat();
  
          /* Initialize TLB Context Id. */
          if (pmap_pcid_enabled) {
                  for (i = 0; i < MAXCPU; i++) {
                          kernel_pmap->pm_pcids[i].pm_pcid = PMAP_PCID_KERN;
                          kernel_pmap->pm_pcids[i].pm_gen = 1;
                  }
  
                  /*
                   * PMAP_PCID_KERN + 1 is used for initialization of
                   * proc0 pmap.  The pmap' pcid state might be used by
                   * EFIRT entry before first context switch, so it
                   * needs to be valid.
                   */
                  PCPU_SET(pcid_next, PMAP_PCID_KERN + 2);
                  PCPU_SET(pcid_gen, 1);
  
                  /*
                   * pcpu area for APs is zeroed during AP startup.
                   * pc_pcid_next and pc_pcid_gen are initialized by AP
                   * during pcpu setup.
                   */
                  load_cr4(rcr4() | CR4_PCIDE);
          }
  }
  
  /*
   * Setup the PAT MSR.
   */
  void
  pmap_init_pat(void)
  {
          uint64_t pat_msr;
          u_long cr0, cr4;
          int i;
  
          /* Bail if this CPU doesn't implement PAT. */
          if ((cpu_feature & CPUID_PAT) == 0)
                  panic("no PAT??");
  
          /* Set default PAT index table. */
          for (i = 0; i < PAT_INDEX_SIZE; i++)
                  pat_index[i] = -1;
          pat_index[PAT_WRITE_BACK] = 0;
          pat_index[PAT_WRITE_THROUGH] = 1;
          pat_index[PAT_UNCACHEABLE] = 3;
          pat_index[PAT_WRITE_COMBINING] = 6;
          pat_index[PAT_WRITE_PROTECTED] = 5;
          pat_index[PAT_UNCACHED] = 2;
  
          /*
           * Initialize default PAT entries.
           * Leave the indices 0-3 at the default of WB, WT, UC-, and UC.
           * Program 5 and 6 as WP and WC.
           *
           * Leave 4 and 7 as WB and UC.  Note that a recursive page table
           * mapping for a 2M page uses a PAT value with the bit 3 set due
           * to its overload with PG_PS.
           */
          pat_msr = PAT_VALUE(0, PAT_WRITE_BACK) |
              PAT_VALUE(1, PAT_WRITE_THROUGH) |
              PAT_VALUE(2, PAT_UNCACHED) |
              PAT_VALUE(3, PAT_UNCACHEABLE) |
              PAT_VALUE(4, PAT_WRITE_BACK) |
              PAT_VALUE(5, PAT_WRITE_PROTECTED) |
              PAT_VALUE(6, PAT_WRITE_COMBINING) |
              PAT_VALUE(7, PAT_UNCACHEABLE);
  
          /* Disable PGE. */
          cr4 = rcr4();
          load_cr4(cr4 & ~CR4_PGE);
  
          /* Disable caches (CD = 1, NW = 0). */
          cr0 = rcr0();
          load_cr0((cr0 & ~CR0_NW) | CR0_CD);
  
          /* Flushes caches and TLBs. */
          wbinvd();
          invltlb();
  
          /* Update PAT and index table. */
          wrmsr(MSR_PAT, pat_msr);
  
          /* Flush caches and TLBs again. */
          wbinvd();
          invltlb();
  
          /* Restore caches and PGE. */
          load_cr0(cr0);
          load_cr4(cr4);
  }
  
  /*
   *      Initialize a vm_page's machine-dependent fields.
   */
  void
  pmap_page_init(vm_page_t m)
  {
  
          TAILQ_INIT(&m->md.pv_list);
          m->md.pat_mode = PAT_WRITE_BACK;
  }
  
  /*
   *      Initialize the pmap module.
   *      Called by vm_init, to initialize any structures that the pmap
   *      system needs to map virtual memory.
   */
  void
  pmap_init(void)
  {
          struct pmap_preinit_mapping *ppim;
          vm_page_t m, mpte;
          vm_size_t s;
          int error, i, pv_npg, ret, skz63;
  
          /* L1TF, reserve page @0 unconditionally */
          vm_page_blacklist_add(0, bootverbose);
  
          /* Detect bare-metal Skylake Server and Skylake-X. */
          if (vm_guest == VM_GUEST_NO && cpu_vendor_id == CPU_VENDOR_INTEL &&
              CPUID_TO_FAMILY(cpu_id) == 0x6 && CPUID_TO_MODEL(cpu_id) == 0x55) {
                  /*
                   * Skylake-X errata SKZ63. Processor May Hang When
                   * Executing Code In an HLE Transaction Region between
                   * 40000000H and 403FFFFFH.
                   *
                   * Mark the pages in the range as preallocated.  It
                   * seems to be impossible to distinguish between
                   * Skylake Server and Skylake X.
                   */
                  skz63 = 1;
                  TUNABLE_INT_FETCH("hw.skz63_enable", &skz63);
                  if (skz63 != 0) {
                          if (bootverbose)
                                  printf("SKZ63: skipping 4M RAM starting "
                                      "at physical 1G\n");
                          for (i = 0; i < atop(0x400000); i++) {
                                  ret = vm_page_blacklist_add(0x40000000 +
                                      ptoa(i), FALSE);
                                  if (!ret && bootverbose)
                                          printf("page at %#lx already used\n",
                                              0x40000000 + ptoa(i));
                          }
                  }
          }
  
          /*
           * Initialize the vm page array entries for the kernel pmap's
           * page table pages.
           */ 
          PMAP_LOCK(kernel_pmap);
          for (i = 0; i < nkpt; i++) {
                  mpte = PHYS_TO_VM_PAGE(KPTphys + (i << PAGE_SHIFT));
                  KASSERT(mpte >= vm_page_array &&
                      mpte < &vm_page_array[vm_page_array_size],
                      ("pmap_init: page table page is out of range"));
                  mpte->pindex = pmap_pde_pindex(KERNBASE) + i;
                  mpte->phys_addr = KPTphys + (i << PAGE_SHIFT);
                  mpte->wire_count = 1;
                  if (i << PDRSHIFT < KERNend &&
                      pmap_insert_pt_page(kernel_pmap, mpte))
                          panic("pmap_init: pmap_insert_pt_page failed");
          }
          PMAP_UNLOCK(kernel_pmap);
          vm_wire_add(nkpt);
  
          /*
           * If the kernel is running on a virtual machine, then it must assume
           * that MCA is enabled by the hypervisor.  Moreover, the kernel must
           * be prepared for the hypervisor changing the vendor and family that
           * are reported by CPUID.  Consequently, the workaround for AMD Family
           * 10h Erratum 383 is enabled if the processor's feature set does not
           * include at least one feature that is only supported by older Intel
           * or newer AMD processors.
           */
          if (vm_guest != VM_GUEST_NO && (cpu_feature & CPUID_SS) == 0 &&
              (cpu_feature2 & (CPUID2_SSSE3 | CPUID2_SSE41 | CPUID2_AESNI |
              CPUID2_AVX | CPUID2_XSAVE)) == 0 && (amd_feature2 & (AMDID2_XOP |
              AMDID2_FMA4)) == 0)
                  workaround_erratum383 = 1;
  
          /*
           * Are large page mappings enabled?
           */
          TUNABLE_INT_FETCH("vm.pmap.pg_ps_enabled", &pg_ps_enabled);
          if (pg_ps_enabled) {
                  KASSERT(MAXPAGESIZES > 1 && pagesizes[1] == 0,
                      ("pmap_init: can't assign to pagesizes[1]"));
                  pagesizes[1] = NBPDR;
          }
  
          /*
           * Initialize the pv chunk list mutex.
           */
          mtx_init(&pv_chunks_mutex, "pmap pv chunk list", NULL, MTX_DEF);
  
          /*
           * Initialize the pool of pv list locks.
           */
          for (i = 0; i < NPV_LIST_LOCKS; i++)
                  rw_init(&pv_list_locks[i], "pmap pv list");
  
          /*
           * Calculate the size of the pv head table for superpages.
           */
          pv_npg = howmany(vm_phys_segs[vm_phys_nsegs - 1].end, NBPDR);
  
          /*
           * Allocate memory for the pv head table for superpages.
           */
          s = (vm_size_t)(pv_npg * sizeof(struct md_page));
          s = round_page(s);
          pv_table = (struct md_page *)kmem_malloc(s, M_WAITOK | M_ZERO);
          for (i = 0; i < pv_npg; i++)
                  TAILQ_INIT(&pv_table[i].pv_list);
          TAILQ_INIT(&pv_dummy.pv_list);
  
          pmap_initialized = 1;
          for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                  ppim = pmap_preinit_mapping + i;
                  if (ppim->va == 0)
                          continue;
                  /* Make the direct map consistent */
                  if (ppim->pa < dmaplimit && ppim->pa + ppim->sz <= dmaplimit) {
                          (void)pmap_change_attr(PHYS_TO_DMAP(ppim->pa),
                              ppim->sz, ppim->mode);
                  }
                  if (!bootverbose)
                          continue;
                  printf("PPIM %u: PA=%#lx, VA=%#lx, size=%#lx, mode=%#x\n", i,
                      ppim->pa, ppim->va, ppim->sz, ppim->mode);
          }
  
          mtx_init(&qframe_mtx, "qfrmlk", NULL, MTX_SPIN);
          error = vmem_alloc(kernel_arena, PAGE_SIZE, M_BESTFIT | M_WAITOK,
              (vmem_addr_t *)&qframe);
          if (error != 0)
                  panic("qframe allocation failed");
  
          lm_ents = 8;
          TUNABLE_INT_FETCH("vm.pmap.large_map_pml4_entries", &lm_ents);
          if (lm_ents > LMEPML4I - LMSPML4I + 1)
                  lm_ents = LMEPML4I - LMSPML4I + 1;
          if (bootverbose)
                  printf("pmap: large map %u PML4 slots (%lu Gb)\n",
                      lm_ents, (u_long)lm_ents * (NBPML4 / 1024 / 1024 / 1024));
          if (lm_ents != 0) {
                  large_vmem = vmem_create("large", LARGEMAP_MIN_ADDRESS,
                      (vmem_size_t)lm_ents * NBPML4, PAGE_SIZE, 0, M_WAITOK);
                  if (large_vmem == NULL) {
                          printf("pmap: cannot create large map\n");
                          lm_ents = 0;
                  }
                  for (i = 0; i < lm_ents; i++) {
                          m = pmap_large_map_getptp_unlocked();
                          kernel_pmap->pm_pml4[LMSPML4I + i] = X86_PG_V |
                              X86_PG_RW | X86_PG_A | X86_PG_M | pg_nx |
                              VM_PAGE_TO_PHYS(m);
                  }
          }
  }
  
  static SYSCTL_NODE(_vm_pmap, OID_AUTO, pde, CTLFLAG_RD, 0,
      "2MB page mapping counters");
  
  static u_long pmap_pde_demotions;
  SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, demotions, CTLFLAG_RD,
      &pmap_pde_demotions, 0, "2MB page demotions");
  
  static u_long pmap_pde_mappings;
  SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, mappings, CTLFLAG_RD,
      &pmap_pde_mappings, 0, "2MB page mappings");
  
  static u_long pmap_pde_p_failures;
  SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, p_failures, CTLFLAG_RD,
      &pmap_pde_p_failures, 0, "2MB page promotion failures");
  
  static u_long pmap_pde_promotions;
  SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, promotions, CTLFLAG_RD,
      &pmap_pde_promotions, 0, "2MB page promotions");
  
  static SYSCTL_NODE(_vm_pmap, OID_AUTO, pdpe, CTLFLAG_RD, 0,
      "1GB page mapping counters");
  
  static u_long pmap_pdpe_demotions;
  SYSCTL_ULONG(_vm_pmap_pdpe, OID_AUTO, demotions, CTLFLAG_RD,
      &pmap_pdpe_demotions, 0, "1GB page demotions");
  
  /***************************************************
   * Low level helper routines.....
   ***************************************************/
  
  static pt_entry_t
  pmap_swap_pat(pmap_t pmap, pt_entry_t entry)
  {
          int x86_pat_bits = X86_PG_PTE_PAT | X86_PG_PDE_PAT;
  
          switch (pmap->pm_type) {
          case PT_X86:
          case PT_RVI:
                  /* Verify that both PAT bits are not set at the same time */
                  KASSERT((entry & x86_pat_bits) != x86_pat_bits,
                      ("Invalid PAT bits in entry %#lx", entry));
  
                  /* Swap the PAT bits if one of them is set */
                  if ((entry & x86_pat_bits) != 0)
                          entry ^= x86_pat_bits;
                  break;
          case PT_EPT:
                  /*
                   * Nothing to do - the memory attributes are represented
                   * the same way for regular pages and superpages.
                   */
                  break;
          default:
                  panic("pmap_switch_pat_bits: bad pm_type %d", pmap->pm_type);
          }
  
          return (entry);
  }
  
  boolean_t
  pmap_is_valid_memattr(pmap_t pmap __unused, vm_memattr_t mode)
  {
  
          return (mode >= 0 && mode < PAT_INDEX_SIZE &&
              pat_index[(int)mode] >= 0);
  }
  
  /*
   * Determine the appropriate bits to set in a PTE or PDE for a specified
   * caching mode.
   */
  int
  pmap_cache_bits(pmap_t pmap, int mode, boolean_t is_pde)
  {
          int cache_bits, pat_flag, pat_idx;
  
          if (!pmap_is_valid_memattr(pmap, mode))
                  panic("Unknown caching mode %d\n", mode);
  
          switch (pmap->pm_type) {
          case PT_X86:
          case PT_RVI:
                  /* The PAT bit is different for PTE's and PDE's. */
                  pat_flag = is_pde ? X86_PG_PDE_PAT : X86_PG_PTE_PAT;
  
                  /* Map the caching mode to a PAT index. */
                  pat_idx = pat_index[mode];
  
                  /* Map the 3-bit index value into the PAT, PCD, and PWT bits. */
                  cache_bits = 0;
                  if (pat_idx & 0x4)
                          cache_bits |= pat_flag;
                  if (pat_idx & 0x2)
                          cache_bits |= PG_NC_PCD;
                  if (pat_idx & 0x1)
                          cache_bits |= PG_NC_PWT;
                  break;
  
          case PT_EPT:
                  cache_bits = EPT_PG_IGNORE_PAT | EPT_PG_MEMORY_TYPE(mode);
                  break;
  
          default:
                  panic("unsupported pmap type %d", pmap->pm_type);
          }
  
          return (cache_bits);
  }
  
  static int
  pmap_cache_mask(pmap_t pmap, boolean_t is_pde)
  {
          int mask;
  
          switch (pmap->pm_type) {
          case PT_X86:
          case PT_RVI:
                  mask = is_pde ? X86_PG_PDE_CACHE : X86_PG_PTE_CACHE;
                  break;
          case PT_EPT:
                  mask = EPT_PG_IGNORE_PAT | EPT_PG_MEMORY_TYPE(0x7);
                  break;
          default:
                  panic("pmap_cache_mask: invalid pm_type %d", pmap->pm_type);
          }
  
          return (mask);
  }
  
  bool
  pmap_ps_enabled(pmap_t pmap)
  {
  
          return (pg_ps_enabled && (pmap->pm_flags & PMAP_PDE_SUPERPAGE) != 0);
  }
  
  static void
  pmap_update_pde_store(pmap_t pmap, pd_entry_t *pde, pd_entry_t newpde)
  {
  
          switch (pmap->pm_type) {
          case PT_X86:
                  break;
          case PT_RVI:
          case PT_EPT:
                  /*
                   * XXX
                   * This is a little bogus since the generation number is
                   * supposed to be bumped up when a region of the address
                   * space is invalidated in the page tables.
                   *
                   * In this case the old PDE entry is valid but yet we want
                   * to make sure that any mappings using the old entry are
                   * invalidated in the TLB.
                   *
                   * The reason this works as expected is because we rendezvous
                   * "all" host cpus and force any vcpu context to exit as a
                   * side-effect.
                   */
                  atomic_add_acq_long(&pmap->pm_eptgen, 1);
                  break;
          default:
                  panic("pmap_update_pde_store: bad pm_type %d", pmap->pm_type);
          }
          pde_store(pde, newpde);
  }
  
  /*
   * After changing the page size for the specified virtual address in the page
   * table, flush the corresponding entries from the processor's TLB.  Only the
   * calling processor's TLB is affected.
   *
   * The calling thread must be pinned to a processor.
   */
  static void
  pmap_update_pde_invalidate(pmap_t pmap, vm_offset_t va, pd_entry_t newpde)
  {
          pt_entry_t PG_G;
  
          if (pmap_type_guest(pmap))
                  return;
  
          KASSERT(pmap->pm_type == PT_X86,
              ("pmap_update_pde_invalidate: invalid type %d", pmap->pm_type));
  
          PG_G = pmap_global_bit(pmap);
  
          if ((newpde & PG_PS) == 0)
                  /* Demotion: flush a specific 2MB page mapping. */
                  invlpg(va);
          else if ((newpde & PG_G) == 0)
                  /*
                   * Promotion: flush every 4KB page mapping from the TLB
                   * because there are too many to flush individually.
                   */
                  invltlb();
          else {
                  /*
                   * Promotion: flush every 4KB page mapping from the TLB,
                   * including any global (PG_G) mappings.
                   */
                  invltlb_glob();
          }
  }
  #ifdef SMP
  
  /*
   * For SMP, these functions have to use the IPI mechanism for coherence.
   *
   * N.B.: Before calling any of the following TLB invalidation functions,
   * the calling processor must ensure that all stores updating a non-
   * kernel page table are globally performed.  Otherwise, another
   * processor could cache an old, pre-update entry without being
   * invalidated.  This can happen one of two ways: (1) The pmap becomes
   * active on another processor after its pm_active field is checked by
   * one of the following functions but before a store updating the page
   * table is globally performed. (2) The pmap becomes active on another
   * processor before its pm_active field is checked but due to
   * speculative loads one of the following functions stills reads the
   * pmap as inactive on the other processor.
   * 
   * The kernel page table is exempt because its pm_active field is
   * immutable.  The kernel page table is always active on every
   * processor.
   */
  
  /*
   * Interrupt the cpus that are executing in the guest context.
   * This will force the vcpu to exit and the cached EPT mappings
   * will be invalidated by the host before the next vmresume.
   */
  static __inline void
  pmap_invalidate_ept(pmap_t pmap)
  {
          int ipinum;
  
          sched_pin();
          KASSERT(!CPU_ISSET(curcpu, &pmap->pm_active),
              ("pmap_invalidate_ept: absurd pm_active"));
  
          /*
           * The TLB mappings associated with a vcpu context are not
           * flushed each time a different vcpu is chosen to execute.
           *
           * This is in contrast with a process's vtop mappings that
           * are flushed from the TLB on each context switch.
           *
           * Therefore we need to do more than just a TLB shootdown on
           * the active cpus in 'pmap->pm_active'. To do this we keep
           * track of the number of invalidations performed on this pmap.
           *
           * Each vcpu keeps a cache of this counter and compares it
           * just before a vmresume. If the counter is out-of-date an
           * invept will be done to flush stale mappings from the TLB.
           */
          atomic_add_acq_long(&pmap->pm_eptgen, 1);
  
          /*
           * Force the vcpu to exit and trap back into the hypervisor.
           */
          ipinum = pmap->pm_flags & PMAP_NESTED_IPIMASK;
          ipi_selected(pmap->pm_active, ipinum);
          sched_unpin();
  }
  
  static cpuset_t
  pmap_invalidate_cpu_mask(pmap_t pmap)
  {
  
          return (pmap == kernel_pmap ? all_cpus : pmap->pm_active);
  }
  
  static inline void
  pmap_invalidate_page_pcid(pmap_t pmap, vm_offset_t va,
      const bool invpcid_works1)
  {
          struct invpcid_descr d;
          uint64_t kcr3, ucr3;
          uint32_t pcid;
          u_int cpuid, i;
  
          cpuid = PCPU_GET(cpuid);
          if (pmap == PCPU_GET(curpmap)) {
                  if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                          /*
                           * Because pm_pcid is recalculated on a
                           * context switch, we must disable switching.
                           * Otherwise, we might use a stale value
                           * below.
                           */
                          critical_enter();
                          pcid = pmap->pm_pcids[cpuid].pm_pcid;
                          if (invpcid_works1) {
                                  d.pcid = pcid | PMAP_PCID_USER_PT;
                                  d.pad = 0;
                                  d.addr = va;
                                  invpcid(&d, INVPCID_ADDR);
                          } else {
                                  kcr3 = pmap->pm_cr3 | pcid | CR3_PCID_SAVE;
                                  ucr3 = pmap->pm_ucr3 | pcid |
                                      PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                  pmap_pti_pcid_invlpg(ucr3, kcr3, va);
                          }
                          critical_exit();
                  }
          } else
                  pmap->pm_pcids[cpuid].pm_gen = 0;
  
          CPU_FOREACH(i) {
                  if (cpuid != i)
                          pmap->pm_pcids[i].pm_gen = 0;
          }
  
          /*
           * The fence is between stores to pm_gen and the read of the
           * pm_active mask.  We need to ensure that it is impossible
           * for us to miss the bit update in pm_active and
           * simultaneously observe a non-zero pm_gen in
           * pmap_activate_sw(), otherwise TLB update is missed.
           * Without the fence, IA32 allows such an outcome.  Note that
           * pm_active is updated by a locked operation, which provides
           * the reciprocal fence.
           */
          atomic_thread_fence_seq_cst();
  }
  
  static void
  pmap_invalidate_page_pcid_invpcid(pmap_t pmap, vm_offset_t va)
  {
  
          pmap_invalidate_page_pcid(pmap, va, true);
  }
  
  static void
  pmap_invalidate_page_pcid_noinvpcid(pmap_t pmap, vm_offset_t va)
  {
  
          pmap_invalidate_page_pcid(pmap, va, false);
  }
  
  static void
  pmap_invalidate_page_nopcid(pmap_t pmap, vm_offset_t va)
  {
  }
  
  DEFINE_IFUNC(static, void, pmap_invalidate_page_mode, (pmap_t, vm_offset_t),
      static)
  {
  
          if (pmap_pcid_enabled)
                  return (invpcid_works ? pmap_invalidate_page_pcid_invpcid :
                      pmap_invalidate_page_pcid_noinvpcid);
          return (pmap_invalidate_page_nopcid);
  }
  
  void
  pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
  {
  
          if (pmap_type_guest(pmap)) {
                  pmap_invalidate_ept(pmap);
                  return;
          }
  
          KASSERT(pmap->pm_type == PT_X86,
              ("pmap_invalidate_page: invalid type %d", pmap->pm_type));
  
          sched_pin();
          if (pmap == kernel_pmap) {
                  invlpg(va);
          } else {
                  if (pmap == PCPU_GET(curpmap))
                          invlpg(va);
                  pmap_invalidate_page_mode(pmap, va);
          }
          smp_masked_invlpg(pmap_invalidate_cpu_mask(pmap), va, pmap);
          sched_unpin();
  }
  
  /* 4k PTEs -- Chosen to exceed the total size of Broadwell L2 TLB */
  #define PMAP_INVLPG_THRESHOLD   (4 * 1024 * PAGE_SIZE)
  
  static void
  pmap_invalidate_range_pcid(pmap_t pmap, vm_offset_t sva, vm_offset_t eva,
      const bool invpcid_works1)
  {
          struct invpcid_descr d;
          uint64_t kcr3, ucr3;
          uint32_t pcid;
          u_int cpuid, i;
  
          cpuid = PCPU_GET(cpuid);
          if (pmap == PCPU_GET(curpmap)) {
                  if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                          critical_enter();
                          pcid = pmap->pm_pcids[cpuid].pm_pcid;
                          if (invpcid_works1) {
                                  d.pcid = pcid | PMAP_PCID_USER_PT;
                                  d.pad = 0;
                                  d.addr = sva;
                                  for (; d.addr < eva; d.addr += PAGE_SIZE)
                                          invpcid(&d, INVPCID_ADDR);
                          } else {
                                  kcr3 = pmap->pm_cr3 | pcid | CR3_PCID_SAVE;
                                  ucr3 = pmap->pm_ucr3 | pcid |
                                      PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                  pmap_pti_pcid_invlrng(ucr3, kcr3, sva, eva);
                          }
                          critical_exit();
                  }
          } else
                  pmap->pm_pcids[cpuid].pm_gen = 0;
  
          CPU_FOREACH(i) {
                  if (cpuid != i)
                          pmap->pm_pcids[i].pm_gen = 0;
          }
          /* See the comment in pmap_invalidate_page_pcid(). */
          atomic_thread_fence_seq_cst();
  }
  
  static void
  pmap_invalidate_range_pcid_invpcid(pmap_t pmap, vm_offset_t sva,
      vm_offset_t eva)
  {
  
          pmap_invalidate_range_pcid(pmap, sva, eva, true);
  }
  
  static void
  pmap_invalidate_range_pcid_noinvpcid(pmap_t pmap, vm_offset_t sva,
      vm_offset_t eva)
  {
  
          pmap_invalidate_range_pcid(pmap, sva, eva, false);
  }
  
  static void
  pmap_invalidate_range_nopcid(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
  }
  
  DEFINE_IFUNC(static, void, pmap_invalidate_range_mode, (pmap_t, vm_offset_t,
      vm_offset_t), static)
  {
  
          if (pmap_pcid_enabled)
                  return (invpcid_works ? pmap_invalidate_range_pcid_invpcid :
                      pmap_invalidate_range_pcid_noinvpcid);
          return (pmap_invalidate_range_nopcid);
  }
  
  void
  pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
          vm_offset_t addr;
  
          if (eva - sva >= PMAP_INVLPG_THRESHOLD) {
                  pmap_invalidate_all(pmap);
                  return;
          }
  
          if (pmap_type_guest(pmap)) {
                  pmap_invalidate_ept(pmap);
                  return;
          }
  
          KASSERT(pmap->pm_type == PT_X86,
              ("pmap_invalidate_range: invalid type %d", pmap->pm_type));
  
          sched_pin();
          if (pmap == kernel_pmap) {
                  for (addr = sva; addr < eva; addr += PAGE_SIZE)
                          invlpg(addr);
          } else {
                  if (pmap == PCPU_GET(curpmap)) {
                          for (addr = sva; addr < eva; addr += PAGE_SIZE)
                                  invlpg(addr);
                  }
                  pmap_invalidate_range_mode(pmap, sva, eva);
          }
          smp_masked_invlpg_range(pmap_invalidate_cpu_mask(pmap), sva, eva, pmap);
          sched_unpin();
  }
  
  static inline void
  pmap_invalidate_all_pcid(pmap_t pmap, bool invpcid_works1)
  {
          struct invpcid_descr d;
          uint64_t kcr3, ucr3;
          uint32_t pcid;
          u_int cpuid, i;
  
          if (pmap == kernel_pmap) {
                  if (invpcid_works1) {
                          bzero(&d, sizeof(d));
                          invpcid(&d, INVPCID_CTXGLOB);
                  } else {
                          invltlb_glob();
                  }
          } else {
                  cpuid = PCPU_GET(cpuid);
                  if (pmap == PCPU_GET(curpmap)) {
                          critical_enter();
                          pcid = pmap->pm_pcids[cpuid].pm_pcid;
                          if (invpcid_works1) {
                                  d.pcid = pcid;
                                  d.pad = 0;
                                  d.addr = 0;
                                  invpcid(&d, INVPCID_CTX);
                                  if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                                          d.pcid |= PMAP_PCID_USER_PT;
                                          invpcid(&d, INVPCID_CTX);
                                  }
                          } else {
                                  kcr3 = pmap->pm_cr3 | pcid;
                                  ucr3 = pmap->pm_ucr3;
                                  if (ucr3 != PMAP_NO_CR3) {
                                          ucr3 |= pcid | PMAP_PCID_USER_PT;
                                          pmap_pti_pcid_invalidate(ucr3, kcr3);
                                  } else {
                                          load_cr3(kcr3);
                                  }
                          }
                          critical_exit();
                  } else
                          pmap->pm_pcids[cpuid].pm_gen = 0;
                  CPU_FOREACH(i) {
                          if (cpuid != i)
                                  pmap->pm_pcids[i].pm_gen = 0;
                  }
          }
          /* See the comment in pmap_invalidate_page_pcid(). */
          atomic_thread_fence_seq_cst();
  }
  
  static void
  pmap_invalidate_all_pcid_invpcid(pmap_t pmap)
  {
  
          pmap_invalidate_all_pcid(pmap, true);
  }
  
  static void
  pmap_invalidate_all_pcid_noinvpcid(pmap_t pmap)
  {
  
          pmap_invalidate_all_pcid(pmap, false);
  }
  
  static void
  pmap_invalidate_all_nopcid(pmap_t pmap)
  {
  
          if (pmap == kernel_pmap)
                  invltlb_glob();
          else if (pmap == PCPU_GET(curpmap))
                  invltlb();
  }
  
  DEFINE_IFUNC(static, void, pmap_invalidate_all_mode, (pmap_t), static)
  {
  
          if (pmap_pcid_enabled)
                  return (invpcid_works ? pmap_invalidate_all_pcid_invpcid :
                      pmap_invalidate_all_pcid_noinvpcid);
          return (pmap_invalidate_all_nopcid);
  }
  
  void
  pmap_invalidate_all(pmap_t pmap)
  {
  
          if (pmap_type_guest(pmap)) {
                  pmap_invalidate_ept(pmap);
                  return;
          }
  
          KASSERT(pmap->pm_type == PT_X86,
              ("pmap_invalidate_all: invalid type %d", pmap->pm_type));
  
          sched_pin();
          pmap_invalidate_all_mode(pmap);
          smp_masked_invltlb(pmap_invalidate_cpu_mask(pmap), pmap);
          sched_unpin();
  }
  
  void
  pmap_invalidate_cache(void)
  {
  
          sched_pin();
          wbinvd();
          smp_cache_flush();
          sched_unpin();
  }
  
  struct pde_action {
          cpuset_t invalidate;    /* processors that invalidate their TLB */
          pmap_t pmap;
          vm_offset_t va;
          pd_entry_t *pde;
          pd_entry_t newpde;
          u_int store;            /* processor that updates the PDE */
  };
  
  static void
  pmap_update_pde_action(void *arg)
  {
          struct pde_action *act = arg;
  
          if (act->store == PCPU_GET(cpuid))
                  pmap_update_pde_store(act->pmap, act->pde, act->newpde);
  }
  
  static void
  pmap_update_pde_teardown(void *arg)
  {
          struct pde_action *act = arg;
  
          if (CPU_ISSET(PCPU_GET(cpuid), &act->invalidate))
                  pmap_update_pde_invalidate(act->pmap, act->va, act->newpde);
  }
  
  /*
   * Change the page size for the specified virtual address in a way that
   * prevents any possibility of the TLB ever having two entries that map the
   * same virtual address using different page sizes.  This is the recommended
   * workaround for Erratum 383 on AMD Family 10h processors.  It prevents a
   * machine check exception for a TLB state that is improperly diagnosed as a
   * hardware error.
   */
  static void
  pmap_update_pde(pmap_t pmap, vm_offset_t va, pd_entry_t *pde, pd_entry_t newpde)
  {
          struct pde_action act;
          cpuset_t active, other_cpus;
          u_int cpuid;
  
          sched_pin();
          cpuid = PCPU_GET(cpuid);
          other_cpus = all_cpus;
          CPU_CLR(cpuid, &other_cpus);
          if (pmap == kernel_pmap || pmap_type_guest(pmap)) 
                  active = all_cpus;
          else {
                  active = pmap->pm_active;
          }
          if (CPU_OVERLAP(&active, &other_cpus)) { 
                  act.store = cpuid;
                  act.invalidate = active;
                  act.va = va;
                  act.pmap = pmap;
                  act.pde = pde;
                  act.newpde = newpde;
                  CPU_SET(cpuid, &active);
                  smp_rendezvous_cpus(active,
                      smp_no_rendezvous_barrier, pmap_update_pde_action,
                      pmap_update_pde_teardown, &act);
          } else {
                  pmap_update_pde_store(pmap, pde, newpde);
                  if (CPU_ISSET(cpuid, &active))
                          pmap_update_pde_invalidate(pmap, va, newpde);
          }
          sched_unpin();
  }
  #else /* !SMP */
  /*
   * Normal, non-SMP, invalidation functions.
   */
  void
  pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
  {
          struct invpcid_descr d;
          uint64_t kcr3, ucr3;
          uint32_t pcid;
  
          if (pmap->pm_type == PT_RVI || pmap->pm_type == PT_EPT) {
                  pmap->pm_eptgen++;
                  return;
          }
          KASSERT(pmap->pm_type == PT_X86,
              ("pmap_invalidate_range: unknown type %d", pmap->pm_type));
  
          if (pmap == kernel_pmap || pmap == PCPU_GET(curpmap)) {
                  invlpg(va);
                  if (pmap == PCPU_GET(curpmap) && pmap_pcid_enabled &&
                      pmap->pm_ucr3 != PMAP_NO_CR3) {
                          critical_enter();
                          pcid = pmap->pm_pcids[0].pm_pcid;
                          if (invpcid_works) {
                                  d.pcid = pcid | PMAP_PCID_USER_PT;
                                  d.pad = 0;
                                  d.addr = va;
                                  invpcid(&d, INVPCID_ADDR);
                          } else {
                                  kcr3 = pmap->pm_cr3 | pcid | CR3_PCID_SAVE;
                                  ucr3 = pmap->pm_ucr3 | pcid |
                                      PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                  pmap_pti_pcid_invlpg(ucr3, kcr3, va);
                          }
                          critical_exit();
                  }
          } else if (pmap_pcid_enabled)
                  pmap->pm_pcids[0].pm_gen = 0;
  }
  
  void
  pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
          struct invpcid_descr d;
          vm_offset_t addr;
          uint64_t kcr3, ucr3;
  
          if (pmap->pm_type == PT_RVI || pmap->pm_type == PT_EPT) {
                  pmap->pm_eptgen++;
                  return;
          }
          KASSERT(pmap->pm_type == PT_X86,
              ("pmap_invalidate_range: unknown type %d", pmap->pm_type));
  
          if (pmap == kernel_pmap || pmap == PCPU_GET(curpmap)) {
                  for (addr = sva; addr < eva; addr += PAGE_SIZE)
                          invlpg(addr);
                  if (pmap == PCPU_GET(curpmap) && pmap_pcid_enabled &&
                      pmap->pm_ucr3 != PMAP_NO_CR3) {
                          critical_enter();
                          if (invpcid_works) {
                                  d.pcid = pmap->pm_pcids[0].pm_pcid |
                                      PMAP_PCID_USER_PT;
                                  d.pad = 0;
                                  d.addr = sva;
                                  for (; d.addr < eva; d.addr += PAGE_SIZE)
                                          invpcid(&d, INVPCID_ADDR);
                          } else {
                                  kcr3 = pmap->pm_cr3 | pmap->pm_pcids[0].
                                      pm_pcid | CR3_PCID_SAVE;
                                  ucr3 = pmap->pm_ucr3 | pmap->pm_pcids[0].
                                      pm_pcid | PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                  pmap_pti_pcid_invlrng(ucr3, kcr3, sva, eva);
                          }
                          critical_exit();
                  }
          } else if (pmap_pcid_enabled) {
                  pmap->pm_pcids[0].pm_gen = 0;
          }
  }
  
  void
  pmap_invalidate_all(pmap_t pmap)
  {
          struct invpcid_descr d;
          uint64_t kcr3, ucr3;
  
          if (pmap->pm_type == PT_RVI || pmap->pm_type == PT_EPT) {
                  pmap->pm_eptgen++;
                  return;
          }
          KASSERT(pmap->pm_type == PT_X86,
              ("pmap_invalidate_all: unknown type %d", pmap->pm_type));
  
          if (pmap == kernel_pmap) {
                  if (pmap_pcid_enabled && invpcid_works) {
                          bzero(&d, sizeof(d));
                          invpcid(&d, INVPCID_CTXGLOB);
                  } else {
                          invltlb_glob();
                  }
          } else if (pmap == PCPU_GET(curpmap)) {
                  if (pmap_pcid_enabled) {
                          critical_enter();
                          if (invpcid_works) {
                                  d.pcid = pmap->pm_pcids[0].pm_pcid;
                                  d.pad = 0;
                                  d.addr = 0;
                                  invpcid(&d, INVPCID_CTX);
                                  if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                                          d.pcid |= PMAP_PCID_USER_PT;
                                          invpcid(&d, INVPCID_CTX);
                                  }
                          } else {
                                  kcr3 = pmap->pm_cr3 | pmap->pm_pcids[0].pm_pcid;
                                  if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                                          ucr3 = pmap->pm_ucr3 | pmap->pm_pcids[
                                              0].pm_pcid | PMAP_PCID_USER_PT;
                                          pmap_pti_pcid_invalidate(ucr3, kcr3);
                                  } else
                                          load_cr3(kcr3);
                          }
                          critical_exit();
                  } else {
                          invltlb();
                  }
          } else if (pmap_pcid_enabled) {
                  pmap->pm_pcids[0].pm_gen = 0;
          }
  }
  
  PMAP_INLINE void
  pmap_invalidate_cache(void)
  {
  
          wbinvd();
  }
  
  static void
  pmap_update_pde(pmap_t pmap, vm_offset_t va, pd_entry_t *pde, pd_entry_t newpde)
  {
  
          pmap_update_pde_store(pmap, pde, newpde);
          if (pmap == kernel_pmap || pmap == PCPU_GET(curpmap))
                  pmap_update_pde_invalidate(pmap, va, newpde);
          else
                  pmap->pm_pcids[0].pm_gen = 0;
  }
  #endif /* !SMP */
  
  static void
  pmap_invalidate_pde_page(pmap_t pmap, vm_offset_t va, pd_entry_t pde)
  {
  
          /*
           * When the PDE has PG_PROMOTED set, the 2MB page mapping was created
           * by a promotion that did not invalidate the 512 4KB page mappings
           * that might exist in the TLB.  Consequently, at this point, the TLB
           * may hold both 4KB and 2MB page mappings for the address range [va,
           * va + NBPDR).  Therefore, the entire range must be invalidated here.
           * In contrast, when PG_PROMOTED is clear, the TLB will not hold any
           * 4KB page mappings for the address range [va, va + NBPDR), and so a
           * single INVLPG suffices to invalidate the 2MB page mapping from the
           * TLB.
           */
          if ((pde & PG_PROMOTED) != 0)
                  pmap_invalidate_range(pmap, va, va + NBPDR - 1);
          else
                  pmap_invalidate_page(pmap, va);
  }
  
  DEFINE_IFUNC(, void, pmap_invalidate_cache_range,
      (vm_offset_t sva, vm_offset_t eva), static)
  {
  
          if ((cpu_feature & CPUID_SS) != 0)
                  return (pmap_invalidate_cache_range_selfsnoop);
          if ((cpu_feature & CPUID_CLFSH) != 0)
                  return (pmap_force_invalidate_cache_range);
          return (pmap_invalidate_cache_range_all);
  }
  
  #define PMAP_CLFLUSH_THRESHOLD   (2 * 1024 * 1024)
  
  static void
  pmap_invalidate_cache_range_check_align(vm_offset_t sva, vm_offset_t eva)
  {
  
          KASSERT((sva & PAGE_MASK) == 0,
              ("pmap_invalidate_cache_range: sva not page-aligned"));
          KASSERT((eva & PAGE_MASK) == 0,
              ("pmap_invalidate_cache_range: eva not page-aligned"));
  }
  
  static void
  pmap_invalidate_cache_range_selfsnoop(vm_offset_t sva, vm_offset_t eva)
  {
  
          pmap_invalidate_cache_range_check_align(sva, eva);
  }
  
  void
  pmap_force_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva)
  {
  
          sva &= ~(vm_offset_t)(cpu_clflush_line_size - 1);
  
          /*
           * XXX: Some CPUs fault, hang, or trash the local APIC
           * registers if we use CLFLUSH on the local APIC range.  The
           * local APIC is always uncached, so we don't need to flush
           * for that range anyway.
           */
          if (pmap_kextract(sva) == lapic_paddr)
                  return;
  
          if ((cpu_stdext_feature & CPUID_STDEXT_CLFLUSHOPT) != 0) {
                  /*
                   * Do per-cache line flush.  Use the sfence
                   * instruction to insure that previous stores are
                   * included in the write-back.  The processor
                   * propagates flush to other processors in the cache
                   * coherence domain.
                   */
                  sfence();
                  for (; sva < eva; sva += cpu_clflush_line_size)
                          clflushopt(sva);
                  sfence();
          } else {
                  /*
                   * Writes are ordered by CLFLUSH on Intel CPUs.
                   */
                  if (cpu_vendor_id != CPU_VENDOR_INTEL)
                          mfence();
                  for (; sva < eva; sva += cpu_clflush_line_size)
                          clflush(sva);
                  if (cpu_vendor_id != CPU_VENDOR_INTEL)
                          mfence();
          }
  }
  
  static void
  pmap_invalidate_cache_range_all(vm_offset_t sva, vm_offset_t eva)
  {
  
          pmap_invalidate_cache_range_check_align(sva, eva);
          pmap_invalidate_cache();
  }
  
  /*
   * Remove the specified set of pages from the data and instruction caches.
   *
   * In contrast to pmap_invalidate_cache_range(), this function does not
   * rely on the CPU's self-snoop feature, because it is intended for use
   * when moving pages into a different cache domain.
   */
  void
  pmap_invalidate_cache_pages(vm_page_t *pages, int count)
  {
          vm_offset_t daddr, eva;
          int i;
          bool useclflushopt;
  
          useclflushopt = (cpu_stdext_feature & CPUID_STDEXT_CLFLUSHOPT) != 0;
          if (count >= PMAP_CLFLUSH_THRESHOLD / PAGE_SIZE ||
              ((cpu_feature & CPUID_CLFSH) == 0 && !useclflushopt))
                  pmap_invalidate_cache();
          else {
                  if (useclflushopt)
                          sfence();
                  else if (cpu_vendor_id != CPU_VENDOR_INTEL)
                          mfence();
                  for (i = 0; i < count; i++) {
                          daddr = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pages[i]));
                          eva = daddr + PAGE_SIZE;
                          for (; daddr < eva; daddr += cpu_clflush_line_size) {
                                  if (useclflushopt)
                                          clflushopt(daddr);
                                  else
                                          clflush(daddr);
                          }
                  }
                  if (useclflushopt)
                          sfence();
                  else if (cpu_vendor_id != CPU_VENDOR_INTEL)
                          mfence();
          }
  }
  
  void
  pmap_flush_cache_range(vm_offset_t sva, vm_offset_t eva)
  {
  
          pmap_invalidate_cache_range_check_align(sva, eva);
  
          if ((cpu_stdext_feature & CPUID_STDEXT_CLWB) == 0) {
                  pmap_force_invalidate_cache_range(sva, eva);
                  return;
          }
  
          /* See comment in pmap_force_invalidate_cache_range(). */
          if (pmap_kextract(sva) == lapic_paddr)
                  return;
  
          sfence();
          for (; sva < eva; sva += cpu_clflush_line_size)
                  clwb(sva);
          sfence();
  }
  
  void
  pmap_flush_cache_phys_range(vm_paddr_t spa, vm_paddr_t epa, vm_memattr_t mattr)
  {
          pt_entry_t *pte;
          vm_offset_t vaddr;
          int error, pte_bits;
  
          KASSERT((spa & PAGE_MASK) == 0,
              ("pmap_flush_cache_phys_range: spa not page-aligned"));
          KASSERT((epa & PAGE_MASK) == 0,
              ("pmap_flush_cache_phys_range: epa not page-aligned"));
  
          if (spa < dmaplimit) {
                  pmap_flush_cache_range(PHYS_TO_DMAP(spa), PHYS_TO_DMAP(MIN(
                      dmaplimit, epa)));
                  if (dmaplimit >= epa)
                          return;
                  spa = dmaplimit;
          }
  
          pte_bits = pmap_cache_bits(kernel_pmap, mattr, 0) | X86_PG_RW |
              X86_PG_V;
          error = vmem_alloc(kernel_arena, PAGE_SIZE, M_BESTFIT | M_WAITOK,
              &vaddr);
          KASSERT(error == 0, ("vmem_alloc failed: %d", error));
          pte = vtopte(vaddr);
          for (; spa < epa; spa += PAGE_SIZE) {
                  sched_pin();
                  pte_store(pte, spa | pte_bits);
                  invlpg(vaddr);
                  /* XXXKIB sfences inside flush_cache_range are excessive */
                  pmap_flush_cache_range(vaddr, vaddr + PAGE_SIZE);
                  sched_unpin();
          }
          vmem_free(kernel_arena, vaddr, PAGE_SIZE);
  }
  
  /*
   *      Routine:        pmap_extract
   *      Function:
   *              Extract the physical page address associated
   *              with the given map/virtual_address pair.
   */
  vm_paddr_t 
  pmap_extract(pmap_t pmap, vm_offset_t va)
  {
          pdp_entry_t *pdpe;
          pd_entry_t *pde;
          pt_entry_t *pte, PG_V;
          vm_paddr_t pa;
  
          pa = 0;
          PG_V = pmap_valid_bit(pmap);
          PMAP_LOCK(pmap);
          pdpe = pmap_pdpe(pmap, va);
          if (pdpe != NULL && (*pdpe & PG_V) != 0) {
                  if ((*pdpe & PG_PS) != 0)
                          pa = (*pdpe & PG_PS_FRAME) | (va & PDPMASK);
                  else {
                          pde = pmap_pdpe_to_pde(pdpe, va);
                          if ((*pde & PG_V) != 0) {
                                  if ((*pde & PG_PS) != 0) {
                                          pa = (*pde & PG_PS_FRAME) |
                                              (va & PDRMASK);
                                  } else {
                                          pte = pmap_pde_to_pte(pde, va);
                                          pa = (*pte & PG_FRAME) |
                                              (va & PAGE_MASK);
                                  }
                          }
                  }
          }
          PMAP_UNLOCK(pmap);
          return (pa);
  }
  
  /*
   *      Routine:        pmap_extract_and_hold
   *      Function:
   *              Atomically extract and hold the physical page
   *              with the given pmap and virtual address pair
   *              if that mapping permits the given protection.
   */
  vm_page_t
  pmap_extract_and_hold(pmap_t pmap, vm_offset_t va, vm_prot_t prot)
  {
          pd_entry_t pde, *pdep;
          pt_entry_t pte, PG_RW, PG_V;
          vm_paddr_t pa;
          vm_page_t m;
  
          pa = 0;
          m = NULL;
          PG_RW = pmap_rw_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PMAP_LOCK(pmap);
  retry:
          pdep = pmap_pde(pmap, va);
          if (pdep != NULL && (pde = *pdep)) {
                  if (pde & PG_PS) {
                          if ((pde & PG_RW) || (prot & VM_PROT_WRITE) == 0) {
                                  if (vm_page_pa_tryrelock(pmap, (pde &
                                      PG_PS_FRAME) | (va & PDRMASK), &pa))
                                          goto retry;
                                  m = PHYS_TO_VM_PAGE(pa);
                          }
                  } else {
                          pte = *pmap_pde_to_pte(pdep, va);
                          if ((pte & PG_V) &&
                              ((pte & PG_RW) || (prot & VM_PROT_WRITE) == 0)) {
                                  if (vm_page_pa_tryrelock(pmap, pte & PG_FRAME,
                                      &pa))
                                          goto retry;
                                  m = PHYS_TO_VM_PAGE(pa);
                          }
                  }
                  if (m != NULL)
                          vm_page_hold(m);
          }
          PA_UNLOCK_COND(pa);
          PMAP_UNLOCK(pmap);
          return (m);
  }
  
  vm_paddr_t
  pmap_kextract(vm_offset_t va)
  {
          pd_entry_t pde;
          vm_paddr_t pa;
  
          if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS) {
                  pa = DMAP_TO_PHYS(va);
          } else {
                  pde = *vtopde(va);
                  if (pde & PG_PS) {
                          pa = (pde & PG_PS_FRAME) | (va & PDRMASK);
                  } else {
                          /*
                           * Beware of a concurrent promotion that changes the
                           * PDE at this point!  For example, vtopte() must not
                           * be used to access the PTE because it would use the
                           * new PDE.  It is, however, safe to use the old PDE
                           * because the page table page is preserved by the
                           * promotion.
                           */
                          pa = *pmap_pde_to_pte(&pde, va);
                          pa = (pa & PG_FRAME) | (va & PAGE_MASK);
                  }
          }
          return (pa);
  }
  
  /***************************************************
   * Low level mapping routines.....
   ***************************************************/
  
  /*
   * Add a wired page to the kva.
   * Note: not SMP coherent.
   */
  PMAP_INLINE void 
  pmap_kenter(vm_offset_t va, vm_paddr_t pa)
  {
          pt_entry_t *pte;
  
          pte = vtopte(va);
          pte_store(pte, pa | X86_PG_RW | X86_PG_V | pg_g);
  }
  
  static __inline void
  pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int mode)
  {
          pt_entry_t *pte;
          int cache_bits;
  
          pte = vtopte(va);
          cache_bits = pmap_cache_bits(kernel_pmap, mode, 0);
          pte_store(pte, pa | X86_PG_RW | X86_PG_V | pg_g | cache_bits);
  }
  
  /*
   * Remove a page from the kernel pagetables.
   * Note: not SMP coherent.
   */
  PMAP_INLINE void
  pmap_kremove(vm_offset_t va)
  {
          pt_entry_t *pte;
  
          pte = vtopte(va);
          pte_clear(pte);
  }
  
  /*
   *      Used to map a range of physical addresses into kernel
   *      virtual address space.
   *
   *      The value passed in '*virt' is a suggested virtual address for
   *      the mapping. Architectures which can support a direct-mapped
   *      physical to virtual region can return the appropriate address
   *      within that region, leaving '*virt' unchanged. Other
   *      architectures should map the pages starting at '*virt' and
   *      update '*virt' with the first usable address after the mapped
   *      region.
   */
  vm_offset_t
  pmap_map(vm_offset_t *virt, vm_paddr_t start, vm_paddr_t end, int prot)
  {
          return PHYS_TO_DMAP(start);
  }
  
  
  /*
   * Add a list of wired pages to the kva
   * this routine is only used for temporary
   * kernel mappings that do not need to have
   * page modification or references recorded.
   * Note that old mappings are simply written
   * over.  The page *must* be wired.
   * Note: SMP coherent.  Uses a ranged shootdown IPI.
   */
  void
  pmap_qenter(vm_offset_t sva, vm_page_t *ma, int count)
  {
          pt_entry_t *endpte, oldpte, pa, *pte;
          vm_page_t m;
          int cache_bits;
  
          oldpte = 0;
          pte = vtopte(sva);
          endpte = pte + count;
          while (pte < endpte) {
                  m = *ma++;
                  cache_bits = pmap_cache_bits(kernel_pmap, m->md.pat_mode, 0);
                  pa = VM_PAGE_TO_PHYS(m) | cache_bits;
                  if ((*pte & (PG_FRAME | X86_PG_PTE_CACHE)) != pa) {
                          oldpte |= *pte;
                          pte_store(pte, pa | pg_g | pg_nx | X86_PG_RW | X86_PG_V);
                  }
                  pte++;
          }
          if (__predict_false((oldpte & X86_PG_V) != 0))
                  pmap_invalidate_range(kernel_pmap, sva, sva + count *
                      PAGE_SIZE);
  }
  
  /*
   * This routine tears out page mappings from the
   * kernel -- it is meant only for temporary mappings.
   * Note: SMP coherent.  Uses a ranged shootdown IPI.
   */
  void
  pmap_qremove(vm_offset_t sva, int count)
  {
          vm_offset_t va;
  
          va = sva;
          while (count-- > 0) {
                  KASSERT(va >= VM_MIN_KERNEL_ADDRESS, ("usermode va %lx", va));
                  pmap_kremove(va);
                  va += PAGE_SIZE;
          }
          pmap_invalidate_range(kernel_pmap, sva, va);
  }
  
  /***************************************************
   * Page table page management routines.....
   ***************************************************/
  /*
   * Schedule the specified unused page table page to be freed.  Specifically,
   * add the page to the specified list of pages that will be released to the
   * physical memory manager after the TLB has been updated.
   */
  static __inline void
  pmap_add_delayed_free_list(vm_page_t m, struct spglist *free,
      boolean_t set_PG_ZERO)
  {
  
          if (set_PG_ZERO)
                  m->flags |= PG_ZERO;
          else
                  m->flags &= ~PG_ZERO;
          SLIST_INSERT_HEAD(free, m, plinks.s.ss);
  }
          
  /*
   * Inserts the specified page table page into the specified pmap's collection
   * of idle page table pages.  Each of a pmap's page table pages is responsible
   * for mapping a distinct range of virtual addresses.  The pmap's collection is
   * ordered by this virtual address range.
   */
  static __inline int
  pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte)
  {
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          return (vm_radix_insert(&pmap->pm_root, mpte));
  }
  
  /*
   * Removes the page table page mapping the specified virtual address from the
   * specified pmap's collection of idle page table pages, and returns it.
   * Otherwise, returns NULL if there is no page table page corresponding to the
   * specified virtual address.
   */
  static __inline vm_page_t
  pmap_remove_pt_page(pmap_t pmap, vm_offset_t va)
  {
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          return (vm_radix_remove(&pmap->pm_root, pmap_pde_pindex(va)));
  }
  
  /*
   * Decrements a page table page's wire count, which is used to record the
   * number of valid page table entries within the page.  If the wire count
   * drops to zero, then the page table page is unmapped.  Returns TRUE if the
   * page table page was unmapped and FALSE otherwise.
   */
  static inline boolean_t
  pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
  {
  
          --m->wire_count;
          if (m->wire_count == 0) {
                  _pmap_unwire_ptp(pmap, va, m, free);
                  return (TRUE);
          } else
                  return (FALSE);
  }
  
  static void
  _pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
  {
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          /*
           * unmap the page table page
           */
          if (m->pindex >= (NUPDE + NUPDPE)) {
                  /* PDP page */
                  pml4_entry_t *pml4;
                  pml4 = pmap_pml4e(pmap, va);
                  *pml4 = 0;
                  if (pmap->pm_pml4u != NULL && va <= VM_MAXUSER_ADDRESS) {
                          pml4 = &pmap->pm_pml4u[pmap_pml4e_index(va)];
                          *pml4 = 0;
                  }
          } else if (m->pindex >= NUPDE) {
                  /* PD page */
                  pdp_entry_t *pdp;
                  pdp = pmap_pdpe(pmap, va);
                  *pdp = 0;
          } else {
                  /* PTE page */
                  pd_entry_t *pd;
                  pd = pmap_pde(pmap, va);
                  *pd = 0;
          }
          pmap_resident_count_dec(pmap, 1);
          if (m->pindex < NUPDE) {
                  /* We just released a PT, unhold the matching PD */
                  vm_page_t pdpg;
  
                  pdpg = PHYS_TO_VM_PAGE(*pmap_pdpe(pmap, va) & PG_FRAME);
                  pmap_unwire_ptp(pmap, va, pdpg, free);
          }
          if (m->pindex >= NUPDE && m->pindex < (NUPDE + NUPDPE)) {
                  /* We just released a PD, unhold the matching PDP */
                  vm_page_t pdppg;
  
                  pdppg = PHYS_TO_VM_PAGE(*pmap_pml4e(pmap, va) & PG_FRAME);
                  pmap_unwire_ptp(pmap, va, pdppg, free);
          }
  
          /* 
           * Put page on a list so that it is released after
           * *ALL* TLB shootdown is done
           */
          pmap_add_delayed_free_list(m, free, TRUE);
  }
  
  /*
   * After removing a page table entry, this routine is used to
   * conditionally free the page, and manage the hold/wire counts.
   */
  static int
  pmap_unuse_pt(pmap_t pmap, vm_offset_t va, pd_entry_t ptepde,
      struct spglist *free)
  {
          vm_page_t mpte;
  
          if (va >= VM_MAXUSER_ADDRESS)
                  return (0);
          KASSERT(ptepde != 0, ("pmap_unuse_pt: ptepde != 0"));
          mpte = PHYS_TO_VM_PAGE(ptepde & PG_FRAME);
          return (pmap_unwire_ptp(pmap, va, mpte, free));
  }
  
  void
  pmap_pinit0(pmap_t pmap)
  {
          struct proc *p;
          int i;
  
          PMAP_LOCK_INIT(pmap);
          pmap->pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(KPML4phys);
          pmap->pm_pml4u = NULL;
          pmap->pm_cr3 = KPML4phys;
          /* hack to keep pmap_pti_pcid_invalidate() alive */
          pmap->pm_ucr3 = PMAP_NO_CR3;
          pmap->pm_root.rt_root = 0;
          CPU_ZERO(&pmap->pm_active);
          TAILQ_INIT(&pmap->pm_pvchunk);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
          pmap->pm_flags = pmap_flags;
          CPU_FOREACH(i) {
                  pmap->pm_pcids[i].pm_pcid = PMAP_PCID_KERN + 1;
                  pmap->pm_pcids[i].pm_gen = 1;
          }
          pmap_activate_boot(pmap);
          if (pti) {
                  p = curproc;
                  PROC_LOCK(p);
                  p->p_md.md_flags |= P_MD_KPTI;
                  PROC_UNLOCK(p);
          }
  
          if ((cpu_stdext_feature2 & CPUID_STDEXT2_PKU) != 0) {
                  pmap_pkru_ranges_zone = uma_zcreate("pkru ranges",
                      sizeof(struct pmap_pkru_range), NULL, NULL, NULL, NULL,
                      UMA_ALIGN_PTR, 0);
          }
  }
  
  void
  pmap_pinit_pml4(vm_page_t pml4pg)
  {
          pml4_entry_t *pm_pml4;
          int i;
  
          pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pml4pg));
  
          /* Wire in kernel global address entries. */
          for (i = 0; i < NKPML4E; i++) {
                  pm_pml4[KPML4BASE + i] = (KPDPphys + ptoa(i)) | X86_PG_RW |
                      X86_PG_V;
          }
          for (i = 0; i < ndmpdpphys; i++) {
                  pm_pml4[DMPML4I + i] = (DMPDPphys + ptoa(i)) | X86_PG_RW |
                      X86_PG_V;
          }
  
          /* install self-referential address mapping entry(s) */
          pm_pml4[PML4PML4I] = VM_PAGE_TO_PHYS(pml4pg) | X86_PG_V | X86_PG_RW |
              X86_PG_A | X86_PG_M;
  
          /* install large map entries if configured */
          for (i = 0; i < lm_ents; i++)
                  pm_pml4[LMSPML4I + i] = kernel_pmap->pm_pml4[LMSPML4I + i];
  }
  
  static void
  pmap_pinit_pml4_pti(vm_page_t pml4pg)
  {
          pml4_entry_t *pm_pml4;
          int i;
  
          pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pml4pg));
          for (i = 0; i < NPML4EPG; i++)
                  pm_pml4[i] = pti_pml4[i];
  }
  
  /*
   * Initialize a preallocated and zeroed pmap structure,
   * such as one in a vmspace structure.
   */
  int
  pmap_pinit_type(pmap_t pmap, enum pmap_type pm_type, int flags)
  {
          vm_page_t pml4pg, pml4pgu;
          vm_paddr_t pml4phys;
          int i;
  
          /*
           * allocate the page directory page
           */
          pml4pg = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
              VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_WAITOK);
  
          pml4phys = VM_PAGE_TO_PHYS(pml4pg);
          pmap->pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(pml4phys);
          CPU_FOREACH(i) {
                  pmap->pm_pcids[i].pm_pcid = PMAP_PCID_NONE;
                  pmap->pm_pcids[i].pm_gen = 0;
          }
          pmap->pm_cr3 = PMAP_NO_CR3;     /* initialize to an invalid value */
          pmap->pm_ucr3 = PMAP_NO_CR3;
          pmap->pm_pml4u = NULL;
  
          pmap->pm_type = pm_type;
          if ((pml4pg->flags & PG_ZERO) == 0)
                  pagezero(pmap->pm_pml4);
  
          /*
           * Do not install the host kernel mappings in the nested page
           * tables. These mappings are meaningless in the guest physical
           * address space.
           * Install minimal kernel mappings in PTI case.
           */
          if (pm_type == PT_X86) {
                  pmap->pm_cr3 = pml4phys;
                  pmap_pinit_pml4(pml4pg);
                  if ((curproc->p_md.md_flags & P_MD_KPTI) != 0) {
                          pml4pgu = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
                              VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_WAITOK);
                          pmap->pm_pml4u = (pml4_entry_t *)PHYS_TO_DMAP(
                              VM_PAGE_TO_PHYS(pml4pgu));
                          pmap_pinit_pml4_pti(pml4pgu);
                          pmap->pm_ucr3 = VM_PAGE_TO_PHYS(pml4pgu);
                  }
                  if ((cpu_stdext_feature2 & CPUID_STDEXT2_PKU) != 0) {
                          rangeset_init(&pmap->pm_pkru, pkru_dup_range,
                              pkru_free_range, pmap, M_NOWAIT);
                  }
          }
  
          pmap->pm_root.rt_root = 0;
          CPU_ZERO(&pmap->pm_active);
          TAILQ_INIT(&pmap->pm_pvchunk);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
          pmap->pm_flags = flags;
          pmap->pm_eptgen = 0;
  
          return (1);
  }
  
  int
  pmap_pinit(pmap_t pmap)
  {
  
          return (pmap_pinit_type(pmap, PT_X86, pmap_flags));
  }
  
  /*
   * This routine is called if the desired page table page does not exist.
   *
   * If page table page allocation fails, this routine may sleep before
   * returning NULL.  It sleeps only if a lock pointer was given.
   *
   * Note: If a page allocation fails at page table level two or three,
   * one or two pages may be held during the wait, only to be released
   * afterwards.  This conservative approach is easily argued to avoid
   * race conditions.
   */
  static vm_page_t
  _pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex, struct rwlock **lockp)
  {
          vm_page_t m, pdppg, pdpg;
          pt_entry_t PG_A, PG_M, PG_RW, PG_V;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
  
          PG_A = pmap_accessed_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
  
          /*
           * Allocate a page table page.
           */
          if ((m = vm_page_alloc(NULL, ptepindex, VM_ALLOC_NOOBJ |
              VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
                  if (lockp != NULL) {
                          RELEASE_PV_LIST_LOCK(lockp);
                          PMAP_UNLOCK(pmap);
                          PMAP_ASSERT_NOT_IN_DI();
                          vm_wait(NULL);
                          PMAP_LOCK(pmap);
                  }
  
                  /*
                   * Indicate the need to retry.  While waiting, the page table
                   * page may have been allocated.
                   */
                  return (NULL);
          }
          if ((m->flags & PG_ZERO) == 0)
                  pmap_zero_page(m);
  
          /*
           * Map the pagetable page into the process address space, if
           * it isn't already there.
           */
  
          if (ptepindex >= (NUPDE + NUPDPE)) {
                  pml4_entry_t *pml4, *pml4u;
                  vm_pindex_t pml4index;
  
                  /* Wire up a new PDPE page */
                  pml4index = ptepindex - (NUPDE + NUPDPE);
                  pml4 = &pmap->pm_pml4[pml4index];
                  *pml4 = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V | PG_A | PG_M;
                  if (pmap->pm_pml4u != NULL && pml4index < NUPML4E) {
                          /*
                           * PTI: Make all user-space mappings in the
                           * kernel-mode page table no-execute so that
                           * we detect any programming errors that leave
                           * the kernel-mode page table active on return
                           * to user space.
                           */
                          if (pmap->pm_ucr3 != PMAP_NO_CR3)
                                  *pml4 |= pg_nx;
  
                          pml4u = &pmap->pm_pml4u[pml4index];
                          *pml4u = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V |
                              PG_A | PG_M;
                  }
  
          } else if (ptepindex >= NUPDE) {
                  vm_pindex_t pml4index;
                  vm_pindex_t pdpindex;
                  pml4_entry_t *pml4;
                  pdp_entry_t *pdp;
  
                  /* Wire up a new PDE page */
                  pdpindex = ptepindex - NUPDE;
                  pml4index = pdpindex >> NPML4EPGSHIFT;
  
                  pml4 = &pmap->pm_pml4[pml4index];
                  if ((*pml4 & PG_V) == 0) {
                          /* Have to allocate a new pdp, recurse */
                          if (_pmap_allocpte(pmap, NUPDE + NUPDPE + pml4index,
                              lockp) == NULL) {
                                  vm_page_unwire_noq(m);
                                  vm_page_free_zero(m);
                                  return (NULL);
                          }
                  } else {
                          /* Add reference to pdp page */
                          pdppg = PHYS_TO_VM_PAGE(*pml4 & PG_FRAME);
                          pdppg->wire_count++;
                  }
                  pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & PG_FRAME);
  
                  /* Now find the pdp page */
                  pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                  *pdp = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V | PG_A | PG_M;
  
          } else {
                  vm_pindex_t pml4index;
                  vm_pindex_t pdpindex;
                  pml4_entry_t *pml4;
                  pdp_entry_t *pdp;
                  pd_entry_t *pd;
  
                  /* Wire up a new PTE page */
                  pdpindex = ptepindex >> NPDPEPGSHIFT;
                  pml4index = pdpindex >> NPML4EPGSHIFT;
  
                  /* First, find the pdp and check that its valid. */
                  pml4 = &pmap->pm_pml4[pml4index];
                  if ((*pml4 & PG_V) == 0) {
                          /* Have to allocate a new pd, recurse */
                          if (_pmap_allocpte(pmap, NUPDE + pdpindex,
                              lockp) == NULL) {
                                  vm_page_unwire_noq(m);
                                  vm_page_free_zero(m);
                                  return (NULL);
                          }
                          pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & PG_FRAME);
                          pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                  } else {
                          pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & PG_FRAME);
                          pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                          if ((*pdp & PG_V) == 0) {
                                  /* Have to allocate a new pd, recurse */
                                  if (_pmap_allocpte(pmap, NUPDE + pdpindex,
                                      lockp) == NULL) {
                                          vm_page_unwire_noq(m);
                                          vm_page_free_zero(m);
                                          return (NULL);
                                  }
                          } else {
                                  /* Add reference to the pd page */
                                  pdpg = PHYS_TO_VM_PAGE(*pdp & PG_FRAME);
                                  pdpg->wire_count++;
                          }
                  }
                  pd = (pd_entry_t *)PHYS_TO_DMAP(*pdp & PG_FRAME);
  
                  /* Now we know where the page directory page is */
                  pd = &pd[ptepindex & ((1ul << NPDEPGSHIFT) - 1)];
                  *pd = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V | PG_A | PG_M;
          }
  
          pmap_resident_count_inc(pmap, 1);
  
          return (m);
  }
  
  static vm_page_t
  pmap_allocpde(pmap_t pmap, vm_offset_t va, struct rwlock **lockp)
  {
          vm_pindex_t pdpindex, ptepindex;
          pdp_entry_t *pdpe, PG_V;
          vm_page_t pdpg;
  
          PG_V = pmap_valid_bit(pmap);
  
  retry:
          pdpe = pmap_pdpe(pmap, va);
          if (pdpe != NULL && (*pdpe & PG_V) != 0) {
                  /* Add a reference to the pd page. */
                  pdpg = PHYS_TO_VM_PAGE(*pdpe & PG_FRAME);
                  pdpg->wire_count++;
          } else {
                  /* Allocate a pd page. */
                  ptepindex = pmap_pde_pindex(va);
                  pdpindex = ptepindex >> NPDPEPGSHIFT;
                  pdpg = _pmap_allocpte(pmap, NUPDE + pdpindex, lockp);
                  if (pdpg == NULL && lockp != NULL)
                          goto retry;
          }
          return (pdpg);
  }
  
  static vm_page_t
  pmap_allocpte(pmap_t pmap, vm_offset_t va, struct rwlock **lockp)
  {
          vm_pindex_t ptepindex;
          pd_entry_t *pd, PG_V;
          vm_page_t m;
  
          PG_V = pmap_valid_bit(pmap);
  
          /*
           * Calculate pagetable page index
           */
          ptepindex = pmap_pde_pindex(va);
  retry:
          /*
           * Get the page directory entry
           */
          pd = pmap_pde(pmap, va);
  
          /*
           * This supports switching from a 2MB page to a
           * normal 4K page.
           */
          if (pd != NULL && (*pd & (PG_PS | PG_V)) == (PG_PS | PG_V)) {
                  if (!pmap_demote_pde_locked(pmap, pd, va, lockp)) {
                          /*
                           * Invalidation of the 2MB page mapping may have caused
                           * the deallocation of the underlying PD page.
                           */
                          pd = NULL;
                  }
          }
  
          /*
           * If the page table page is mapped, we just increment the
           * hold count, and activate it.
           */
          if (pd != NULL && (*pd & PG_V) != 0) {
                  m = PHYS_TO_VM_PAGE(*pd & PG_FRAME);
                  m->wire_count++;
          } else {
                  /*
                   * Here if the pte page isn't mapped, or if it has been
                   * deallocated.
                   */
                  m = _pmap_allocpte(pmap, ptepindex, lockp);
                  if (m == NULL && lockp != NULL)
                          goto retry;
          }
          return (m);
  }
  
  
  /***************************************************
   * Pmap allocation/deallocation routines.
   ***************************************************/
  
  /*
   * Release any resources held by the given physical map.
   * Called when a pmap initialized by pmap_pinit is being released.
   * Should only be called if the map contains no valid mappings.
   */
  void
  pmap_release(pmap_t pmap)
  {
          vm_page_t m;
          int i;
  
          KASSERT(pmap->pm_stats.resident_count == 0,
              ("pmap_release: pmap resident count %ld != 0",
              pmap->pm_stats.resident_count));
          KASSERT(vm_radix_is_empty(&pmap->pm_root),
              ("pmap_release: pmap has reserved page table page(s)"));
          KASSERT(CPU_EMPTY(&pmap->pm_active),
              ("releasing active pmap %p", pmap));
  
          m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pmap->pm_pml4));
  
          for (i = 0; i < NKPML4E; i++)   /* KVA */
                  pmap->pm_pml4[KPML4BASE + i] = 0;
          for (i = 0; i < ndmpdpphys; i++)/* Direct Map */
                  pmap->pm_pml4[DMPML4I + i] = 0;
          pmap->pm_pml4[PML4PML4I] = 0;   /* Recursive Mapping */
          for (i = 0; i < lm_ents; i++)   /* Large Map */
                  pmap->pm_pml4[LMSPML4I + i] = 0;
  
          vm_page_unwire_noq(m);
          vm_page_free_zero(m);
  
          if (pmap->pm_pml4u != NULL) {
                  m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pmap->pm_pml4u));
                  vm_page_unwire_noq(m);
                  vm_page_free(m);
          }
          if (pmap->pm_type == PT_X86 &&
              (cpu_stdext_feature2 & CPUID_STDEXT2_PKU) != 0)
                  rangeset_fini(&pmap->pm_pkru);
  }
  
  static int
  kvm_size(SYSCTL_HANDLER_ARGS)
  {
          unsigned long ksize = VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS;
  
          return sysctl_handle_long(oidp, &ksize, 0, req);
  }
  SYSCTL_PROC(_vm, OID_AUTO, kvm_size, CTLTYPE_LONG|CTLFLAG_RD, 
      0, 0, kvm_size, "LU", "Size of KVM");
  
  static int
  kvm_free(SYSCTL_HANDLER_ARGS)
  {
          unsigned long kfree = VM_MAX_KERNEL_ADDRESS - kernel_vm_end;
  
          return sysctl_handle_long(oidp, &kfree, 0, req);
  }
  SYSCTL_PROC(_vm, OID_AUTO, kvm_free, CTLTYPE_LONG|CTLFLAG_RD, 
      0, 0, kvm_free, "LU", "Amount of KVM free");
  
  /*
   * grow the number of kernel page table entries, if needed
   */
  void
  pmap_growkernel(vm_offset_t addr)
  {
          vm_paddr_t paddr;
          vm_page_t nkpg;
          pd_entry_t *pde, newpdir;
          pdp_entry_t *pdpe;
  
          mtx_assert(&kernel_map->system_mtx, MA_OWNED);
  
          /*
           * Return if "addr" is within the range of kernel page table pages
           * that were preallocated during pmap bootstrap.  Moreover, leave
           * "kernel_vm_end" and the kernel page table as they were.
           *
           * The correctness of this action is based on the following
           * argument: vm_map_insert() allocates contiguous ranges of the
           * kernel virtual address space.  It calls this function if a range
           * ends after "kernel_vm_end".  If the kernel is mapped between
           * "kernel_vm_end" and "addr", then the range cannot begin at
           * "kernel_vm_end".  In fact, its beginning address cannot be less
           * than the kernel.  Thus, there is no immediate need to allocate
           * any new kernel page table pages between "kernel_vm_end" and
           * "KERNBASE".
           */
          if (KERNBASE < addr && addr <= KERNBASE + nkpt * NBPDR)
                  return;
  
          addr = roundup2(addr, NBPDR);
          if (addr - 1 >= vm_map_max(kernel_map))
                  addr = vm_map_max(kernel_map);
          while (kernel_vm_end < addr) {
                  pdpe = pmap_pdpe(kernel_pmap, kernel_vm_end);
                  if ((*pdpe & X86_PG_V) == 0) {
                          /* We need a new PDP entry */
                          nkpg = vm_page_alloc(NULL, kernel_vm_end >> PDPSHIFT,
                              VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ |
                              VM_ALLOC_WIRED | VM_ALLOC_ZERO);
                          if (nkpg == NULL)
                                  panic("pmap_growkernel: no memory to grow kernel");
                          if ((nkpg->flags & PG_ZERO) == 0)
                                  pmap_zero_page(nkpg);
                          paddr = VM_PAGE_TO_PHYS(nkpg);
                          *pdpe = (pdp_entry_t)(paddr | X86_PG_V | X86_PG_RW |
                              X86_PG_A | X86_PG_M);
                          continue; /* try again */
                  }
                  pde = pmap_pdpe_to_pde(pdpe, kernel_vm_end);
                  if ((*pde & X86_PG_V) != 0) {
                          kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                          if (kernel_vm_end - 1 >= vm_map_max(kernel_map)) {
                                  kernel_vm_end = vm_map_max(kernel_map);
                                  break;                       
                          }
                          continue;
                  }
  
                  nkpg = vm_page_alloc(NULL, pmap_pde_pindex(kernel_vm_end),
                      VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED |
                      VM_ALLOC_ZERO);
                  if (nkpg == NULL)
                          panic("pmap_growkernel: no memory to grow kernel");
                  if ((nkpg->flags & PG_ZERO) == 0)
                          pmap_zero_page(nkpg);
                  paddr = VM_PAGE_TO_PHYS(nkpg);
                  newpdir = paddr | X86_PG_V | X86_PG_RW | X86_PG_A | X86_PG_M;
                  pde_store(pde, newpdir);
  
                  kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                  if (kernel_vm_end - 1 >= vm_map_max(kernel_map)) {
                          kernel_vm_end = vm_map_max(kernel_map);
                          break;                       
                  }
          }
  }
  
  
  /***************************************************
   * page management routines.
   ***************************************************/
  
  CTASSERT(sizeof(struct pv_chunk) == PAGE_SIZE);
  CTASSERT(_NPCM == 3);
  CTASSERT(_NPCPV == 168);
  
  static __inline struct pv_chunk *
  pv_to_chunk(pv_entry_t pv)
  {
  
          return ((struct pv_chunk *)((uintptr_t)pv & ~(uintptr_t)PAGE_MASK));
  }
  
  #define PV_PMAP(pv) (pv_to_chunk(pv)->pc_pmap)
  
  #define PC_FREE0        0xfffffffffffffffful
  #define PC_FREE1        0xfffffffffffffffful
  #define PC_FREE2        0x000000fffffffffful
  
  static const uint64_t pc_freemask[_NPCM] = { PC_FREE0, PC_FREE1, PC_FREE2 };
  
  #ifdef PV_STATS
  static int pc_chunk_count, pc_chunk_allocs, pc_chunk_frees, pc_chunk_tryfail;
  
  SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_count, CTLFLAG_RD, &pc_chunk_count, 0,
          "Current number of pv entry chunks");
  SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_allocs, CTLFLAG_RD, &pc_chunk_allocs, 0,
          "Current number of pv entry chunks allocated");
  SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_frees, CTLFLAG_RD, &pc_chunk_frees, 0,
          "Current number of pv entry chunks frees");
  SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_tryfail, CTLFLAG_RD, &pc_chunk_tryfail, 0,
          "Number of times tried to get a chunk page but failed.");
  
  static long pv_entry_frees, pv_entry_allocs, pv_entry_count;
  static int pv_entry_spare;
  
  SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_frees, CTLFLAG_RD, &pv_entry_frees, 0,
          "Current number of pv entry frees");
  SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_allocs, CTLFLAG_RD, &pv_entry_allocs, 0,
          "Current number of pv entry allocs");
  SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_count, CTLFLAG_RD, &pv_entry_count, 0,
          "Current number of pv entries");
  SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_spare, CTLFLAG_RD, &pv_entry_spare, 0,
          "Current number of spare pv entries");
  #endif
  
  static void
  reclaim_pv_chunk_leave_pmap(pmap_t pmap, pmap_t locked_pmap, bool start_di)
  {
  
          if (pmap == NULL)
                  return;
          pmap_invalidate_all(pmap);
          if (pmap != locked_pmap)
                  PMAP_UNLOCK(pmap);
          if (start_di)
                  pmap_delayed_invl_finished();
  }
  
  /*
   * We are in a serious low memory condition.  Resort to
   * drastic measures to free some pages so we can allocate
   * another pv entry chunk.
   *
   * Returns NULL if PV entries were reclaimed from the specified pmap.
   *
   * We do not, however, unmap 2mpages because subsequent accesses will
   * allocate per-page pv entries until repromotion occurs, thereby
   * exacerbating the shortage of free pv entries.
   */
  static vm_page_t
  reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp)
  {
          struct pv_chunk *pc, *pc_marker, *pc_marker_end;
          struct pv_chunk_header pc_marker_b, pc_marker_end_b;
          struct md_page *pvh;
          pd_entry_t *pde;
          pmap_t next_pmap, pmap;
          pt_entry_t *pte, tpte;
          pt_entry_t PG_G, PG_A, PG_M, PG_RW;
          pv_entry_t pv;
          vm_offset_t va;
          vm_page_t m, m_pc;
          struct spglist free;
          uint64_t inuse;
          int bit, field, freed;
          bool start_di;
          static int active_reclaims = 0;
  
          PMAP_LOCK_ASSERT(locked_pmap, MA_OWNED);
          KASSERT(lockp != NULL, ("reclaim_pv_chunk: lockp is NULL"));
          pmap = NULL;
          m_pc = NULL;
          PG_G = PG_A = PG_M = PG_RW = 0;
          SLIST_INIT(&free);
          bzero(&pc_marker_b, sizeof(pc_marker_b));
          bzero(&pc_marker_end_b, sizeof(pc_marker_end_b));
          pc_marker = (struct pv_chunk *)&pc_marker_b;
          pc_marker_end = (struct pv_chunk *)&pc_marker_end_b;
  
          /*
           * A delayed invalidation block should already be active if
           * pmap_advise() or pmap_remove() called this function by way
           * of pmap_demote_pde_locked().
           */
          start_di = pmap_not_in_di();
  
          mtx_lock(&pv_chunks_mutex);
          active_reclaims++;
          TAILQ_INSERT_HEAD(&pv_chunks, pc_marker, pc_lru);
          TAILQ_INSERT_TAIL(&pv_chunks, pc_marker_end, pc_lru);
          while ((pc = TAILQ_NEXT(pc_marker, pc_lru)) != pc_marker_end &&
              SLIST_EMPTY(&free)) {
                  next_pmap = pc->pc_pmap;
                  if (next_pmap == NULL) {
                          /*
                           * The next chunk is a marker.  However, it is
                           * not our marker, so active_reclaims must be
                           * > 1.  Consequently, the next_chunk code
                           * will not rotate the pv_chunks list.
                           */
                          goto next_chunk;
                  }
                  mtx_unlock(&pv_chunks_mutex);
  
                  /*
                   * A pv_chunk can only be removed from the pc_lru list
                   * when both pc_chunks_mutex is owned and the
                   * corresponding pmap is locked.
                   */
                  if (pmap != next_pmap) {
                          reclaim_pv_chunk_leave_pmap(pmap, locked_pmap,
                              start_di);
                          pmap = next_pmap;
                          /* Avoid deadlock and lock recursion. */
                          if (pmap > locked_pmap) {
                                  RELEASE_PV_LIST_LOCK(lockp);
                                  PMAP_LOCK(pmap);
                                  if (start_di)
                                          pmap_delayed_invl_started();
                                  mtx_lock(&pv_chunks_mutex);
                                  continue;
                          } else if (pmap != locked_pmap) {
                                  if (PMAP_TRYLOCK(pmap)) {
                                          if (start_di)
                                                  pmap_delayed_invl_started();
                                          mtx_lock(&pv_chunks_mutex);
                                          continue;
                                  } else {
                                          pmap = NULL; /* pmap is not locked */
                                          mtx_lock(&pv_chunks_mutex);
                                          pc = TAILQ_NEXT(pc_marker, pc_lru);
                                          if (pc == NULL ||
                                              pc->pc_pmap != next_pmap)
                                                  continue;
                                          goto next_chunk;
                                  }
                          } else if (start_di)
                                  pmap_delayed_invl_started();
                          PG_G = pmap_global_bit(pmap);
                          PG_A = pmap_accessed_bit(pmap);
                          PG_M = pmap_modified_bit(pmap);
                          PG_RW = pmap_rw_bit(pmap);
                  }
  
                  /*
                   * Destroy every non-wired, 4 KB page mapping in the chunk.
                   */
                  freed = 0;
                  for (field = 0; field < _NPCM; field++) {
                          for (inuse = ~pc->pc_map[field] & pc_freemask[field];
                              inuse != 0; inuse &= ~(1UL << bit)) {
                                  bit = bsfq(inuse);
                                  pv = &pc->pc_pventry[field * 64 + bit];
                                  va = pv->pv_va;
                                  pde = pmap_pde(pmap, va);
                                  if ((*pde & PG_PS) != 0)
                                          continue;
                                  pte = pmap_pde_to_pte(pde, va);
                                  if ((*pte & PG_W) != 0)
                                          continue;
                                  tpte = pte_load_clear(pte);
                                  if ((tpte & PG_G) != 0)
                                          pmap_invalidate_page(pmap, va);
                                  m = PHYS_TO_VM_PAGE(tpte & PG_FRAME);
                                  if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                          vm_page_dirty(m);
                                  if ((tpte & PG_A) != 0)
                                          vm_page_aflag_set(m, PGA_REFERENCED);
                                  CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                                  m->md.pv_gen++;
                                  if (TAILQ_EMPTY(&m->md.pv_list) &&
                                      (m->flags & PG_FICTITIOUS) == 0) {
                                          pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                                          if (TAILQ_EMPTY(&pvh->pv_list)) {
                                                  vm_page_aflag_clear(m,
                                                      PGA_WRITEABLE);
                                          }
                                  }
                                  pmap_delayed_invl_page(m);
                                  pc->pc_map[field] |= 1UL << bit;
                                  pmap_unuse_pt(pmap, va, *pde, &free);
                                  freed++;
                          }
                  }
                  if (freed == 0) {
                          mtx_lock(&pv_chunks_mutex);
                          goto next_chunk;
                  }
                  /* Every freed mapping is for a 4 KB page. */
                  pmap_resident_count_dec(pmap, freed);
                  PV_STAT(atomic_add_long(&pv_entry_frees, freed));
                  PV_STAT(atomic_add_int(&pv_entry_spare, freed));
                  PV_STAT(atomic_subtract_long(&pv_entry_count, freed));
                  TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                  if (pc->pc_map[0] == PC_FREE0 && pc->pc_map[1] == PC_FREE1 &&
                      pc->pc_map[2] == PC_FREE2) {
                          PV_STAT(atomic_subtract_int(&pv_entry_spare, _NPCPV));
                          PV_STAT(atomic_subtract_int(&pc_chunk_count, 1));
                          PV_STAT(atomic_add_int(&pc_chunk_frees, 1));
                          /* Entire chunk is free; return it. */
                          m_pc = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pc));
                          dump_drop_page(m_pc->phys_addr);
                          mtx_lock(&pv_chunks_mutex);
                          TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
                          break;
                  }
                  TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                  mtx_lock(&pv_chunks_mutex);
                  /* One freed pv entry in locked_pmap is sufficient. */
                  if (pmap == locked_pmap)
                          break;
  next_chunk:
                  TAILQ_REMOVE(&pv_chunks, pc_marker, pc_lru);
                  TAILQ_INSERT_AFTER(&pv_chunks, pc, pc_marker, pc_lru);
                  if (active_reclaims == 1 && pmap != NULL) {
                          /*
                           * Rotate the pv chunks list so that we do not
                           * scan the same pv chunks that could not be
                           * freed (because they contained a wired
                           * and/or superpage mapping) on every
                           * invocation of reclaim_pv_chunk().
                           */
                          while ((pc = TAILQ_FIRST(&pv_chunks)) != pc_marker) {
                                  MPASS(pc->pc_pmap != NULL);
                                  TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
                                  TAILQ_INSERT_TAIL(&pv_chunks, pc, pc_lru);
                          }
                  }
          }
          TAILQ_REMOVE(&pv_chunks, pc_marker, pc_lru);
          TAILQ_REMOVE(&pv_chunks, pc_marker_end, pc_lru);
          active_reclaims--;
          mtx_unlock(&pv_chunks_mutex);
          reclaim_pv_chunk_leave_pmap(pmap, locked_pmap, start_di);
          if (m_pc == NULL && !SLIST_EMPTY(&free)) {
                  m_pc = SLIST_FIRST(&free);
                  SLIST_REMOVE_HEAD(&free, plinks.s.ss);
                  /* Recycle a freed page table page. */
                  m_pc->wire_count = 1;
          }
          vm_page_free_pages_toq(&free, true);
          return (m_pc);
  }
  
  /*
   * free the pv_entry back to the free list
   */
  static void
  free_pv_entry(pmap_t pmap, pv_entry_t pv)
  {
          struct pv_chunk *pc;
          int idx, field, bit;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          PV_STAT(atomic_add_long(&pv_entry_frees, 1));
          PV_STAT(atomic_add_int(&pv_entry_spare, 1));
          PV_STAT(atomic_subtract_long(&pv_entry_count, 1));
          pc = pv_to_chunk(pv);
          idx = pv - &pc->pc_pventry[0];
          field = idx / 64;
          bit = idx % 64;
          pc->pc_map[field] |= 1ul << bit;
          if (pc->pc_map[0] != PC_FREE0 || pc->pc_map[1] != PC_FREE1 ||
              pc->pc_map[2] != PC_FREE2) {
                  /* 98% of the time, pc is already at the head of the list. */
                  if (__predict_false(pc != TAILQ_FIRST(&pmap->pm_pvchunk))) {
                          TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                          TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                  }
                  return;
          }
          TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
          free_pv_chunk(pc);
  }
  
  static void
  free_pv_chunk(struct pv_chunk *pc)
  {
          vm_page_t m;
  
          mtx_lock(&pv_chunks_mutex);
          TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
          mtx_unlock(&pv_chunks_mutex);
          PV_STAT(atomic_subtract_int(&pv_entry_spare, _NPCPV));
          PV_STAT(atomic_subtract_int(&pc_chunk_count, 1));
          PV_STAT(atomic_add_int(&pc_chunk_frees, 1));
          /* entire chunk is free, return it */
          m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pc));
          dump_drop_page(m->phys_addr);
          vm_page_unwire(m, PQ_NONE);
          vm_page_free(m);
  }
  
  /*
   * Returns a new PV entry, allocating a new PV chunk from the system when
   * needed.  If this PV chunk allocation fails and a PV list lock pointer was
   * given, a PV chunk is reclaimed from an arbitrary pmap.  Otherwise, NULL is
   * returned.
   *
   * The given PV list lock may be released.
   */
  static pv_entry_t
  get_pv_entry(pmap_t pmap, struct rwlock **lockp)
  {
          int bit, field;
          pv_entry_t pv;
          struct pv_chunk *pc;
          vm_page_t m;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          PV_STAT(atomic_add_long(&pv_entry_allocs, 1));
  retry:
          pc = TAILQ_FIRST(&pmap->pm_pvchunk);
          if (pc != NULL) {
                  for (field = 0; field < _NPCM; field++) {
                          if (pc->pc_map[field]) {
                                  bit = bsfq(pc->pc_map[field]);
                                  break;
                          }
                  }
                  if (field < _NPCM) {
                          pv = &pc->pc_pventry[field * 64 + bit];
                          pc->pc_map[field] &= ~(1ul << bit);
                          /* If this was the last item, move it to tail */
                          if (pc->pc_map[0] == 0 && pc->pc_map[1] == 0 &&
                              pc->pc_map[2] == 0) {
                                  TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                                  TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc,
                                      pc_list);
                          }
                          PV_STAT(atomic_add_long(&pv_entry_count, 1));
                          PV_STAT(atomic_subtract_int(&pv_entry_spare, 1));
                          return (pv);
                  }
          }
          /* No free items, allocate another chunk */
          m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
              VM_ALLOC_WIRED);
          if (m == NULL) {
                  if (lockp == NULL) {
                          PV_STAT(pc_chunk_tryfail++);
                          return (NULL);
                  }
                  m = reclaim_pv_chunk(pmap, lockp);
                  if (m == NULL)
                          goto retry;
          }
          PV_STAT(atomic_add_int(&pc_chunk_count, 1));
          PV_STAT(atomic_add_int(&pc_chunk_allocs, 1));
          dump_add_page(m->phys_addr);
          pc = (void *)PHYS_TO_DMAP(m->phys_addr);
          pc->pc_pmap = pmap;
          pc->pc_map[0] = PC_FREE0 & ~1ul;        /* preallocated bit 0 */
          pc->pc_map[1] = PC_FREE1;
          pc->pc_map[2] = PC_FREE2;
          mtx_lock(&pv_chunks_mutex);
          TAILQ_INSERT_TAIL(&pv_chunks, pc, pc_lru);
          mtx_unlock(&pv_chunks_mutex);
          pv = &pc->pc_pventry[0];
          TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
          PV_STAT(atomic_add_long(&pv_entry_count, 1));
          PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV - 1));
          return (pv);
  }
  
  /*
   * Returns the number of one bits within the given PV chunk map.
   *
   * The erratas for Intel processors state that "POPCNT Instruction May
   * Take Longer to Execute Than Expected".  It is believed that the
   * issue is the spurious dependency on the destination register.
   * Provide a hint to the register rename logic that the destination
   * value is overwritten, by clearing it, as suggested in the
   * optimization manual.  It should be cheap for unaffected processors
   * as well.
   *
   * Reference numbers for erratas are
   * 4th Gen Core: HSD146
   * 5th Gen Core: BDM85
   * 6th Gen Core: SKL029
   */
  static int
  popcnt_pc_map_pq(uint64_t *map)
  {
          u_long result, tmp;
  
          __asm __volatile("xorl %k0,%k0;popcntq %2,%0;"
              "xorl %k1,%k1;popcntq %3,%1;addl %k1,%k0;"
              "xorl %k1,%k1;popcntq %4,%1;addl %k1,%k0"
              : "=&r" (result), "=&r" (tmp)
              : "m" (map[0]), "m" (map[1]), "m" (map[2]));
          return (result);
  }
  
  /*
   * Ensure that the number of spare PV entries in the specified pmap meets or
   * exceeds the given count, "needed".
   *
   * The given PV list lock may be released.
   */
  static void
  reserve_pv_entries(pmap_t pmap, int needed, struct rwlock **lockp)
  {
          struct pch new_tail;
          struct pv_chunk *pc;
          vm_page_t m;
          int avail, free;
          bool reclaimed;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          KASSERT(lockp != NULL, ("reserve_pv_entries: lockp is NULL"));
  
          /*
           * Newly allocated PV chunks must be stored in a private list until
           * the required number of PV chunks have been allocated.  Otherwise,
           * reclaim_pv_chunk() could recycle one of these chunks.  In
           * contrast, these chunks must be added to the pmap upon allocation.
           */
          TAILQ_INIT(&new_tail);
  retry:
          avail = 0;
          TAILQ_FOREACH(pc, &pmap->pm_pvchunk, pc_list) {
  #ifndef __POPCNT__
                  if ((cpu_feature2 & CPUID2_POPCNT) == 0)
                          bit_count((bitstr_t *)pc->pc_map, 0,
                              sizeof(pc->pc_map) * NBBY, &free);
                  else
  #endif
                  free = popcnt_pc_map_pq(pc->pc_map);
                  if (free == 0)
                          break;
                  avail += free;
                  if (avail >= needed)
                          break;
          }
          for (reclaimed = false; avail < needed; avail += _NPCPV) {
                  m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
                      VM_ALLOC_WIRED);
                  if (m == NULL) {
                          m = reclaim_pv_chunk(pmap, lockp);
                          if (m == NULL)
                                  goto retry;
                          reclaimed = true;
                  }
                  PV_STAT(atomic_add_int(&pc_chunk_count, 1));
                  PV_STAT(atomic_add_int(&pc_chunk_allocs, 1));
                  dump_add_page(m->phys_addr);
                  pc = (void *)PHYS_TO_DMAP(m->phys_addr);
                  pc->pc_pmap = pmap;
                  pc->pc_map[0] = PC_FREE0;
                  pc->pc_map[1] = PC_FREE1;
                  pc->pc_map[2] = PC_FREE2;
                  TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                  TAILQ_INSERT_TAIL(&new_tail, pc, pc_lru);
                  PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV));
  
                  /*
                   * The reclaim might have freed a chunk from the current pmap.
                   * If that chunk contained available entries, we need to
                   * re-count the number of available entries.
                   */
                  if (reclaimed)
                          goto retry;
          }
          if (!TAILQ_EMPTY(&new_tail)) {
                  mtx_lock(&pv_chunks_mutex);
                  TAILQ_CONCAT(&pv_chunks, &new_tail, pc_lru);
                  mtx_unlock(&pv_chunks_mutex);
          }
  }
  
  /*
   * First find and then remove the pv entry for the specified pmap and virtual
   * address from the specified pv list.  Returns the pv entry if found and NULL
   * otherwise.  This operation can be performed on pv lists for either 4KB or
   * 2MB page mappings.
   */
  static __inline pv_entry_t
  pmap_pvh_remove(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
  {
          pv_entry_t pv;
  
          TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                  if (pmap == PV_PMAP(pv) && va == pv->pv_va) {
                          TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                          pvh->pv_gen++;
                          break;
                  }
          }
          return (pv);
  }
  
  /*
   * After demotion from a 2MB page mapping to 512 4KB page mappings,
   * destroy the pv entry for the 2MB page mapping and reinstantiate the pv
   * entries for each of the 4KB page mappings.
   */
  static void
  pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
      struct rwlock **lockp)
  {
          struct md_page *pvh;
          struct pv_chunk *pc;
          pv_entry_t pv;
          vm_offset_t va_last;
          vm_page_t m;
          int bit, field;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          KASSERT((pa & PDRMASK) == 0,
              ("pmap_pv_demote_pde: pa is not 2mpage aligned"));
          CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa);
  
          /*
           * Transfer the 2mpage's pv entry for this mapping to the first
           * page's pv list.  Once this transfer begins, the pv list lock
           * must not be released until the last pv entry is reinstantiated.
           */
          pvh = pa_to_pvh(pa);
          va = trunc_2mpage(va);
          pv = pmap_pvh_remove(pvh, pmap, va);
          KASSERT(pv != NULL, ("pmap_pv_demote_pde: pv not found"));
          m = PHYS_TO_VM_PAGE(pa);
          TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
          m->md.pv_gen++;
          /* Instantiate the remaining NPTEPG - 1 pv entries. */
          PV_STAT(atomic_add_long(&pv_entry_allocs, NPTEPG - 1));
          va_last = va + NBPDR - PAGE_SIZE;
          for (;;) {
                  pc = TAILQ_FIRST(&pmap->pm_pvchunk);
                  KASSERT(pc->pc_map[0] != 0 || pc->pc_map[1] != 0 ||
                      pc->pc_map[2] != 0, ("pmap_pv_demote_pde: missing spare"));
                  for (field = 0; field < _NPCM; field++) {
                          while (pc->pc_map[field]) {
                                  bit = bsfq(pc->pc_map[field]);
                                  pc->pc_map[field] &= ~(1ul << bit);
                                  pv = &pc->pc_pventry[field * 64 + bit];
                                  va += PAGE_SIZE;
                                  pv->pv_va = va;
                                  m++;
                                  KASSERT((m->oflags & VPO_UNMANAGED) == 0,
                              ("pmap_pv_demote_pde: page %p is not managed", m));
                                  TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                                  m->md.pv_gen++;
                                  if (va == va_last)
                                          goto out;
                          }
                  }
                  TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                  TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc, pc_list);
          }
  out:
          if (pc->pc_map[0] == 0 && pc->pc_map[1] == 0 && pc->pc_map[2] == 0) {
                  TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                  TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc, pc_list);
          }
          PV_STAT(atomic_add_long(&pv_entry_count, NPTEPG - 1));
          PV_STAT(atomic_subtract_int(&pv_entry_spare, NPTEPG - 1));
  }
  
  #if VM_NRESERVLEVEL > 0
  /*
   * After promotion from 512 4KB page mappings to a single 2MB page mapping,
   * replace the many pv entries for the 4KB page mappings by a single pv entry
   * for the 2MB page mapping.
   */
  static void
  pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
      struct rwlock **lockp)
  {
          struct md_page *pvh;
          pv_entry_t pv;
          vm_offset_t va_last;
          vm_page_t m;
  
          KASSERT((pa & PDRMASK) == 0,
              ("pmap_pv_promote_pde: pa is not 2mpage aligned"));
          CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa);
  
          /*
           * Transfer the first page's pv entry for this mapping to the 2mpage's
           * pv list.  Aside from avoiding the cost of a call to get_pv_entry(),
           * a transfer avoids the possibility that get_pv_entry() calls
           * reclaim_pv_chunk() and that reclaim_pv_chunk() removes one of the
           * mappings that is being promoted.
           */
          m = PHYS_TO_VM_PAGE(pa);
          va = trunc_2mpage(va);
          pv = pmap_pvh_remove(&m->md, pmap, va);
          KASSERT(pv != NULL, ("pmap_pv_promote_pde: pv not found"));
          pvh = pa_to_pvh(pa);
          TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
          pvh->pv_gen++;
          /* Free the remaining NPTEPG - 1 pv entries. */
          va_last = va + NBPDR - PAGE_SIZE;
          do {
                  m++;
                  va += PAGE_SIZE;
                  pmap_pvh_free(&m->md, pmap, va);
          } while (va < va_last);
  }
  #endif /* VM_NRESERVLEVEL > 0 */
  
  /*
   * First find and then destroy the pv entry for the specified pmap and virtual
   * address.  This operation can be performed on pv lists for either 4KB or 2MB
   * page mappings.
   */
  static void
  pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
  {
          pv_entry_t pv;
  
          pv = pmap_pvh_remove(pvh, pmap, va);
          KASSERT(pv != NULL, ("pmap_pvh_free: pv not found"));
          free_pv_entry(pmap, pv);
  }
  
  /*
   * Conditionally create the PV entry for a 4KB page mapping if the required
   * memory can be allocated without resorting to reclamation.
   */
  static boolean_t
  pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va, vm_page_t m,
      struct rwlock **lockp)
  {
          pv_entry_t pv;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          /* Pass NULL instead of the lock pointer to disable reclamation. */
          if ((pv = get_pv_entry(pmap, NULL)) != NULL) {
                  pv->pv_va = va;
                  CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                  TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                  m->md.pv_gen++;
                  return (TRUE);
          } else
                  return (FALSE);
  }
  
  /*
   * Create the PV entry for a 2MB page mapping.  Always returns true unless the
   * flag PMAP_ENTER_NORECLAIM is specified.  If that flag is specified, returns
   * false if the PV entry cannot be allocated without resorting to reclamation.
   */
  static bool
  pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, pd_entry_t pde, u_int flags,
      struct rwlock **lockp)
  {
          struct md_page *pvh;
          pv_entry_t pv;
          vm_paddr_t pa;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          /* Pass NULL instead of the lock pointer to disable reclamation. */
          if ((pv = get_pv_entry(pmap, (flags & PMAP_ENTER_NORECLAIM) != 0 ?
              NULL : lockp)) == NULL)
                  return (false);
          pv->pv_va = va;
          pa = pde & PG_PS_FRAME;
          CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa);
          pvh = pa_to_pvh(pa);
          TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
          pvh->pv_gen++;
          return (true);
  }
  
  /*
   * Fills a page table page with mappings to consecutive physical pages.
   */
  static void
  pmap_fill_ptp(pt_entry_t *firstpte, pt_entry_t newpte)
  {
          pt_entry_t *pte;
  
          for (pte = firstpte; pte < firstpte + NPTEPG; pte++) {
                  *pte = newpte;
                  newpte += PAGE_SIZE;
          }
  }
  
  /*
   * Tries to demote a 2MB page mapping.  If demotion fails, the 2MB page
   * mapping is invalidated.
   */
  static boolean_t
  pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
  {
          struct rwlock *lock;
          boolean_t rv;
  
          lock = NULL;
          rv = pmap_demote_pde_locked(pmap, pde, va, &lock);
          if (lock != NULL)
                  rw_wunlock(lock);
          return (rv);
  }
  
  static boolean_t
  pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
      struct rwlock **lockp)
  {
          pd_entry_t newpde, oldpde;
          pt_entry_t *firstpte, newpte;
          pt_entry_t PG_A, PG_G, PG_M, PG_PKU_MASK, PG_RW, PG_V;
          vm_paddr_t mptepa;
          vm_page_t mpte;
          struct spglist free;
          vm_offset_t sva;
          int PG_PTE_CACHE;
  
          PG_G = pmap_global_bit(pmap);
          PG_A = pmap_accessed_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PG_PTE_CACHE = pmap_cache_mask(pmap, 0);
          PG_PKU_MASK = pmap_pku_mask_bit(pmap);
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          oldpde = *pde;
          KASSERT((oldpde & (PG_PS | PG_V)) == (PG_PS | PG_V),
              ("pmap_demote_pde: oldpde is missing PG_PS and/or PG_V"));
          if ((oldpde & PG_A) == 0 || (mpte = pmap_remove_pt_page(pmap, va)) ==
              NULL) {
                  KASSERT((oldpde & PG_W) == 0,
                      ("pmap_demote_pde: page table page for a wired mapping"
                      " is missing"));
  
                  /*
                   * Invalidate the 2MB page mapping and return "failure" if the
                   * mapping was never accessed or the allocation of the new
                   * page table page fails.  If the 2MB page mapping belongs to
                   * the direct map region of the kernel's address space, then
                   * the page allocation request specifies the highest possible
                   * priority (VM_ALLOC_INTERRUPT).  Otherwise, the priority is
                   * normal.  Page table pages are preallocated for every other
                   * part of the kernel address space, so the direct map region
                   * is the only part of the kernel address space that must be
                   * handled here.
                   */
                  if ((oldpde & PG_A) == 0 || (mpte = vm_page_alloc(NULL,
                      pmap_pde_pindex(va), (va >= DMAP_MIN_ADDRESS && va <
                      DMAP_MAX_ADDRESS ? VM_ALLOC_INTERRUPT : VM_ALLOC_NORMAL) |
                      VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
                          SLIST_INIT(&free);
                          sva = trunc_2mpage(va);
                          pmap_remove_pde(pmap, pde, sva, &free, lockp);
                          if ((oldpde & PG_G) == 0)
                                  pmap_invalidate_pde_page(pmap, sva, oldpde);
                          vm_page_free_pages_toq(&free, true);
                          CTR2(KTR_PMAP, "pmap_demote_pde: failure for va %#lx"
                              " in pmap %p", va, pmap);
                          return (FALSE);
                  }
                  if (va < VM_MAXUSER_ADDRESS)
                          pmap_resident_count_inc(pmap, 1);
          }
          mptepa = VM_PAGE_TO_PHYS(mpte);
          firstpte = (pt_entry_t *)PHYS_TO_DMAP(mptepa);
          newpde = mptepa | PG_M | PG_A | (oldpde & PG_U) | PG_RW | PG_V;
          KASSERT((oldpde & PG_A) != 0,
              ("pmap_demote_pde: oldpde is missing PG_A"));
          KASSERT((oldpde & (PG_M | PG_RW)) != PG_RW,
              ("pmap_demote_pde: oldpde is missing PG_M"));
          newpte = oldpde & ~PG_PS;
          newpte = pmap_swap_pat(pmap, newpte);
  
          /*
           * If the page table page is new, initialize it.
           */
          if (mpte->wire_count == 1) {
                  mpte->wire_count = NPTEPG;
                  pmap_fill_ptp(firstpte, newpte);
          }
          KASSERT((*firstpte & PG_FRAME) == (newpte & PG_FRAME),
              ("pmap_demote_pde: firstpte and newpte map different physical"
              " addresses"));
  
          /*
           * If the mapping has changed attributes, update the page table
           * entries.
           */
          if ((*firstpte & PG_PTE_PROMOTE) != (newpte & PG_PTE_PROMOTE))
                  pmap_fill_ptp(firstpte, newpte);
  
          /*
           * The spare PV entries must be reserved prior to demoting the
           * mapping, that is, prior to changing the PDE.  Otherwise, the state
           * of the PDE and the PV lists will be inconsistent, which can result
           * in reclaim_pv_chunk() attempting to remove a PV entry from the
           * wrong PV list and pmap_pv_demote_pde() failing to find the expected
           * PV entry for the 2MB page mapping that is being demoted.
           */
          if ((oldpde & PG_MANAGED) != 0)
                  reserve_pv_entries(pmap, NPTEPG - 1, lockp);
  
          /*
           * Demote the mapping.  This pmap is locked.  The old PDE has
           * PG_A set.  If the old PDE has PG_RW set, it also has PG_M
           * set.  Thus, there is no danger of a race with another
           * processor changing the setting of PG_A and/or PG_M between
           * the read above and the store below. 
           */
          if (workaround_erratum383)
                  pmap_update_pde(pmap, va, pde, newpde);
          else
                  pde_store(pde, newpde);
  
          /*
           * Invalidate a stale recursive mapping of the page table page.
           */
          if (va >= VM_MAXUSER_ADDRESS)
                  pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));
  
          /*
           * Demote the PV entry.
           */
          if ((oldpde & PG_MANAGED) != 0)
                  pmap_pv_demote_pde(pmap, va, oldpde & PG_PS_FRAME, lockp);
  
          atomic_add_long(&pmap_pde_demotions, 1);
          CTR2(KTR_PMAP, "pmap_demote_pde: success for va %#lx"
              " in pmap %p", va, pmap);
          return (TRUE);
  }
  
  /*
   * pmap_remove_kernel_pde: Remove a kernel superpage mapping.
   */
  static void
  pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
  {
          pd_entry_t newpde;
          vm_paddr_t mptepa;
          vm_page_t mpte;
  
          KASSERT(pmap == kernel_pmap, ("pmap %p is not kernel_pmap", pmap));
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          mpte = pmap_remove_pt_page(pmap, va);
          if (mpte == NULL)
                  panic("pmap_remove_kernel_pde: Missing pt page.");
  
          mptepa = VM_PAGE_TO_PHYS(mpte);
          newpde = mptepa | X86_PG_M | X86_PG_A | X86_PG_RW | X86_PG_V;
  
          /*
           * Initialize the page table page.
           */
          pagezero((void *)PHYS_TO_DMAP(mptepa));
  
          /*
           * Demote the mapping.
           */
          if (workaround_erratum383)
                  pmap_update_pde(pmap, va, pde, newpde);
          else
                  pde_store(pde, newpde);
  
          /*
           * Invalidate a stale recursive mapping of the page table page.
           */
          pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));
  }
  
  /*
   * pmap_remove_pde: do the things to unmap a superpage in a process
   */
  static int
  pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
      struct spglist *free, struct rwlock **lockp)
  {
          struct md_page *pvh;
          pd_entry_t oldpde;
          vm_offset_t eva, va;
          vm_page_t m, mpte;
          pt_entry_t PG_G, PG_A, PG_M, PG_RW;
  
          PG_G = pmap_global_bit(pmap);
          PG_A = pmap_accessed_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          KASSERT((sva & PDRMASK) == 0,
              ("pmap_remove_pde: sva is not 2mpage aligned"));
          oldpde = pte_load_clear(pdq);
          if (oldpde & PG_W)
                  pmap->pm_stats.wired_count -= NBPDR / PAGE_SIZE;
          if ((oldpde & PG_G) != 0)
                  pmap_invalidate_pde_page(kernel_pmap, sva, oldpde);
          pmap_resident_count_dec(pmap, NBPDR / PAGE_SIZE);
          if (oldpde & PG_MANAGED) {
                  CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, oldpde & PG_PS_FRAME);
                  pvh = pa_to_pvh(oldpde & PG_PS_FRAME);
                  pmap_pvh_free(pvh, pmap, sva);
                  eva = sva + NBPDR;
                  for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
                      va < eva; va += PAGE_SIZE, m++) {
                          if ((oldpde & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                  vm_page_dirty(m);
                          if (oldpde & PG_A)
                                  vm_page_aflag_set(m, PGA_REFERENCED);
                          if (TAILQ_EMPTY(&m->md.pv_list) &&
                              TAILQ_EMPTY(&pvh->pv_list))
                                  vm_page_aflag_clear(m, PGA_WRITEABLE);
                          pmap_delayed_invl_page(m);
                  }
          }
          if (pmap == kernel_pmap) {
                  pmap_remove_kernel_pde(pmap, pdq, sva);
          } else {
                  mpte = pmap_remove_pt_page(pmap, sva);
                  if (mpte != NULL) {
                          pmap_resident_count_dec(pmap, 1);
                          KASSERT(mpte->wire_count == NPTEPG,
                              ("pmap_remove_pde: pte page wire count error"));
                          mpte->wire_count = 0;
                          pmap_add_delayed_free_list(mpte, free, FALSE);
                  }
          }
          return (pmap_unuse_pt(pmap, sva, *pmap_pdpe(pmap, sva), free));
  }
  
  /*
   * pmap_remove_pte: do the things to unmap a page in a process
   */
  static int
  pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t va, 
      pd_entry_t ptepde, struct spglist *free, struct rwlock **lockp)
  {
          struct md_page *pvh;
          pt_entry_t oldpte, PG_A, PG_M, PG_RW;
          vm_page_t m;
  
          PG_A = pmap_accessed_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          oldpte = pte_load_clear(ptq);
          if (oldpte & PG_W)
                  pmap->pm_stats.wired_count -= 1;
          pmap_resident_count_dec(pmap, 1);
          if (oldpte & PG_MANAGED) {
                  m = PHYS_TO_VM_PAGE(oldpte & PG_FRAME);
                  if ((oldpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                          vm_page_dirty(m);
                  if (oldpte & PG_A)
                          vm_page_aflag_set(m, PGA_REFERENCED);
                  CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                  pmap_pvh_free(&m->md, pmap, va);
                  if (TAILQ_EMPTY(&m->md.pv_list) &&
                      (m->flags & PG_FICTITIOUS) == 0) {
                          pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                          if (TAILQ_EMPTY(&pvh->pv_list))
                                  vm_page_aflag_clear(m, PGA_WRITEABLE);
                  }
                  pmap_delayed_invl_page(m);
          }
          return (pmap_unuse_pt(pmap, va, ptepde, free));
  }
  
  /*
   * Remove a single page from a process address space
   */
  static void
  pmap_remove_page(pmap_t pmap, vm_offset_t va, pd_entry_t *pde,
      struct spglist *free)
  {
          struct rwlock *lock;
          pt_entry_t *pte, PG_V;
  
          PG_V = pmap_valid_bit(pmap);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          if ((*pde & PG_V) == 0)
                  return;
          pte = pmap_pde_to_pte(pde, va);
          if ((*pte & PG_V) == 0)
                  return;
          lock = NULL;
          pmap_remove_pte(pmap, pte, va, *pde, free, &lock);
          if (lock != NULL)
                  rw_wunlock(lock);
          pmap_invalidate_page(pmap, va);
  }
  
  /*
   * Removes the specified range of addresses from the page table page.
   */
  static bool
  pmap_remove_ptes(pmap_t pmap, vm_offset_t sva, vm_offset_t eva,
      pd_entry_t *pde, struct spglist *free, struct rwlock **lockp)
  {
          pt_entry_t PG_G, *pte;
          vm_offset_t va;
          bool anyvalid;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          PG_G = pmap_global_bit(pmap);
          anyvalid = false;
          va = eva;
          for (pte = pmap_pde_to_pte(pde, sva); sva != eva; pte++,
              sva += PAGE_SIZE) {
                  if (*pte == 0) {
                          if (va != eva) {
                                  pmap_invalidate_range(pmap, va, sva);
                                  va = eva;
                          }
                          continue;
                  }
                  if ((*pte & PG_G) == 0)
                          anyvalid = true;
                  else if (va == eva)
                          va = sva;
                  if (pmap_remove_pte(pmap, pte, sva, *pde, free, lockp)) {
                          sva += PAGE_SIZE;
                          break;
                  }
          }
          if (va != eva)
                  pmap_invalidate_range(pmap, va, sva);
          return (anyvalid);
  }
  
  /*
   *      Remove the given range of addresses from the specified map.
   *
   *      It is assumed that the start and end are properly
   *      rounded to the page size.
   */
  void
  pmap_remove(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
          struct rwlock *lock;
          vm_offset_t va_next;
          pml4_entry_t *pml4e;
          pdp_entry_t *pdpe;
          pd_entry_t ptpaddr, *pde;
          pt_entry_t PG_G, PG_V;
          struct spglist free;
          int anyvalid;
  
          PG_G = pmap_global_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
  
          /*
           * Perform an unsynchronized read.  This is, however, safe.
           */
          if (pmap->pm_stats.resident_count == 0)
                  return;
  
          anyvalid = 0;
          SLIST_INIT(&free);
  
          pmap_delayed_invl_started();
          PMAP_LOCK(pmap);
  
          /*
           * special handling of removing one page.  a very
           * common operation and easy to short circuit some
           * code.
           */
          if (sva + PAGE_SIZE == eva) {
                  pde = pmap_pde(pmap, sva);
                  if (pde && (*pde & PG_PS) == 0) {
                          pmap_remove_page(pmap, sva, pde, &free);
                          goto out;
                  }
          }
  
          lock = NULL;
          for (; sva < eva; sva = va_next) {
  
                  if (pmap->pm_stats.resident_count == 0)
                          break;
  
                  pml4e = pmap_pml4e(pmap, sva);
                  if ((*pml4e & PG_V) == 0) {
                          va_next = (sva + NBPML4) & ~PML4MASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
  
                  pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
                  if ((*pdpe & PG_V) == 0) {
                          va_next = (sva + NBPDP) & ~PDPMASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
  
                  /*
                   * Calculate index for next page table.
                   */
                  va_next = (sva + NBPDR) & ~PDRMASK;
                  if (va_next < sva)
                          va_next = eva;
  
                  pde = pmap_pdpe_to_pde(pdpe, sva);
                  ptpaddr = *pde;
  
                  /*
                   * Weed out invalid mappings.
                   */
                  if (ptpaddr == 0)
                          continue;
  
                  /*
                   * Check for large page.
                   */
                  if ((ptpaddr & PG_PS) != 0) {
                          /*
                           * Are we removing the entire large page?  If not,
                           * demote the mapping and fall through.
                           */
                          if (sva + NBPDR == va_next && eva >= va_next) {
                                  /*
                                   * The TLB entry for a PG_G mapping is
                                   * invalidated by pmap_remove_pde().
                                   */
                                  if ((ptpaddr & PG_G) == 0)
                                          anyvalid = 1;
                                  pmap_remove_pde(pmap, pde, sva, &free, &lock);
                                  continue;
                          } else if (!pmap_demote_pde_locked(pmap, pde, sva,
                              &lock)) {
                                  /* The large page mapping was destroyed. */
                                  continue;
                          } else
                                  ptpaddr = *pde;
                  }
  
                  /*
                   * Limit our scan to either the end of the va represented
                   * by the current page table page, or to the end of the
                   * range being removed.
                   */
                  if (va_next > eva)
                          va_next = eva;
  
                  if (pmap_remove_ptes(pmap, sva, va_next, pde, &free, &lock))
                          anyvalid = 1;
          }
          if (lock != NULL)
                  rw_wunlock(lock);
  out:
          if (anyvalid)
                  pmap_invalidate_all(pmap);
          pmap_pkru_on_remove(pmap, sva, eva);
          PMAP_UNLOCK(pmap);
          pmap_delayed_invl_finished();
          vm_page_free_pages_toq(&free, true);
  }
  
  /*
   *      Routine:        pmap_remove_all
   *      Function:
   *              Removes this physical page from
   *              all physical maps in which it resides.
   *              Reflects back modify bits to the pager.
   *
   *      Notes:
   *              Original versions of this routine were very
   *              inefficient because they iteratively called
   *              pmap_remove (slow...)
   */
  
  void
  pmap_remove_all(vm_page_t m)
  {
          struct md_page *pvh;
          pv_entry_t pv;
          pmap_t pmap;
          struct rwlock *lock;
          pt_entry_t *pte, tpte, PG_A, PG_M, PG_RW;
          pd_entry_t *pde;
          vm_offset_t va;
          struct spglist free;
          int pvh_gen, md_gen;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_remove_all: page %p is not managed", m));
          SLIST_INIT(&free);
          lock = VM_PAGE_TO_PV_LIST_LOCK(m);
          pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy :
              pa_to_pvh(VM_PAGE_TO_PHYS(m));
  retry:
          rw_wlock(lock);
          while ((pv = TAILQ_FIRST(&pvh->pv_list)) != NULL) {
                  pmap = PV_PMAP(pv);
                  if (!PMAP_TRYLOCK(pmap)) {
                          pvh_gen = pvh->pv_gen;
                          rw_wunlock(lock);
                          PMAP_LOCK(pmap);
                          rw_wlock(lock);
                          if (pvh_gen != pvh->pv_gen) {
                                  rw_wunlock(lock);
                                  PMAP_UNLOCK(pmap);
                                  goto retry;
                          }
                  }
                  va = pv->pv_va;
                  pde = pmap_pde(pmap, va);
                  (void)pmap_demote_pde_locked(pmap, pde, va, &lock);
                  PMAP_UNLOCK(pmap);
          }
          while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                  pmap = PV_PMAP(pv);
                  if (!PMAP_TRYLOCK(pmap)) {
                          pvh_gen = pvh->pv_gen;
                          md_gen = m->md.pv_gen;
                          rw_wunlock(lock);
                          PMAP_LOCK(pmap);
                          rw_wlock(lock);
                          if (pvh_gen != pvh->pv_gen || md_gen != m->md.pv_gen) {
                                  rw_wunlock(lock);
                                  PMAP_UNLOCK(pmap);
                                  goto retry;
                          }
                  }
                  PG_A = pmap_accessed_bit(pmap);
                  PG_M = pmap_modified_bit(pmap);
                  PG_RW = pmap_rw_bit(pmap);
                  pmap_resident_count_dec(pmap, 1);
                  pde = pmap_pde(pmap, pv->pv_va);
                  KASSERT((*pde & PG_PS) == 0, ("pmap_remove_all: found"
                      " a 2mpage in page %p's pv list", m));
                  pte = pmap_pde_to_pte(pde, pv->pv_va);
                  tpte = pte_load_clear(pte);
                  if (tpte & PG_W)
                          pmap->pm_stats.wired_count--;
                  if (tpte & PG_A)
                          vm_page_aflag_set(m, PGA_REFERENCED);
  
                  /*
                   * Update the vm_page_t clean and reference bits.
                   */
                  if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                          vm_page_dirty(m);
                  pmap_unuse_pt(pmap, pv->pv_va, *pde, &free);
                  pmap_invalidate_page(pmap, pv->pv_va);
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                  m->md.pv_gen++;
                  free_pv_entry(pmap, pv);
                  PMAP_UNLOCK(pmap);
          }
          vm_page_aflag_clear(m, PGA_WRITEABLE);
          rw_wunlock(lock);
          pmap_delayed_invl_wait(m);
          vm_page_free_pages_toq(&free, true);
  }
  
  /*
   * pmap_protect_pde: do the things to protect a 2mpage in a process
   */
  static boolean_t
  pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva, vm_prot_t prot)
  {
          pd_entry_t newpde, oldpde;
          vm_offset_t eva, va;
          vm_page_t m;
          boolean_t anychanged;
          pt_entry_t PG_G, PG_M, PG_RW;
  
          PG_G = pmap_global_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          KASSERT((sva & PDRMASK) == 0,
              ("pmap_protect_pde: sva is not 2mpage aligned"));
          anychanged = FALSE;
  retry:
          oldpde = newpde = *pde;
          if ((oldpde & (PG_MANAGED | PG_M | PG_RW)) ==
              (PG_MANAGED | PG_M | PG_RW)) {
                  eva = sva + NBPDR;
                  for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
                      va < eva; va += PAGE_SIZE, m++)
                          vm_page_dirty(m);
          }
          if ((prot & VM_PROT_WRITE) == 0)
                  newpde &= ~(PG_RW | PG_M);
          if ((prot & VM_PROT_EXECUTE) == 0)
                  newpde |= pg_nx;
          if (newpde != oldpde) {
                  /*
                   * As an optimization to future operations on this PDE, clear
                   * PG_PROMOTED.  The impending invalidation will remove any
                   * lingering 4KB page mappings from the TLB.
                   */
                  if (!atomic_cmpset_long(pde, oldpde, newpde & ~PG_PROMOTED))
                          goto retry;
                  if ((oldpde & PG_G) != 0)
                          pmap_invalidate_pde_page(kernel_pmap, sva, oldpde);
                  else
                          anychanged = TRUE;
          }
          return (anychanged);
  }
  
  /*
   *      Set the physical protection on the
   *      specified range of this map as requested.
   */
  void
  pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
  {
          vm_offset_t va_next;
          pml4_entry_t *pml4e;
          pdp_entry_t *pdpe;
          pd_entry_t ptpaddr, *pde;
          pt_entry_t *pte, PG_G, PG_M, PG_RW, PG_V;
          boolean_t anychanged;
  
          KASSERT((prot & ~VM_PROT_ALL) == 0, ("invalid prot %x", prot));
          if (prot == VM_PROT_NONE) {
                  pmap_remove(pmap, sva, eva);
                  return;
          }
  
          if ((prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) ==
              (VM_PROT_WRITE|VM_PROT_EXECUTE))
                  return;
  
          PG_G = pmap_global_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
          anychanged = FALSE;
  
          /*
           * Although this function delays and batches the invalidation
           * of stale TLB entries, it does not need to call
           * pmap_delayed_invl_started() and
           * pmap_delayed_invl_finished(), because it does not
           * ordinarily destroy mappings.  Stale TLB entries from
           * protection-only changes need only be invalidated before the
           * pmap lock is released, because protection-only changes do
           * not destroy PV entries.  Even operations that iterate over
           * a physical page's PV list of mappings, like
           * pmap_remove_write(), acquire the pmap lock for each
           * mapping.  Consequently, for protection-only changes, the
           * pmap lock suffices to synchronize both page table and TLB
           * updates.
           *
           * This function only destroys a mapping if pmap_demote_pde()
           * fails.  In that case, stale TLB entries are immediately
           * invalidated.
           */
          
          PMAP_LOCK(pmap);
          for (; sva < eva; sva = va_next) {
  
                  pml4e = pmap_pml4e(pmap, sva);
                  if ((*pml4e & PG_V) == 0) {
                          va_next = (sva + NBPML4) & ~PML4MASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
  
                  pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
                  if ((*pdpe & PG_V) == 0) {
                          va_next = (sva + NBPDP) & ~PDPMASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
  
                  va_next = (sva + NBPDR) & ~PDRMASK;
                  if (va_next < sva)
                          va_next = eva;
  
                  pde = pmap_pdpe_to_pde(pdpe, sva);
                  ptpaddr = *pde;
  
                  /*
                   * Weed out invalid mappings.
                   */
                  if (ptpaddr == 0)
                          continue;
  
                  /*
                   * Check for large page.
                   */
                  if ((ptpaddr & PG_PS) != 0) {
                          /*
                           * Are we protecting the entire large page?  If not,
                           * demote the mapping and fall through.
                           */
                          if (sva + NBPDR == va_next && eva >= va_next) {
                                  /*
                                   * The TLB entry for a PG_G mapping is
                                   * invalidated by pmap_protect_pde().
                                   */
                                  if (pmap_protect_pde(pmap, pde, sva, prot))
                                          anychanged = TRUE;
                                  continue;
                          } else if (!pmap_demote_pde(pmap, pde, sva)) {
                                  /*
                                   * The large page mapping was destroyed.
                                   */
                                  continue;
                          }
                  }
  
                  if (va_next > eva)
                          va_next = eva;
  
                  for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
                      sva += PAGE_SIZE) {
                          pt_entry_t obits, pbits;
                          vm_page_t m;
  
  retry:
                          obits = pbits = *pte;
                          if ((pbits & PG_V) == 0)
                                  continue;
  
                          if ((prot & VM_PROT_WRITE) == 0) {
                                  if ((pbits & (PG_MANAGED | PG_M | PG_RW)) ==
                                      (PG_MANAGED | PG_M | PG_RW)) {
                                          m = PHYS_TO_VM_PAGE(pbits & PG_FRAME);
                                          vm_page_dirty(m);
                                  }
                                  pbits &= ~(PG_RW | PG_M);
                          }
                          if ((prot & VM_PROT_EXECUTE) == 0)
                                  pbits |= pg_nx;
  
                          if (pbits != obits) {
                                  if (!atomic_cmpset_long(pte, obits, pbits))
                                          goto retry;
                                  if (obits & PG_G)
                                          pmap_invalidate_page(pmap, sva);
                                  else
                                          anychanged = TRUE;
                          }
                  }
          }
          if (anychanged)
                  pmap_invalidate_all(pmap);
          PMAP_UNLOCK(pmap);
  }
  
  #if VM_NRESERVLEVEL > 0
  /*
   * Tries to promote the 512, contiguous 4KB page mappings that are within a
   * single page table page (PTP) to a single 2MB page mapping.  For promotion
   * to occur, two conditions must be met: (1) the 4KB page mappings must map
   * aligned, contiguous physical memory and (2) the 4KB page mappings must have
   * identical characteristics. 
   */
  static void
  pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
      struct rwlock **lockp)
  {
          pd_entry_t newpde;
          pt_entry_t *firstpte, oldpte, pa, *pte;
          pt_entry_t PG_G, PG_A, PG_M, PG_RW, PG_V, PG_PKU_MASK;
          vm_page_t mpte;
          int PG_PTE_CACHE;
  
          PG_A = pmap_accessed_bit(pmap);
          PG_G = pmap_global_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
          PG_PKU_MASK = pmap_pku_mask_bit(pmap);
          PG_PTE_CACHE = pmap_cache_mask(pmap, 0);
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
  
          /*
           * Examine the first PTE in the specified PTP.  Abort if this PTE is
           * either invalid, unused, or does not map the first 4KB physical page
           * within a 2MB page. 
           */
          firstpte = (pt_entry_t *)PHYS_TO_DMAP(*pde & PG_FRAME);
  setpde:
          newpde = *firstpte;
          if ((newpde & ((PG_FRAME & PDRMASK) | PG_A | PG_V)) != (PG_A | PG_V)) {
                  atomic_add_long(&pmap_pde_p_failures, 1);
                  CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#lx"
                      " in pmap %p", va, pmap);
                  return;
          }
          if ((newpde & (PG_M | PG_RW)) == PG_RW) {
                  /*
                   * When PG_M is already clear, PG_RW can be cleared without
                   * a TLB invalidation.
                   */
                  if (!atomic_cmpset_long(firstpte, newpde, newpde & ~PG_RW))
                          goto setpde;
                  newpde &= ~PG_RW;
          }
  
          /*
           * Examine each of the other PTEs in the specified PTP.  Abort if this
           * PTE maps an unexpected 4KB physical page or does not have identical
           * characteristics to the first PTE.
           */
          pa = (newpde & (PG_PS_FRAME | PG_A | PG_V)) + NBPDR - PAGE_SIZE;
          for (pte = firstpte + NPTEPG - 1; pte > firstpte; pte--) {
  setpte:
                  oldpte = *pte;
                  if ((oldpte & (PG_FRAME | PG_A | PG_V)) != pa) {
                          atomic_add_long(&pmap_pde_p_failures, 1);
                          CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#lx"
                              " in pmap %p", va, pmap);
                          return;
                  }
                  if ((oldpte & (PG_M | PG_RW)) == PG_RW) {
                          /*
                           * When PG_M is already clear, PG_RW can be cleared
                           * without a TLB invalidation.
                           */
                          if (!atomic_cmpset_long(pte, oldpte, oldpte & ~PG_RW))
                                  goto setpte;
                          oldpte &= ~PG_RW;
                          CTR2(KTR_PMAP, "pmap_promote_pde: protect for va %#lx"
                              " in pmap %p", (oldpte & PG_FRAME & PDRMASK) |
                              (va & ~PDRMASK), pmap);
                  }
                  if ((oldpte & PG_PTE_PROMOTE) != (newpde & PG_PTE_PROMOTE)) {
                          atomic_add_long(&pmap_pde_p_failures, 1);
                          CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#lx"
                              " in pmap %p", va, pmap);
                          return;
                  }
                  pa -= PAGE_SIZE;
          }
  
          /*
           * Save the page table page in its current state until the PDE
           * mapping the superpage is demoted by pmap_demote_pde() or
           * destroyed by pmap_remove_pde(). 
           */
          mpte = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
          KASSERT(mpte >= vm_page_array &&
              mpte < &vm_page_array[vm_page_array_size],
              ("pmap_promote_pde: page table page is out of range"));
          KASSERT(mpte->pindex == pmap_pde_pindex(va),
              ("pmap_promote_pde: page table page's pindex is wrong"));
          if (pmap_insert_pt_page(pmap, mpte)) {
                  atomic_add_long(&pmap_pde_p_failures, 1);
                  CTR2(KTR_PMAP,
                      "pmap_promote_pde: failure for va %#lx in pmap %p", va,
                      pmap);
                  return;
          }
  
          /*
           * Promote the pv entries.
           */
          if ((newpde & PG_MANAGED) != 0)
                  pmap_pv_promote_pde(pmap, va, newpde & PG_PS_FRAME, lockp);
  
          /*
           * Propagate the PAT index to its proper position.
           */
          newpde = pmap_swap_pat(pmap, newpde);
  
          /*
           * Map the superpage.
           */
          if (workaround_erratum383)
                  pmap_update_pde(pmap, va, pde, PG_PS | newpde);
          else
                  pde_store(pde, PG_PROMOTED | PG_PS | newpde);
  
          atomic_add_long(&pmap_pde_promotions, 1);
          CTR2(KTR_PMAP, "pmap_promote_pde: success for va %#lx"
              " in pmap %p", va, pmap);
  }
  #endif /* VM_NRESERVLEVEL > 0 */
  
  /*
   *      Insert the given physical page (p) at
   *      the specified virtual address (v) in the
   *      target physical map with the protection requested.
   *
   *      If specified, the page will be wired down, meaning
   *      that the related pte can not be reclaimed.
   *
   *      NB:  This is the only routine which MAY NOT lazy-evaluate
   *      or lose information.  That is, this routine must actually
   *      insert this page into the given map NOW.
   *
   *      When destroying both a page table and PV entry, this function
   *      performs the TLB invalidation before releasing the PV list
   *      lock, so we do not need pmap_delayed_invl_page() calls here.
   */
  int
  pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
      u_int flags, int8_t psind)
  {
          struct rwlock *lock;
          pd_entry_t *pde;
          pt_entry_t *pte, PG_G, PG_A, PG_M, PG_RW, PG_V;
          pt_entry_t newpte, origpte;
          pv_entry_t pv;
          vm_paddr_t opa, pa;
          vm_page_t mpte, om;
          int rv;
          boolean_t nosleep;
  
          PG_A = pmap_accessed_bit(pmap);
          PG_G = pmap_global_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
  
          va = trunc_page(va);
          KASSERT(va <= VM_MAX_KERNEL_ADDRESS, ("pmap_enter: toobig"));
          KASSERT(va < UPT_MIN_ADDRESS || va >= UPT_MAX_ADDRESS,
              ("pmap_enter: invalid to pmap_enter page table pages (va: 0x%lx)",
              va));
          KASSERT((m->oflags & VPO_UNMANAGED) != 0 || va < kmi.clean_sva ||
              va >= kmi.clean_eva,
              ("pmap_enter: managed mapping within the clean submap"));
          if ((m->oflags & VPO_UNMANAGED) == 0 && !vm_page_xbusied(m))
                  VM_OBJECT_ASSERT_LOCKED(m->object);
          KASSERT((flags & PMAP_ENTER_RESERVED) == 0,
              ("pmap_enter: flags %u has reserved bits set", flags));
          pa = VM_PAGE_TO_PHYS(m);
          newpte = (pt_entry_t)(pa | PG_A | PG_V);
          if ((flags & VM_PROT_WRITE) != 0)
                  newpte |= PG_M;
          if ((prot & VM_PROT_WRITE) != 0)
                  newpte |= PG_RW;
          KASSERT((newpte & (PG_M | PG_RW)) != PG_M,
              ("pmap_enter: flags includes VM_PROT_WRITE but prot doesn't"));
          if ((prot & VM_PROT_EXECUTE) == 0)
                  newpte |= pg_nx;
          if ((flags & PMAP_ENTER_WIRED) != 0)
                  newpte |= PG_W;
          if (va < VM_MAXUSER_ADDRESS)
                  newpte |= PG_U;
          if (pmap == kernel_pmap)
                  newpte |= PG_G;
          newpte |= pmap_cache_bits(pmap, m->md.pat_mode, psind > 0);
  
          /*
           * Set modified bit gratuitously for writeable mappings if
           * the page is unmanaged. We do not want to take a fault
           * to do the dirty bit accounting for these mappings.
           */
          if ((m->oflags & VPO_UNMANAGED) != 0) {
                  if ((newpte & PG_RW) != 0)
                          newpte |= PG_M;
          } else
                  newpte |= PG_MANAGED;
  
          lock = NULL;
          PMAP_LOCK(pmap);
          if (psind == 1) {
                  /* Assert the required virtual and physical alignment. */ 
                  KASSERT((va & PDRMASK) == 0, ("pmap_enter: va unaligned"));
                  KASSERT(m->psind > 0, ("pmap_enter: m->psind < psind"));
                  rv = pmap_enter_pde(pmap, va, newpte | PG_PS, flags, m, &lock);
                  goto out;
          }
          mpte = NULL;
  
          /*
           * In the case that a page table page is not
           * resident, we are creating it here.
           */
  retry:
          pde = pmap_pde(pmap, va);
          if (pde != NULL && (*pde & PG_V) != 0 && ((*pde & PG_PS) == 0 ||
              pmap_demote_pde_locked(pmap, pde, va, &lock))) {
                  pte = pmap_pde_to_pte(pde, va);
                  if (va < VM_MAXUSER_ADDRESS && mpte == NULL) {
                          mpte = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
                          mpte->wire_count++;
                  }
          } else if (va < VM_MAXUSER_ADDRESS) {
                  /*
                   * Here if the pte page isn't mapped, or if it has been
                   * deallocated.
                   */
                  nosleep = (flags & PMAP_ENTER_NOSLEEP) != 0;
                  mpte = _pmap_allocpte(pmap, pmap_pde_pindex(va),
                      nosleep ? NULL : &lock);
                  if (mpte == NULL && nosleep) {
                          rv = KERN_RESOURCE_SHORTAGE;
                          goto out;
                  }
                  goto retry;
          } else
                  panic("pmap_enter: invalid page directory va=%#lx", va);
  
          origpte = *pte;
          pv = NULL;
          if (va < VM_MAXUSER_ADDRESS && pmap->pm_type == PT_X86)
                  newpte |= pmap_pkru_get(pmap, va);
  
          /*
           * Is the specified virtual address already mapped?
           */
          if ((origpte & PG_V) != 0) {
                  /*
                   * Wiring change, just update stats. We don't worry about
                   * wiring PT pages as they remain resident as long as there
                   * are valid mappings in them. Hence, if a user page is wired,
                   * the PT page will be also.
                   */
                  if ((newpte & PG_W) != 0 && (origpte & PG_W) == 0)
                          pmap->pm_stats.wired_count++;
                  else if ((newpte & PG_W) == 0 && (origpte & PG_W) != 0)
                          pmap->pm_stats.wired_count--;
  
                  /*
                   * Remove the extra PT page reference.
                   */
                  if (mpte != NULL) {
                          mpte->wire_count--;
                          KASSERT(mpte->wire_count > 0,
                              ("pmap_enter: missing reference to page table page,"
                               " va: 0x%lx", va));
                  }
  
                  /*
                   * Has the physical page changed?
                   */
                  opa = origpte & PG_FRAME;
                  if (opa == pa) {
                          /*
                           * No, might be a protection or wiring change.
                           */
                          if ((origpte & PG_MANAGED) != 0 &&
                              (newpte & PG_RW) != 0)
                                  vm_page_aflag_set(m, PGA_WRITEABLE);
                          if (((origpte ^ newpte) & ~(PG_M | PG_A)) == 0)
                                  goto unchanged;
                          goto validate;
                  }
  
                  /*
                   * The physical page has changed.  Temporarily invalidate
                   * the mapping.  This ensures that all threads sharing the
                   * pmap keep a consistent view of the mapping, which is
                   * necessary for the correct handling of COW faults.  It
                   * also permits reuse of the old mapping's PV entry,
                   * avoiding an allocation.
                   *
                   * For consistency, handle unmanaged mappings the same way.
                   */
                  origpte = pte_load_clear(pte);
                  KASSERT((origpte & PG_FRAME) == opa,
                      ("pmap_enter: unexpected pa update for %#lx", va));
                  if ((origpte & PG_MANAGED) != 0) {
                          om = PHYS_TO_VM_PAGE(opa);
  
                          /*
                           * The pmap lock is sufficient to synchronize with
                           * concurrent calls to pmap_page_test_mappings() and
                           * pmap_ts_referenced().
                           */
                          if ((origpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                  vm_page_dirty(om);
                          if ((origpte & PG_A) != 0)
                                  vm_page_aflag_set(om, PGA_REFERENCED);
                          CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, opa);
                          pv = pmap_pvh_remove(&om->md, pmap, va);
                          KASSERT(pv != NULL,
                              ("pmap_enter: no PV entry for %#lx", va));
                          if ((newpte & PG_MANAGED) == 0)
                                  free_pv_entry(pmap, pv);
                          if ((om->aflags & PGA_WRITEABLE) != 0 &&
                              TAILQ_EMPTY(&om->md.pv_list) &&
                              ((om->flags & PG_FICTITIOUS) != 0 ||
                              TAILQ_EMPTY(&pa_to_pvh(opa)->pv_list)))
                                  vm_page_aflag_clear(om, PGA_WRITEABLE);
                  }
                  if ((origpte & PG_A) != 0)
                          pmap_invalidate_page(pmap, va);
                  origpte = 0;
          } else {
                  /*
                   * Increment the counters.
                   */
                  if ((newpte & PG_W) != 0)
                          pmap->pm_stats.wired_count++;
                  pmap_resident_count_inc(pmap, 1);
          }
  
          /*
           * Enter on the PV list if part of our managed memory.
           */
          if ((newpte & PG_MANAGED) != 0) {
                  if (pv == NULL) {
                          pv = get_pv_entry(pmap, &lock);
                          pv->pv_va = va;
                  }
                  CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, pa);
                  TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                  m->md.pv_gen++;
                  if ((newpte & PG_RW) != 0)
                          vm_page_aflag_set(m, PGA_WRITEABLE);
          }
  
          /*
           * Update the PTE.
           */
          if ((origpte & PG_V) != 0) {
  validate:
                  origpte = pte_load_store(pte, newpte);
                  KASSERT((origpte & PG_FRAME) == pa,
                      ("pmap_enter: unexpected pa update for %#lx", va));
                  if ((newpte & PG_M) == 0 && (origpte & (PG_M | PG_RW)) ==
                      (PG_M | PG_RW)) {
                          if ((origpte & PG_MANAGED) != 0)
                                  vm_page_dirty(m);
  
                          /*
                           * Although the PTE may still have PG_RW set, TLB
                           * invalidation may nonetheless be required because
                           * the PTE no longer has PG_M set.
                           */
                  } else if ((origpte & PG_NX) != 0 || (newpte & PG_NX) == 0) {
                          /*
                           * This PTE change does not require TLB invalidation.
                           */
                          goto unchanged;
                  }
                  if ((origpte & PG_A) != 0)
                          pmap_invalidate_page(pmap, va);
          } else
                  pte_store(pte, newpte);
  
  unchanged:
  
  #if VM_NRESERVLEVEL > 0
          /*
           * If both the page table page and the reservation are fully
           * populated, then attempt promotion.
           */
          if ((mpte == NULL || mpte->wire_count == NPTEPG) &&
              pmap_ps_enabled(pmap) &&
              (m->flags & PG_FICTITIOUS) == 0 &&
              vm_reserv_level_iffullpop(m) == 0)
                  pmap_promote_pde(pmap, pde, va, &lock);
  #endif
  
          rv = KERN_SUCCESS;
  out:
          if (lock != NULL)
                  rw_wunlock(lock);
          PMAP_UNLOCK(pmap);
          return (rv);
  }
  
  /*
   * Tries to create a read- and/or execute-only 2MB page mapping.  Returns true
   * if successful.  Returns false if (1) a page table page cannot be allocated
   * without sleeping, (2) a mapping already exists at the specified virtual
   * address, or (3) a PV entry cannot be allocated without reclaiming another
   * PV entry.
   */
  static bool
  pmap_enter_2mpage(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
      struct rwlock **lockp)
  {
          pd_entry_t newpde;
          pt_entry_t PG_V;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          PG_V = pmap_valid_bit(pmap);
          newpde = VM_PAGE_TO_PHYS(m) | pmap_cache_bits(pmap, m->md.pat_mode, 1) |
              PG_PS | PG_V;
          if ((m->oflags & VPO_UNMANAGED) == 0)
                  newpde |= PG_MANAGED;
          if ((prot & VM_PROT_EXECUTE) == 0)
                  newpde |= pg_nx;
          if (va < VM_MAXUSER_ADDRESS)
                  newpde |= PG_U;
          return (pmap_enter_pde(pmap, va, newpde, PMAP_ENTER_NOSLEEP |
              PMAP_ENTER_NOREPLACE | PMAP_ENTER_NORECLAIM, NULL, lockp) ==
              KERN_SUCCESS);
  }
  
  /*
   * Tries to create the specified 2MB page mapping.  Returns KERN_SUCCESS if
   * the mapping was created, and either KERN_FAILURE or KERN_RESOURCE_SHORTAGE
   * otherwise.  Returns KERN_FAILURE if PMAP_ENTER_NOREPLACE was specified and
   * a mapping already exists at the specified virtual address.  Returns
   * KERN_RESOURCE_SHORTAGE if PMAP_ENTER_NOSLEEP was specified and a page table
   * page allocation failed.  Returns KERN_RESOURCE_SHORTAGE if
   * PMAP_ENTER_NORECLAIM was specified and a PV entry allocation failed.
   *
   * The parameter "m" is only used when creating a managed, writeable mapping.
   */
  static int
  pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t newpde, u_int flags,
      vm_page_t m, struct rwlock **lockp)
  {
          struct spglist free;
          pd_entry_t oldpde, *pde;
          pt_entry_t PG_G, PG_RW, PG_V;
          vm_page_t mt, pdpg;
  
          KASSERT(pmap == kernel_pmap || (newpde & PG_W) == 0,
              ("pmap_enter_pde: cannot create wired user mapping"));
          PG_G = pmap_global_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
          KASSERT((newpde & (pmap_modified_bit(pmap) | PG_RW)) != PG_RW,
              ("pmap_enter_pde: newpde is missing PG_M"));
          PG_V = pmap_valid_bit(pmap);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
  
          if ((pdpg = pmap_allocpde(pmap, va, (flags & PMAP_ENTER_NOSLEEP) != 0 ?
              NULL : lockp)) == NULL) {
                  CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                      " in pmap %p", va, pmap);
                  return (KERN_RESOURCE_SHORTAGE);
          }
  
          /*
           * If pkru is not same for the whole pde range, return failure
           * and let vm_fault() cope.  Check after pde allocation, since
           * it could sleep.
           */
          if (!pmap_pkru_same(pmap, va, va + NBPDR)) {
                  SLIST_INIT(&free);
                  if (pmap_unwire_ptp(pmap, va, pdpg, &free)) {
                          pmap_invalidate_page(pmap, va);
                          vm_page_free_pages_toq(&free, true);
                  }
                  return (KERN_FAILURE);
          }
          if (va < VM_MAXUSER_ADDRESS && pmap->pm_type == PT_X86) {
                  newpde &= ~X86_PG_PKU_MASK;
                  newpde |= pmap_pkru_get(pmap, va);
          }
  
          pde = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pdpg));
          pde = &pde[pmap_pde_index(va)];
          oldpde = *pde;
          if ((oldpde & PG_V) != 0) {
                  KASSERT(pdpg->wire_count > 1,
                      ("pmap_enter_pde: pdpg's wire count is too low"));
                  if ((flags & PMAP_ENTER_NOREPLACE) != 0) {
                          pdpg->wire_count--;
                          CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                              " in pmap %p", va, pmap);
                          return (KERN_FAILURE);
                  }
                  /* Break the existing mapping(s). */
                  SLIST_INIT(&free);
                  if ((oldpde & PG_PS) != 0) {
                          /*
                           * The reference to the PD page that was acquired by
                           * pmap_allocpde() ensures that it won't be freed.
                           * However, if the PDE resulted from a promotion, then
                           * a reserved PT page could be freed.
                           */
                          (void)pmap_remove_pde(pmap, pde, va, &free, lockp);
                          if ((oldpde & PG_G) == 0)
                                  pmap_invalidate_pde_page(pmap, va, oldpde);
                  } else {
                          pmap_delayed_invl_started();
                          if (pmap_remove_ptes(pmap, va, va + NBPDR, pde, &free,
                              lockp))
                                 pmap_invalidate_all(pmap);
                          pmap_delayed_invl_finished();
                  }
                  vm_page_free_pages_toq(&free, true);
                  if (va >= VM_MAXUSER_ADDRESS) {
                          mt = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
                          if (pmap_insert_pt_page(pmap, mt)) {
                                  /*
                                   * XXX Currently, this can't happen because
                                   * we do not perform pmap_enter(psind == 1)
                                   * on the kernel pmap.
                                   */
                                  panic("pmap_enter_pde: trie insert failed");
                          }
                  } else
                          KASSERT(*pde == 0, ("pmap_enter_pde: non-zero pde %p",
                              pde));
          }
          if ((newpde & PG_MANAGED) != 0) {
                  /*
                   * Abort this mapping if its PV entry could not be created.
                   */
                  if (!pmap_pv_insert_pde(pmap, va, newpde, flags, lockp)) {
                          SLIST_INIT(&free);
                          if (pmap_unwire_ptp(pmap, va, pdpg, &free)) {
                                  /*
                                   * Although "va" is not mapped, paging-
                                   * structure caches could nonetheless have
                                   * entries that refer to the freed page table
                                   * pages.  Invalidate those entries.
                                   */
                                  pmap_invalidate_page(pmap, va);
                                  vm_page_free_pages_toq(&free, true);
                          }
                          CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                              " in pmap %p", va, pmap);
                          return (KERN_RESOURCE_SHORTAGE);
                  }
                  if ((newpde & PG_RW) != 0) {
                          for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                  vm_page_aflag_set(mt, PGA_WRITEABLE);
                  }
          }
  
          /*
           * Increment counters.
           */
          if ((newpde & PG_W) != 0)
                  pmap->pm_stats.wired_count += NBPDR / PAGE_SIZE;
          pmap_resident_count_inc(pmap, NBPDR / PAGE_SIZE);
  
          /*
           * Map the superpage.  (This is not a promoted mapping; there will not
           * be any lingering 4KB page mappings in the TLB.)
           */
          pde_store(pde, newpde);
  
          atomic_add_long(&pmap_pde_mappings, 1);
          CTR2(KTR_PMAP, "pmap_enter_pde: success for va %#lx"
              " in pmap %p", va, pmap);
          return (KERN_SUCCESS);
  }
  
  /*
   * Maps a sequence of resident pages belonging to the same object.
   * The sequence begins with the given page m_start.  This page is
   * mapped at the given virtual address start.  Each subsequent page is
   * mapped at a virtual address that is offset from start by the same
   * amount as the page is offset from m_start within the object.  The
   * last page in the sequence is the page with the largest offset from
   * m_start that can be mapped at a virtual address less than the given
   * virtual address end.  Not every virtual page between start and end
   * is mapped; only those for which a resident page exists with the
   * corresponding offset from m_start are mapped.
   */
  void
  pmap_enter_object(pmap_t pmap, vm_offset_t start, vm_offset_t end,
      vm_page_t m_start, vm_prot_t prot)
  {
          struct rwlock *lock;
          vm_offset_t va;
          vm_page_t m, mpte;
          vm_pindex_t diff, psize;
  
          VM_OBJECT_ASSERT_LOCKED(m_start->object);
  
          psize = atop(end - start);
          mpte = NULL;
          m = m_start;
          lock = NULL;
          PMAP_LOCK(pmap);
          while (m != NULL && (diff = m->pindex - m_start->pindex) < psize) {
                  va = start + ptoa(diff);
                  if ((va & PDRMASK) == 0 && va + NBPDR <= end &&
                      m->psind == 1 && pmap_ps_enabled(pmap) &&
                      pmap_enter_2mpage(pmap, va, m, prot, &lock))
                          m = &m[NBPDR / PAGE_SIZE - 1];
                  else
                          mpte = pmap_enter_quick_locked(pmap, va, m, prot,
                              mpte, &lock);
                  m = TAILQ_NEXT(m, listq);
          }
          if (lock != NULL)
                  rw_wunlock(lock);
          PMAP_UNLOCK(pmap);
  }
  
  /*
   * this code makes some *MAJOR* assumptions:
   * 1. Current pmap & pmap exists.
   * 2. Not wired.
   * 3. Read access.
   * 4. No page table pages.
   * but is *MUCH* faster than pmap_enter...
   */
  
  void
  pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
  {
          struct rwlock *lock;
  
          lock = NULL;
          PMAP_LOCK(pmap);
          (void)pmap_enter_quick_locked(pmap, va, m, prot, NULL, &lock);
          if (lock != NULL)
                  rw_wunlock(lock);
          PMAP_UNLOCK(pmap);
  }
  
  static vm_page_t
  pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, vm_page_t m,
      vm_prot_t prot, vm_page_t mpte, struct rwlock **lockp)
  {
          struct spglist free;
          pt_entry_t newpte, *pte, PG_V;
  
          KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
              (m->oflags & VPO_UNMANAGED) != 0,
              ("pmap_enter_quick_locked: managed mapping within the clean submap"));
          PG_V = pmap_valid_bit(pmap);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
  
          /*
           * In the case that a page table page is not
           * resident, we are creating it here.
           */
          if (va < VM_MAXUSER_ADDRESS) {
                  vm_pindex_t ptepindex;
                  pd_entry_t *ptepa;
  
                  /*
                   * Calculate pagetable page index
                   */
                  ptepindex = pmap_pde_pindex(va);
                  if (mpte && (mpte->pindex == ptepindex)) {
                          mpte->wire_count++;
                  } else {
                          /*
                           * Get the page directory entry
                           */
                          ptepa = pmap_pde(pmap, va);
  
                          /*
                           * If the page table page is mapped, we just increment
                           * the hold count, and activate it.  Otherwise, we
                           * attempt to allocate a page table page.  If this
                           * attempt fails, we don't retry.  Instead, we give up.
                           */
                          if (ptepa && (*ptepa & PG_V) != 0) {
                                  if (*ptepa & PG_PS)
                                          return (NULL);
                                  mpte = PHYS_TO_VM_PAGE(*ptepa & PG_FRAME);
                                  mpte->wire_count++;
                          } else {
                                  /*
                                   * Pass NULL instead of the PV list lock
                                   * pointer, because we don't intend to sleep.
                                   */
                                  mpte = _pmap_allocpte(pmap, ptepindex, NULL);
                                  if (mpte == NULL)
                                          return (mpte);
                          }
                  }
                  pte = (pt_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mpte));
                  pte = &pte[pmap_pte_index(va)];
          } else {
                  mpte = NULL;
                  pte = vtopte(va);
          }
          if (*pte) {
                  if (mpte != NULL) {
                          mpte->wire_count--;
                          mpte = NULL;
                  }
                  return (mpte);
          }
  
          /*
           * Enter on the PV list if part of our managed memory.
           */
          if ((m->oflags & VPO_UNMANAGED) == 0 &&
              !pmap_try_insert_pv_entry(pmap, va, m, lockp)) {
                  if (mpte != NULL) {
                          SLIST_INIT(&free);
                          if (pmap_unwire_ptp(pmap, va, mpte, &free)) {
                                  /*
                                   * Although "va" is not mapped, paging-
                                   * structure caches could nonetheless have
                                   * entries that refer to the freed page table
                                   * pages.  Invalidate those entries.
                                   */
                                  pmap_invalidate_page(pmap, va);
                                  vm_page_free_pages_toq(&free, true);
                          }
                          mpte = NULL;
                  }
                  return (mpte);
          }
  
          /*
           * Increment counters
           */
          pmap_resident_count_inc(pmap, 1);
  
          newpte = VM_PAGE_TO_PHYS(m) | PG_V |
              pmap_cache_bits(pmap, m->md.pat_mode, 0);
          if ((m->oflags & VPO_UNMANAGED) == 0)
                  newpte |= PG_MANAGED;
          if ((prot & VM_PROT_EXECUTE) == 0)
                  newpte |= pg_nx;
          if (va < VM_MAXUSER_ADDRESS)
                  newpte |= PG_U | pmap_pkru_get(pmap, va);
          pte_store(pte, newpte);
          return (mpte);
  }
  
  /*
   * Make a temporary mapping for a physical address.  This is only intended
   * to be used for panic dumps.
   */
  void *
  pmap_kenter_temporary(vm_paddr_t pa, int i)
  {
          vm_offset_t va;
  
          va = (vm_offset_t)crashdumpmap + (i * PAGE_SIZE);
          pmap_kenter(va, pa);
          invlpg(va);
          return ((void *)crashdumpmap);
  }
  
  /*
   * This code maps large physical mmap regions into the
   * processor address space.  Note that some shortcuts
   * are taken, but the code works.
   */
  void
  pmap_object_init_pt(pmap_t pmap, vm_offset_t addr, vm_object_t object,
      vm_pindex_t pindex, vm_size_t size)
  {
          pd_entry_t *pde;
          pt_entry_t PG_A, PG_M, PG_RW, PG_V;
          vm_paddr_t pa, ptepa;
          vm_page_t p, pdpg;
          int pat_mode;
  
          PG_A = pmap_accessed_bit(pmap);
          PG_M = pmap_modified_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
  
          VM_OBJECT_ASSERT_WLOCKED(object);
          KASSERT(object->type == OBJT_DEVICE || object->type == OBJT_SG,
              ("pmap_object_init_pt: non-device object"));
          if ((addr & (NBPDR - 1)) == 0 && (size & (NBPDR - 1)) == 0) {
                  if (!pmap_ps_enabled(pmap))
                          return;
                  if (!vm_object_populate(object, pindex, pindex + atop(size)))
                          return;
                  p = vm_page_lookup(object, pindex);
                  KASSERT(p->valid == VM_PAGE_BITS_ALL,
                      ("pmap_object_init_pt: invalid page %p", p));
                  pat_mode = p->md.pat_mode;
  
                  /*
                   * Abort the mapping if the first page is not physically
                   * aligned to a 2MB page boundary.
                   */
                  ptepa = VM_PAGE_TO_PHYS(p);
                  if (ptepa & (NBPDR - 1))
                          return;
  
                  /*
                   * Skip the first page.  Abort the mapping if the rest of
                   * the pages are not physically contiguous or have differing
                   * memory attributes.
                   */
                  p = TAILQ_NEXT(p, listq);
                  for (pa = ptepa + PAGE_SIZE; pa < ptepa + size;
                      pa += PAGE_SIZE) {
                          KASSERT(p->valid == VM_PAGE_BITS_ALL,
                              ("pmap_object_init_pt: invalid page %p", p));
                          if (pa != VM_PAGE_TO_PHYS(p) ||
                              pat_mode != p->md.pat_mode)
                                  return;
                          p = TAILQ_NEXT(p, listq);
                  }
  
                  /*
                   * Map using 2MB pages.  Since "ptepa" is 2M aligned and
                   * "size" is a multiple of 2M, adding the PAT setting to "pa"
                   * will not affect the termination of this loop.
                   */ 
                  PMAP_LOCK(pmap);
                  for (pa = ptepa | pmap_cache_bits(pmap, pat_mode, 1);
                      pa < ptepa + size; pa += NBPDR) {
                          pdpg = pmap_allocpde(pmap, addr, NULL);
                          if (pdpg == NULL) {
                                  /*
                                   * The creation of mappings below is only an
                                   * optimization.  If a page directory page
                                   * cannot be allocated without blocking,
                                   * continue on to the next mapping rather than
                                   * blocking.
                                   */
                                  addr += NBPDR;
                                  continue;
                          }
                          pde = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pdpg));
                          pde = &pde[pmap_pde_index(addr)];
                          if ((*pde & PG_V) == 0) {
                                  pde_store(pde, pa | PG_PS | PG_M | PG_A |
                                      PG_U | PG_RW | PG_V);
                                  pmap_resident_count_inc(pmap, NBPDR / PAGE_SIZE);
                                  atomic_add_long(&pmap_pde_mappings, 1);
                          } else {
                                  /* Continue on if the PDE is already valid. */
                                  pdpg->wire_count--;
                                  KASSERT(pdpg->wire_count > 0,
                                      ("pmap_object_init_pt: missing reference "
                                      "to page directory page, va: 0x%lx", addr));
                          }
                          addr += NBPDR;
                  }
                  PMAP_UNLOCK(pmap);
          }
  }
  
  /*
   *      Clear the wired attribute from the mappings for the specified range of
   *      addresses in the given pmap.  Every valid mapping within that range
   *      must have the wired attribute set.  In contrast, invalid mappings
   *      cannot have the wired attribute set, so they are ignored.
   *
   *      The wired attribute of the page table entry is not a hardware
   *      feature, so there is no need to invalidate any TLB entries.
   *      Since pmap_demote_pde() for the wired entry must never fail,
   *      pmap_delayed_invl_started()/finished() calls around the
   *      function are not needed.
   */
  void
  pmap_unwire(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
          vm_offset_t va_next;
          pml4_entry_t *pml4e;
          pdp_entry_t *pdpe;
          pd_entry_t *pde;
          pt_entry_t *pte, PG_V;
  
          PG_V = pmap_valid_bit(pmap);
          PMAP_LOCK(pmap);
          for (; sva < eva; sva = va_next) {
                  pml4e = pmap_pml4e(pmap, sva);
                  if ((*pml4e & PG_V) == 0) {
                          va_next = (sva + NBPML4) & ~PML4MASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
                  pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
                  if ((*pdpe & PG_V) == 0) {
                          va_next = (sva + NBPDP) & ~PDPMASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
                  va_next = (sva + NBPDR) & ~PDRMASK;
                  if (va_next < sva)
                          va_next = eva;
                  pde = pmap_pdpe_to_pde(pdpe, sva);
                  if ((*pde & PG_V) == 0)
                          continue;
                  if ((*pde & PG_PS) != 0) {
                          if ((*pde & PG_W) == 0)
                                  panic("pmap_unwire: pde %#jx is missing PG_W",
                                      (uintmax_t)*pde);
  
                          /*
                           * Are we unwiring the entire large page?  If not,
                           * demote the mapping and fall through.
                           */
                          if (sva + NBPDR == va_next && eva >= va_next) {
                                  atomic_clear_long(pde, PG_W);
                                  pmap->pm_stats.wired_count -= NBPDR /
                                      PAGE_SIZE;
                                  continue;
                          } else if (!pmap_demote_pde(pmap, pde, sva))
                                  panic("pmap_unwire: demotion failed");
                  }
                  if (va_next > eva)
                          va_next = eva;
                  for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
                      sva += PAGE_SIZE) {
                          if ((*pte & PG_V) == 0)
                                  continue;
                          if ((*pte & PG_W) == 0)
                                  panic("pmap_unwire: pte %#jx is missing PG_W",
                                      (uintmax_t)*pte);
  
                          /*
                           * PG_W must be cleared atomically.  Although the pmap
                           * lock synchronizes access to PG_W, another processor
                           * could be setting PG_M and/or PG_A concurrently.
                           */
                          atomic_clear_long(pte, PG_W);
                          pmap->pm_stats.wired_count--;
                  }
          }
          PMAP_UNLOCK(pmap);
  }
  
  /*
   *      Copy the range specified by src_addr/len
   *      from the source map to the range dst_addr/len
   *      in the destination map.
   *
   *      This routine is only advisory and need not do anything.
   */
  
  void
  pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len,
      vm_offset_t src_addr)
  {
          struct rwlock *lock;
          struct spglist free;
          vm_offset_t addr;
          vm_offset_t end_addr = src_addr + len;
          vm_offset_t va_next;
          vm_page_t dst_pdpg, dstmpte, srcmpte;
          pt_entry_t PG_A, PG_M, PG_V;
  
          if (dst_addr != src_addr)
                  return;
  
          if (dst_pmap->pm_type != src_pmap->pm_type)
                  return;
  
          /*
           * EPT page table entries that require emulation of A/D bits are
           * sensitive to clearing the PG_A bit (aka EPT_PG_READ). Although
           * we clear PG_M (aka EPT_PG_WRITE) concomitantly, the PG_U bit
           * (aka EPT_PG_EXECUTE) could still be set. Since some EPT
           * implementations flag an EPT misconfiguration for exec-only
           * mappings we skip this function entirely for emulated pmaps.
           */
          if (pmap_emulate_ad_bits(dst_pmap))
                  return;
  
          lock = NULL;
          if (dst_pmap < src_pmap) {
                  PMAP_LOCK(dst_pmap);
                  PMAP_LOCK(src_pmap);
          } else {
                  PMAP_LOCK(src_pmap);
                  PMAP_LOCK(dst_pmap);
          }
  
          PG_A = pmap_accessed_bit(dst_pmap);
          PG_M = pmap_modified_bit(dst_pmap);
          PG_V = pmap_valid_bit(dst_pmap);
  
          for (addr = src_addr; addr < end_addr; addr = va_next) {
                  pt_entry_t *src_pte, *dst_pte;
                  pml4_entry_t *pml4e;
                  pdp_entry_t *pdpe;
                  pd_entry_t srcptepaddr, *pde;
  
                  KASSERT(addr < UPT_MIN_ADDRESS,
                      ("pmap_copy: invalid to pmap_copy page tables"));
  
                  pml4e = pmap_pml4e(src_pmap, addr);
                  if ((*pml4e & PG_V) == 0) {
                          va_next = (addr + NBPML4) & ~PML4MASK;
                          if (va_next < addr)
                                  va_next = end_addr;
                          continue;
                  }
  
                  pdpe = pmap_pml4e_to_pdpe(pml4e, addr);
                  if ((*pdpe & PG_V) == 0) {
                          va_next = (addr + NBPDP) & ~PDPMASK;
                          if (va_next < addr)
                                  va_next = end_addr;
                          continue;
                  }
  
                  va_next = (addr + NBPDR) & ~PDRMASK;
                  if (va_next < addr)
                          va_next = end_addr;
  
                  pde = pmap_pdpe_to_pde(pdpe, addr);
                  srcptepaddr = *pde;
                  if (srcptepaddr == 0)
                          continue;
                          
                  if (srcptepaddr & PG_PS) {
                          if ((addr & PDRMASK) != 0 || addr + NBPDR > end_addr)
                                  continue;
                          dst_pdpg = pmap_allocpde(dst_pmap, addr, NULL);
                          if (dst_pdpg == NULL)
                                  break;
                          pde = (pd_entry_t *)
                              PHYS_TO_DMAP(VM_PAGE_TO_PHYS(dst_pdpg));
                          pde = &pde[pmap_pde_index(addr)];
                          if (*pde == 0 && ((srcptepaddr & PG_MANAGED) == 0 ||
                              pmap_pv_insert_pde(dst_pmap, addr, srcptepaddr,
                              PMAP_ENTER_NORECLAIM, &lock))) {
                                  *pde = srcptepaddr & ~PG_W;
                                  pmap_resident_count_inc(dst_pmap, NBPDR / PAGE_SIZE);
                                  atomic_add_long(&pmap_pde_mappings, 1);
                          } else
                                  dst_pdpg->wire_count--;
                          continue;
                  }
  
                  srcptepaddr &= PG_FRAME;
                  srcmpte = PHYS_TO_VM_PAGE(srcptepaddr);
                  KASSERT(srcmpte->wire_count > 0,
                      ("pmap_copy: source page table page is unused"));
  
                  if (va_next > end_addr)
                          va_next = end_addr;
  
                  src_pte = (pt_entry_t *)PHYS_TO_DMAP(srcptepaddr);
                  src_pte = &src_pte[pmap_pte_index(addr)];
                  dstmpte = NULL;
                  while (addr < va_next) {
                          pt_entry_t ptetemp;
                          ptetemp = *src_pte;
                          /*
                           * we only virtual copy managed pages
                           */
                          if ((ptetemp & PG_MANAGED) != 0) {
                                  if (dstmpte != NULL &&
                                      dstmpte->pindex == pmap_pde_pindex(addr))
                                          dstmpte->wire_count++;
                                  else if ((dstmpte = pmap_allocpte(dst_pmap,
                                      addr, NULL)) == NULL)
                                          goto out;
                                  dst_pte = (pt_entry_t *)
                                      PHYS_TO_DMAP(VM_PAGE_TO_PHYS(dstmpte));
                                  dst_pte = &dst_pte[pmap_pte_index(addr)];
                                  if (*dst_pte == 0 &&
                                      pmap_try_insert_pv_entry(dst_pmap, addr,
                                      PHYS_TO_VM_PAGE(ptetemp & PG_FRAME),
                                      &lock)) {
                                          /*
                                           * Clear the wired, modified, and
                                           * accessed (referenced) bits
                                           * during the copy.
                                           */
                                          *dst_pte = ptetemp & ~(PG_W | PG_M |
                                              PG_A);
                                          pmap_resident_count_inc(dst_pmap, 1);
                                  } else {
                                          SLIST_INIT(&free);
                                          if (pmap_unwire_ptp(dst_pmap, addr,
                                              dstmpte, &free)) {
                                                  /*
                                                   * Although "addr" is not
                                                   * mapped, paging-structure
                                                   * caches could nonetheless
                                                   * have entries that refer to
                                                   * the freed page table pages.
                                                   * Invalidate those entries.
                                                   */
                                                  pmap_invalidate_page(dst_pmap,
                                                      addr);
                                                  vm_page_free_pages_toq(&free,
                                                      true);
                                          }
                                          goto out;
                                  }
                                  if (dstmpte->wire_count >= srcmpte->wire_count)
                                          break;
                          }
                          addr += PAGE_SIZE;
                          src_pte++;
                  }
          }
  out:
          if (lock != NULL)
                  rw_wunlock(lock);
          PMAP_UNLOCK(src_pmap);
          PMAP_UNLOCK(dst_pmap);
  }
  
  int
  pmap_vmspace_copy(pmap_t dst_pmap, pmap_t src_pmap)
  {
          int error;
  
          if (dst_pmap->pm_type != src_pmap->pm_type ||
              dst_pmap->pm_type != PT_X86 ||
              (cpu_stdext_feature2 & CPUID_STDEXT2_PKU) == 0)
                  return (0);
          for (;;) {
                  if (dst_pmap < src_pmap) {
                          PMAP_LOCK(dst_pmap);
                          PMAP_LOCK(src_pmap);
                  } else {
                          PMAP_LOCK(src_pmap);
                          PMAP_LOCK(dst_pmap);
                  }
                  error = pmap_pkru_copy(dst_pmap, src_pmap);
                  /* Clean up partial copy on failure due to no memory. */
                  if (error == ENOMEM)
                          pmap_pkru_deassign_all(dst_pmap);
                  PMAP_UNLOCK(src_pmap);
                  PMAP_UNLOCK(dst_pmap);
                  if (error != ENOMEM)
                          break;
                  vm_wait(NULL);
          }
          return (error);
  }
  
  /*
   * Zero the specified hardware page.
   */
  void
  pmap_zero_page(vm_page_t m)
  {
          vm_offset_t va = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));
  
          pagezero((void *)va);
  }
  
  /*
   * Zero an an area within a single hardware page.  off and size must not
   * cover an area beyond a single hardware page.
   */
  void
  pmap_zero_page_area(vm_page_t m, int off, int size)
  {
          vm_offset_t va = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));
  
          if (off == 0 && size == PAGE_SIZE)
                  pagezero((void *)va);
          else
                  bzero((char *)va + off, size);
  }
  
  /*
   * Copy 1 specified hardware page to another.
   */
  void
  pmap_copy_page(vm_page_t msrc, vm_page_t mdst)
  {
          vm_offset_t src = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(msrc));
          vm_offset_t dst = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mdst));
  
          pagecopy((void *)src, (void *)dst);
  }
  
  int unmapped_buf_allowed = 1;
  
  void
  pmap_copy_pages(vm_page_t ma[], vm_offset_t a_offset, vm_page_t mb[],
      vm_offset_t b_offset, int xfersize)
  {
          void *a_cp, *b_cp;
          vm_page_t pages[2];
          vm_offset_t vaddr[2], a_pg_offset, b_pg_offset;
          int cnt;
          boolean_t mapped;
  
          while (xfersize > 0) {
                  a_pg_offset = a_offset & PAGE_MASK;
                  pages[0] = ma[a_offset >> PAGE_SHIFT];
                  b_pg_offset = b_offset & PAGE_MASK;
                  pages[1] = mb[b_offset >> PAGE_SHIFT];
                  cnt = min(xfersize, PAGE_SIZE - a_pg_offset);
                  cnt = min(cnt, PAGE_SIZE - b_pg_offset);
                  mapped = pmap_map_io_transient(pages, vaddr, 2, FALSE);
                  a_cp = (char *)vaddr[0] + a_pg_offset;
                  b_cp = (char *)vaddr[1] + b_pg_offset;
                  bcopy(a_cp, b_cp, cnt);
                  if (__predict_false(mapped))
                          pmap_unmap_io_transient(pages, vaddr, 2, FALSE);
                  a_offset += cnt;
                  b_offset += cnt;
                  xfersize -= cnt;
          }
  }
  
  /*
   * Returns true if the pmap's pv is one of the first
   * 16 pvs linked to from this page.  This count may
   * be changed upwards or downwards in the future; it
   * is only necessary that true be returned for a small
   * subset of pmaps for proper page aging.
   */
  boolean_t
  pmap_page_exists_quick(pmap_t pmap, vm_page_t m)
  {
          struct md_page *pvh;
          struct rwlock *lock;
          pv_entry_t pv;
          int loops = 0;
          boolean_t rv;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_page_exists_quick: page %p is not managed", m));
          rv = FALSE;
          lock = VM_PAGE_TO_PV_LIST_LOCK(m);
          rw_rlock(lock);
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                  if (PV_PMAP(pv) == pmap) {
                          rv = TRUE;
                          break;
                  }
                  loops++;
                  if (loops >= 16)
                          break;
          }
          if (!rv && loops < 16 && (m->flags & PG_FICTITIOUS) == 0) {
                  pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                  TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                          if (PV_PMAP(pv) == pmap) {
                                  rv = TRUE;
                                  break;
                          }
                          loops++;
                          if (loops >= 16)
                                  break;
                  }
          }
          rw_runlock(lock);
          return (rv);
  }
  
  /*
   *      pmap_page_wired_mappings:
   *
   *      Return the number of managed mappings to the given physical page
   *      that are wired.
   */
  int
  pmap_page_wired_mappings(vm_page_t m)
  {
          struct rwlock *lock;
          struct md_page *pvh;
          pmap_t pmap;
          pt_entry_t *pte;
          pv_entry_t pv;
          int count, md_gen, pvh_gen;
  
          if ((m->oflags & VPO_UNMANAGED) != 0)
                  return (0);
          lock = VM_PAGE_TO_PV_LIST_LOCK(m);
          rw_rlock(lock);
  restart:
          count = 0;
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  if (!PMAP_TRYLOCK(pmap)) {
                          md_gen = m->md.pv_gen;
                          rw_runlock(lock);
                          PMAP_LOCK(pmap);
                          rw_rlock(lock);
                          if (md_gen != m->md.pv_gen) {
                                  PMAP_UNLOCK(pmap);
                                  goto restart;
                          }
                  }
                  pte = pmap_pte(pmap, pv->pv_va);
                  if ((*pte & PG_W) != 0)
                          count++;
                  PMAP_UNLOCK(pmap);
          }
          if ((m->flags & PG_FICTITIOUS) == 0) {
                  pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                  TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                          pmap = PV_PMAP(pv);
                          if (!PMAP_TRYLOCK(pmap)) {
                                  md_gen = m->md.pv_gen;
                                  pvh_gen = pvh->pv_gen;
                                  rw_runlock(lock);
                                  PMAP_LOCK(pmap);
                                  rw_rlock(lock);
                                  if (md_gen != m->md.pv_gen ||
                                      pvh_gen != pvh->pv_gen) {
                                          PMAP_UNLOCK(pmap);
                                          goto restart;
                                  }
                          }
                          pte = pmap_pde(pmap, pv->pv_va);
                          if ((*pte & PG_W) != 0)
                                  count++;
                          PMAP_UNLOCK(pmap);
                  }
          }
          rw_runlock(lock);
          return (count);
  }
  
  /*
   * Returns TRUE if the given page is mapped individually or as part of
   * a 2mpage.  Otherwise, returns FALSE.
   */
  boolean_t
  pmap_page_is_mapped(vm_page_t m)
  {
          struct rwlock *lock;
          boolean_t rv;
  
          if ((m->oflags & VPO_UNMANAGED) != 0)
                  return (FALSE);
          lock = VM_PAGE_TO_PV_LIST_LOCK(m);
          rw_rlock(lock);
          rv = !TAILQ_EMPTY(&m->md.pv_list) ||
              ((m->flags & PG_FICTITIOUS) == 0 &&
              !TAILQ_EMPTY(&pa_to_pvh(VM_PAGE_TO_PHYS(m))->pv_list));
          rw_runlock(lock);
          return (rv);
  }
  
  /*
   * Destroy all managed, non-wired mappings in the given user-space
   * pmap.  This pmap cannot be active on any processor besides the
   * caller.
   *
   * This function cannot be applied to the kernel pmap.  Moreover, it
   * is not intended for general use.  It is only to be used during
   * process termination.  Consequently, it can be implemented in ways
   * that make it faster than pmap_remove().  First, it can more quickly
   * destroy mappings by iterating over the pmap's collection of PV
   * entries, rather than searching the page table.  Second, it doesn't
   * have to test and clear the page table entries atomically, because
   * no processor is currently accessing the user address space.  In
   * particular, a page table entry's dirty bit won't change state once
   * this function starts.
   *
   * Although this function destroys all of the pmap's managed,
   * non-wired mappings, it can delay and batch the invalidation of TLB
   * entries without calling pmap_delayed_invl_started() and
   * pmap_delayed_invl_finished().  Because the pmap is not active on
   * any other processor, none of these TLB entries will ever be used
   * before their eventual invalidation.  Consequently, there is no need
   * for either pmap_remove_all() or pmap_remove_write() to wait for
   * that eventual TLB invalidation.
   */
  void
  pmap_remove_pages(pmap_t pmap)
  {
          pd_entry_t ptepde;
          pt_entry_t *pte, tpte;
          pt_entry_t PG_M, PG_RW, PG_V;
          struct spglist free;
          vm_page_t m, mpte, mt;
          pv_entry_t pv;
          struct md_page *pvh;
          struct pv_chunk *pc, *npc;
          struct rwlock *lock;
          int64_t bit;
          uint64_t inuse, bitmask;
          int allfree, field, freed, idx;
          boolean_t superpage;
          vm_paddr_t pa;
  
          /*
           * Assert that the given pmap is only active on the current
           * CPU.  Unfortunately, we cannot block another CPU from
           * activating the pmap while this function is executing.
           */
          KASSERT(pmap == PCPU_GET(curpmap), ("non-current pmap %p", pmap));
  #ifdef INVARIANTS
          {
                  cpuset_t other_cpus;
  
                  other_cpus = all_cpus;
                  critical_enter();
                  CPU_CLR(PCPU_GET(cpuid), &other_cpus);
                  CPU_AND(&other_cpus, &pmap->pm_active);
                  critical_exit();
                  KASSERT(CPU_EMPTY(&other_cpus), ("pmap active %p", pmap));
          }
  #endif
  
          lock = NULL;
          PG_M = pmap_modified_bit(pmap);
          PG_V = pmap_valid_bit(pmap);
          PG_RW = pmap_rw_bit(pmap);
  
          SLIST_INIT(&free);
          PMAP_LOCK(pmap);
          TAILQ_FOREACH_SAFE(pc, &pmap->pm_pvchunk, pc_list, npc) {
                  allfree = 1;
                  freed = 0;
                  for (field = 0; field < _NPCM; field++) {
                          inuse = ~pc->pc_map[field] & pc_freemask[field];
                          while (inuse != 0) {
                                  bit = bsfq(inuse);
                                  bitmask = 1UL << bit;
                                  idx = field * 64 + bit;
                                  pv = &pc->pc_pventry[idx];
                                  inuse &= ~bitmask;
  
                                  pte = pmap_pdpe(pmap, pv->pv_va);
                                  ptepde = *pte;
                                  pte = pmap_pdpe_to_pde(pte, pv->pv_va);
                                  tpte = *pte;
                                  if ((tpte & (PG_PS | PG_V)) == PG_V) {
                                          superpage = FALSE;
                                          ptepde = tpte;
                                          pte = (pt_entry_t *)PHYS_TO_DMAP(tpte &
                                              PG_FRAME);
                                          pte = &pte[pmap_pte_index(pv->pv_va)];
                                          tpte = *pte;
                                  } else {
                                          /*
                                           * Keep track whether 'tpte' is a
                                           * superpage explicitly instead of
                                           * relying on PG_PS being set.
                                           *
                                           * This is because PG_PS is numerically
                                           * identical to PG_PTE_PAT and thus a
                                           * regular page could be mistaken for
                                           * a superpage.
                                           */
                                          superpage = TRUE;
                                  }
  
                                  if ((tpte & PG_V) == 0) {
                                          panic("bad pte va %lx pte %lx",
                                              pv->pv_va, tpte);
                                  }
  
  /*
   * We cannot remove wired pages from a process' mapping at this time
   */
                                  if (tpte & PG_W) {
                                          allfree = 0;
                                          continue;
                                  }
  
                                  if (superpage)
                                          pa = tpte & PG_PS_FRAME;
                                  else
                                          pa = tpte & PG_FRAME;
  
                                  m = PHYS_TO_VM_PAGE(pa);
                                  KASSERT(m->phys_addr == pa,
                                      ("vm_page_t %p phys_addr mismatch %016jx %016jx",
                                      m, (uintmax_t)m->phys_addr,
                                      (uintmax_t)tpte));
  
                                  KASSERT((m->flags & PG_FICTITIOUS) != 0 ||
                                      m < &vm_page_array[vm_page_array_size],
                                      ("pmap_remove_pages: bad tpte %#jx",
                                      (uintmax_t)tpte));
  
                                  pte_clear(pte);
  
                                  /*
                                   * Update the vm_page_t clean/reference bits.
                                   */
                                  if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                          if (superpage) {
                                                  for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                          vm_page_dirty(mt);
                                          } else
                                                  vm_page_dirty(m);
                                  }
  
                                  CHANGE_PV_LIST_LOCK_TO_VM_PAGE(&lock, m);
  
                                  /* Mark free */
                                  pc->pc_map[field] |= bitmask;
                                  if (superpage) {
                                          pmap_resident_count_dec(pmap, NBPDR / PAGE_SIZE);
                                          pvh = pa_to_pvh(tpte & PG_PS_FRAME);
                                          TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                                          pvh->pv_gen++;
                                          if (TAILQ_EMPTY(&pvh->pv_list)) {
                                                  for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                          if ((mt->aflags & PGA_WRITEABLE) != 0 &&
                                                              TAILQ_EMPTY(&mt->md.pv_list))
                                                                  vm_page_aflag_clear(mt, PGA_WRITEABLE);
                                          }
                                          mpte = pmap_remove_pt_page(pmap, pv->pv_va);
                                          if (mpte != NULL) {
                                                  pmap_resident_count_dec(pmap, 1);
                                                  KASSERT(mpte->wire_count == NPTEPG,
                                                      ("pmap_remove_pages: pte page wire count error"));
                                                  mpte->wire_count = 0;
                                                  pmap_add_delayed_free_list(mpte, &free, FALSE);
                                          }
                                  } else {
                                          pmap_resident_count_dec(pmap, 1);
                                          TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                                          m->md.pv_gen++;
                                          if ((m->aflags & PGA_WRITEABLE) != 0 &&
                                              TAILQ_EMPTY(&m->md.pv_list) &&
                                              (m->flags & PG_FICTITIOUS) == 0) {
                                                  pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                                                  if (TAILQ_EMPTY(&pvh->pv_list))
                                                          vm_page_aflag_clear(m, PGA_WRITEABLE);
                                          }
                                  }
                                  pmap_unuse_pt(pmap, pv->pv_va, ptepde, &free);
                                  freed++;
                          }
                  }
                  PV_STAT(atomic_add_long(&pv_entry_frees, freed));
                  PV_STAT(atomic_add_int(&pv_entry_spare, freed));
                  PV_STAT(atomic_subtract_long(&pv_entry_count, freed));
                  if (allfree) {
                          TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                          free_pv_chunk(pc);
                  }
          }
          if (lock != NULL)
                  rw_wunlock(lock);
          pmap_invalidate_all(pmap);
          pmap_pkru_deassign_all(pmap);
          PMAP_UNLOCK(pmap);
          vm_page_free_pages_toq(&free, true);
  }
  
  static boolean_t
  pmap_page_test_mappings(vm_page_t m, boolean_t accessed, boolean_t modified)
  {
          struct rwlock *lock;
          pv_entry_t pv;
          struct md_page *pvh;
          pt_entry_t *pte, mask;
          pt_entry_t PG_A, PG_M, PG_RW, PG_V;
          pmap_t pmap;
          int md_gen, pvh_gen;
          boolean_t rv;
  
          rv = FALSE;
          lock = VM_PAGE_TO_PV_LIST_LOCK(m);
          rw_rlock(lock);
  restart:
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  if (!PMAP_TRYLOCK(pmap)) {
                          md_gen = m->md.pv_gen;
                          rw_runlock(lock);
                          PMAP_LOCK(pmap);
                          rw_rlock(lock);
                          if (md_gen != m->md.pv_gen) {
                                  PMAP_UNLOCK(pmap);
                                  goto restart;
                          }
                  }
                  pte = pmap_pte(pmap, pv->pv_va);
                  mask = 0;
                  if (modified) {
                          PG_M = pmap_modified_bit(pmap);
                          PG_RW = pmap_rw_bit(pmap);
                          mask |= PG_RW | PG_M;
                  }
                  if (accessed) {
                          PG_A = pmap_accessed_bit(pmap);
                          PG_V = pmap_valid_bit(pmap);
                          mask |= PG_V | PG_A;
                  }
                  rv = (*pte & mask) == mask;
                  PMAP_UNLOCK(pmap);
                  if (rv)
                          goto out;
          }
          if ((m->flags & PG_FICTITIOUS) == 0) {
                  pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                  TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                          pmap = PV_PMAP(pv);
                          if (!PMAP_TRYLOCK(pmap)) {
                                  md_gen = m->md.pv_gen;
                                  pvh_gen = pvh->pv_gen;
                                  rw_runlock(lock);
                                  PMAP_LOCK(pmap);
                                  rw_rlock(lock);
                                  if (md_gen != m->md.pv_gen ||
                                      pvh_gen != pvh->pv_gen) {
                                          PMAP_UNLOCK(pmap);
                                          goto restart;
                                  }
                          }
                          pte = pmap_pde(pmap, pv->pv_va);
                          mask = 0;
                          if (modified) {
                                  PG_M = pmap_modified_bit(pmap);
                                  PG_RW = pmap_rw_bit(pmap);
                                  mask |= PG_RW | PG_M;
                          }
                          if (accessed) {
                                  PG_A = pmap_accessed_bit(pmap);
                                  PG_V = pmap_valid_bit(pmap);
                                  mask |= PG_V | PG_A;
                          }
                          rv = (*pte & mask) == mask;
                          PMAP_UNLOCK(pmap);
                          if (rv)
                                  goto out;
                  }
          }
  out:
          rw_runlock(lock);
          return (rv);
  }
  
  /*
   *      pmap_is_modified:
   *
   *      Return whether or not the specified physical page was modified
   *      in any physical maps.
   */
  boolean_t
  pmap_is_modified(vm_page_t m)
  {
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_is_modified: page %p is not managed", m));
  
          /*
           * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
           * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
           * is clear, no PTEs can have PG_M set.
           */
          VM_OBJECT_ASSERT_WLOCKED(m->object);
          if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
                  return (FALSE);
          return (pmap_page_test_mappings(m, FALSE, TRUE));
  }
  
  /*
   *      pmap_is_prefaultable:
   *
   *      Return whether or not the specified virtual address is eligible