FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/pmap.c

     /*-
      * 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) 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.
     * 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.
     *
     * 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /*
     *      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_apic.h"
   #include "opt_cpu.h"
   #include "opt_pmap.h"
   #include "opt_smp.h"
   #include "opt_xbox.h"
   
   #include <sys/param.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/msgbuf.h>
   #include <sys/mutex.h>
   #include <sys/proc.h>
   #include <sys/rwlock.h>
   #include <sys/sf_buf.h>
   #include <sys/sx.h>
   #include <sys/vmmeter.h>
   #include <sys/sched.h>
   #include <sys/sysctl.h>
   #ifdef SMP
   #include <sys/smp.h>
   #else
   #include <sys/cpuset.h>
   #endif
   
   #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>
   
   #ifdef DEV_APIC
   #include <sys/bus.h>
   #include <machine/intr_machdep.h>
   #include <machine/apicvar.h>
   #endif
   #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
   
   #ifdef XBOX
   #include <machine/xbox.h>
   #endif
   
   #if !defined(CPU_DISABLE_SSE) && defined(I686_CPU)
   #define CPU_ENABLE_SSE
   #endif
   
   #ifndef PMAP_SHPGPERPROC
   #define PMAP_SHPGPERPROC 200
   #endif
   
   #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)])
   
   /*
    * Get PDEs and PTEs for user/kernel address space
    */
   #define pmap_pde(m, v)  (&((m)->pm_pdir[(vm_offset_t)(v) >> PDRSHIFT]))
   #define pdir_pde(m, v) (m[(vm_offset_t)(v) >> PDRSHIFT])
   
   #define pmap_pde_v(pte)         ((*(int *)pte & PG_V) != 0)
   #define pmap_pte_w(pte)         ((*(int *)pte & PG_W) != 0)
   #define pmap_pte_m(pte)         ((*(int *)pte & PG_M) != 0)
   #define pmap_pte_u(pte)         ((*(int *)pte & PG_A) != 0)
   #define pmap_pte_v(pte)         ((*(int *)pte & PG_V) != 0)
   
   #define pmap_pte_set_w(pte, v)  ((v) ? atomic_set_int((u_int *)(pte), PG_W) : \
       atomic_clear_int((u_int *)(pte), PG_W))
   #define pmap_pte_set_prot(pte, v) ((*(int *)pte &= ~PG_PROT), (*(int *)pte |= (v)))
   
   struct pmap kernel_pmap_store;
   LIST_HEAD(pmaplist, pmap);
   static struct pmaplist allpmaps;
   static struct mtx allpmaps_lock;
   
   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 pgeflag = 0;                /* PG_G or-in */
   int pseflag = 0;                /* PG_PS or-in */
   
   static int nkpt = NKPT;
   vm_offset_t kernel_vm_end = KERNBASE + NKPT * NBPDR;
   extern u_int32_t KERNend;
   extern u_int32_t KPTphys;
   
   #if defined(PAE) || defined(PAE_TABLES)
   pt_entry_t pg_nx;
   static uma_zone_t pdptzone;
   #endif
   
   static SYSCTL_NODE(_vm, OID_AUTO, pmap, CTLFLAG_RD, 0, "VM/pmap parameters");
   
   static int pat_works = 1;
   SYSCTL_INT(_vm_pmap, OID_AUTO, pat_works, CTLFLAG_RD, &pat_works, 1,
       "Is page attribute table fully functional?");
   
   static int pg_ps_enabled = 1;
   SYSCTL_INT(_vm_pmap, OID_AUTO, pg_ps_enabled, CTLFLAG_RDTUN, &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 */
   
   /*
    * 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;
   
   static struct rwlock_padalign pvh_global_lock;
   
   /*
    * Data for the pv entry allocation mechanism
    */
   static TAILQ_HEAD(pch, pv_chunk) pv_chunks = TAILQ_HEAD_INITIALIZER(pv_chunks);
   static int pv_entry_count = 0, pv_entry_max = 0, pv_entry_high_water = 0;
   static struct md_page *pv_table;
   static int shpgperproc = PMAP_SHPGPERPROC;
   
   struct pv_chunk *pv_chunkbase;          /* KVA block for pv_chunks */
   int pv_maxchunks;                       /* How many chunks we have KVA for */
   vm_offset_t pv_vafree;                  /* freelist stored in the PTE */
   
   /*
    * All those kernel PT submaps that BSD is so fond of
    */
   struct sysmaps {
           struct  mtx lock;
           pt_entry_t *CMAP1;
           pt_entry_t *CMAP2;
           caddr_t CADDR1;
           caddr_t CADDR2;
   };
   static struct sysmaps sysmaps_pcpu[MAXCPU];
   pt_entry_t *CMAP3;
   static pd_entry_t *KPTD;
   caddr_t ptvmmap = 0;
   caddr_t CADDR3;
   struct msgbuf *msgbufp = 0;
   
   /*
    * Crashdump maps.
    */
   static caddr_t crashdumpmap;
   
   static pt_entry_t *PMAP1 = 0, *PMAP2;
   static pt_entry_t *PADDR1 = 0, *PADDR2;
   #ifdef SMP
   static int PMAP1cpu;
   static int PMAP1changedcpu;
   SYSCTL_INT(_debug, OID_AUTO, PMAP1changedcpu, CTLFLAG_RD, 
              &PMAP1changedcpu, 0,
              "Number of times pmap_pte_quick changed CPU with same PMAP1");
   #endif
   static int PMAP1changed;
   SYSCTL_INT(_debug, OID_AUTO, PMAP1changed, CTLFLAG_RD, 
              &PMAP1changed, 0,
              "Number of times pmap_pte_quick changed PMAP1");
   static int PMAP1unchanged;
   SYSCTL_INT(_debug, OID_AUTO, PMAP1unchanged, CTLFLAG_RD, 
              &PMAP1unchanged, 0,
              "Number of times pmap_pte_quick didn't change PMAP1");
   static struct mtx PMAP2mutex;
   
   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, boolean_t try);
   static void     pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa);
   static boolean_t pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa);
   static void     pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa);
   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_pvh_wired_mappings(struct md_page *pvh, int count);
   
   static boolean_t pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va);
   static boolean_t pmap_enter_pde(pmap_t pmap, vm_offset_t va, vm_page_t m,
       vm_prot_t prot);
   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);
   static void pmap_flush_page(vm_page_t m);
   static int pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte);
   static void pmap_invalidate_pde_page(pmap_t pmap, vm_offset_t va,
                       pd_entry_t pde);
   static void pmap_fill_ptp(pt_entry_t *firstpte, pt_entry_t newpte);
   static boolean_t pmap_is_modified_pvh(struct md_page *pvh);
   static boolean_t pmap_is_referenced_pvh(struct md_page *pvh);
   static void pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int mode);
   static void pmap_kenter_pde(vm_offset_t va, pd_entry_t newpde);
   static vm_page_t pmap_lookup_pt_page(pmap_t pmap, vm_offset_t va);
   static void pmap_pde_attr(pd_entry_t *pde, int cache_bits);
   static void pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va);
   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);
   static void pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
       struct spglist *free);
   static int pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t sva,
       struct spglist *free);
   static void pmap_remove_pt_page(pmap_t pmap, vm_page_t mpte);
   static void pmap_remove_page(struct pmap *pmap, vm_offset_t va,
       struct spglist *free);
   static void pmap_remove_entry(struct pmap *pmap, vm_page_t m,
                                           vm_offset_t va);
   static void pmap_insert_entry(pmap_t pmap, vm_offset_t va, vm_page_t m);
   static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va,
       vm_page_t m);
   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(vm_offset_t va, pd_entry_t newpde);
   
   static vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va, u_int flags);
   
   static vm_page_t _pmap_allocpte(pmap_t pmap, u_int ptepindex, u_int flags);
   static void _pmap_unwire_ptp(pmap_t pmap, vm_page_t m, struct spglist *free);
   static pt_entry_t *pmap_pte_quick(pmap_t pmap, vm_offset_t va);
   static void pmap_pte_release(pt_entry_t *pte);
   static int pmap_unuse_pt(pmap_t, vm_offset_t, struct spglist *);
   #if defined(PAE) || defined(PAE_TABLES)
   static void *pmap_pdpt_allocf(uma_zone_t zone, vm_size_t bytes, uint8_t *flags,
       int wait);
   #endif
   static void pmap_set_pg(void);
   
   static __inline void pagezero(void *page);
   
   CTASSERT(1 << PDESHIFT == sizeof(pd_entry_t));
   CTASSERT(1 << PTESHIFT == sizeof(pt_entry_t));
   
   /*
    * If you get an error here, then you set KVA_PAGES wrong! See the
    * description of KVA_PAGES in sys/i386/include/pmap.h. It must be
    * multiple of 4 for a normal kernel, or a multiple of 8 for a PAE.
    */
   CTASSERT(KERNBASE % (1 << 24) == 0);
   
   /*
    *      Bootstrap the system enough to run with virtual memory.
    *
    *      On the i386 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, *unused;
           struct sysmaps *sysmaps;
           int i;
   
           /*
            * 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));
   
           /*
            * Initialize the first available kernel virtual address.  However,
            * using "firstaddr" may waste a few pages of the kernel virtual
            * address space, because locore may not have mapped every physical
            * page that it allocated.  Preferably, locore would provide a first
            * unused virtual address in addition to "firstaddr".
            */
           virtual_avail = (vm_offset_t) KERNBASE + firstaddr;
   
           virtual_end = VM_MAX_KERNEL_ADDRESS;
   
           /*
            * Initialize the kernel pmap (which is statically allocated).
            */
           PMAP_LOCK_INIT(kernel_pmap);
           kernel_pmap->pm_pdir = (pd_entry_t *) (KERNBASE + (u_int)IdlePTD);
   #if defined(PAE) || defined(PAE_TABLES)
           kernel_pmap->pm_pdpt = (pdpt_entry_t *) (KERNBASE + (u_int)IdlePDPT);
   #endif
           CPU_FILL(&kernel_pmap->pm_active);      /* don't allow deactivation */
           TAILQ_INIT(&kernel_pmap->pm_pvchunk);
   
           /*
            * Initialize the global pv list lock.
            */
           rw_init(&pvh_global_lock, "pmap pv global");
   
           LIST_INIT(&allpmaps);
   
           /*
            * Request a spin mutex so that changes to allpmaps cannot be
            * preempted by smp_rendezvous_cpus().  Otherwise,
            * pmap_update_pde_kernel() could access allpmaps while it is
            * being changed.
            */
           mtx_init(&allpmaps_lock, "allpmaps", NULL, MTX_SPIN);
           mtx_lock_spin(&allpmaps_lock);
           LIST_INSERT_HEAD(&allpmaps, kernel_pmap, pm_list);
           mtx_unlock_spin(&allpmaps_lock);
   
           /*
            * 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);
   
           /*
            * CMAP1/CMAP2 are used for zeroing and copying pages.
            * CMAP3 is used for the idle process page zeroing.
            */
           for (i = 0; i < MAXCPU; i++) {
                   sysmaps = &sysmaps_pcpu[i];
                   mtx_init(&sysmaps->lock, "SYSMAPS", NULL, MTX_DEF);
                   SYSMAP(caddr_t, sysmaps->CMAP1, sysmaps->CADDR1, 1)
                   SYSMAP(caddr_t, sysmaps->CMAP2, sysmaps->CADDR2, 1)
           }
           SYSMAP(caddr_t, CMAP3, CADDR3, 1)
   
           /*
            * Crashdump maps.
            */
           SYSMAP(caddr_t, unused, crashdumpmap, MAXDUMPPGS)
   
           /*
            * ptvmmap is used for reading arbitrary physical pages via /dev/mem.
            */
           SYSMAP(caddr_t, unused, ptvmmap, 1)
   
           /*
            * msgbufp is used to map the system message buffer.
            */
           SYSMAP(struct msgbuf *, unused, msgbufp, atop(round_page(msgbufsize)))
   
           /*
            * KPTmap is used by pmap_kextract().
            *
            * KPTmap is first initialized by locore.  However, that initial
            * KPTmap can only support NKPT page table pages.  Here, a larger
            * KPTmap is created that can support KVA_PAGES page table pages.
            */
           SYSMAP(pt_entry_t *, KPTD, KPTmap, KVA_PAGES)
   
           for (i = 0; i < NKPT; i++)
                   KPTD[i] = (KPTphys + (i << PAGE_SHIFT)) | pgeflag | PG_RW | PG_V;
   
           /*
            * Adjust the start of the KPTD and KPTmap so that the implementation
            * of pmap_kextract() and pmap_growkernel() can be made simpler.
            */
           KPTD -= KPTDI;
           KPTmap -= i386_btop(KPTDI << PDRSHIFT);
   
           /*
            * PADDR1 and PADDR2 are used by pmap_pte_quick() and pmap_pte(),
            * respectively.
            */
           SYSMAP(pt_entry_t *, PMAP1, PADDR1, 1)
           SYSMAP(pt_entry_t *, PMAP2, PADDR2, 1)
   
           mtx_init(&PMAP2mutex, "PMAP2", NULL, MTX_DEF);
   
           virtual_avail = va;
   
           /*
            * Leave in place an identity mapping (virt == phys) for the low 1 MB
            * physical memory region that is used by the ACPI wakeup code.  This
            * mapping must not have PG_G set. 
            */
   #ifdef XBOX
           /* FIXME: This is gross, but needed for the XBOX. Since we are in such
            * an early stadium, we cannot yet neatly map video memory ... :-(
            * Better fixes are very welcome! */
           if (!arch_i386_is_xbox)
   #endif
           for (i = 1; i < NKPT; i++)
                   PTD[i] = 0;
   
           /*
            * Initialize the PAT MSR if present.
            * 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.  We assume
            * that PAT support implies PGE and in reverse, PGE presence
            * comes with PAT.  Both features were added for Pentium Pro.
            */
           pmap_init_pat();
   
           /* Turn on PG_G on kernel page(s) */
           pmap_set_pg();
   }
   
   /*
    * Setup the PAT MSR.
    */
   void
   pmap_init_pat(void)
   {
           int pat_table[PAT_INDEX_SIZE];
           uint64_t pat_msr;
           u_long cr0, cr4;
           int i;
   
           /* Set default PAT index table. */
           for (i = 0; i < PAT_INDEX_SIZE; i++)
                   pat_table[i] = -1;
           pat_table[PAT_WRITE_BACK] = 0;
           pat_table[PAT_WRITE_THROUGH] = 1;
           pat_table[PAT_UNCACHEABLE] = 3;
           pat_table[PAT_WRITE_COMBINING] = 3;
           pat_table[PAT_WRITE_PROTECTED] = 3;
           pat_table[PAT_UNCACHED] = 3;
   
           /*
            * Bail if this CPU doesn't implement PAT.
            * We assume that PAT support implies PGE.
            */
           if ((cpu_feature & CPUID_PAT) == 0) {
                   for (i = 0; i < PAT_INDEX_SIZE; i++)
                           pat_index[i] = pat_table[i];
                   pat_works = 0;
                   return;
           }
   
           /*
            * Due to some Intel errata, we can only safely use the lower 4
            * PAT entries.
            *
            *   Intel Pentium III Processor Specification Update
            * Errata E.27 (Upper Four PAT Entries Not Usable With Mode B
            * or Mode C Paging)
            *
            *   Intel Pentium IV  Processor Specification Update
            * Errata N46 (PAT Index MSB May Be Calculated Incorrectly)
            */
           if (cpu_vendor_id == CPU_VENDOR_INTEL &&
               !(CPUID_TO_FAMILY(cpu_id) == 6 && CPUID_TO_MODEL(cpu_id) >= 0xe))
                   pat_works = 0;
   
           /* Initialize default PAT entries. */
           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_THROUGH) |
               PAT_VALUE(6, PAT_UNCACHED) |
               PAT_VALUE(7, PAT_UNCACHEABLE);
   
           if (pat_works) {
                   /*
                    * 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.
                    */
                   pat_msr &= ~(PAT_MASK(5) | PAT_MASK(6));
                   pat_msr |= PAT_VALUE(5, PAT_WRITE_PROTECTED) |
                       PAT_VALUE(6, PAT_WRITE_COMBINING);
                   pat_table[PAT_UNCACHED] = 2;
                   pat_table[PAT_WRITE_PROTECTED] = 5;
                   pat_table[PAT_WRITE_COMBINING] = 6;
           } else {
                   /*
                    * Just replace PAT Index 2 with WC instead of UC-.
                    */
                   pat_msr &= ~PAT_MASK(2);
                   pat_msr |= PAT_VALUE(2, PAT_WRITE_COMBINING);
                   pat_table[PAT_WRITE_COMBINING] = 2;
           }
   
           /* 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);
           for (i = 0; i < PAT_INDEX_SIZE; i++)
                   pat_index[i] = pat_table[i];
   
           /* Flush caches and TLBs again. */
           wbinvd();
           invltlb();
   
           /* Restore caches and PGE. */
           load_cr0(cr0);
           load_cr4(cr4);
   }
   
   /*
    * Set PG_G on kernel pages.  Only the BSP calls this when SMP is turned on.
    */
   static void
   pmap_set_pg(void)
   {
           pt_entry_t *pte;
           vm_offset_t va, endva;
   
           if (pgeflag == 0)
                   return;
   
           endva = KERNBASE + KERNend;
   
           if (pseflag) {
                   va = KERNBASE + KERNLOAD;
                   while (va  < endva) {
                           pdir_pde(PTD, va) |= pgeflag;
                           invltlb();      /* Play it safe, invltlb() every time */
                           va += NBPDR;
                   }
           } else {
                   va = (vm_offset_t)btext;
                   while (va < endva) {
                           pte = vtopte(va);
                           if (*pte)
                                   *pte |= pgeflag;
                           invltlb();      /* Play it safe, invltlb() every time */
                           va += PAGE_SIZE;
                   }
           }
   }
   
   /*
    * 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;
   }
   
   #if defined(PAE) || defined(PAE_TABLES)
   static void *
   pmap_pdpt_allocf(uma_zone_t zone, vm_size_t bytes, uint8_t *flags, int wait)
   {
   
           /* Inform UMA that this allocator uses kernel_map/object. */
           *flags = UMA_SLAB_KERNEL;
           return ((void *)kmem_alloc_contig(kernel_arena, bytes, wait, 0x0ULL,
               0xffffffffULL, 1, 0, VM_MEMATTR_DEFAULT));
   }
   #endif
   
   /*
    * Abuse the pte nodes for unmapped kva to thread a kva freelist through.
    * Requirements:
    *  - Must deal with pages in order to ensure that none of the PG_* bits
    *    are ever set, PG_V in particular.
    *  - Assumes we can write to ptes without pte_store() atomic ops, even
    *    on PAE systems.  This should be ok.
    *  - Assumes nothing will ever test these addresses for 0 to indicate
    *    no mapping instead of correctly checking PG_V.
    *  - Assumes a vm_offset_t will fit in a pte (true for i386).
    * Because PG_V is never set, there can be no mappings to invalidate.
    */
   static vm_offset_t
   pmap_ptelist_alloc(vm_offset_t *head)
   {
           pt_entry_t *pte;
           vm_offset_t va;
   
           va = *head;
           if (va == 0)
                   panic("pmap_ptelist_alloc: exhausted ptelist KVA");
           pte = vtopte(va);
           *head = *pte;
           if (*head & PG_V)
                   panic("pmap_ptelist_alloc: va with PG_V set!");
           *pte = 0;
           return (va);
   }
   
   static void
   pmap_ptelist_free(vm_offset_t *head, vm_offset_t va)
   {
           pt_entry_t *pte;
   
           if (va & PG_V)
                   panic("pmap_ptelist_free: freeing va with PG_V set!");
           pte = vtopte(va);
           *pte = *head;           /* virtual! PG_V is 0 though */
           *head = va;
   }
   
   static void
   pmap_ptelist_init(vm_offset_t *head, void *base, int npages)
   {
           int i;
           vm_offset_t va;
   
           *head = 0;
           for (i = npages - 1; i >= 0; i--) {
                   va = (vm_offset_t)base + i * PAGE_SIZE;
                   pmap_ptelist_free(head, va);
           }
   }
   
   
   /*
    *      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 mpte;
           vm_size_t s;
           int i, pv_npg;
   
           /*
            * Initialize the vm page array entries for the kernel pmap's
            * page table pages.
            */ 
           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 = i + KPTDI;
                   mpte->phys_addr = KPTphys + (i << PAGE_SHIFT);
           }
   
           /*
            * Initialize the address space (zone) for the pv entries.  Set a
            * high water mark so that the system can recover from excessive
            * numbers of pv entries.
            */
           TUNABLE_INT_FETCH("vm.pmap.shpgperproc", &shpgperproc);
           pv_entry_max = shpgperproc * maxproc + cnt.v_page_count;
           TUNABLE_INT_FETCH("vm.pmap.pv_entries", &pv_entry_max);
           pv_entry_max = roundup(pv_entry_max, _NPCPV);
           pv_entry_high_water = 9 * (pv_entry_max / 10);
   
           /*
            * 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_VM && (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 supported and enabled?
            */
           TUNABLE_INT_FETCH("vm.pmap.pg_ps_enabled", &pg_ps_enabled);
           if (pseflag == 0)
                   pg_ps_enabled = 0;
           else if (pg_ps_enabled) {
                   KASSERT(MAXPAGESIZES > 1 && pagesizes[1] == 0,
                       ("pmap_init: can't assign to pagesizes[1]"));
                   pagesizes[1] = NBPDR;
           }
   
           /*
            * Calculate the size of the pv head table for superpages.
            * Handle the possibility that "vm_phys_segs[...].end" is zero.
            */
           pv_npg = trunc_4mpage(vm_phys_segs[vm_phys_nsegs - 1].end -
               PAGE_SIZE) / NBPDR + 1;
   
           /*
            * 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(kernel_arena, s,
               M_WAITOK | M_ZERO);
           for (i = 0; i < pv_npg; i++)
                   TAILQ_INIT(&pv_table[i].pv_list);
   
           pv_maxchunks = MAX(pv_entry_max / _NPCPV, maxproc);
           pv_chunkbase = (struct pv_chunk *)kva_alloc(PAGE_SIZE * pv_maxchunks);
           if (pv_chunkbase == NULL)
                   panic("pmap_init: not enough kvm for pv chunks");
           pmap_ptelist_init(&pv_vafree, pv_chunkbase, pv_maxchunks);
   #if defined(PAE) || defined(PAE_TABLES)
           pdptzone = uma_zcreate("PDPT", NPGPTD * sizeof(pdpt_entry_t), NULL,
               NULL, NULL, NULL, (NPGPTD * sizeof(pdpt_entry_t)) - 1,
               UMA_ZONE_VM | UMA_ZONE_NOFREE);
           uma_zone_set_allocf(pdptzone, pmap_pdpt_allocf);
   #endif
   
           pmap_initialized = 1;
           if (!bootverbose)
                   return;
           for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                   ppim = pmap_preinit_mapping + i;
                   if (ppim->va == 0)
                           continue;
                   printf("PPIM %u: PA=%#jx, VA=%#x, size=%#x, mode=%#x\n", i,
                       (uintmax_t)ppim->pa, ppim->va, ppim->sz, ppim->mode);
           }
   }
   
   
   SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_max, CTLFLAG_RD, &pv_entry_max, 0,
           "Max number of PV entries");
   SYSCTL_INT(_vm_pmap, OID_AUTO, shpgperproc, CTLFLAG_RD, &shpgperproc, 0,
           "Page share factor per proc");
   
   static SYSCTL_NODE(_vm_pmap, OID_AUTO, pde, CTLFLAG_RD, 0,
       "2/4MB page mapping counters");
   
   static u_long pmap_pde_demotions;
   SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, demotions, CTLFLAG_RD,
       &pmap_pde_demotions, 0, "2/4MB page demotions");
   
   static u_long pmap_pde_mappings;
   SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, mappings, CTLFLAG_RD,
       &pmap_pde_mappings, 0, "2/4MB 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, "2/4MB page promotion failures");
   
   static u_long pmap_pde_promotions;
   SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, promotions, CTLFLAG_RD,
       &pmap_pde_promotions, 0, "2/4MB page promotions");
   
   /***************************************************
    * Low level helper routines.....
    ***************************************************/
   
   /*
    * Determine the appropriate bits to set in a PTE or PDE for a specified
    * caching mode.
    */
   int
   pmap_cache_bits(int mode, boolean_t is_pde)
   {
           int cache_bits, pat_flag, pat_idx;
   
           if (mode < 0 || mode >= PAT_INDEX_SIZE || pat_index[mode] < 0)
                   panic("Unknown caching mode %d\n", mode);
   
           /* The PAT bit is different for PTE's and PDE's. */
           pat_flag = is_pde ? PG_PDE_PAT : 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;
           return (cache_bits);
   }
   
   /*
    * The caller is responsible for maintaining TLB consistency.
    */
   static void
   pmap_kenter_pde(vm_offset_t va, pd_entry_t newpde)
   {
           pd_entry_t *pde;
           pmap_t pmap;
           boolean_t PTD_updated;
   
           PTD_updated = FALSE;
           mtx_lock_spin(&allpmaps_lock);
           LIST_FOREACH(pmap, &allpmaps, pm_list) {
                   if ((pmap->pm_pdir[PTDPTDI] & PG_FRAME) == (PTDpde[0] &
                       PG_FRAME))
                           PTD_updated = TRUE;
                   pde = pmap_pde(pmap, va);
                   pde_store(pde, newpde);
           }
           mtx_unlock_spin(&allpmaps_lock);
           KASSERT(PTD_updated,
               ("pmap_kenter_pde: current page table is not in allpmaps"));
   }
   
   /*
    * 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(vm_offset_t va, pd_entry_t newpde)
   {
           u_long cr4;
   
           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.
                    */
                   cr4 = rcr4();
                   load_cr4(cr4 & ~CR4_PGE);
                   /*
                    * Although preemption at this point could be detrimental to
                    * performance, it would not lead to an error.  PG_G is simply
                    * ignored if CR4.PGE is clear.  Moreover, in case this block
                    * is re-entered, the load_cr4() either above or below will
                    * modify CR4.PGE flushing the TLB.
                    */
                   load_cr4(cr4 | CR4_PGE);
           }
   }
   #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.
    */
   void
   pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
   {
           cpuset_t other_cpus;
          u_int cpuid;
  
          sched_pin();
          if (pmap == kernel_pmap || !CPU_CMP(&pmap->pm_active, &all_cpus)) {
                  invlpg(va);
                  smp_invlpg(va);
          } else {
                  cpuid = PCPU_GET(cpuid);
                  other_cpus = all_cpus;
                  CPU_CLR(cpuid, &other_cpus);
                  if (CPU_ISSET(cpuid, &pmap->pm_active))
                          invlpg(va);
                  CPU_AND(&other_cpus, &pmap->pm_active);
                  if (!CPU_EMPTY(&other_cpus))
                          smp_masked_invlpg(other_cpus, va);
          }
          sched_unpin();
  }
  
  void
  pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
          cpuset_t other_cpus;
          vm_offset_t addr;
          u_int cpuid;
  
          sched_pin();
          if (pmap == kernel_pmap || !CPU_CMP(&pmap->pm_active, &all_cpus)) {
                  for (addr = sva; addr < eva; addr += PAGE_SIZE)
                          invlpg(addr);
                  smp_invlpg_range(sva, eva);
          } else {
                  cpuid = PCPU_GET(cpuid);
                  other_cpus = all_cpus;
                  CPU_CLR(cpuid, &other_cpus);
                  if (CPU_ISSET(cpuid, &pmap->pm_active))
                          for (addr = sva; addr < eva; addr += PAGE_SIZE)
                                  invlpg(addr);
                  CPU_AND(&other_cpus, &pmap->pm_active);
                  if (!CPU_EMPTY(&other_cpus))
                          smp_masked_invlpg_range(other_cpus, sva, eva);
          }
          sched_unpin();
  }
  
  void
  pmap_invalidate_all(pmap_t pmap)
  {
          cpuset_t other_cpus;
          u_int cpuid;
  
          sched_pin();
          if (pmap == kernel_pmap || !CPU_CMP(&pmap->pm_active, &all_cpus)) {
                  invltlb();
                  smp_invltlb();
          } else {
                  cpuid = PCPU_GET(cpuid);
                  other_cpus = all_cpus;
                  CPU_CLR(cpuid, &other_cpus);
                  if (CPU_ISSET(cpuid, &pmap->pm_active))
                          invltlb();
                  CPU_AND(&other_cpus, &pmap->pm_active);
                  if (!CPU_EMPTY(&other_cpus))
                          smp_masked_invltlb(other_cpus);
          }
          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 */
          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_kernel(void *arg)
  {
          struct pde_action *act = arg;
          pd_entry_t *pde;
          pmap_t pmap;
  
          if (act->store == PCPU_GET(cpuid)) {
  
                  /*
                   * Elsewhere, this operation requires allpmaps_lock for
                   * synchronization.  Here, it does not because it is being
                   * performed in the context of an all_cpus rendezvous.
                   */
                  LIST_FOREACH(pmap, &allpmaps, pm_list) {
                          pde = pmap_pde(pmap, act->va);
                          pde_store(pde, act->newpde);
                  }
          }
  }
  
  static void
  pmap_update_pde_user(void *arg)
  {
          struct pde_action *act = arg;
  
          if (act->store == PCPU_GET(cpuid))
                  pde_store(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->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)
                  active = all_cpus;
          else
                  active = pmap->pm_active;
          if (CPU_OVERLAP(&active, &other_cpus)) {
                  act.store = cpuid;
                  act.invalidate = active;
                  act.va = va;
                  act.pde = pde;
                  act.newpde = newpde;
                  CPU_SET(cpuid, &active);
                  smp_rendezvous_cpus(active,
                      smp_no_rendevous_barrier, pmap == kernel_pmap ?
                      pmap_update_pde_kernel : pmap_update_pde_user,
                      pmap_update_pde_teardown, &act);
          } else {
                  if (pmap == kernel_pmap)
                          pmap_kenter_pde(va, newpde);
                  else
                          pde_store(pde, newpde);
                  if (CPU_ISSET(cpuid, &active))
                          pmap_update_pde_invalidate(va, newpde);
          }
          sched_unpin();
  }
  #else /* !SMP */
  /*
   * Normal, non-SMP, 486+ invalidation functions.
   * We inline these within pmap.c for speed.
   */
  PMAP_INLINE void
  pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
  {
  
          if (pmap == kernel_pmap || !CPU_EMPTY(&pmap->pm_active))
                  invlpg(va);
  }
  
  PMAP_INLINE void
  pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
          vm_offset_t addr;
  
          if (pmap == kernel_pmap || !CPU_EMPTY(&pmap->pm_active))
                  for (addr = sva; addr < eva; addr += PAGE_SIZE)
                          invlpg(addr);
  }
  
  PMAP_INLINE void
  pmap_invalidate_all(pmap_t pmap)
  {
  
          if (pmap == kernel_pmap || !CPU_EMPTY(&pmap->pm_active))
                  invltlb();
  }
  
  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)
  {
  
          if (pmap == kernel_pmap)
                  pmap_kenter_pde(va, newpde);
          else
                  pde_store(pde, newpde);
          if (pmap == kernel_pmap || !CPU_EMPTY(&pmap->pm_active))
                  pmap_update_pde_invalidate(va, newpde);
  }
  #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 2- or 4MB page mapping was
           * created by a promotion that did not invalidate the 512 or 1024 4KB
           * page mappings that might exist in the TLB.  Consequently, at this
           * point, the TLB may hold both 4KB and 2- or 4MB 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
           * 2- or 4MB 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 PMAP_CLFLUSH_THRESHOLD  (2 * 1024 * 1024)
  
  void
  pmap_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva, boolean_t force)
  {
  
          if (force) {
                  sva &= ~(vm_offset_t)(cpu_clflush_line_size - 1);
          } else {
                  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"));
          }
  
          if ((cpu_feature & CPUID_SS) != 0 && !force)
                  ; /* If "Self Snoop" is supported and allowed, do nothing. */
          else if ((cpu_stdext_feature & CPUID_STDEXT_CLFLUSHOPT) != 0 &&
              eva - sva < PMAP_CLFLUSH_THRESHOLD) {
  #ifdef DEV_APIC
                  /*
                   * 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;
  #endif
                  /*
                   * Otherwise, 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 if ((cpu_feature & CPUID_CLFSH) != 0 &&
              eva - sva < PMAP_CLFLUSH_THRESHOLD) {
  #ifdef DEV_APIC
                  if (pmap_kextract(sva) == lapic_paddr)
                          return;
  #endif
                  /*
                   * 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();
          } else {
  
                  /*
                   * No targeted cache flush methods are supported by CPU,
                   * or the supplied range is bigger than 2MB.
                   * Globally invalidate cache.
                   */
                  pmap_invalidate_cache();
          }
  }
  
  void
  pmap_invalidate_cache_pages(vm_page_t *pages, int count)
  {
          int i;
  
          if (count >= PMAP_CLFLUSH_THRESHOLD / PAGE_SIZE ||
              (cpu_feature & CPUID_CLFSH) == 0) {
                  pmap_invalidate_cache();
          } else {
                  for (i = 0; i < count; i++)
                          pmap_flush_page(pages[i]);
          }
  }
  
  /*
   * Are we current address space or kernel?  N.B. We return FALSE when
   * a pmap's page table is in use because a kernel thread is borrowing
   * it.  The borrowed page table can change spontaneously, making any
   * dependence on its continued use subject to a race condition.
   */
  static __inline int
  pmap_is_current(pmap_t pmap)
  {
  
          return (pmap == kernel_pmap ||
              (pmap == vmspace_pmap(curthread->td_proc->p_vmspace) &&
              (pmap->pm_pdir[PTDPTDI] & PG_FRAME) == (PTDpde[0] & PG_FRAME)));
  }
  
  /*
   * If the given pmap is not the current or kernel pmap, the returned pte must
   * be released by passing it to pmap_pte_release().
   */
  pt_entry_t *
  pmap_pte(pmap_t pmap, vm_offset_t va)
  {
          pd_entry_t newpf;
          pd_entry_t *pde;
  
          pde = pmap_pde(pmap, va);
          if (*pde & PG_PS)
                  return (pde);
          if (*pde != 0) {
                  /* are we current address space or kernel? */
                  if (pmap_is_current(pmap))
                          return (vtopte(va));
                  mtx_lock(&PMAP2mutex);
                  newpf = *pde & PG_FRAME;
                  if ((*PMAP2 & PG_FRAME) != newpf) {
                          *PMAP2 = newpf | PG_RW | PG_V | PG_A | PG_M;
                          pmap_invalidate_page(kernel_pmap, (vm_offset_t)PADDR2);
                  }
                  return (PADDR2 + (i386_btop(va) & (NPTEPG - 1)));
          }
          return (NULL);
  }
  
  /*
   * Releases a pte that was obtained from pmap_pte().  Be prepared for the pte
   * being NULL.
   */
  static __inline void
  pmap_pte_release(pt_entry_t *pte)
  {
  
          if ((pt_entry_t *)((vm_offset_t)pte & ~PAGE_MASK) == PADDR2)
                  mtx_unlock(&PMAP2mutex);
  }
  
  /*
   * NB:  The sequence of updating a page table followed by accesses to the
   * corresponding pages is subject to the situation described in the "AMD64
   * Architecture Programmer's Manual Volume 2: System Programming" rev. 3.23,
   * "7.3.1 Special Coherency Considerations".  Therefore, issuing the INVLPG
   * right after modifying the PTE bits is crucial.
   */
  static __inline void
  invlcaddr(void *caddr)
  {
  
          invlpg((u_int)caddr);
  }
  
  /*
   * Super fast pmap_pte routine best used when scanning
   * the pv lists.  This eliminates many coarse-grained
   * invltlb calls.  Note that many of the pv list
   * scans are across different pmaps.  It is very wasteful
   * to do an entire invltlb for checking a single mapping.
   *
   * If the given pmap is not the current pmap, pvh_global_lock
   * must be held and curthread pinned to a CPU.
   */
  static pt_entry_t *
  pmap_pte_quick(pmap_t pmap, vm_offset_t va)
  {
          pd_entry_t newpf;
          pd_entry_t *pde;
  
          pde = pmap_pde(pmap, va);
          if (*pde & PG_PS)
                  return (pde);
          if (*pde != 0) {
                  /* are we current address space or kernel? */
                  if (pmap_is_current(pmap))
                          return (vtopte(va));
                  rw_assert(&pvh_global_lock, RA_WLOCKED);
                  KASSERT(curthread->td_pinned > 0, ("curthread not pinned"));
                  newpf = *pde & PG_FRAME;
                  if ((*PMAP1 & PG_FRAME) != newpf) {
                          *PMAP1 = newpf | PG_RW | PG_V | PG_A | PG_M;
  #ifdef SMP
                          PMAP1cpu = PCPU_GET(cpuid);
  #endif
                          invlcaddr(PADDR1);
                          PMAP1changed++;
                  } else
  #ifdef SMP
                  if (PMAP1cpu != PCPU_GET(cpuid)) {
                          PMAP1cpu = PCPU_GET(cpuid);
                          invlcaddr(PADDR1);
                          PMAP1changedcpu++;
                  } else
  #endif
                          PMAP1unchanged++;
                  return (PADDR1 + (i386_btop(va) & (NPTEPG - 1)));
          }
          return (0);
  }
  
  /*
   *      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)
  {
          vm_paddr_t rtval;
          pt_entry_t *pte;
          pd_entry_t pde;
  
          rtval = 0;
          PMAP_LOCK(pmap);
          pde = pmap->pm_pdir[va >> PDRSHIFT];
          if (pde != 0) {
                  if ((pde & PG_PS) != 0)
                          rtval = (pde & PG_PS_FRAME) | (va & PDRMASK);
                  else {
                          pte = pmap_pte(pmap, va);
                          rtval = (*pte & PG_FRAME) | (va & PAGE_MASK);
                          pmap_pte_release(pte);
                  }
          }
          PMAP_UNLOCK(pmap);
          return (rtval);
  }
  
  /*
   *      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;
          pt_entry_t pte, *ptep;
          vm_page_t m;
          vm_paddr_t pa;
  
          pa = 0;
          m = NULL;
          PMAP_LOCK(pmap);
  retry:
          pde = *pmap_pde(pmap, va);
          if (pde != 0) {
                  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((pde & PG_PS_FRAME) |
                                      (va & PDRMASK));
                                  vm_page_hold(m);
                          }
                  } else {
                          ptep = pmap_pte(pmap, va);
                          pte = *ptep;
                          pmap_pte_release(ptep);
                          if (pte != 0 &&
                              ((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(pte & PG_FRAME);
                                  vm_page_hold(m);
                          }
                  }
          }
          PA_UNLOCK_COND(pa);
          PMAP_UNLOCK(pmap);
          return (m);
  }
  
  /***************************************************
   * Low level mapping routines.....
   ***************************************************/
  
  /*
   * Add a wired page to the kva.
   * Note: not SMP coherent.
   *
   * This function may be used before pmap_bootstrap() is called.
   */
  PMAP_INLINE void 
  pmap_kenter(vm_offset_t va, vm_paddr_t pa)
  {
          pt_entry_t *pte;
  
          pte = vtopte(va);
          pte_store(pte, pa | PG_RW | PG_V | pgeflag);
  }
  
  static __inline void
  pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int mode)
  {
          pt_entry_t *pte;
  
          pte = vtopte(va);
          pte_store(pte, pa | PG_RW | PG_V | pgeflag | pmap_cache_bits(mode, 0));
  }
  
  /*
   * Remove a page from the kernel pagetables.
   * Note: not SMP coherent.
   *
   * This function may be used before pmap_bootstrap() is called.
   */
  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)
  {
          vm_offset_t va, sva;
          vm_paddr_t superpage_offset;
          pd_entry_t newpde;
  
          va = *virt;
          /*
           * Does the physical address range's size and alignment permit at
           * least one superpage mapping to be created?
           */ 
          superpage_offset = start & PDRMASK;
          if ((end - start) - ((NBPDR - superpage_offset) & PDRMASK) >= NBPDR) {
                  /*
                   * Increase the starting virtual address so that its alignment
                   * does not preclude the use of superpage mappings.
                   */
                  if ((va & PDRMASK) < superpage_offset)
                          va = (va & ~PDRMASK) + superpage_offset;
                  else if ((va & PDRMASK) > superpage_offset)
                          va = ((va + PDRMASK) & ~PDRMASK) + superpage_offset;
          }
          sva = va;
          while (start < end) {
                  if ((start & PDRMASK) == 0 && end - start >= NBPDR &&
                      pseflag) {
                          KASSERT((va & PDRMASK) == 0,
                              ("pmap_map: misaligned va %#x", va));
                          newpde = start | PG_PS | pgeflag | PG_RW | PG_V;
                          pmap_kenter_pde(va, newpde);
                          va += NBPDR;
                          start += NBPDR;
                  } else {
                          pmap_kenter(va, start);
                          va += PAGE_SIZE;
                          start += PAGE_SIZE;
                  }
          }
          pmap_invalidate_range(kernel_pmap, sva, va);
          *virt = va;
          return (sva);
  }
  
  
  /*
   * 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;
  
          oldpte = 0;
          pte = vtopte(sva);
          endpte = pte + count;
          while (pte < endpte) {
                  m = *ma++;
                  pa = VM_PAGE_TO_PHYS(m) | pmap_cache_bits(m->md.pat_mode, 0);
                  if ((*pte & (PG_FRAME | PG_PTE_CACHE)) != pa) {
                          oldpte |= *pte;
                          pte_store(pte, pa | pgeflag | PG_RW | PG_V);
                  }
                  pte++;
          }
          if (__predict_false((oldpte & 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) {
                  pmap_kremove(va);
                  va += PAGE_SIZE;
          }
          pmap_invalidate_range(kernel_pmap, sva, va);
  }
  
  /***************************************************
   * Page table page management routines.....
   ***************************************************/
  static __inline void
  pmap_free_zero_pages(struct spglist *free)
  {
          vm_page_t m;
  
          while ((m = SLIST_FIRST(free)) != NULL) {
                  SLIST_REMOVE_HEAD(free, plinks.s.ss);
                  /* Preserve the page's PG_ZERO setting. */
                  vm_page_free_toq(m);
          }
  }
  
  /*
   * 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));
  }
  
  /*
   * Looks for a page table page mapping the specified virtual address in the
   * specified pmap's collection of idle page table pages.  Returns NULL if there
   * is no page table page corresponding to the specified virtual address.
   */
  static __inline vm_page_t
  pmap_lookup_pt_page(pmap_t pmap, vm_offset_t va)
  {
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          return (vm_radix_lookup(&pmap->pm_root, va >> PDRSHIFT));
  }
  
  /*
   * Removes the specified page table page from the specified pmap's collection
   * of idle page table pages.  The specified page table page must be a member of
   * the pmap's collection.
   */
  static __inline void
  pmap_remove_pt_page(pmap_t pmap, vm_page_t mpte)
  {
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          vm_radix_remove(&pmap->pm_root, mpte->pindex);
  }
  
  /*
   * 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_page_t m, struct spglist *free)
  {
  
          --m->wire_count;
          if (m->wire_count == 0) {
                  _pmap_unwire_ptp(pmap, m, free);
                  return (TRUE);
          } else
                  return (FALSE);
  }
  
  static void
  _pmap_unwire_ptp(pmap_t pmap, vm_page_t m, struct spglist *free)
  {
          vm_offset_t pteva;
  
          /*
           * unmap the page table page
           */
          pmap->pm_pdir[m->pindex] = 0;
          --pmap->pm_stats.resident_count;
  
          /*
           * This is a release store so that the ordinary store unmapping
           * the page table page is globally performed before TLB shoot-
           * down is begun.
           */
          atomic_subtract_rel_int(&cnt.v_wire_count, 1);
  
          /*
           * Do an invltlb to make the invalidated mapping
           * take effect immediately.
           */
          pteva = VM_MAXUSER_ADDRESS + i386_ptob(m->pindex);
          pmap_invalidate_page(pmap, pteva);
  
          /* 
           * 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, struct spglist *free)
  {
          pd_entry_t ptepde;
          vm_page_t mpte;
  
          if (va >= VM_MAXUSER_ADDRESS)
                  return (0);
          ptepde = *pmap_pde(pmap, va);
          mpte = PHYS_TO_VM_PAGE(ptepde & PG_FRAME);
          return (pmap_unwire_ptp(pmap, mpte, free));
  }
  
  /*
   * Initialize the pmap for the swapper process.
   */
  void
  pmap_pinit0(pmap_t pmap)
  {
  
          PMAP_LOCK_INIT(pmap);
          /*
           * Since the page table directory is shared with the kernel pmap,
           * which is already included in the list "allpmaps", this pmap does
           * not need to be inserted into that list.
           */
          pmap->pm_pdir = (pd_entry_t *)(KERNBASE + (vm_offset_t)IdlePTD);
  #if defined(PAE) || defined(PAE_TABLES)
          pmap->pm_pdpt = (pdpt_entry_t *)(KERNBASE + (vm_offset_t)IdlePDPT);
  #endif
          pmap->pm_root.rt_root = 0;
          CPU_ZERO(&pmap->pm_active);
          PCPU_SET(curpmap, pmap);
          TAILQ_INIT(&pmap->pm_pvchunk);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
  }
  
  /*
   * Initialize a preallocated and zeroed pmap structure,
   * such as one in a vmspace structure.
   */
  int
  pmap_pinit(pmap_t pmap)
  {
          vm_page_t m, ptdpg[NPGPTD];
          vm_paddr_t pa;
          int i;
  
          /*
           * No need to allocate page table space yet but we do need a valid
           * page directory table.
           */
          if (pmap->pm_pdir == NULL) {
                  pmap->pm_pdir = (pd_entry_t *)kva_alloc(NBPTD);
                  if (pmap->pm_pdir == NULL)
                          return (0);
  #if defined(PAE) || defined(PAE_TABLES)
                  pmap->pm_pdpt = uma_zalloc(pdptzone, M_WAITOK | M_ZERO);
                  KASSERT(((vm_offset_t)pmap->pm_pdpt &
                      ((NPGPTD * sizeof(pdpt_entry_t)) - 1)) == 0,
                      ("pmap_pinit: pdpt misaligned"));
                  KASSERT(pmap_kextract((vm_offset_t)pmap->pm_pdpt) < (4ULL<<30),
                      ("pmap_pinit: pdpt above 4g"));
  #endif
                  pmap->pm_root.rt_root = 0;
          }
          KASSERT(vm_radix_is_empty(&pmap->pm_root),
              ("pmap_pinit: pmap has reserved page table page(s)"));
  
          /*
           * allocate the page directory page(s)
           */
          for (i = 0; i < NPGPTD;) {
                  m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
                      VM_ALLOC_WIRED | VM_ALLOC_ZERO);
                  if (m == NULL)
                          VM_WAIT;
                  else {
                          ptdpg[i++] = m;
                  }
          }
  
          pmap_qenter((vm_offset_t)pmap->pm_pdir, ptdpg, NPGPTD);
  
          for (i = 0; i < NPGPTD; i++)
                  if ((ptdpg[i]->flags & PG_ZERO) == 0)
                          pagezero(pmap->pm_pdir + (i * NPDEPG));
  
          mtx_lock_spin(&allpmaps_lock);
          LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
          /* Copy the kernel page table directory entries. */
          bcopy(PTD + KPTDI, pmap->pm_pdir + KPTDI, nkpt * sizeof(pd_entry_t));
          mtx_unlock_spin(&allpmaps_lock);
  
          /* install self-referential address mapping entry(s) */
          for (i = 0; i < NPGPTD; i++) {
                  pa = VM_PAGE_TO_PHYS(ptdpg[i]);
                  pmap->pm_pdir[PTDPTDI + i] = pa | PG_V | PG_RW | PG_A | PG_M;
  #if defined(PAE) || defined(PAE_TABLES)
                  pmap->pm_pdpt[i] = pa | PG_V;
  #endif
          }
  
          CPU_ZERO(&pmap->pm_active);
          TAILQ_INIT(&pmap->pm_pvchunk);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
  
          return (1);
  }
  
  /*
   * this routine is called if the page table page is not
   * mapped correctly.
   */
  static vm_page_t
  _pmap_allocpte(pmap_t pmap, u_int ptepindex, u_int flags)
  {
          vm_paddr_t ptepa;
          vm_page_t m;
  
          /*
           * Allocate a page table page.
           */
          if ((m = vm_page_alloc(NULL, ptepindex, VM_ALLOC_NOOBJ |
              VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
                  if ((flags & PMAP_ENTER_NOSLEEP) == 0) {
                          PMAP_UNLOCK(pmap);
                          rw_wunlock(&pvh_global_lock);
                          VM_WAIT;
                          rw_wlock(&pvh_global_lock);
                          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.
           */
  
          pmap->pm_stats.resident_count++;
  
          ptepa = VM_PAGE_TO_PHYS(m);
          pmap->pm_pdir[ptepindex] =
                  (pd_entry_t) (ptepa | PG_U | PG_RW | PG_V | PG_A | PG_M);
  
          return (m);
  }
  
  static vm_page_t
  pmap_allocpte(pmap_t pmap, vm_offset_t va, u_int flags)
  {
          u_int ptepindex;
          pd_entry_t ptepa;
          vm_page_t m;
  
          /*
           * Calculate pagetable page index
           */
          ptepindex = va >> PDRSHIFT;
  retry:
          /*
           * Get the page directory entry
           */
          ptepa = pmap->pm_pdir[ptepindex];
  
          /*
           * This supports switching from a 4MB page to a
           * normal 4K page.
           */
          if (ptepa & PG_PS) {
                  (void)pmap_demote_pde(pmap, &pmap->pm_pdir[ptepindex], va);
                  ptepa = pmap->pm_pdir[ptepindex];
          }
  
          /*
           * If the page table page is mapped, we just increment the
           * hold count, and activate it.
           */
          if (ptepa) {
                  m = PHYS_TO_VM_PAGE(ptepa & 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, flags);
                  if (m == NULL && (flags & PMAP_ENTER_NOSLEEP) == 0)
                          goto retry;
          }
          return (m);
  }
  
  
  /***************************************************
  * Pmap allocation/deallocation routines.
   ***************************************************/
  
  #ifdef SMP
  /*
   * Deal with a SMP shootdown of other users of the pmap that we are
   * trying to dispose of.  This can be a bit hairy.
   */
  static cpuset_t *lazymask;
  static u_int lazyptd;
  static volatile u_int lazywait;
  
  void pmap_lazyfix_action(void);
  
  void
  pmap_lazyfix_action(void)
  {
  
  #ifdef COUNT_IPIS
          (*ipi_lazypmap_counts[PCPU_GET(cpuid)])++;
  #endif
          if (rcr3() == lazyptd)
                  load_cr3(curpcb->pcb_cr3);
          CPU_CLR_ATOMIC(PCPU_GET(cpuid), lazymask);
          atomic_store_rel_int(&lazywait, 1);
  }
  
  static void
  pmap_lazyfix_self(u_int cpuid)
  {
  
          if (rcr3() == lazyptd)
                  load_cr3(curpcb->pcb_cr3);
          CPU_CLR_ATOMIC(cpuid, lazymask);
  }
  
  
  static void
  pmap_lazyfix(pmap_t pmap)
  {
          cpuset_t mymask, mask;
          u_int cpuid, spins;
          int lsb;
  
          mask = pmap->pm_active;
          while (!CPU_EMPTY(&mask)) {
                  spins = 50000000;
  
                  /* Find least significant set bit. */
                  lsb = CPU_FFS(&mask);
                  MPASS(lsb != 0);
                  lsb--;
                  CPU_SETOF(lsb, &mask);
                  mtx_lock_spin(&smp_ipi_mtx);
  #if defined(PAE) || defined(PAE_TABLES)
                  lazyptd = vtophys(pmap->pm_pdpt);
  #else
                  lazyptd = vtophys(pmap->pm_pdir);
  #endif
                  cpuid = PCPU_GET(cpuid);
  
                  /* Use a cpuset just for having an easy check. */
                  CPU_SETOF(cpuid, &mymask);
                  if (!CPU_CMP(&mask, &mymask)) {
                          lazymask = &pmap->pm_active;
                          pmap_lazyfix_self(cpuid);
                  } else {
                          atomic_store_rel_int((u_int *)&lazymask,
                              (u_int)&pmap->pm_active);
                          atomic_store_rel_int(&lazywait, 0);
                          ipi_selected(mask, IPI_LAZYPMAP);
                          while (lazywait == 0) {
                                  ia32_pause();
                                  if (--spins == 0)
                                          break;
                          }
                  }
                  mtx_unlock_spin(&smp_ipi_mtx);
                  if (spins == 0)
                          printf("pmap_lazyfix: spun for 50000000\n");
                  mask = pmap->pm_active;
          }
  }
  
  #else   /* SMP */
  
  /*
   * Cleaning up on uniprocessor is easy.  For various reasons, we're
   * unlikely to have to even execute this code, including the fact
   * that the cleanup is deferred until the parent does a wait(2), which
   * means that another userland process has run.
   */
  static void
  pmap_lazyfix(pmap_t pmap)
  {
          u_int cr3;
  
          cr3 = vtophys(pmap->pm_pdir);
          if (cr3 == rcr3()) {
                  load_cr3(curpcb->pcb_cr3);
                  CPU_CLR(PCPU_GET(cpuid), &pmap->pm_active);
          }
  }
  #endif  /* SMP */
  
  /*
   * 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, ptdpg[NPGPTD];
          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)"));
  
          pmap_lazyfix(pmap);
          mtx_lock_spin(&allpmaps_lock);
          LIST_REMOVE(pmap, pm_list);
          mtx_unlock_spin(&allpmaps_lock);
  
          for (i = 0; i < NPGPTD; i++)
                  ptdpg[i] = PHYS_TO_VM_PAGE(pmap->pm_pdir[PTDPTDI + i] &
                      PG_FRAME);
  
          bzero(pmap->pm_pdir + PTDPTDI, (nkpt + NPGPTD) *
              sizeof(*pmap->pm_pdir));
  
          pmap_qremove((vm_offset_t)pmap->pm_pdir, NPGPTD);
  
          for (i = 0; i < NPGPTD; i++) {
                  m = ptdpg[i];
  #if defined(PAE) || defined(PAE_TABLES)
                  KASSERT(VM_PAGE_TO_PHYS(m) == (pmap->pm_pdpt[i] & PG_FRAME),
                      ("pmap_release: got wrong ptd page"));
  #endif
                  m->wire_count--;
                  atomic_subtract_int(&cnt.v_wire_count, 1);
                  vm_page_free_zero(m);
          }
  }
  
  static int
  kvm_size(SYSCTL_HANDLER_ARGS)
  {
          unsigned long ksize = VM_MAX_KERNEL_ADDRESS - KERNBASE;
  
          return (sysctl_handle_long(oidp, &ksize, 0, req));
  }
  SYSCTL_PROC(_vm, OID_AUTO, kvm_size, CTLTYPE_LONG|CTLFLAG_RD, 
      0, 0, kvm_size, "IU", "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, "IU", "Amount of KVM free");
  
  /*
   * grow the number of kernel page table entries, if needed
   */
  void
  pmap_growkernel(vm_offset_t addr)
  {
          vm_paddr_t ptppaddr;
          vm_page_t nkpg;
          pd_entry_t newpdir;
  
          mtx_assert(&kernel_map->system_mtx, MA_OWNED);
          addr = roundup2(addr, NBPDR);
          if (addr - 1 >= kernel_map->max_offset)
                  addr = kernel_map->max_offset;
          while (kernel_vm_end < addr) {
                  if (pdir_pde(PTD, kernel_vm_end)) {
                          kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                          if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                                  kernel_vm_end = kernel_map->max_offset;
                                  break;
                          }
                          continue;
                  }
  
                  nkpg = vm_page_alloc(NULL, kernel_vm_end >> PDRSHIFT,
                      VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED |
                      VM_ALLOC_ZERO);
                  if (nkpg == NULL)
                          panic("pmap_growkernel: no memory to grow kernel");
  
                  nkpt++;
  
                  if ((nkpg->flags & PG_ZERO) == 0)
                          pmap_zero_page(nkpg);
                  ptppaddr = VM_PAGE_TO_PHYS(nkpg);
                  newpdir = (pd_entry_t) (ptppaddr | PG_V | PG_RW | PG_A | PG_M);
                  pdir_pde(KPTD, kernel_vm_end) = pgeflag | newpdir;
  
                  pmap_kenter_pde(kernel_vm_end, newpdir);
                  kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                  if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                          kernel_vm_end = kernel_map->max_offset;
                          break;
                  }
          }
  }
  
  
  /***************************************************
   * page management routines.
   ***************************************************/
  
  CTASSERT(sizeof(struct pv_chunk) == PAGE_SIZE);
  CTASSERT(_NPCM == 11);
  CTASSERT(_NPCPV == 336);
  
  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_9      0xfffffffful    /* Free values for index 0 through 9 */
  #define PC_FREE10       0x0000fffful    /* Free values for index 10 */
  
  static const uint32_t pc_freemask[_NPCM] = {
          PC_FREE0_9, PC_FREE0_9, PC_FREE0_9,
          PC_FREE0_9, PC_FREE0_9, PC_FREE0_9,
          PC_FREE0_9, PC_FREE0_9, PC_FREE0_9,
          PC_FREE0_9, PC_FREE10
  };
  
  SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_count, CTLFLAG_RD, &pv_entry_count, 0,
          "Current number of pv entries");
  
  #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;
  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_INT(_vm_pmap, OID_AUTO, pv_entry_spare, CTLFLAG_RD, &pv_entry_spare, 0,
          "Current number of spare pv entries");
  #endif
  
  /*
   * We are in a serious low memory condition.  Resort to
   * drastic measures to free some pages so we can allocate
   * another pv entry chunk.
   */
  static vm_page_t
  pmap_pv_reclaim(pmap_t locked_pmap)
  {
          struct pch newtail;
          struct pv_chunk *pc;
          struct md_page *pvh;
          pd_entry_t *pde;
          pmap_t pmap;
          pt_entry_t *pte, tpte;
          pv_entry_t pv;
          vm_offset_t va;
          vm_page_t m, m_pc;
          struct spglist free;
          uint32_t inuse;
          int bit, field, freed;
  
          PMAP_LOCK_ASSERT(locked_pmap, MA_OWNED);
          pmap = NULL;
          m_pc = NULL;
          SLIST_INIT(&free);
          TAILQ_INIT(&newtail);
          while ((pc = TAILQ_FIRST(&pv_chunks)) != NULL && (pv_vafree == 0 ||
              SLIST_EMPTY(&free))) {
                  TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
                  if (pmap != pc->pc_pmap) {
                          if (pmap != NULL) {
                                  pmap_invalidate_all(pmap);
                                  if (pmap != locked_pmap)
                                          PMAP_UNLOCK(pmap);
                          }
                          pmap = pc->pc_pmap;
                          /* Avoid deadlock and lock recursion. */
                          if (pmap > locked_pmap)
                                  PMAP_LOCK(pmap);
                          else if (pmap != locked_pmap && !PMAP_TRYLOCK(pmap)) {
                                  pmap = NULL;
                                  TAILQ_INSERT_TAIL(&newtail, pc, pc_lru);
                                  continue;
                          }
                  }
  
                  /*
                   * 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 = bsfl(inuse);
                                  pv = &pc->pc_pventry[field * 32 + bit];
                                  va = pv->pv_va;
                                  pde = pmap_pde(pmap, va);
                                  if ((*pde & PG_PS) != 0)
                                          continue;
                                  pte = pmap_pte(pmap, va);
                                  tpte = *pte;
                                  if ((tpte & PG_W) == 0)
                                          tpte = pte_load_clear(pte);
                                  pmap_pte_release(pte);
                                  if ((tpte & PG_W) != 0)
                                          continue;
                                  KASSERT(tpte != 0,
                                      ("pmap_pv_reclaim: pmap %p va %x zero pte",
                                      pmap, va));
                                  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);
                                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                                  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);
                                          }
                                  }
                                  pc->pc_map[field] |= 1UL << bit;
                                  pmap_unuse_pt(pmap, va, &free);
                                  freed++;
                          }
                  }
                  if (freed == 0) {
                          TAILQ_INSERT_TAIL(&newtail, pc, pc_lru);
                          continue;
                  }
                  /* Every freed mapping is for a 4 KB page. */
                  pmap->pm_stats.resident_count -= freed;
                  PV_STAT(pv_entry_frees += freed);
                  PV_STAT(pv_entry_spare += freed);
                  pv_entry_count -= freed;
                  TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                  for (field = 0; field < _NPCM; field++)
                          if (pc->pc_map[field] != pc_freemask[field]) {
                                  TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc,
                                      pc_list);
                                  TAILQ_INSERT_TAIL(&newtail, pc, pc_lru);
  
                                  /*
                                   * One freed pv entry in locked_pmap is
                                   * sufficient.
                                   */
                                  if (pmap == locked_pmap)
                                          goto out;
                                  break;
                          }
                  if (field == _NPCM) {
                          PV_STAT(pv_entry_spare -= _NPCPV);
                          PV_STAT(pc_chunk_count--);
                          PV_STAT(pc_chunk_frees++);
                          /* Entire chunk is free; return it. */
                          m_pc = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)pc));
                          pmap_qremove((vm_offset_t)pc, 1);
                          pmap_ptelist_free(&pv_vafree, (vm_offset_t)pc);
                          break;
                  }
          }
  out:
          TAILQ_CONCAT(&pv_chunks, &newtail, pc_lru);
          if (pmap != NULL) {
                  pmap_invalidate_all(pmap);
                  if (pmap != locked_pmap)
                          PMAP_UNLOCK(pmap);
          }
          if (m_pc == NULL && pv_vafree != 0 && 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;
                  atomic_add_int(&cnt.v_wire_count, 1);
          }
          pmap_free_zero_pages(&free);
          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;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          PV_STAT(pv_entry_frees++);
          PV_STAT(pv_entry_spare++);
          pv_entry_count--;
          pc = pv_to_chunk(pv);
          idx = pv - &pc->pc_pventry[0];
          field = idx / 32;
          bit = idx % 32;
          pc->pc_map[field] |= 1ul << bit;
          for (idx = 0; idx < _NPCM; idx++)
                  if (pc->pc_map[idx] != pc_freemask[idx]) {
                          /*
                           * 98% of the time, pc is already at the head of the
                           * list.  If it isn't already, move it to the head.
                           */
                          if (__predict_false(TAILQ_FIRST(&pmap->pm_pvchunk) !=
                              pc)) {
                                  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;
  
          TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
          PV_STAT(pv_entry_spare -= _NPCPV);
          PV_STAT(pc_chunk_count--);
          PV_STAT(pc_chunk_frees++);
          /* entire chunk is free, return it */
          m = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)pc));
          pmap_qremove((vm_offset_t)pc, 1);
          vm_page_unwire(m, 0);
          vm_page_free(m);
          pmap_ptelist_free(&pv_vafree, (vm_offset_t)pc);
  }
  
  /*
   * get a new pv_entry, allocating a block from the system
   * when needed.
   */
  static pv_entry_t
  get_pv_entry(pmap_t pmap, boolean_t try)
  {
          static const struct timeval printinterval = { 60, 0 };
          static struct timeval lastprint;
          int bit, field;
          pv_entry_t pv;
          struct pv_chunk *pc;
          vm_page_t m;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          PV_STAT(pv_entry_allocs++);
          pv_entry_count++;
          if (pv_entry_count > pv_entry_high_water)
                  if (ratecheck(&lastprint, &printinterval))
                          printf("Approaching the limit on PV entries, consider "
                              "increasing either the vm.pmap.shpgperproc or the "
                              "vm.pmap.pv_entry_max tunable.\n");
  retry:
          pc = TAILQ_FIRST(&pmap->pm_pvchunk);
          if (pc != NULL) {
                  for (field = 0; field < _NPCM; field++) {
                          if (pc->pc_map[field]) {
                                  bit = bsfl(pc->pc_map[field]);
                                  break;
                          }
                  }
                  if (field < _NPCM) {
                          pv = &pc->pc_pventry[field * 32 + bit];
                          pc->pc_map[field] &= ~(1ul << bit);
                          /* If this was the last item, move it to tail */
                          for (field = 0; field < _NPCM; field++)
                                  if (pc->pc_map[field] != 0) {
                                          PV_STAT(pv_entry_spare--);
                                          return (pv);    /* not full, return */
                                  }
                          TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                          TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc, pc_list);
                          PV_STAT(pv_entry_spare--);
                          return (pv);
                  }
          }
          /*
           * Access to the ptelist "pv_vafree" is synchronized by the pvh
           * global lock.  If "pv_vafree" is currently non-empty, it will
           * remain non-empty until pmap_ptelist_alloc() completes.
           */
          if (pv_vafree == 0 || (m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
              VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
                  if (try) {
                          pv_entry_count--;
                          PV_STAT(pc_chunk_tryfail++);
                          return (NULL);
                  }
                  m = pmap_pv_reclaim(pmap);
                  if (m == NULL)
                          goto retry;
          }
          PV_STAT(pc_chunk_count++);
          PV_STAT(pc_chunk_allocs++);
          pc = (struct pv_chunk *)pmap_ptelist_alloc(&pv_vafree);
          pmap_qenter((vm_offset_t)pc, &m, 1);
          pc->pc_pmap = pmap;
          pc->pc_map[0] = pc_freemask[0] & ~1ul;  /* preallocated bit 0 */
          for (field = 1; field < _NPCM; field++)
                  pc->pc_map[field] = pc_freemask[field];
          TAILQ_INSERT_TAIL(&pv_chunks, pc, pc_lru);
          pv = &pc->pc_pventry[0];
          TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
          PV_STAT(pv_entry_spare += _NPCPV - 1);
          return (pv);
  }
  
  static __inline pv_entry_t
  pmap_pvh_remove(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
  {
          pv_entry_t pv;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          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);
                          break;
                  }
          }
          return (pv);
  }
  
  static void
  pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa)
  {
          struct md_page *pvh;
          pv_entry_t pv;
          vm_offset_t va_last;
          vm_page_t m;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          KASSERT((pa & PDRMASK) == 0,
              ("pmap_pv_demote_pde: pa is not 4mpage aligned"));
  
          /*
           * Transfer the 4mpage's pv entry for this mapping to the first
           * page's pv list.
           */
          pvh = pa_to_pvh(pa);
          va = trunc_4mpage(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);
          /* Instantiate the remaining NPTEPG - 1 pv entries. */
          va_last = va + NBPDR - PAGE_SIZE;
          do {
                  m++;
                  KASSERT((m->oflags & VPO_UNMANAGED) == 0,
                      ("pmap_pv_demote_pde: page %p is not managed", m));
                  va += PAGE_SIZE;
                  pmap_insert_entry(pmap, va, m);
          } while (va < va_last);
  }
  
  static void
  pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa)
  {
          struct md_page *pvh;
          pv_entry_t pv;
          vm_offset_t va_last;
          vm_page_t m;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          KASSERT((pa & PDRMASK) == 0,
              ("pmap_pv_promote_pde: pa is not 4mpage aligned"));
  
          /*
           * Transfer the first page's pv entry for this mapping to the
           * 4mpage'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 pmap_collect() and that pmap_collect()
           * removes one of the mappings that is being promoted.
           */
          m = PHYS_TO_VM_PAGE(pa);
          va = trunc_4mpage(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);
          /* 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);
  }
  
  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);
  }
  
  static void
  pmap_remove_entry(pmap_t pmap, vm_page_t m, vm_offset_t va)
  {
          struct md_page *pvh;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          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);
          }
  }
  
  /*
   * Create a pv entry for page at pa for
   * (pmap, va).
   */
  static void
  pmap_insert_entry(pmap_t pmap, vm_offset_t va, vm_page_t m)
  {
          pv_entry_t pv;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          pv = get_pv_entry(pmap, FALSE);
          pv->pv_va = va;
          TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
  }
  
  /*
   * Conditionally create a pv entry.
   */
  static boolean_t
  pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va, vm_page_t m)
  {
          pv_entry_t pv;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          if (pv_entry_count < pv_entry_high_water && 
              (pv = get_pv_entry(pmap, TRUE)) != NULL) {
                  pv->pv_va = va;
                  TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                  return (TRUE);
          } else
                  return (FALSE);
  }
  
  /*
   * Create the pv entries for each of the pages within a superpage.
   */
  static boolean_t
  pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa)
  {
          struct md_page *pvh;
          pv_entry_t pv;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          if (pv_entry_count < pv_entry_high_water && 
              (pv = get_pv_entry(pmap, TRUE)) != NULL) {
                  pv->pv_va = va;
                  pvh = pa_to_pvh(pa);
                  TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
                  return (TRUE);
          } else
                  return (FALSE);
  }
  
  /*
   * 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 2- or 4MB page mapping.  If demotion fails, the
   * 2- or 4MB page mapping is invalidated.
   */
  static boolean_t
  pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
  {
          pd_entry_t newpde, oldpde;
          pt_entry_t *firstpte, newpte;
          vm_paddr_t mptepa;
          vm_page_t mpte;
          struct spglist free;
          vm_offset_t sva;
  
          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_lookup_pt_page(pmap, va)) !=
              NULL)
                  pmap_remove_pt_page(pmap, mpte);
          else {
                  KASSERT((oldpde & PG_W) == 0,
                      ("pmap_demote_pde: page table page for a wired mapping"
                      " is missing"));
  
                  /*
                   * Invalidate the 2- or 4MB page mapping and return
                   * "failure" if the mapping was never accessed or the
                   * allocation of the new page table page fails.
                   */
                  if ((oldpde & PG_A) == 0 || (mpte = vm_page_alloc(NULL,
                      va >> PDRSHIFT, VM_ALLOC_NOOBJ | VM_ALLOC_NORMAL |
                      VM_ALLOC_WIRED)) == NULL) {
                          SLIST_INIT(&free);
                          sva = trunc_4mpage(va);
                          pmap_remove_pde(pmap, pde, sva, &free);
                          if ((oldpde & PG_G) == 0)
                                  pmap_invalidate_pde_page(pmap, sva, oldpde);
                          pmap_free_zero_pages(&free);
                          CTR2(KTR_PMAP, "pmap_demote_pde: failure for va %#x"
                              " in pmap %p", va, pmap);
                          return (FALSE);
                  }
                  if (va < VM_MAXUSER_ADDRESS)
                          pmap->pm_stats.resident_count++;
          }
          mptepa = VM_PAGE_TO_PHYS(mpte);
  
          /*
           * If the page mapping is in the kernel's address space, then the
           * KPTmap can provide access to the page table page.  Otherwise,
           * temporarily map the page table page (mpte) into the kernel's
           * address space at either PADDR1 or PADDR2. 
           */
          if (va >= KERNBASE)
                  firstpte = &KPTmap[i386_btop(trunc_4mpage(va))];
          else if (curthread->td_pinned > 0 && rw_wowned(&pvh_global_lock)) {
                  if ((*PMAP1 & PG_FRAME) != mptepa) {
                          *PMAP1 = mptepa | PG_RW | PG_V | PG_A | PG_M;
  #ifdef SMP
                          PMAP1cpu = PCPU_GET(cpuid);
  #endif
                          invlcaddr(PADDR1);
                          PMAP1changed++;
                  } else
  #ifdef SMP
                  if (PMAP1cpu != PCPU_GET(cpuid)) {
                          PMAP1cpu = PCPU_GET(cpuid);
                          invlcaddr(PADDR1);
                          PMAP1changedcpu++;
                  } else
  #endif
                          PMAP1unchanged++;
                  firstpte = PADDR1;
          } else {
                  mtx_lock(&PMAP2mutex);
                  if ((*PMAP2 & PG_FRAME) != mptepa) {
                          *PMAP2 = mptepa | PG_RW | PG_V | PG_A | PG_M;
                          pmap_invalidate_page(kernel_pmap, (vm_offset_t)PADDR2);
                  }
                  firstpte = PADDR2;
          }
          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;
          if ((newpte & PG_PDE_PAT) != 0)
                  newpte ^= PG_PDE_PAT | PG_PTE_PAT;
  
          /*
           * 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);
          
          /*
           * 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 if (pmap == kernel_pmap)
                  pmap_kenter_pde(va, newpde);
          else
                  pde_store(pde, newpde); 
          if (firstpte == PADDR2)
                  mtx_unlock(&PMAP2mutex);
  
          /*
           * Invalidate the recursive mapping of the page table page.
           */
          pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));
  
          /*
           * Demote the pv entry.  This depends on the earlier demotion
           * of the mapping.  Specifically, the (re)creation of a per-
           * page pv entry might trigger the execution of pmap_collect(),
           * which might reclaim a newly (re)created per-page pv entry
           * and destroy the associated mapping.  In order to destroy
           * the mapping, the PDE must have already changed from mapping
           * the 2mpage to referencing the page table page.
           */
          if ((oldpde & PG_MANAGED) != 0)
                  pmap_pv_demote_pde(pmap, va, oldpde & PG_PS_FRAME);
  
          pmap_pde_demotions++;
          CTR2(KTR_PMAP, "pmap_demote_pde: success for va %#x"
              " in pmap %p", va, pmap);
          return (TRUE);
  }
  
  /*
   * Removes a 2- or 4MB page mapping from the kernel pmap.
   */
  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;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          mpte = pmap_lookup_pt_page(pmap, va);
          if (mpte == NULL)
                  panic("pmap_remove_kernel_pde: Missing pt page.");
  
          pmap_remove_pt_page(pmap, mpte);
          mptepa = VM_PAGE_TO_PHYS(mpte);
          newpde = mptepa | PG_M | PG_A | PG_RW | PG_V;
  
          /*
           * Initialize the page table page.
           */
          pagezero((void *)&KPTmap[i386_btop(trunc_4mpage(va))]);
  
          /*
           * Remove the mapping.
           */
          if (workaround_erratum383)
                  pmap_update_pde(pmap, va, pde, newpde);
          else 
                  pmap_kenter_pde(va, newpde);
  
          /*
           * Invalidate the 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 void
  pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
      struct spglist *free)
  {
          struct md_page *pvh;
          pd_entry_t oldpde;
          vm_offset_t eva, va;
          vm_page_t m, mpte;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          KASSERT((sva & PDRMASK) == 0,
              ("pmap_remove_pde: sva is not 4mpage aligned"));
          oldpde = pte_load_clear(pdq);
          if (oldpde & PG_W)
                  pmap->pm_stats.wired_count -= NBPDR / PAGE_SIZE;
  
          /*
           * Machines that don't support invlpg, also don't support
           * PG_G.
           */
          if ((oldpde & PG_G) != 0)
                  pmap_invalidate_pde_page(kernel_pmap, sva, oldpde);
  
          pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
          if (oldpde & PG_MANAGED) {
                  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);
                  }
          }
          if (pmap == kernel_pmap) {
                  pmap_remove_kernel_pde(pmap, pdq, sva);
          } else {
                  mpte = pmap_lookup_pt_page(pmap, sva);
                  if (mpte != NULL) {
                          pmap_remove_pt_page(pmap, mpte);
                          pmap->pm_stats.resident_count--;
                          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);
                          atomic_subtract_int(&cnt.v_wire_count, 1);
                  }
          }
  }
  
  /*
   * 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,
      struct spglist *free)
  {
          pt_entry_t oldpte;
          vm_page_t m;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          oldpte = pte_load_clear(ptq);
          KASSERT(oldpte != 0,
              ("pmap_remove_pte: pmap %p va %x zero pte", pmap, va));
          if (oldpte & PG_W)
                  pmap->pm_stats.wired_count -= 1;
          /*
           * Machines that don't support invlpg, also don't support
           * PG_G.
           */
          if (oldpte & PG_G)
                  pmap_invalidate_page(kernel_pmap, va);
          pmap->pm_stats.resident_count -= 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);
                  pmap_remove_entry(pmap, m, va);
          }
          return (pmap_unuse_pt(pmap, va, free));
  }
  
  /*
   * Remove a single page from a process address space
   */
  static void
  pmap_remove_page(pmap_t pmap, vm_offset_t va, struct spglist *free)
  {
          pt_entry_t *pte;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          KASSERT(curthread->td_pinned > 0, ("curthread not pinned"));
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          if ((pte = pmap_pte_quick(pmap, va)) == NULL || *pte == 0)
                  return;
          pmap_remove_pte(pmap, pte, va, free);
          pmap_invalidate_page(pmap, va);
  }
  
  /*
   *      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)
  {
          vm_offset_t pdnxt;
          pd_entry_t ptpaddr;
          pt_entry_t *pte;
          struct spglist free;
          int anyvalid;
  
          /*
           * Perform an unsynchronized read.  This is, however, safe.
           */
          if (pmap->pm_stats.resident_count == 0)
                  return;
  
          anyvalid = 0;
          SLIST_INIT(&free);
  
          rw_wlock(&pvh_global_lock);
          sched_pin();
          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) && 
              ((pmap->pm_pdir[(sva >> PDRSHIFT)] & PG_PS) == 0)) {
                  pmap_remove_page(pmap, sva, &free);
                  goto out;
          }
  
          for (; sva < eva; sva = pdnxt) {
                  u_int pdirindex;
  
                  /*
                   * Calculate index for next page table.
                   */
                  pdnxt = (sva + NBPDR) & ~PDRMASK;
                  if (pdnxt < sva)
                          pdnxt = eva;
                  if (pmap->pm_stats.resident_count == 0)
                          break;
  
                  pdirindex = sva >> PDRSHIFT;
                  ptpaddr = pmap->pm_pdir[pdirindex];
  
                  /*
                   * Weed out invalid mappings. Note: we assume that the page
                   * directory table is always allocated, and in kernel virtual.
                   */
                  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 == pdnxt && eva >= pdnxt) {
                                  /*
                                   * 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,
                                      &pmap->pm_pdir[pdirindex], sva, &free);
                                  continue;
                          } else if (!pmap_demote_pde(pmap,
                              &pmap->pm_pdir[pdirindex], sva)) {
                                  /* The large page mapping was destroyed. */
                                  continue;
                          }
                  }
  
                  /*
                   * 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 (pdnxt > eva)
                          pdnxt = eva;
  
                  for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++,
                      sva += PAGE_SIZE) {
                          if (*pte == 0)
                                  continue;
  
                          /*
                           * The TLB entry for a PG_G mapping is invalidated
                           * by pmap_remove_pte().
                           */
                          if ((*pte & PG_G) == 0)
                                  anyvalid = 1;
                          if (pmap_remove_pte(pmap, pte, sva, &free))
                                  break;
                  }
          }
  out:
          sched_unpin();
          if (anyvalid)
                  pmap_invalidate_all(pmap);
          rw_wunlock(&pvh_global_lock);
          PMAP_UNLOCK(pmap);
          pmap_free_zero_pages(&free);
  }
  
  /*
   *      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;
          pt_entry_t *pte, tpte;
          pd_entry_t *pde;
          vm_offset_t va;
          struct spglist free;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_remove_all: page %p is not managed", m));
          SLIST_INIT(&free);
          rw_wlock(&pvh_global_lock);
          sched_pin();
          if ((m->flags & PG_FICTITIOUS) != 0)
                  goto small_mappings;
          pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
          while ((pv = TAILQ_FIRST(&pvh->pv_list)) != NULL) {
                  va = pv->pv_va;
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pde = pmap_pde(pmap, va);
                  (void)pmap_demote_pde(pmap, pde, va);
                  PMAP_UNLOCK(pmap);
          }
  small_mappings:
          while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pmap->pm_stats.resident_count--;
                  pde = pmap_pde(pmap, pv->pv_va);
                  KASSERT((*pde & PG_PS) == 0, ("pmap_remove_all: found"
                      " a 4mpage in page %p's pv list", m));
                  pte = pmap_pte_quick(pmap, pv->pv_va);
                  tpte = pte_load_clear(pte);
                  KASSERT(tpte != 0, ("pmap_remove_all: pmap %p va %x zero pte",
                      pmap, pv->pv_va));
                  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, &free);
                  pmap_invalidate_page(pmap, pv->pv_va);
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                  free_pv_entry(pmap, pv);
                  PMAP_UNLOCK(pmap);
          }
          vm_page_aflag_clear(m, PGA_WRITEABLE);
          sched_unpin();
          rw_wunlock(&pvh_global_lock);
          pmap_free_zero_pages(&free);
  }
  
  /*
   * pmap_protect_pde: do the things to protect a 4mpage 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;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          KASSERT((sva & PDRMASK) == 0,
              ("pmap_protect_pde: sva is not 4mpage aligned"));
          anychanged = FALSE;
  retry:
          oldpde = newpde = *pde;
          if (oldpde & PG_MANAGED) {
                  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 ((prot & VM_PROT_WRITE) == 0)
                  newpde &= ~(PG_RW | PG_M);
  #if defined(PAE) || defined(PAE_TABLES)
          if ((prot & VM_PROT_EXECUTE) == 0)
                  newpde |= pg_nx;
  #endif
          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 (!pde_cmpset(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 pdnxt;
          pd_entry_t ptpaddr;
          pt_entry_t *pte;
          boolean_t anychanged, pv_lists_locked;
  
          KASSERT((prot & ~VM_PROT_ALL) == 0, ("invalid prot %x", prot));
          if (prot == VM_PROT_NONE) {
                  pmap_remove(pmap, sva, eva);
                  return;
          }
  
  #if defined(PAE) || defined(PAE_TABLES)
          if ((prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) ==
              (VM_PROT_WRITE|VM_PROT_EXECUTE))
                  return;
  #else
          if (prot & VM_PROT_WRITE)
                  return;
  #endif
  
          if (pmap_is_current(pmap))
                  pv_lists_locked = FALSE;
          else {
                  pv_lists_locked = TRUE;
  resume:
                  rw_wlock(&pvh_global_lock);
                  sched_pin();
          }
          anychanged = FALSE;
  
          PMAP_LOCK(pmap);
          for (; sva < eva; sva = pdnxt) {
                  pt_entry_t obits, pbits;
                  u_int pdirindex;
  
                  pdnxt = (sva + NBPDR) & ~PDRMASK;
                  if (pdnxt < sva)
                          pdnxt = eva;
  
                  pdirindex = sva >> PDRSHIFT;
                  ptpaddr = pmap->pm_pdir[pdirindex];
  
                  /*
                   * Weed out invalid mappings. Note: we assume that the page
                   * directory table is always allocated, and in kernel virtual.
                   */
                  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 == pdnxt && eva >= pdnxt) {
                                  /*
                                   * The TLB entry for a PG_G mapping is
                                   * invalidated by pmap_protect_pde().
                                   */
                                  if (pmap_protect_pde(pmap,
                                      &pmap->pm_pdir[pdirindex], sva, prot))
                                          anychanged = TRUE;
                                  continue;
                          } else {
                                  if (!pv_lists_locked) {
                                          pv_lists_locked = TRUE;
                                          if (!rw_try_wlock(&pvh_global_lock)) {
                                                  if (anychanged)
                                                          pmap_invalidate_all(
                                                              pmap);
                                                  PMAP_UNLOCK(pmap);
                                                  goto resume;
                                          }
                                          sched_pin();
                                  }
                                  if (!pmap_demote_pde(pmap,
                                      &pmap->pm_pdir[pdirindex], sva)) {
                                          /*
                                           * The large page mapping was
                                           * destroyed.
                                           */
                                          continue;
                                  }
                          }
                  }
  
                  if (pdnxt > eva)
                          pdnxt = eva;
  
                  for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++,
                      sva += PAGE_SIZE) {
                          vm_page_t m;
  
  retry:
                          /*
                           * Regardless of whether a pte is 32 or 64 bits in
                           * size, PG_RW, PG_A, and PG_M are among the least
                           * significant 32 bits.
                           */
                          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 defined(PAE) || defined(PAE_TABLES)
                          if ((prot & VM_PROT_EXECUTE) == 0)
                                  pbits |= pg_nx;
  #endif
  
                          if (pbits != obits) {
  #if defined(PAE) || defined(PAE_TABLES)
                                  if (!atomic_cmpset_64(pte, obits, pbits))
                                          goto retry;
  #else
                                  if (!atomic_cmpset_int((u_int *)pte, obits,
                                      pbits))
                                          goto retry;
  #endif
                                  if (obits & PG_G)
                                          pmap_invalidate_page(pmap, sva);
                                  else
                                          anychanged = TRUE;
                          }
                  }
          }
          if (anychanged)
                  pmap_invalidate_all(pmap);
          if (pv_lists_locked) {
                  sched_unpin();
                  rw_wunlock(&pvh_global_lock);
          }
          PMAP_UNLOCK(pmap);
  }
  
  /*
   * Tries to promote the 512 or 1024, contiguous 4KB page mappings that are
   * within a single page table page (PTP) to a single 2- or 4MB 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.
   *
   * Managed (PG_MANAGED) mappings within the kernel address space are not
   * promoted.  The reason is that kernel PDEs are replicated in each pmap but
   * pmap_clear_ptes() and pmap_ts_referenced() only read the PDE from the kernel
   * pmap.
   */
  static void
  pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
  {
          pd_entry_t newpde;
          pt_entry_t *firstpte, oldpte, pa, *pte;
          vm_offset_t oldpteva;
          vm_page_t mpte;
  
          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 2- or 4MB page.
           */
          firstpte = pmap_pte_quick(pmap, trunc_4mpage(va));
  setpde:
          newpde = *firstpte;
          if ((newpde & ((PG_FRAME & PDRMASK) | PG_A | PG_V)) != (PG_A | PG_V)) {
                  pmap_pde_p_failures++;
                  CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#x"
                      " in pmap %p", va, pmap);
                  return;
          }
          if ((*firstpte & PG_MANAGED) != 0 && pmap == kernel_pmap) {
                  pmap_pde_p_failures++;
                  CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#x"
                      " 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_int((u_int *)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) {
                          pmap_pde_p_failures++;
                          CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#x"
                              " 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_int((u_int *)pte, oldpte,
                              oldpte & ~PG_RW))
                                  goto setpte;
                          oldpte &= ~PG_RW;
                          oldpteva = (oldpte & PG_FRAME & PDRMASK) |
                              (va & ~PDRMASK);
                          CTR2(KTR_PMAP, "pmap_promote_pde: protect for va %#x"
                              " in pmap %p", oldpteva, pmap);
                  }
                  if ((oldpte & PG_PTE_PROMOTE) != (newpde & PG_PTE_PROMOTE)) {
                          pmap_pde_p_failures++;
                          CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#x"
                              " 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 == va >> PDRSHIFT,
              ("pmap_promote_pde: page table page's pindex is wrong"));
          if (pmap_insert_pt_page(pmap, mpte)) {
                  pmap_pde_p_failures++;
                  CTR2(KTR_PMAP,
                      "pmap_promote_pde: failure for va %#x 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);
  
          /*
           * Propagate the PAT index to its proper position.
           */
          if ((newpde & PG_PTE_PAT) != 0)
                  newpde ^= PG_PDE_PAT | PG_PTE_PAT;
  
          /*
           * Map the superpage.
           */
          if (workaround_erratum383)
                  pmap_update_pde(pmap, va, pde, PG_PS | newpde);
          else if (pmap == kernel_pmap)
                  pmap_kenter_pde(va, PG_PROMOTED | PG_PS | newpde);
          else
                  pde_store(pde, PG_PROMOTED | PG_PS | newpde);
  
          pmap_pde_promotions++;
          CTR2(KTR_PMAP, "pmap_promote_pde: success for va %#x"
              " in pmap %p", va, pmap);
  }
  
  /*
   *      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.
   */
  int
  pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
      u_int flags, int8_t psind)
  {
          pd_entry_t *pde;
          pt_entry_t *pte;
          pt_entry_t newpte, origpte;
          pv_entry_t pv;
          vm_paddr_t opa, pa;
          vm_page_t mpte, om;
          boolean_t invlva, wired;
  
          va = trunc_page(va);
          mpte = NULL;
          wired = (flags & PMAP_ENTER_WIRED) != 0;
  
          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%x)",
              va));
          if ((m->oflags & VPO_UNMANAGED) == 0 && !vm_page_xbusied(m))
                  VM_OBJECT_ASSERT_LOCKED(m->object);
  
          rw_wlock(&pvh_global_lock);
          PMAP_LOCK(pmap);
          sched_pin();
  
          /*
           * In the case that a page table page is not
           * resident, we are creating it here.
           */
          if (va < VM_MAXUSER_ADDRESS) {
                  mpte = pmap_allocpte(pmap, va, flags);
                  if (mpte == NULL) {
                          KASSERT((flags & PMAP_ENTER_NOSLEEP) != 0,
                              ("pmap_allocpte failed with sleep allowed"));
                          sched_unpin();
                          rw_wunlock(&pvh_global_lock);
                          PMAP_UNLOCK(pmap);
                          return (KERN_RESOURCE_SHORTAGE);
                  }
          }
  
          pde = pmap_pde(pmap, va);
          if ((*pde & PG_PS) != 0)
                  panic("pmap_enter: attempted pmap_enter on 4MB page");
          pte = pmap_pte_quick(pmap, va);
  
          /*
           * Page Directory table entry not valid, we need a new PT page
           */
          if (pte == NULL) {
                  panic("pmap_enter: invalid page directory pdir=%#jx, va=%#x",
                          (uintmax_t)pmap->pm_pdir[PTDPTDI], va);
          }
  
          pa = VM_PAGE_TO_PHYS(m);
          om = NULL;
          origpte = *pte;
          opa = origpte & PG_FRAME;
  
          /*
           * Mapping has not changed, must be protection or wiring change.
           */
          if (origpte && (opa == pa)) {
                  /*
                   * 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 (wired && ((origpte & PG_W) == 0))
                          pmap->pm_stats.wired_count++;
                  else if (!wired && (origpte & PG_W))
                          pmap->pm_stats.wired_count--;
  
                  /*
                   * Remove extra pte reference
                   */
                  if (mpte)
                          mpte->wire_count--;
  
                  if (origpte & PG_MANAGED) {
                          om = m;
                          pa |= PG_MANAGED;
                  }
                  goto validate;
          } 
  
          pv = NULL;
  
          /*
           * Mapping has changed, invalidate old range and fall through to
           * handle validating new mapping.
           */
          if (opa) {
                  if (origpte & PG_W)
                          pmap->pm_stats.wired_count--;
                  if (origpte & PG_MANAGED) {
                          om = PHYS_TO_VM_PAGE(opa);
                          pv = pmap_pvh_remove(&om->md, pmap, va);
                  }
                  if (mpte != NULL) {
                          mpte->wire_count--;
                          KASSERT(mpte->wire_count > 0,
                              ("pmap_enter: missing reference to page table page,"
                               " va: 0x%x", va));
                  }
          } else
                  pmap->pm_stats.resident_count++;
  
          /*
           * Enter on the PV list if part of our managed memory.
           */
          if ((m->oflags & VPO_UNMANAGED) == 0) {
                  KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva,
                      ("pmap_enter: managed mapping within the clean submap"));
                  if (pv == NULL)
                          pv = get_pv_entry(pmap, FALSE);
                  pv->pv_va = va;
                  TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                  pa |= PG_MANAGED;
          } else if (pv != NULL)
                  free_pv_entry(pmap, pv);
  
          /*
           * Increment counters
           */
          if (wired)
                  pmap->pm_stats.wired_count++;
  
  validate:
          /*
           * Now validate mapping with desired protection/wiring.
           */
          newpte = (pt_entry_t)(pa | pmap_cache_bits(m->md.pat_mode, 0) | PG_V);
          if ((prot & VM_PROT_WRITE) != 0) {
                  newpte |= PG_RW;
                  if ((newpte & PG_MANAGED) != 0)
                          vm_page_aflag_set(m, PGA_WRITEABLE);
          }
  #if defined(PAE) || defined(PAE_TABLES)
          if ((prot & VM_PROT_EXECUTE) == 0)
                  newpte |= pg_nx;
  #endif
          if (wired)
                  newpte |= PG_W;
          if (va < VM_MAXUSER_ADDRESS)
                  newpte |= PG_U;
          if (pmap == kernel_pmap)
                  newpte |= pgeflag;
  
          /*
           * if the mapping or permission bits are different, we need
           * to update the pte.
           */
          if ((origpte & ~(PG_M|PG_A)) != newpte) {
                  newpte |= PG_A;
                  if ((flags & VM_PROT_WRITE) != 0)
                          newpte |= PG_M;
                  if (origpte & PG_V) {
                          invlva = FALSE;
                          origpte = pte_load_store(pte, newpte);
                          if (origpte & PG_A) {
                                  if (origpte & PG_MANAGED)
                                          vm_page_aflag_set(om, PGA_REFERENCED);
                                  if (opa != VM_PAGE_TO_PHYS(m))
                                          invlva = TRUE;
  #if defined(PAE) || defined(PAE_TABLES)
                                  if ((origpte & PG_NX) == 0 &&
                                      (newpte & PG_NX) != 0)
                                          invlva = TRUE;
  #endif
                          }
                          if ((origpte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                  if ((origpte & PG_MANAGED) != 0)
                                          vm_page_dirty(om);
                                  if ((prot & VM_PROT_WRITE) == 0)
                                          invlva = TRUE;
                          }
                          if ((origpte & PG_MANAGED) != 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 (invlva)
                                  pmap_invalidate_page(pmap, va);
                  } else
                          pte_store(pte, newpte);
          }
  
          /*
           * If both the page table page and the reservation are fully
           * populated, then attempt promotion.
           */
          if ((mpte == NULL || mpte->wire_count == NPTEPG) &&
              pg_ps_enabled && (m->flags & PG_FICTITIOUS) == 0 &&
              vm_reserv_level_iffullpop(m) == 0)
                  pmap_promote_pde(pmap, pde, va);
  
          sched_unpin();
          rw_wunlock(&pvh_global_lock);
          PMAP_UNLOCK(pmap);
          return (KERN_SUCCESS);
  }
  
  /*
   * Tries to create a 2- or 4MB page mapping.  Returns TRUE if successful and
   * FALSE otherwise.  Fails if (1) a page table page cannot be allocated without
   * blocking, (2) a mapping already exists at the specified virtual address, or
   * (3) a pv entry cannot be allocated without reclaiming another pv entry. 
   */
  static boolean_t
  pmap_enter_pde(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
  {
          pd_entry_t *pde, newpde;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          pde = pmap_pde(pmap, va);
          if (*pde != 0) {
                  CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                      " in pmap %p", va, pmap);
                  return (FALSE);
          }
          newpde = VM_PAGE_TO_PHYS(m) | pmap_cache_bits(m->md.pat_mode, 1) |
              PG_PS | PG_V;
          if ((m->oflags & VPO_UNMANAGED) == 0) {
                  newpde |= PG_MANAGED;
  
                  /*
                   * Abort this mapping if its PV entry could not be created.
                   */
                  if (!pmap_pv_insert_pde(pmap, va, VM_PAGE_TO_PHYS(m))) {
                          CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                              " in pmap %p", va, pmap);
                          return (FALSE);
                  }
          }
  #if defined(PAE) || defined(PAE_TABLES)
          if ((prot & VM_PROT_EXECUTE) == 0)
                  newpde |= pg_nx;
  #endif
          if (va < VM_MAXUSER_ADDRESS)
                  newpde |= PG_U;
  
          /*
           * Increment counters.
           */
          pmap->pm_stats.resident_count += 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);
  
          pmap_pde_mappings++;
          CTR2(KTR_PMAP, "pmap_enter_pde: success for va %#lx"
              " in pmap %p", va, pmap);
          return (TRUE);
  }
  
  /*
   * 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)
  {
          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;
          rw_wlock(&pvh_global_lock);
          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 && pg_ps_enabled &&
                      pmap_enter_pde(pmap, va, m, prot))
                          m = &m[NBPDR / PAGE_SIZE - 1];
                  else
                          mpte = pmap_enter_quick_locked(pmap, va, m, prot,
                              mpte);
                  m = TAILQ_NEXT(m, listq);
          }
          rw_wunlock(&pvh_global_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)
  {
  
          rw_wlock(&pvh_global_lock);
          PMAP_LOCK(pmap);
          (void)pmap_enter_quick_locked(pmap, va, m, prot, NULL);
          rw_wunlock(&pvh_global_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)
  {
          pt_entry_t *pte;
          vm_paddr_t pa;
          struct spglist free;
  
          KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
              (m->oflags & VPO_UNMANAGED) != 0,
              ("pmap_enter_quick_locked: managed mapping within the clean submap"));
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          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) {
                  u_int ptepindex;
                  pd_entry_t ptepa;
  
                  /*
                   * Calculate pagetable page index
                   */
                  ptepindex = va >> PDRSHIFT;
                  if (mpte && (mpte->pindex == ptepindex)) {
                          mpte->wire_count++;
                  } else {
                          /*
                           * Get the page directory entry
                           */
                          ptepa = pmap->pm_pdir[ptepindex];
  
                          /*
                           * If the page table page is mapped, we just increment
                           * the hold count, and activate it.
                           */
                          if (ptepa) {
                                  if (ptepa & PG_PS)
                                          return (NULL);
                                  mpte = PHYS_TO_VM_PAGE(ptepa & PG_FRAME);
                                  mpte->wire_count++;
                          } else {
                                  mpte = _pmap_allocpte(pmap, ptepindex,
                                      PMAP_ENTER_NOSLEEP);
                                  if (mpte == NULL)
                                          return (mpte);
                          }
                  }
          } else {
                  mpte = NULL;
          }
  
          /*
           * This call to vtopte makes the assumption that we are
           * entering the page into the current pmap.  In order to support
           * quick entry into any pmap, one would likely use pmap_pte_quick.
           * But that isn't as quick as vtopte.
           */
          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)) {
                  if (mpte != NULL) {
                          SLIST_INIT(&free);
                          if (pmap_unwire_ptp(pmap, mpte, &free)) {
                                  pmap_invalidate_page(pmap, va);
                                  pmap_free_zero_pages(&free);
                          }
                          
                          mpte = NULL;
                  }
                  return (mpte);
          }
  
          /*
           * Increment counters
           */
          pmap->pm_stats.resident_count++;
  
          pa = VM_PAGE_TO_PHYS(m) | pmap_cache_bits(m->md.pat_mode, 0);
  #if defined(PAE) || defined(PAE_TABLES)
          if ((prot & VM_PROT_EXECUTE) == 0)
                  pa |= pg_nx;
  #endif
  
          /*
           * Now validate mapping with RO protection
           */
          if ((m->oflags & VPO_UNMANAGED) != 0)
                  pte_store(pte, pa | PG_V | PG_U);
          else
                  pte_store(pte, pa | PG_V | PG_U | PG_MANAGED);
          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;
          vm_paddr_t pa, ptepa;
          vm_page_t p;
          int pat_mode;
  
          VM_OBJECT_ASSERT_WLOCKED(object);
          KASSERT(object->type == OBJT_DEVICE || object->type == OBJT_SG,
              ("pmap_object_init_pt: non-device object"));
          if (pseflag && 
              (addr & (NBPDR - 1)) == 0 && (size & (NBPDR - 1)) == 0) {
                  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 2/4MB 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 2/4MB pages.  Since "ptepa" is 2/4M aligned and
                   * "size" is a multiple of 2/4M, adding the PAT setting to
                   * "pa" will not affect the termination of this loop.
                   */
                  PMAP_LOCK(pmap);
                  for (pa = ptepa | pmap_cache_bits(pat_mode, 1); pa < ptepa +
                      size; pa += NBPDR) {
                          pde = pmap_pde(pmap, addr);
                          if (*pde == 0) {
                                  pde_store(pde, pa | PG_PS | PG_M | PG_A |
                                      PG_U | PG_RW | PG_V);
                                  pmap->pm_stats.resident_count += NBPDR /
                                      PAGE_SIZE;
                                  pmap_pde_mappings++;
                          }
                          /* Else continue on if the PDE is already valid. */
                          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.
   */
  void
  pmap_unwire(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
  {
          vm_offset_t pdnxt;
          pd_entry_t *pde;
          pt_entry_t *pte;
          boolean_t pv_lists_locked;
  
          if (pmap_is_current(pmap))
                  pv_lists_locked = FALSE;
          else {
                  pv_lists_locked = TRUE;
  resume:
                  rw_wlock(&pvh_global_lock);
                  sched_pin();
          }
          PMAP_LOCK(pmap);
          for (; sva < eva; sva = pdnxt) {
                  pdnxt = (sva + NBPDR) & ~PDRMASK;
                  if (pdnxt < sva)
                          pdnxt = eva;
                  pde = pmap_pde(pmap, 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 == pdnxt && eva >= pdnxt) {
                                  /*
                                   * Regardless of whether a pde (or pte) is 32
                                   * or 64 bits in size, PG_W is among the least
                                   * significant 32 bits.
                                   */
                                  atomic_clear_int((u_int *)pde, PG_W);
                                  pmap->pm_stats.wired_count -= NBPDR /
                                      PAGE_SIZE;
                                  continue;
                          } else {
                                  if (!pv_lists_locked) {
                                          pv_lists_locked = TRUE;
                                          if (!rw_try_wlock(&pvh_global_lock)) {
                                                  PMAP_UNLOCK(pmap);
                                                  /* Repeat sva. */
                                                  goto resume;
                                          }
                                          sched_pin();
                                  }
                                  if (!pmap_demote_pde(pmap, pde, sva))
                                          panic("pmap_unwire: demotion failed");
                          }
                  }
                  if (pdnxt > eva)
                          pdnxt = eva;
                  for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; 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.
                           *
                           * PG_W is among the least significant 32 bits.
                           */
                          atomic_clear_int((u_int *)pte, PG_W);
                          pmap->pm_stats.wired_count--;
                  }
          }
          if (pv_lists_locked) {
                  sched_unpin();
                  rw_wunlock(&pvh_global_lock);
          }
          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 spglist free;
          vm_offset_t addr;
          vm_offset_t end_addr = src_addr + len;
          vm_offset_t pdnxt;
  
          if (dst_addr != src_addr)
                  return;
  
          if (!pmap_is_current(src_pmap))
                  return;
  
          rw_wlock(&pvh_global_lock);
          if (dst_pmap < src_pmap) {
                  PMAP_LOCK(dst_pmap);
                  PMAP_LOCK(src_pmap);
          } else {
                  PMAP_LOCK(src_pmap);
                  PMAP_LOCK(dst_pmap);
          }
          sched_pin();
          for (addr = src_addr; addr < end_addr; addr = pdnxt) {
                  pt_entry_t *src_pte, *dst_pte;
                  vm_page_t dstmpte, srcmpte;
                  pd_entry_t srcptepaddr;
                  u_int ptepindex;
  
                  KASSERT(addr < UPT_MIN_ADDRESS,
                      ("pmap_copy: invalid to pmap_copy page tables"));
  
                  pdnxt = (addr + NBPDR) & ~PDRMASK;
                  if (pdnxt < addr)
                          pdnxt = end_addr;
                  ptepindex = addr >> PDRSHIFT;
  
                  srcptepaddr = src_pmap->pm_pdir[ptepindex];
                  if (srcptepaddr == 0)
                          continue;
                          
                  if (srcptepaddr & PG_PS) {
                          if ((addr & PDRMASK) != 0 || addr + NBPDR > end_addr)
                                  continue;
                          if (dst_pmap->pm_pdir[ptepindex] == 0 &&
                              ((srcptepaddr & PG_MANAGED) == 0 ||
                              pmap_pv_insert_pde(dst_pmap, addr, srcptepaddr &
                              PG_PS_FRAME))) {
                                  dst_pmap->pm_pdir[ptepindex] = srcptepaddr &
                                      ~PG_W;
                                  dst_pmap->pm_stats.resident_count +=
                                      NBPDR / PAGE_SIZE;
                          }
                          continue;
                  }
  
                  srcmpte = PHYS_TO_VM_PAGE(srcptepaddr & PG_FRAME);
                  KASSERT(srcmpte->wire_count > 0,
                      ("pmap_copy: source page table page is unused"));
  
                  if (pdnxt > end_addr)
                          pdnxt = end_addr;
  
                  src_pte = vtopte(addr);
                  while (addr < pdnxt) {
                          pt_entry_t ptetemp;
                          ptetemp = *src_pte;
                          /*
                           * we only virtual copy managed pages
                           */
                          if ((ptetemp & PG_MANAGED) != 0) {
                                  dstmpte = pmap_allocpte(dst_pmap, addr,
                                      PMAP_ENTER_NOSLEEP);
                                  if (dstmpte == NULL)
                                          goto out;
                                  dst_pte = pmap_pte_quick(dst_pmap, addr);
                                  if (*dst_pte == 0 &&
                                      pmap_try_insert_pv_entry(dst_pmap, addr,
                                      PHYS_TO_VM_PAGE(ptetemp & PG_FRAME))) {
                                          /*
                                           * Clear the wired, modified, and
                                           * accessed (referenced) bits
                                           * during the copy.
                                           */
                                          *dst_pte = ptetemp & ~(PG_W | PG_M |
                                              PG_A);
                                          dst_pmap->pm_stats.resident_count++;
                                  } else {
                                          SLIST_INIT(&free);
                                          if (pmap_unwire_ptp(dst_pmap, dstmpte,
                                              &free)) {
                                                  pmap_invalidate_page(dst_pmap,
                                                      addr);
                                                  pmap_free_zero_pages(&free);
                                          }
                                          goto out;
                                  }
                                  if (dstmpte->wire_count >= srcmpte->wire_count)
                                          break;
                          }
                          addr += PAGE_SIZE;
                          src_pte++;
                  }
          }
  out:
          sched_unpin();
          rw_wunlock(&pvh_global_lock);
          PMAP_UNLOCK(src_pmap);
          PMAP_UNLOCK(dst_pmap);
  }       
  
  static __inline void
  pagezero(void *page)
  {
  #if defined(I686_CPU)
          if (cpu_class == CPUCLASS_686) {
  #if defined(CPU_ENABLE_SSE)
                  if (cpu_feature & CPUID_SSE2)
                          sse2_pagezero(page);
                  else
  #endif
                          i686_pagezero(page);
          } else
  #endif
                  bzero(page, PAGE_SIZE);
  }
  
  /*
   *      pmap_zero_page zeros the specified hardware page by mapping 
   *      the page into KVM and using bzero to clear its contents.
   */
  void
  pmap_zero_page(vm_page_t m)
  {
          struct sysmaps *sysmaps;
  
          sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
          mtx_lock(&sysmaps->lock);
          if (*sysmaps->CMAP2)
                  panic("pmap_zero_page: CMAP2 busy");
          sched_pin();
          *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
              pmap_cache_bits(m->md.pat_mode, 0);
          invlcaddr(sysmaps->CADDR2);
          pagezero(sysmaps->CADDR2);
          *sysmaps->CMAP2 = 0;
          sched_unpin();
          mtx_unlock(&sysmaps->lock);
  }
  
  /*
   *      pmap_zero_page_area zeros the specified hardware page by mapping 
   *      the page into KVM and using bzero to clear its contents.
   *
   *      off and size may not cover an area beyond a single hardware page.
   */
  void
  pmap_zero_page_area(vm_page_t m, int off, int size)
  {
          struct sysmaps *sysmaps;
  
          sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
          mtx_lock(&sysmaps->lock);
          if (*sysmaps->CMAP2)
                  panic("pmap_zero_page_area: CMAP2 busy");
          sched_pin();
          *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
              pmap_cache_bits(m->md.pat_mode, 0);
          invlcaddr(sysmaps->CADDR2);
          if (off == 0 && size == PAGE_SIZE) 
                  pagezero(sysmaps->CADDR2);
          else
                  bzero((char *)sysmaps->CADDR2 + off, size);
          *sysmaps->CMAP2 = 0;
          sched_unpin();
          mtx_unlock(&sysmaps->lock);
  }
  
  /*
   *      pmap_zero_page_idle zeros the specified hardware page by mapping 
   *      the page into KVM and using bzero to clear its contents.  This
   *      is intended to be called from the vm_pagezero process only and
   *      outside of Giant.
   */
  void
  pmap_zero_page_idle(vm_page_t m)
  {
  
          if (*CMAP3)
                  panic("pmap_zero_page_idle: CMAP3 busy");
          sched_pin();
          *CMAP3 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
              pmap_cache_bits(m->md.pat_mode, 0);
          invlcaddr(CADDR3);
          pagezero(CADDR3);
          *CMAP3 = 0;
          sched_unpin();
  }
  
  /*
   *      pmap_copy_page copies the specified (machine independent)
   *      page by mapping the page into virtual memory and using
   *      bcopy to copy the page, one machine dependent page at a
   *      time.
   */
  void
  pmap_copy_page(vm_page_t src, vm_page_t dst)
  {
          struct sysmaps *sysmaps;
  
          sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
          mtx_lock(&sysmaps->lock);
          if (*sysmaps->CMAP1)
                  panic("pmap_copy_page: CMAP1 busy");
          if (*sysmaps->CMAP2)
                  panic("pmap_copy_page: CMAP2 busy");
          sched_pin();
          *sysmaps->CMAP1 = PG_V | VM_PAGE_TO_PHYS(src) | PG_A |
              pmap_cache_bits(src->md.pat_mode, 0);
          invlcaddr(sysmaps->CADDR1);
          *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(dst) | PG_A | PG_M |
              pmap_cache_bits(dst->md.pat_mode, 0);
          invlcaddr(sysmaps->CADDR2);
          bcopy(sysmaps->CADDR1, sysmaps->CADDR2, PAGE_SIZE);
          *sysmaps->CMAP1 = 0;
          *sysmaps->CMAP2 = 0;
          sched_unpin();
          mtx_unlock(&sysmaps->lock);
  }
  
  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)
  {
          struct sysmaps *sysmaps;
          vm_page_t a_pg, b_pg;
          char *a_cp, *b_cp;
          vm_offset_t a_pg_offset, b_pg_offset;
          int cnt;
  
          sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
          mtx_lock(&sysmaps->lock);
          if (*sysmaps->CMAP1 != 0)
                  panic("pmap_copy_pages: CMAP1 busy");
          if (*sysmaps->CMAP2 != 0)
                  panic("pmap_copy_pages: CMAP2 busy");
          sched_pin();
          while (xfersize > 0) {
                  a_pg = ma[a_offset >> PAGE_SHIFT];
                  a_pg_offset = a_offset & PAGE_MASK;
                  cnt = min(xfersize, PAGE_SIZE - a_pg_offset);
                  b_pg = mb[b_offset >> PAGE_SHIFT];
                  b_pg_offset = b_offset & PAGE_MASK;
                  cnt = min(cnt, PAGE_SIZE - b_pg_offset);
                  *sysmaps->CMAP1 = PG_V | VM_PAGE_TO_PHYS(a_pg) | PG_A |
                      pmap_cache_bits(a_pg->md.pat_mode, 0);
                  invlcaddr(sysmaps->CADDR1);
                  *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(b_pg) | PG_A |
                      PG_M | pmap_cache_bits(b_pg->md.pat_mode, 0);
                  invlcaddr(sysmaps->CADDR2);
                  a_cp = sysmaps->CADDR1 + a_pg_offset;
                  b_cp = sysmaps->CADDR2 + b_pg_offset;
                  bcopy(a_cp, b_cp, cnt);
                  a_offset += cnt;
                  b_offset += cnt;
                  xfersize -= cnt;
          }
          *sysmaps->CMAP1 = 0;
          *sysmaps->CMAP2 = 0;
          sched_unpin();
          mtx_unlock(&sysmaps->lock);
  }
  
  /*
   * 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;
          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;
          rw_wlock(&pvh_global_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_wunlock(&pvh_global_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)
  {
          int count;
  
          count = 0;
          if ((m->oflags & VPO_UNMANAGED) != 0)
                  return (count);
          rw_wlock(&pvh_global_lock);
          count = pmap_pvh_wired_mappings(&m->md, count);
          if ((m->flags & PG_FICTITIOUS) == 0) {
              count = pmap_pvh_wired_mappings(pa_to_pvh(VM_PAGE_TO_PHYS(m)),
                  count);
          }
          rw_wunlock(&pvh_global_lock);
          return (count);
  }
  
  /*
   *      pmap_pvh_wired_mappings:
   *
   *      Return the updated number "count" of managed mappings that are wired.
   */
  static int
  pmap_pvh_wired_mappings(struct md_page *pvh, int count)
  {
          pmap_t pmap;
          pt_entry_t *pte;
          pv_entry_t pv;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          sched_pin();
          TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pte = pmap_pte_quick(pmap, pv->pv_va);
                  if ((*pte & PG_W) != 0)
                          count++;
                  PMAP_UNLOCK(pmap);
          }
          sched_unpin();
          return (count);
  }
  
  /*
   * Returns TRUE if the given page is mapped individually or as part of
   * a 4mpage.  Otherwise, returns FALSE.
   */
  boolean_t
  pmap_page_is_mapped(vm_page_t m)
  {
          boolean_t rv;
  
          if ((m->oflags & VPO_UNMANAGED) != 0)
                  return (FALSE);
          rw_wlock(&pvh_global_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_wunlock(&pvh_global_lock);
          return (rv);
  }
  
  /*
   * Remove all pages from specified address space
   * this aids process exit speeds.  Also, this code
   * is special cased for current process only, but
   * can have the more generic (and slightly slower)
   * mode enabled.  This is much faster than pmap_remove
   * in the case of running down an entire address space.
   */
  void
  pmap_remove_pages(pmap_t pmap)
  {
          pt_entry_t *pte, tpte;
          vm_page_t m, mpte, mt;
          pv_entry_t pv;
          struct md_page *pvh;
          struct pv_chunk *pc, *npc;
          struct spglist free;
          int field, idx;
          int32_t bit;
          uint32_t inuse, bitmask;
          int allfree;
  
          if (pmap != PCPU_GET(curpmap)) {
                  printf("warning: pmap_remove_pages called with non-current pmap\n");
                  return;
          }
          SLIST_INIT(&free);
          rw_wlock(&pvh_global_lock);
          PMAP_LOCK(pmap);
          sched_pin();
          TAILQ_FOREACH_SAFE(pc, &pmap->pm_pvchunk, pc_list, npc) {
                  KASSERT(pc->pc_pmap == pmap, ("Wrong pmap %p %p", pmap,
                      pc->pc_pmap));
                  allfree = 1;
                  for (field = 0; field < _NPCM; field++) {
                          inuse = ~pc->pc_map[field] & pc_freemask[field];
                          while (inuse != 0) {
                                  bit = bsfl(inuse);
                                  bitmask = 1UL << bit;
                                  idx = field * 32 + bit;
                                  pv = &pc->pc_pventry[idx];
                                  inuse &= ~bitmask;
  
                                  pte = pmap_pde(pmap, pv->pv_va);
                                  tpte = *pte;
                                  if ((tpte & PG_PS) == 0) {
                                          pte = vtopte(pv->pv_va);
                                          tpte = *pte & ~PG_PTE_PAT;
                                  }
  
                                  if (tpte == 0) {
                                          printf(
                                              "TPTE at %p  IS ZERO @ VA %08x\n",
                                              pte, pv->pv_va);
                                          panic("bad pte");
                                  }
  
  /*
   * We cannot remove wired pages from a process' mapping at this time
   */
                                  if (tpte & PG_W) {
                                          allfree = 0;
                                          continue;
                                  }
  
                                  m = PHYS_TO_VM_PAGE(tpte & PG_FRAME);
                                  KASSERT(m->phys_addr == (tpte & PG_FRAME),
                                      ("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 ((tpte & PG_PS) != 0) {
                                                  for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                          vm_page_dirty(mt);
                                          } else
                                                  vm_page_dirty(m);
                                  }
  
                                  /* Mark free */
                                  PV_STAT(pv_entry_frees++);
                                  PV_STAT(pv_entry_spare++);
                                  pv_entry_count--;
                                  pc->pc_map[field] |= bitmask;
                                  if ((tpte & PG_PS) != 0) {
                                          pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                                          pvh = pa_to_pvh(tpte & PG_PS_FRAME);
                                          TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                                          if (TAILQ_EMPTY(&pvh->pv_list)) {
                                                  for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                          if (TAILQ_EMPTY(&mt->md.pv_list))
                                                                  vm_page_aflag_clear(mt, PGA_WRITEABLE);
                                          }
                                          mpte = pmap_lookup_pt_page(pmap, pv->pv_va);
                                          if (mpte != NULL) {
                                                  pmap_remove_pt_page(pmap, mpte);
                                                  pmap->pm_stats.resident_count--;
                                                  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);
                                                  atomic_subtract_int(&cnt.v_wire_count, 1);
                                          }
                                  } else {
                                          pmap->pm_stats.resident_count--;
                                          TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                                          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_unuse_pt(pmap, pv->pv_va, &free);
                                  }
                          }
                  }
                  if (allfree) {
                          TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                          free_pv_chunk(pc);
                  }
          }
          sched_unpin();
          pmap_invalidate_all(pmap);
          rw_wunlock(&pvh_global_lock);
          PMAP_UNLOCK(pmap);
          pmap_free_zero_pages(&free);
  }
  
  /*
   *      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)
  {
          boolean_t rv;
  
          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);
          rw_wlock(&pvh_global_lock);
          rv = pmap_is_modified_pvh(&m->md) ||
              ((m->flags & PG_FICTITIOUS) == 0 &&
              pmap_is_modified_pvh(pa_to_pvh(VM_PAGE_TO_PHYS(m))));
          rw_wunlock(&pvh_global_lock);
          return (rv);
  }
  
  /*
   * Returns TRUE if any of the given mappings were used to modify
   * physical memory.  Otherwise, returns FALSE.  Both page and 2mpage
   * mappings are supported.
   */
  static boolean_t
  pmap_is_modified_pvh(struct md_page *pvh)
  {
          pv_entry_t pv;
          pt_entry_t *pte;
          pmap_t pmap;
          boolean_t rv;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          rv = FALSE;
          sched_pin();
          TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pte = pmap_pte_quick(pmap, pv->pv_va);
                  rv = (*pte & (PG_M | PG_RW)) == (PG_M | PG_RW);
                  PMAP_UNLOCK(pmap);
                  if (rv)
                          break;
          }
          sched_unpin();
          return (rv);
  }
  
  /*
   *      pmap_is_prefaultable:
   *
   *      Return whether or not the specified virtual address is elgible
   *      for prefault.
   */
  boolean_t
  pmap_is_prefaultable(pmap_t pmap, vm_offset_t addr)
  {
          pd_entry_t *pde;
          pt_entry_t *pte;
          boolean_t rv;
  
          rv = FALSE;
          PMAP_LOCK(pmap);
          pde = pmap_pde(pmap, addr);
          if (*pde != 0 && (*pde & PG_PS) == 0) {
                  pte = vtopte(addr);
                  rv = *pte == 0;
          }
          PMAP_UNLOCK(pmap);
          return (rv);
  }
  
  /*
   *      pmap_is_referenced:
   *
   *      Return whether or not the specified physical page was referenced
   *      in any physical maps.
   */
  boolean_t
  pmap_is_referenced(vm_page_t m)
  {
          boolean_t rv;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_is_referenced: page %p is not managed", m));
          rw_wlock(&pvh_global_lock);
          rv = pmap_is_referenced_pvh(&m->md) ||
              ((m->flags & PG_FICTITIOUS) == 0 &&
              pmap_is_referenced_pvh(pa_to_pvh(VM_PAGE_TO_PHYS(m))));
          rw_wunlock(&pvh_global_lock);
          return (rv);
  }
  
  /*
   * Returns TRUE if any of the given mappings were referenced and FALSE
   * otherwise.  Both page and 4mpage mappings are supported.
   */
  static boolean_t
  pmap_is_referenced_pvh(struct md_page *pvh)
  {
          pv_entry_t pv;
          pt_entry_t *pte;
          pmap_t pmap;
          boolean_t rv;
  
          rw_assert(&pvh_global_lock, RA_WLOCKED);
          rv = FALSE;
          sched_pin();
          TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pte = pmap_pte_quick(pmap, pv->pv_va);
                  rv = (*pte & (PG_A | PG_V)) == (PG_A | PG_V);
                  PMAP_UNLOCK(pmap);
                  if (rv)
                          break;
          }
          sched_unpin();
          return (rv);
  }
  
  /*
   * Clear the write and modified bits in each of the given page's mappings.
   */
  void
  pmap_remove_write(vm_page_t m)
  {
          struct md_page *pvh;
          pv_entry_t next_pv, pv;
          pmap_t pmap;
          pd_entry_t *pde;
          pt_entry_t oldpte, *pte;
          vm_offset_t va;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_remove_write: page %p is not managed", m));
  
          /*
           * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
           * set by another thread while the object is locked.  Thus,
           * if PGA_WRITEABLE is clear, no page table entries need updating.
           */
          VM_OBJECT_ASSERT_WLOCKED(m->object);
          if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
                  return;
          rw_wlock(&pvh_global_lock);
          sched_pin();
          if ((m->flags & PG_FICTITIOUS) != 0)
                  goto small_mappings;
          pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
          TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_next, next_pv) {
                  va = pv->pv_va;
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pde = pmap_pde(pmap, va);
                  if ((*pde & PG_RW) != 0)
                          (void)pmap_demote_pde(pmap, pde, va);
                  PMAP_UNLOCK(pmap);
          }
  small_mappings:
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pde = pmap_pde(pmap, pv->pv_va);
                  KASSERT((*pde & PG_PS) == 0, ("pmap_clear_write: found"
                      " a 4mpage in page %p's pv list", m));
                  pte = pmap_pte_quick(pmap, pv->pv_va);
  retry:
                  oldpte = *pte;
                  if ((oldpte & PG_RW) != 0) {
                          /*
                           * Regardless of whether a pte is 32 or 64 bits
                           * in size, PG_RW and PG_M are among the least
                           * significant 32 bits.
                           */
                          if (!atomic_cmpset_int((u_int *)pte, oldpte,
                              oldpte & ~(PG_RW | PG_M)))
                                  goto retry;
                          if ((oldpte & PG_M) != 0)
                                  vm_page_dirty(m);
                          pmap_invalidate_page(pmap, pv->pv_va);
                  }
                  PMAP_UNLOCK(pmap);
          }
          vm_page_aflag_clear(m, PGA_WRITEABLE);
          sched_unpin();
          rw_wunlock(&pvh_global_lock);
  }
  
  #define PMAP_TS_REFERENCED_MAX  5
  
  /*
   *      pmap_ts_referenced:
   *
   *      Return a count of reference bits for a page, clearing those bits.
   *      It is not necessary for every reference bit to be cleared, but it
   *      is necessary that 0 only be returned when there are truly no
   *      reference bits set.
   *
   *      XXX: The exact number of bits to check and clear is a matter that
   *      should be tested and standardized at some point in the future for
   *      optimal aging of shared pages.
   */
  int
  pmap_ts_referenced(vm_page_t m)
  {
          struct md_page *pvh;
          pv_entry_t pv, pvf;
          pmap_t pmap;
          pd_entry_t *pde;
          pt_entry_t *pte;
          vm_paddr_t pa;
          int rtval = 0;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_ts_referenced: page %p is not managed", m));
          pa = VM_PAGE_TO_PHYS(m);
          pvh = pa_to_pvh(pa);
          rw_wlock(&pvh_global_lock);
          sched_pin();
          if ((m->flags & PG_FICTITIOUS) != 0 ||
              (pvf = TAILQ_FIRST(&pvh->pv_list)) == NULL)
                  goto small_mappings;
          pv = pvf;
          do {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pde = pmap_pde(pmap, pv->pv_va);
                  if ((*pde & PG_A) != 0) {
                          /*
                           * Since this reference bit is shared by either 1024
                           * or 512 4KB pages, it should not be cleared every
                           * time it is tested.  Apply a simple "hash" function
                           * on the physical page number, the virtual superpage
                           * number, and the pmap address to select one 4KB page
                           * out of the 1024 or 512 on which testing the
                           * reference bit will result in clearing that bit.
                           * This function is designed to avoid the selection of
                           * the same 4KB page for every 2- or 4MB page mapping.
                           *
                           * On demotion, a mapping that hasn't been referenced
                           * is simply destroyed.  To avoid the possibility of a
                           * subsequent page fault on a demoted wired mapping,
                           * always leave its reference bit set.  Moreover,
                           * since the superpage is wired, the current state of
                           * its reference bit won't affect page replacement.
                           */
                          if ((((pa >> PAGE_SHIFT) ^ (pv->pv_va >> PDRSHIFT) ^
                              (uintptr_t)pmap) & (NPTEPG - 1)) == 0 &&
                              (*pde & PG_W) == 0) {
                                  atomic_clear_int((u_int *)pde, PG_A);
                                  pmap_invalidate_page(pmap, pv->pv_va);
                          }
                          rtval++;
                  }
                  PMAP_UNLOCK(pmap);
                  /* Rotate the PV list if it has more than one entry. */
                  if (TAILQ_NEXT(pv, pv_next) != NULL) {
                          TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                          TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
                  }
                  if (rtval >= PMAP_TS_REFERENCED_MAX)
                          goto out;
          } while ((pv = TAILQ_FIRST(&pvh->pv_list)) != pvf);
  small_mappings:
          if ((pvf = TAILQ_FIRST(&m->md.pv_list)) == NULL)
                  goto out;
          pv = pvf;
          do {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pde = pmap_pde(pmap, pv->pv_va);
                  KASSERT((*pde & PG_PS) == 0,
                      ("pmap_ts_referenced: found a 4mpage in page %p's pv list",
                      m));
                  pte = pmap_pte_quick(pmap, pv->pv_va);
                  if ((*pte & PG_A) != 0) {
                          atomic_clear_int((u_int *)pte, PG_A);
                          pmap_invalidate_page(pmap, pv->pv_va);
                          rtval++;
                  }
                  PMAP_UNLOCK(pmap);
                  /* Rotate the PV list if it has more than one entry. */
                  if (TAILQ_NEXT(pv, pv_next) != NULL) {
                          TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                          TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                  }
          } while ((pv = TAILQ_FIRST(&m->md.pv_list)) != pvf && rtval <
              PMAP_TS_REFERENCED_MAX);
  out:
          sched_unpin();
          rw_wunlock(&pvh_global_lock);
          return (rtval);
  }
  
  /*
   *      Apply the given advice to the specified range of addresses within the
   *      given pmap.  Depending on the advice, clear the referenced and/or
   *      modified flags in each mapping and set the mapped page's dirty field.
   */
  void
  pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
  {
          pd_entry_t oldpde, *pde;
          pt_entry_t *pte;
          vm_offset_t pdnxt;
          vm_page_t m;
          boolean_t anychanged, pv_lists_locked;
  
          if (advice != MADV_DONTNEED && advice != MADV_FREE)
                  return;
          if (pmap_is_current(pmap))
                  pv_lists_locked = FALSE;
          else {
                  pv_lists_locked = TRUE;
  resume:
                  rw_wlock(&pvh_global_lock);
                  sched_pin();
          }
          anychanged = FALSE;
          PMAP_LOCK(pmap);
          for (; sva < eva; sva = pdnxt) {
                  pdnxt = (sva + NBPDR) & ~PDRMASK;
                  if (pdnxt < sva)
                          pdnxt = eva;
                  pde = pmap_pde(pmap, sva);
                  oldpde = *pde;
                  if ((oldpde & PG_V) == 0)
                          continue;
                  else if ((oldpde & PG_PS) != 0) {
                          if ((oldpde & PG_MANAGED) == 0)
                                  continue;
                          if (!pv_lists_locked) {
                                  pv_lists_locked = TRUE;
                                  if (!rw_try_wlock(&pvh_global_lock)) {
                                          if (anychanged)
                                                  pmap_invalidate_all(pmap);
                                          PMAP_UNLOCK(pmap);
                                          goto resume;
                                  }
                                  sched_pin();
                          }
                          if (!pmap_demote_pde(pmap, pde, sva)) {
                                  /*
                                   * The large page mapping was destroyed.
                                   */
                                  continue;
                          }
  
                          /*
                           * Unless the page mappings are wired, remove the
                           * mapping to a single page so that a subsequent
                           * access may repromote.  Since the underlying page
                           * table page is fully populated, this removal never
                           * frees a page table page.
                           */
                          if ((oldpde & PG_W) == 0) {
                                  pte = pmap_pte_quick(pmap, sva);
                                  KASSERT((*pte & PG_V) != 0,
                                      ("pmap_advise: invalid PTE"));
                                  pmap_remove_pte(pmap, pte, sva, NULL);
                                  anychanged = TRUE;
                          }
                  }
                  if (pdnxt > eva)
                          pdnxt = eva;
                  for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++,
                      sva += PAGE_SIZE) {
                          if ((*pte & (PG_MANAGED | PG_V)) != (PG_MANAGED |
                              PG_V))
                                  continue;
                          else if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                  if (advice == MADV_DONTNEED) {
                                          /*
                                           * Future calls to pmap_is_modified()
                                           * can be avoided by making the page
                                           * dirty now.
                                           */
                                          m = PHYS_TO_VM_PAGE(*pte & PG_FRAME);
                                          vm_page_dirty(m);
                                  }
                                  atomic_clear_int((u_int *)pte, PG_M | PG_A);
                          } else if ((*pte & PG_A) != 0)
                                  atomic_clear_int((u_int *)pte, PG_A);
                          else
                                  continue;
                          if ((*pte & PG_G) != 0)
                                  pmap_invalidate_page(pmap, sva);
                          else
                                  anychanged = TRUE;
                  }
          }
          if (anychanged)
                  pmap_invalidate_all(pmap);
          if (pv_lists_locked) {
                  sched_unpin();
                  rw_wunlock(&pvh_global_lock);
          }
          PMAP_UNLOCK(pmap);
  }
  
  /*
   *      Clear the modify bits on the specified physical page.
   */
  void
  pmap_clear_modify(vm_page_t m)
  {
          struct md_page *pvh;
          pv_entry_t next_pv, pv;
          pmap_t pmap;
          pd_entry_t oldpde, *pde;
          pt_entry_t oldpte, *pte;
          vm_offset_t va;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_clear_modify: page %p is not managed", m));
          VM_OBJECT_ASSERT_WLOCKED(m->object);
          KASSERT(!vm_page_xbusied(m),
              ("pmap_clear_modify: page %p is exclusive busied", m));
  
          /*
           * If the page is not PGA_WRITEABLE, then no PTEs can have PG_M set.
           * If the object containing the page is locked and the page is not
           * exclusive busied, then PGA_WRITEABLE cannot be concurrently set.
           */
          if ((m->aflags & PGA_WRITEABLE) == 0)
                  return;
          rw_wlock(&pvh_global_lock);
          sched_pin();
          if ((m->flags & PG_FICTITIOUS) != 0)
                  goto small_mappings;
          pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
          TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_next, next_pv) {
                  va = pv->pv_va;
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pde = pmap_pde(pmap, va);
                  oldpde = *pde;
                  if ((oldpde & PG_RW) != 0) {
                          if (pmap_demote_pde(pmap, pde, va)) {
                                  if ((oldpde & PG_W) == 0) {
                                          /*
                                           * Write protect the mapping to a
                                           * single page so that a subsequent
                                           * write access may repromote.
                                           */
                                          va += VM_PAGE_TO_PHYS(m) - (oldpde &
                                              PG_PS_FRAME);
                                          pte = pmap_pte_quick(pmap, va);
                                          oldpte = *pte;
                                          if ((oldpte & PG_V) != 0) {
                                                  /*
                                                   * Regardless of whether a pte is 32 or 64 bits
                                                   * in size, PG_RW and PG_M are among the least
                                                   * significant 32 bits.
                                                   */
                                                  while (!atomic_cmpset_int((u_int *)pte,
                                                      oldpte,
                                                      oldpte & ~(PG_M | PG_RW)))
                                                          oldpte = *pte;
                                                  vm_page_dirty(m);
                                                  pmap_invalidate_page(pmap, va);
                                          }
                                  }
                          }
                  }
                  PMAP_UNLOCK(pmap);
          }
  small_mappings:
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  PMAP_LOCK(pmap);
                  pde = pmap_pde(pmap, pv->pv_va);
                  KASSERT((*pde & PG_PS) == 0, ("pmap_clear_modify: found"
                      " a 4mpage in page %p's pv list", m));
                  pte = pmap_pte_quick(pmap, pv->pv_va);
                  if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                          /*
                           * Regardless of whether a pte is 32 or 64 bits
                           * in size, PG_M is among the least significant
                           * 32 bits. 
                           */
                          atomic_clear_int((u_int *)pte, PG_M);
                          pmap_invalidate_page(pmap, pv->pv_va);
                  }
                  PMAP_UNLOCK(pmap);
          }
          sched_unpin();
          rw_wunlock(&pvh_global_lock);
  }
  
  /*
   * Miscellaneous support routines follow
   */
  
  /* Adjust the cache mode for a 4KB page mapped via a PTE. */
  static __inline void
  pmap_pte_attr(pt_entry_t *pte, int cache_bits)
  {
          u_int opte, npte;
  
          /*
           * The cache mode bits are all in the low 32-bits of the
           * PTE, so we can just spin on updating the low 32-bits.
           */
          do {
                  opte = *(u_int *)pte;
                  npte = opte & ~PG_PTE_CACHE;
                  npte |= cache_bits;
          } while (npte != opte && !atomic_cmpset_int((u_int *)pte, opte, npte));
  }
  
  /* Adjust the cache mode for a 2/4MB page mapped via a PDE. */
  static __inline void
  pmap_pde_attr(pd_entry_t *pde, int cache_bits)
  {
          u_int opde, npde;
  
          /*
           * The cache mode bits are all in the low 32-bits of the
           * PDE, so we can just spin on updating the low 32-bits.
           */
          do {
                  opde = *(u_int *)pde;
                  npde = opde & ~PG_PDE_CACHE;
                  npde |= cache_bits;
          } while (npde != opde && !atomic_cmpset_int((u_int *)pde, opde, npde));
  }
  
  /*
   * Map a set of physical memory pages into the kernel virtual
   * address space. Return a pointer to where it is mapped. This
   * routine is intended to be used for mapping device memory,
   * NOT real memory.
   */
  void *
  pmap_mapdev_attr(vm_paddr_t pa, vm_size_t size, int mode)
  {
          struct pmap_preinit_mapping *ppim;
          vm_offset_t va, offset;
          vm_size_t tmpsize;
          int i;
  
          offset = pa & PAGE_MASK;
          size = round_page(offset + size);
          pa = pa & PG_FRAME;
  
          if (pa < KERNLOAD && pa + size <= KERNLOAD)
                  va = KERNBASE + pa;
          else if (!pmap_initialized) {
                  va = 0;
                  for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                          ppim = pmap_preinit_mapping + i;
                          if (ppim->va == 0) {
                                  ppim->pa = pa;
                                  ppim->sz = size;
                                  ppim->mode = mode;
                                  ppim->va = virtual_avail;
                                  virtual_avail += size;
                                  va = ppim->va;
                                  break;
                          }
                  }
                  if (va == 0)
                          panic("%s: too many preinit mappings", __func__);
          } else {
                  /*
                   * If we have a preinit mapping, re-use it.
                   */
                  for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                          ppim = pmap_preinit_mapping + i;
                          if (ppim->pa == pa && ppim->sz == size &&
                              ppim->mode == mode)
                                  return ((void *)(ppim->va + offset));
                  }
                  va = kva_alloc(size);
                  if (va == 0)
                          panic("%s: Couldn't allocate KVA", __func__);
          }
          for (tmpsize = 0; tmpsize < size; tmpsize += PAGE_SIZE)
                  pmap_kenter_attr(va + tmpsize, pa + tmpsize, mode);
          pmap_invalidate_range(kernel_pmap, va, va + tmpsize);
          pmap_invalidate_cache_range(va, va + size, FALSE);
          return ((void *)(va + offset));
  }
  
  void *
  pmap_mapdev(vm_paddr_t pa, vm_size_t size)
  {
  
          return (pmap_mapdev_attr(pa, size, PAT_UNCACHEABLE));
  }
  
  void *
  pmap_mapbios(vm_paddr_t pa, vm_size_t size)
  {
  
          return (pmap_mapdev_attr(pa, size, PAT_WRITE_BACK));
  }
  
  void
  pmap_unmapdev(vm_offset_t va, vm_size_t size)
  {
          struct pmap_preinit_mapping *ppim;
          vm_offset_t offset;
          int i;
  
          if (va >= KERNBASE && va + size <= KERNBASE + KERNLOAD)
                  return;
          offset = va & PAGE_MASK;
          size = round_page(offset + size);
          va = trunc_page(va);
          for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                  ppim = pmap_preinit_mapping + i;
                  if (ppim->va == va && ppim->sz == size) {
                          if (pmap_initialized)
                                  return;
                          ppim->pa = 0;
                          ppim->va = 0;
                          ppim->sz = 0;
                          ppim->mode = 0;
                          if (va + size == virtual_avail)
                                  virtual_avail = va;
                          return;
                  }
          }
          if (pmap_initialized)
                  kva_free(va, size);
  }
  
  /*
   * Sets the memory attribute for the specified page.
   */
  void
  pmap_page_set_memattr(vm_page_t m, vm_memattr_t ma)
  {
  
          m->md.pat_mode = ma;
          if ((m->flags & PG_FICTITIOUS) != 0)
                  return;
  
          /*
           * If "m" is a normal page, flush it from the cache.
           * See pmap_invalidate_cache_range().
           *
           * First, try to find an existing mapping of the page by sf
           * buffer. sf_buf_invalidate_cache() modifies mapping and
           * flushes the cache.
           */    
          if (sf_buf_invalidate_cache(m))
                  return;
  
          /*
           * If page is not mapped by sf buffer, but CPU does not
           * support self snoop, map the page transient and do
           * invalidation. In the worst case, whole cache is flushed by
           * pmap_invalidate_cache_range().
           */
          if ((cpu_feature & CPUID_SS) == 0)
                  pmap_flush_page(m);
  }
  
  static void
  pmap_flush_page(vm_page_t m)
  {
          struct sysmaps *sysmaps;
          vm_offset_t sva, eva;
          bool useclflushopt;
  
          useclflushopt = (cpu_stdext_feature & CPUID_STDEXT_CLFLUSHOPT) != 0;
          if (useclflushopt || (cpu_feature & CPUID_CLFSH) != 0) {
                  sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
                  mtx_lock(&sysmaps->lock);
                  if (*sysmaps->CMAP2)
                          panic("pmap_flush_page: CMAP2 busy");
                  sched_pin();
                  *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) |
                      PG_A | PG_M | pmap_cache_bits(m->md.pat_mode, 0);
                  invlcaddr(sysmaps->CADDR2);
                  sva = (vm_offset_t)sysmaps->CADDR2;
                  eva = sva + PAGE_SIZE;
  
                  /*
                   * Use mfence or sfence despite the ordering implied by
                   * mtx_{un,}lock() because clflush on non-Intel CPUs
                   * and clflushopt are not guaranteed to be ordered by
                   * any other instruction.
                   */
                  if (useclflushopt)
                          sfence();
                  else if (cpu_vendor_id != CPU_VENDOR_INTEL)
                          mfence();
                  for (; sva < eva; sva += cpu_clflush_line_size) {
                          if (useclflushopt)
                                  clflushopt(sva);
                          else
                                  clflush(sva);
                  }
                  if (useclflushopt)
                          sfence();
                  else if (cpu_vendor_id != CPU_VENDOR_INTEL)
                          mfence();
                  *sysmaps->CMAP2 = 0;
                  sched_unpin();
                  mtx_unlock(&sysmaps->lock);
          } else
                  pmap_invalidate_cache();
  }
  
  /*
   * Changes the specified virtual address range's memory type to that given by
   * the parameter "mode".  The specified virtual address range must be
   * completely contained within either the kernel map.
   *
   * Returns zero if the change completed successfully, and either EINVAL or
   * ENOMEM if the change failed.  Specifically, EINVAL is returned if some part
   * of the virtual address range was not mapped, and ENOMEM is returned if
   * there was insufficient memory available to complete the change.
   */
  int
  pmap_change_attr(vm_offset_t va, vm_size_t size, int mode)
  {
          vm_offset_t base, offset, tmpva;
          pd_entry_t *pde;
          pt_entry_t *pte;
          int cache_bits_pte, cache_bits_pde;
          boolean_t changed;
  
          base = trunc_page(va);
          offset = va & PAGE_MASK;
          size = round_page(offset + size);
  
          /*
           * Only supported on kernel virtual addresses above the recursive map.
           */
          if (base < VM_MIN_KERNEL_ADDRESS)
                  return (EINVAL);
  
          cache_bits_pde = pmap_cache_bits(mode, 1);
          cache_bits_pte = pmap_cache_bits(mode, 0);
          changed = FALSE;
  
          /*
           * Pages that aren't mapped aren't supported.  Also break down
           * 2/4MB pages into 4KB pages if required.
           */
          PMAP_LOCK(kernel_pmap);
          for (tmpva = base; tmpva < base + size; ) {
                  pde = pmap_pde(kernel_pmap, tmpva);
                  if (*pde == 0) {
                          PMAP_UNLOCK(kernel_pmap);
                          return (EINVAL);
                  }
                  if (*pde & PG_PS) {
                          /*
                           * If the current 2/4MB page already has
                           * the required memory type, then we need not
                           * demote this page.  Just increment tmpva to
                           * the next 2/4MB page frame.
                           */
                          if ((*pde & PG_PDE_CACHE) == cache_bits_pde) {
                                  tmpva = trunc_4mpage(tmpva) + NBPDR;
                                  continue;
                          }
  
                          /*
                           * If the current offset aligns with a 2/4MB
                           * page frame and there is at least 2/4MB left
                           * within the range, then we need not break
                           * down this page into 4KB pages.
                           */
                          if ((tmpva & PDRMASK) == 0 &&
                              tmpva + PDRMASK < base + size) {
                                  tmpva += NBPDR;
                                  continue;
                          }
                          if (!pmap_demote_pde(kernel_pmap, pde, tmpva)) {
                                  PMAP_UNLOCK(kernel_pmap);
                                  return (ENOMEM);
                          }
                  }
                  pte = vtopte(tmpva);
                  if (*pte == 0) {
                          PMAP_UNLOCK(kernel_pmap);
                          return (EINVAL);
                  }
                  tmpva += PAGE_SIZE;
          }
          PMAP_UNLOCK(kernel_pmap);
  
          /*
           * Ok, all the pages exist, so run through them updating their
           * cache mode if required.
           */
          for (tmpva = base; tmpva < base + size; ) {
                  pde = pmap_pde(kernel_pmap, tmpva);
                  if (*pde & PG_PS) {
                          if ((*pde & PG_PDE_CACHE) != cache_bits_pde) {
                                  pmap_pde_attr(pde, cache_bits_pde);
                                  changed = TRUE;
                          }
                          tmpva = trunc_4mpage(tmpva) + NBPDR;
                  } else {
                          pte = vtopte(tmpva);
                          if ((*pte & PG_PTE_CACHE) != cache_bits_pte) {
                                  pmap_pte_attr(pte, cache_bits_pte);
                                  changed = TRUE;
                          }
                          tmpva += PAGE_SIZE;
                  }
          }
  
          /*
           * Flush CPU caches to make sure any data isn't cached that
           * shouldn't be, etc.
           */
          if (changed) {
                  pmap_invalidate_range(kernel_pmap, base, tmpva);
                  pmap_invalidate_cache_range(base, tmpva, FALSE);
          }
          return (0);
  }
  
  /*
   * perform the pmap work for mincore
   */
  int
  pmap_mincore(pmap_t pmap, vm_offset_t addr, vm_paddr_t *locked_pa)
  {
          pd_entry_t *pdep;
          pt_entry_t *ptep, pte;
          vm_paddr_t pa;
          int val;
  
          PMAP_LOCK(pmap);
  retry:
          pdep = pmap_pde(pmap, addr);
          if (*pdep != 0) {
                  if (*pdep & PG_PS) {
                          pte = *pdep;
                          /* Compute the physical address of the 4KB page. */
                          pa = ((*pdep & PG_PS_FRAME) | (addr & PDRMASK)) &
                              PG_FRAME;
                          val = MINCORE_SUPER;
                  } else {
                          ptep = pmap_pte(pmap, addr);
                          pte = *ptep;
                          pmap_pte_release(ptep);
                          pa = pte & PG_FRAME;
                          val = 0;
                  }
          } else {
                  pte = 0;
                  pa = 0;
                  val = 0;
          }
          if ((pte & PG_V) != 0) {
                  val |= MINCORE_INCORE;
                  if ((pte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                          val |= MINCORE_MODIFIED | MINCORE_MODIFIED_OTHER;
                  if ((pte & PG_A) != 0)
                          val |= MINCORE_REFERENCED | MINCORE_REFERENCED_OTHER;
          }
          if ((val & (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER)) !=
              (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER) &&
              (pte & (PG_MANAGED | PG_V)) == (PG_MANAGED | PG_V)) {
                  /* Ensure that "PHYS_TO_VM_PAGE(pa)->object" doesn't change. */
                  if (vm_page_pa_tryrelock(pmap, pa, locked_pa))
                          goto retry;
          } else
                  PA_UNLOCK_COND(*locked_pa);
          PMAP_UNLOCK(pmap);
          return (val);
  }
  
  void
  pmap_activate(struct thread *td)
  {
          pmap_t  pmap, oldpmap;
          u_int   cpuid;
          u_int32_t  cr3;
  
          critical_enter();
          pmap = vmspace_pmap(td->td_proc->p_vmspace);
          oldpmap = PCPU_GET(curpmap);
          cpuid = PCPU_GET(cpuid);
  #if defined(SMP)
          CPU_CLR_ATOMIC(cpuid, &oldpmap->pm_active);
          CPU_SET_ATOMIC(cpuid, &pmap->pm_active);
  #else
          CPU_CLR(cpuid, &oldpmap->pm_active);
          CPU_SET(cpuid, &pmap->pm_active);
  #endif
  #if defined(PAE) || defined(PAE_TABLES)
          cr3 = vtophys(pmap->pm_pdpt);
  #else
          cr3 = vtophys(pmap->pm_pdir);
  #endif
          /*
           * pmap_activate is for the current thread on the current cpu
           */
          td->td_pcb->pcb_cr3 = cr3;
          load_cr3(cr3);
          PCPU_SET(curpmap, pmap);
          critical_exit();
  }
  
  void
  pmap_sync_icache(pmap_t pm, vm_offset_t va, vm_size_t sz)
  {
  }
  
  /*
   *      Increase the starting virtual address of the given mapping if a
   *      different alignment might result in more superpage mappings.
   */
  void
  pmap_align_superpage(vm_object_t object, vm_ooffset_t offset,
      vm_offset_t *addr, vm_size_t size)
  {
          vm_offset_t superpage_offset;
  
          if (size < NBPDR)
                  return;
          if (object != NULL && (object->flags & OBJ_COLORED) != 0)
                  offset += ptoa(object->pg_color);
          superpage_offset = offset & PDRMASK;
          if (size - ((NBPDR - superpage_offset) & PDRMASK) < NBPDR ||
              (*addr & PDRMASK) == superpage_offset)
                  return;
          if ((*addr & PDRMASK) < superpage_offset)
                  *addr = (*addr & ~PDRMASK) + superpage_offset;
          else
                  *addr = ((*addr + PDRMASK) & ~PDRMASK) + superpage_offset;
  }
  
  
  #if defined(PMAP_DEBUG)
  pmap_pid_dump(int pid)
  {
          pmap_t pmap;
          struct proc *p;
          int npte = 0;
          int index;
  
          sx_slock(&allproc_lock);
          FOREACH_PROC_IN_SYSTEM(p) {
                  if (p->p_pid != pid)
                          continue;
  
                  if (p->p_vmspace) {
                          int i,j;
                          index = 0;
                          pmap = vmspace_pmap(p->p_vmspace);
                          for (i = 0; i < NPDEPTD; i++) {
                                  pd_entry_t *pde;
                                  pt_entry_t *pte;
                                  vm_offset_t base = i << PDRSHIFT;
                                  
                                  pde = &pmap->pm_pdir[i];
                                  if (pde && pmap_pde_v(pde)) {
                                          for (j = 0; j < NPTEPG; j++) {
                                                  vm_offset_t va = base + (j << PAGE_SHIFT);
                                                  if (va >= (vm_offset_t) VM_MIN_KERNEL_ADDRESS) {
                                                          if (index) {
                                                                  index = 0;
                                                                  printf("\n");
                                                          }
                                                          sx_sunlock(&allproc_lock);
                                                          return (npte);
                                                  }
                                                  pte = pmap_pte(pmap, va);
                                                  if (pte && pmap_pte_v(pte)) {
                                                          pt_entry_t pa;
                                                          vm_page_t m;
                                                          pa = *pte;
                                                          m = PHYS_TO_VM_PAGE(pa & PG_FRAME);
                                                          printf("va: 0x%x, pt: 0x%x, h: %d, w: %d, f: 0x%x",
                                                                  va, pa, m->hold_count, m->wire_count, m->flags);
                                                          npte++;
                                                          index++;
                                                          if (index >= 2) {
                                                                  index = 0;
                                                                  printf("\n");
                                                          } else {
                                                                  printf(" ");
                                                          }
                                                  }
                                          }
                                  }
                          }
                  }
          }
          sx_sunlock(&allproc_lock);
          return (npte);
  }
  #endif
  
  #if defined(DEBUG)
  
  static void     pads(pmap_t pm);
  void            pmap_pvdump(vm_paddr_t pa);
  
  /* print address space of pmap*/
  static void
  pads(pmap_t pm)
  {
          int i, j;
          vm_paddr_t va;
          pt_entry_t *ptep;
  
          if (pm == kernel_pmap)
                  return;
          for (i = 0; i < NPDEPTD; i++)
                  if (pm->pm_pdir[i])
                          for (j = 0; j < NPTEPG; j++) {
                                  va = (i << PDRSHIFT) + (j << PAGE_SHIFT);
                                  if (pm == kernel_pmap && va < KERNBASE)
                                          continue;
                                  if (pm != kernel_pmap && va > UPT_MAX_ADDRESS)
                                          continue;
                                  ptep = pmap_pte(pm, va);
                                  if (pmap_pte_v(ptep))
                                          printf("%x:%x ", va, *ptep);
                          };
  
  }
  
  void
  pmap_pvdump(vm_paddr_t pa)
  {
          pv_entry_t pv;
          pmap_t pmap;
          vm_page_t m;
  
          printf("pa %x", pa);
          m = PHYS_TO_VM_PAGE(pa);
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                  pmap = PV_PMAP(pv);
                  printf(" -> pmap %p, va %x", (void *)pmap, pv->pv_va);
                  pads(pmap);
          }
          printf(" ");
  }
  #endif