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 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: releng/6.2/sys/i386/i386/pmap.c 162707 2006-09-27 18:10:16Z alc $");
    
    /*
     *      Manages physical address maps.
     *
     *      In addition to hardware address maps, this
     *      module is called upon to provide software-use-only
     *      maps which may or may not be stored in the same
     *      form as hardware maps.  These pseudo-maps are
     *      used to store intermediate results from copy
     *      operations to and from address spaces.
     *
     *      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_cpu.h"
   #include "opt_pmap.h"
   #include "opt_msgbuf.h"
   #include "opt_xbox.h"
   
   #include <sys/param.h>
   #include <sys/systm.h>
   #include <sys/kernel.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/sx.h>
   #include <sys/vmmeter.h>
   #include <sys/sched.h>
   #include <sys/sysctl.h>
   #ifdef SMP
   #include <sys/smp.h>
   #endif
   
   #ifdef XBOX
   #include <machine/xbox.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/uma.h>
   
   #include <machine/cpu.h>
   #include <machine/cputypes.h>
   #include <machine/md_var.h>
   #include <machine/pcb.h>
   #include <machine/specialreg.h>
   #ifdef SMP
   #include <machine/smp.h>
   #endif
   
   #if !defined(CPU_DISABLE_SSE) && defined(I686_CPU)
   #define CPU_ENABLE_SSE
   #endif
   
   #ifndef PMAP_SHPGPERPROC
   #define PMAP_SHPGPERPROC 200
   #endif
   
   #if defined(DIAGNOSTIC)
   #define PMAP_DIAGNOSTIC
   #endif
   
   #if !defined(PMAP_DIAGNOSTIC)
   #define PMAP_INLINE __inline
   #else
   #define PMAP_INLINE
   #endif
   
   /*
    * 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_paddr_t avail_end;   /* PA of last available physical page */
   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;
   vm_offset_t kernel_vm_end;
   extern u_int32_t KERNend;
   
   #ifdef PAE
   static uma_zone_t pdptzone;
   #endif
   
   /*
    * Data for the pv entry allocation mechanism
    */
   static uma_zone_t pvzone;
   static struct vm_object pvzone_obj;
   static int pv_entry_count = 0, pv_entry_max = 0, pv_entry_high_water = 0;
   int pmap_pagedaemon_waken;
   
   /*
    * 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 *CMAP1 = 0;
   static pt_entry_t *CMAP3;
   caddr_t CADDR1 = 0, ptvmmap = 0;
   static caddr_t CADDR3;
   struct msgbuf *msgbufp = 0;
   
   /*
    * Crashdump maps.
    */
   static caddr_t crashdumpmap;
   
   #ifdef SMP
   extern pt_entry_t *SMPpt;
   #endif
   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 PMAP_INLINE void free_pv_entry(pv_entry_t pv);
   static pv_entry_t get_pv_entry(void);
   static void     pmap_clear_ptes(vm_page_t m, int bit);
   
   static int pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t sva);
   static void pmap_remove_page(struct pmap *pmap, vm_offset_t va);
   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 vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va, int flags);
   
   static vm_page_t _pmap_allocpte(pmap_t pmap, unsigned ptepindex, int flags);
   static int _pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m);
   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);
   static vm_offset_t pmap_kmem_choose(vm_offset_t addr);
   #ifdef PAE
   static void *pmap_pdpt_allocf(uma_zone_t zone, int bytes, u_int8_t *flags, int wait);
   #endif
   
   CTASSERT(1 << PDESHIFT == sizeof(pd_entry_t));
   CTASSERT(1 << PTESHIFT == sizeof(pt_entry_t));
   
   /*
    * Move the kernel virtual free pointer to the next
    * 4MB.  This is used to help improve performance
    * by using a large (4MB) page for much of the kernel
    * (.text, .data, .bss)
    */
   static vm_offset_t
   pmap_kmem_choose(vm_offset_t addr)
   {
           vm_offset_t newaddr = addr;
   
   #ifndef DISABLE_PSE
           if (cpu_feature & CPUID_PSE)
                   newaddr = (addr + PDRMASK) & ~PDRMASK;
   #endif
           return newaddr;
   }
   
   /*
    *      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(firstaddr, loadaddr)
           vm_paddr_t firstaddr;
           vm_paddr_t loadaddr;
   {
           vm_offset_t va;
           pt_entry_t *pte, *unused;
           struct sysmaps *sysmaps;
           int i;
   
           /*
            * XXX The calculation of virtual_avail is wrong. It's NKPT*PAGE_SIZE too
            * large. It should instead be correctly calculated in locore.s and
            * not based on 'first' (which is a physical address, not a virtual
            * address, for the start of unused physical memory). The kernel
            * page tables are NOT double mapped and thus should not be included
            * in this calculation.
            */
           virtual_avail = (vm_offset_t) KERNBASE + firstaddr;
           virtual_avail = pmap_kmem_choose(virtual_avail);
   
           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);
   #ifdef PAE
           kernel_pmap->pm_pdpt = (pdpt_entry_t *) (KERNBASE + (u_int)IdlePDPT);
   #endif
           kernel_pmap->pm_active = -1;    /* don't allow deactivation */
           TAILQ_INIT(&kernel_pmap->pm_pvlist);
           LIST_INIT(&allpmaps);
           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);
           nkpt = NKPT;
   
           /*
            * 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, CMAP1, CADDR1, 1)
           SYSMAP(caddr_t, CMAP3, CADDR3, 1)
           *CMAP3 = 0;
   
           /*
            * 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(MSGBUF_SIZE)))
   
           /*
            * ptemap is used for pmap_pte_quick
            */
           SYSMAP(pt_entry_t *, PMAP1, PADDR1, 1);
           SYSMAP(pt_entry_t *, PMAP2, PADDR2, 1);
   
           mtx_init(&PMAP2mutex, "PMAP2", NULL, MTX_DEF);
   
           virtual_avail = va;
   
           *CMAP1 = 0;
   
   #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 = 0; i < NKPT; i++)
                   PTD[i] = 0;
   
           /* Turn on PG_G on kernel page(s) */
           pmap_set_pg();
   }
   
   /*
    * Set PG_G on kernel pages.  Only the BSP calls this when SMP is turned on.
    */
   void
   pmap_set_pg(void)
   {
           pd_entry_t pdir;
           pt_entry_t *pte;
           vm_offset_t va, endva;
           int i; 
   
           if (pgeflag == 0)
                   return;
   
           i = KERNLOAD/NBPDR;
           endva = KERNBASE + KERNend;
   
           if (pseflag) {
                   va = KERNBASE + KERNLOAD;
                   while (va  < endva) {
                           pdir = kernel_pmap->pm_pdir[KPTDI+i];
                           pdir |= pgeflag;
                           kernel_pmap->pm_pdir[KPTDI+i] = PTD[KPTDI+i] = pdir;
                           invltlb();      /* Play it safe, invltlb() every time */
                           i++;
                           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.pv_list_count = 0;
   }
   
   #ifdef PAE
   
   static MALLOC_DEFINE(M_PMAPPDPT, "pmap", "pmap pdpt");
   
   static void *
   pmap_pdpt_allocf(uma_zone_t zone, int bytes, u_int8_t *flags, int wait)
   {
           *flags = UMA_SLAB_PRIV;
           return (contigmalloc(PAGE_SIZE, M_PMAPPDPT, 0, 0x0ULL, 0xffffffffULL,
               1, 0));
   }
   #endif
   
   /*
    *      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)
   {
           int shpgperproc = PMAP_SHPGPERPROC;
   
           /*
            * 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.
            */
           pvzone = uma_zcreate("PV ENTRY", sizeof(struct pv_entry), NULL, NULL, 
               NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_VM | UMA_ZONE_NOFREE);
           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_high_water = 9 * (pv_entry_max / 10);
           uma_zone_set_obj(pvzone, &pvzone_obj, pv_entry_max);
   
   #ifdef PAE
           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
   }
   
   void
   pmap_init2()
   {
   }
   
   
   /***************************************************
    * Low level helper routines.....
    ***************************************************/
   
   #if defined(PMAP_DIAGNOSTIC)
   
   /*
    * This code checks for non-writeable/modified pages.
    * This should be an invalid condition.
    */
   static int
   pmap_nw_modified(pt_entry_t ptea)
   {
           int pte;
   
           pte = (int) ptea;
   
           if ((pte & (PG_M|PG_RW)) == PG_M)
                   return 1;
           else
                   return 0;
   }
   #endif
   
   
   /*
    * this routine defines the region(s) of memory that should
    * not be tested for the modified bit.
    */
   static PMAP_INLINE int
   pmap_track_modified(vm_offset_t va)
   {
           if ((va < kmi.clean_sva) || (va >= kmi.clean_eva)) 
                   return 1;
           else
                   return 0;
   }
   
   #ifdef SMP
   /*
    * For SMP, these functions have to use the IPI mechanism for coherence.
    */
   void
   pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
   {
           u_int cpumask;
           u_int other_cpus;
   
           if (smp_started) {
                   if (!(read_eflags() & PSL_I))
                           panic("%s: interrupts disabled", __func__);
                   mtx_lock_spin(&smp_ipi_mtx);
           } else
                   critical_enter();
           /*
            * We need to disable interrupt preemption but MUST NOT have
            * interrupts disabled here.
            * XXX we may need to hold schedlock to get a coherent pm_active
            * XXX critical sections disable interrupts again
            */
           if (pmap == kernel_pmap || pmap->pm_active == all_cpus) {
                   invlpg(va);
                   smp_invlpg(va);
           } else {
                   cpumask = PCPU_GET(cpumask);
                   other_cpus = PCPU_GET(other_cpus);
                   if (pmap->pm_active & cpumask)
                           invlpg(va);
                   if (pmap->pm_active & other_cpus)
                           smp_masked_invlpg(pmap->pm_active & other_cpus, va);
           }
           if (smp_started)
                   mtx_unlock_spin(&smp_ipi_mtx);
           else
                   critical_exit();
   }
   
   void
   pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
   {
           u_int cpumask;
           u_int other_cpus;
           vm_offset_t addr;
   
           if (smp_started) {
                   if (!(read_eflags() & PSL_I))
                           panic("%s: interrupts disabled", __func__);
                   mtx_lock_spin(&smp_ipi_mtx);
           } else
                   critical_enter();
           /*
            * We need to disable interrupt preemption but MUST NOT have
            * interrupts disabled here.
            * XXX we may need to hold schedlock to get a coherent pm_active
            * XXX critical sections disable interrupts again
            */
           if (pmap == kernel_pmap || pmap->pm_active == all_cpus) {
                   for (addr = sva; addr < eva; addr += PAGE_SIZE)
                           invlpg(addr);
                   smp_invlpg_range(sva, eva);
           } else {
                   cpumask = PCPU_GET(cpumask);
                   other_cpus = PCPU_GET(other_cpus);
                   if (pmap->pm_active & cpumask)
                           for (addr = sva; addr < eva; addr += PAGE_SIZE)
                                   invlpg(addr);
                   if (pmap->pm_active & other_cpus)
                           smp_masked_invlpg_range(pmap->pm_active & other_cpus,
                               sva, eva);
           }
           if (smp_started)
                   mtx_unlock_spin(&smp_ipi_mtx);
           else
                   critical_exit();
   }
   
   void
   pmap_invalidate_all(pmap_t pmap)
   {
           u_int cpumask;
           u_int other_cpus;
   
           if (smp_started) {
                   if (!(read_eflags() & PSL_I))
                           panic("%s: interrupts disabled", __func__);
                   mtx_lock_spin(&smp_ipi_mtx);
           } else
                   critical_enter();
           /*
            * We need to disable interrupt preemption but MUST NOT have
            * interrupts disabled here.
            * XXX we may need to hold schedlock to get a coherent pm_active
            * XXX critical sections disable interrupts again
            */
           if (pmap == kernel_pmap || pmap->pm_active == all_cpus) {
                   invltlb();
                   smp_invltlb();
           } else {
                   cpumask = PCPU_GET(cpumask);
                   other_cpus = PCPU_GET(other_cpus);
                   if (pmap->pm_active & cpumask)
                           invltlb();
                   if (pmap->pm_active & other_cpus)
                           smp_masked_invltlb(pmap->pm_active & other_cpus);
           }
           if (smp_started)
                   mtx_unlock_spin(&smp_ipi_mtx);
           else
                   critical_exit();
   }
   #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 || 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 || 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 || pmap->pm_active)
                   invltlb();
   }
   #endif /* !SMP */
   
   /*
    * 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 (0);
   }
   
   /*
    * 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);
   }
   
   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, vm_page_queue_mtx
    * 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));
                   mtx_assert(&vm_page_queue_mtx, MA_OWNED);
                   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 & ~PDRMASK) | (va & PDRMASK);
                           PMAP_UNLOCK(pmap);
                           return rtval;
                   }
                   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;
           vm_page_t m;
   
           m = NULL;
           vm_page_lock_queues();
           PMAP_LOCK(pmap);
           pde = *pmap_pde(pmap, va);
           if (pde != 0) {
                   if (pde & PG_PS) {
                           if ((pde & PG_RW) || (prot & VM_PROT_WRITE) == 0) {
                                   m = PHYS_TO_VM_PAGE((pde & ~PDRMASK) |
                                       (va & PDRMASK));
                                   vm_page_hold(m);
                           }
                   } else {
                           sched_pin();
                           pte = *pmap_pte_quick(pmap, va);
                           if (pte != 0 &&
                               ((pte & PG_RW) || (prot & VM_PROT_WRITE) == 0)) {
                                   m = PHYS_TO_VM_PAGE(pte & PG_FRAME);
                                   vm_page_hold(m);
                           }
                           sched_unpin();
                   }
           }
           vm_page_unlock_queues();
           PMAP_UNLOCK(pmap);
           return (m);
   }
   
   /***************************************************
    * Low level mapping routines.....
    ***************************************************/
   
   /*
    * Add a wired page to the kva.
    * Note: not SMP coherent.
    */
   PMAP_INLINE void 
   pmap_kenter(vm_offset_t va, vm_paddr_t pa)
   {
           pt_entry_t *pte;
   
           pte = vtopte(va);
           pte_store(pte, pa | PG_RW | PG_V | pgeflag);
   }
   
   /*
    * Remove a page from the kernel pagetables.
    * Note: not SMP coherent.
    */
   PMAP_INLINE void
   pmap_kremove(vm_offset_t va)
   {
           pt_entry_t *pte;
   
           pte = vtopte(va);
           pte_clear(pte);
   }
   
   /*
    *      Used to map a range of physical addresses into kernel
    *      virtual address space.
    *
    *      The value passed in '*virt' is a suggested virtual address for
    *      the mapping. Architectures which can support a direct-mapped
    *      physical to virtual region can return the appropriate address
    *      within that region, leaving '*virt' unchanged. Other
    *      architectures should map the pages starting at '*virt' and
    *      update '*virt' with the first usable address after the mapped
    *      region.
    */
   vm_offset_t
   pmap_map(vm_offset_t *virt, vm_paddr_t start, vm_paddr_t end, int prot)
   {
           vm_offset_t va, sva;
   
           va = sva = *virt;
           while (start < end) {
                   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 *m, int count)
   {
           vm_offset_t va;
   
           va = sva;
           while (count-- > 0) {
                   pmap_kenter(va, VM_PAGE_TO_PHYS(*m));
                   va += PAGE_SIZE;
                   m++;
           }
           pmap_invalidate_range(kernel_pmap, sva, va);
   }
   
   /*
    * 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.....
    ***************************************************/
   
   /*
    * This routine unholds page table pages, and if the hold count
    * drops to zero, then it decrements the wire count.
    */
   static PMAP_INLINE int
   pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m)
   {
   
           --m->wire_count;
           if (m->wire_count == 0)
                   return _pmap_unwire_pte_hold(pmap, m);
           else
                   return 0;
   }
   
   static int 
   _pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m)
   {
           vm_offset_t pteva;
  
          /*
           * unmap the page table page
           */
          pmap->pm_pdir[m->pindex] = 0;
          --pmap->pm_stats.resident_count;
  
          /*
           * Do an invltlb to make the invalidated mapping
           * take effect immediately.
           */
          pteva = VM_MAXUSER_ADDRESS + i386_ptob(m->pindex);
          pmap_invalidate_page(pmap, pteva);
  
          vm_page_free_zero(m);
          atomic_subtract_int(&cnt.v_wire_count, 1);
          return 1;
  }
  
  /*
   * After removing a page table entry, this routine is used to
   * conditionally free the page, and manage the hold/wire counts.
   */
  static int
  pmap_unuse_pt(pmap_t pmap, vm_offset_t va)
  {
          pd_entry_t ptepde;
          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_pte_hold(pmap, mpte);
  }
  
  void
  pmap_pinit0(pmap)
          struct pmap *pmap;
  {
  
          PMAP_LOCK_INIT(pmap);
          pmap->pm_pdir = (pd_entry_t *)(KERNBASE + (vm_offset_t)IdlePTD);
  #ifdef PAE
          pmap->pm_pdpt = (pdpt_entry_t *)(KERNBASE + (vm_offset_t)IdlePDPT);
  #endif
          pmap->pm_active = 0;
          PCPU_SET(curpmap, pmap);
          TAILQ_INIT(&pmap->pm_pvlist);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
          mtx_lock_spin(&allpmaps_lock);
          LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
          mtx_unlock_spin(&allpmaps_lock);
  }
  
  /*
   * Initialize a preallocated and zeroed pmap structure,
   * such as one in a vmspace structure.
   */
  void
  pmap_pinit(pmap)
          register struct pmap *pmap;
  {
          vm_page_t m, ptdpg[NPGPTD];
          vm_paddr_t pa;
          static int color;
          int i;
  
          PMAP_LOCK_INIT(pmap);
  
          /*
           * 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 *)kmem_alloc_nofault(kernel_map,
                      NBPTD);
  #ifdef PAE
                  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
          }
  
          /*
           * allocate the page directory page(s)
           */
          for (i = 0; i < NPGPTD;) {
                  m = vm_page_alloc(NULL, color++,
                      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)
                          bzero(pmap->pm_pdir + (i * NPDEPG), PAGE_SIZE);
          }
  
          mtx_lock_spin(&allpmaps_lock);
          LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
          mtx_unlock_spin(&allpmaps_lock);
          /* Wire in kernel global address entries. */
          /* XXX copies current process, does not fill in MPPTDI */
          bcopy(PTD + KPTDI, pmap->pm_pdir + KPTDI, nkpt * sizeof(pd_entry_t));
  #ifdef SMP
          pmap->pm_pdir[MPPTDI] = PTD[MPPTDI];
  #endif
  
          /* 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;
  #ifdef PAE
                  pmap->pm_pdpt[i] = pa | PG_V;
  #endif
          }
  
          pmap->pm_active = 0;
          TAILQ_INIT(&pmap->pm_pvlist);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
  }
  
  /*
   * this routine is called if the page table page is not
   * mapped correctly.
   */
  static vm_page_t
  _pmap_allocpte(pmap_t pmap, unsigned ptepindex, int flags)
  {
          vm_paddr_t ptepa;
          vm_page_t m;
  
          KASSERT((flags & (M_NOWAIT | M_WAITOK)) == M_NOWAIT ||
              (flags & (M_NOWAIT | M_WAITOK)) == M_WAITOK,
              ("_pmap_allocpte: flags is neither M_NOWAIT nor M_WAITOK"));
  
          /*
           * Allocate a page table page.
           */
          if ((m = vm_page_alloc(NULL, ptepindex, VM_ALLOC_NOOBJ |
              VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
                  if (flags & M_WAITOK) {
                          PMAP_UNLOCK(pmap);
                          vm_page_unlock_queues();
                          VM_WAIT;
                          vm_page_lock_queues();
                          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, int flags)
  {
          unsigned ptepindex;
          pd_entry_t ptepa;
          vm_page_t m;
  
          KASSERT((flags & (M_NOWAIT | M_WAITOK)) == M_NOWAIT ||
              (flags & (M_NOWAIT | M_WAITOK)) == M_WAITOK,
              ("pmap_allocpte: flags is neither M_NOWAIT nor M_WAITOK"));
  
          /*
           * 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) {
                  pmap->pm_pdir[ptepindex] = 0;
                  ptepa = 0;
                  pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                  pmap_invalidate_all(kernel_pmap);
          }
  
          /*
           * If the page table page is mapped, we just increment the
           * hold count, and activate it.
           */
          if (ptepa) {
                  m = PHYS_TO_VM_PAGE(ptepa);
                  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 & M_WAITOK))
                          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 u_int *lazymask;
  static u_int lazyptd;
  static volatile u_int lazywait;
  
  void pmap_lazyfix_action(void);
  
  void
  pmap_lazyfix_action(void)
  {
          u_int mymask = PCPU_GET(cpumask);
  
          if (rcr3() == lazyptd)
                  load_cr3(PCPU_GET(curpcb)->pcb_cr3);
          atomic_clear_int(lazymask, mymask);
          atomic_store_rel_int(&lazywait, 1);
  }
  
  static void
  pmap_lazyfix_self(u_int mymask)
  {
  
          if (rcr3() == lazyptd)
                  load_cr3(PCPU_GET(curpcb)->pcb_cr3);
          atomic_clear_int(lazymask, mymask);
  }
  
  
  static void
  pmap_lazyfix(pmap_t pmap)
  {
          u_int mymask;
          u_int mask;
          register u_int spins;
  
          while ((mask = pmap->pm_active) != 0) {
                  spins = 50000000;
                  mask = mask & -mask;    /* Find least significant set bit */
                  mtx_lock_spin(&smp_ipi_mtx);
  #ifdef PAE
                  lazyptd = vtophys(pmap->pm_pdpt);
  #else
                  lazyptd = vtophys(pmap->pm_pdir);
  #endif
                  mymask = PCPU_GET(cpumask);
                  if (mask == mymask) {
                          lazymask = &pmap->pm_active;
                          pmap_lazyfix_self(mymask);
                  } 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");
          }
  }
  
  #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(PCPU_GET(curpcb)->pcb_cr3);
                  pmap->pm_active &= ~(PCPU_GET(cpumask));
          }
  }
  #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));
  
          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]);
  
          bzero(pmap->pm_pdir + PTDPTDI, (nkpt + NPGPTD) *
              sizeof(*pmap->pm_pdir));
  #ifdef SMP
          pmap->pm_pdir[MPPTDI] = 0;
  #endif
  
          pmap_qremove((vm_offset_t)pmap->pm_pdir, NPGPTD);
  
          vm_page_lock_queues();
          for (i = 0; i < NPGPTD; i++) {
                  m = ptdpg[i];
  #ifdef PAE
                  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);
          }
          vm_page_unlock_queues();
          PMAP_LOCK_DESTROY(pmap);
  }
  
  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)
  {
          struct pmap *pmap;
          vm_paddr_t ptppaddr;
          vm_page_t nkpg;
          pd_entry_t newpdir;
          pt_entry_t *pde;
  
          mtx_assert(&kernel_map->system_mtx, MA_OWNED);
          if (kernel_vm_end == 0) {
                  kernel_vm_end = KERNBASE;
                  nkpt = 0;
                  while (pdir_pde(PTD, kernel_vm_end)) {
                          kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
                          nkpt++;
                          if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                                  kernel_vm_end = kernel_map->max_offset;
                                  break;
                          }
                  }
          }
          addr = roundup2(addr, PAGE_SIZE * NPTEPG);
          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 + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
                          if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                                  kernel_vm_end = kernel_map->max_offset;
                                  break;
                          }
                          continue;
                  }
  
                  /*
                   * This index is bogus, but out of the way
                   */
                  nkpg = vm_page_alloc(NULL, nkpt,
                      VM_ALLOC_NOOBJ | VM_ALLOC_SYSTEM | VM_ALLOC_WIRED);
                  if (!nkpg)
                          panic("pmap_growkernel: no memory to grow kernel");
  
                  nkpt++;
  
                  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(PTD, kernel_vm_end) = newpdir;
  
                  mtx_lock_spin(&allpmaps_lock);
                  LIST_FOREACH(pmap, &allpmaps, pm_list) {
                          pde = pmap_pde(pmap, kernel_vm_end);
                          pde_store(pde, newpdir);
                  }
                  mtx_unlock_spin(&allpmaps_lock);
                  kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
                  if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                          kernel_vm_end = kernel_map->max_offset;
                          break;
                  }
          }
  }
  
  
  /***************************************************
   * page management routines.
   ***************************************************/
  
  /*
   * free the pv_entry back to the free list
   */
  static PMAP_INLINE void
  free_pv_entry(pv_entry_t pv)
  {
          pv_entry_count--;
          uma_zfree(pvzone, pv);
  }
  
  /*
   * get a new pv_entry, allocating a block from the system
   * when needed.
   * the memory allocation is performed bypassing the malloc code
   * because of the possibility of allocations at interrupt time.
   */
  static pv_entry_t
  get_pv_entry(void)
  {
          pv_entry_count++;
          if ((pv_entry_count > pv_entry_high_water) &&
                  (pmap_pagedaemon_waken == 0)) {
                  pmap_pagedaemon_waken = 1;
                  wakeup (&vm_pages_needed);
          }
          return uma_zalloc(pvzone, M_NOWAIT);
  }
  
  
  static void
  pmap_remove_entry(pmap_t pmap, vm_page_t m, vm_offset_t va)
  {
          pv_entry_t pv;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          if (m->md.pv_list_count < pmap->pm_stats.resident_count) {
                  TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                          if (pmap == pv->pv_pmap && va == pv->pv_va) 
                                  break;
                  }
          } else {
                  TAILQ_FOREACH(pv, &pmap->pm_pvlist, pv_plist) {
                          if (va == pv->pv_va) 
                                  break;
                  }
          }
          KASSERT(pv != NULL, ("pmap_remove_entry: pv not found"));
          TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
          m->md.pv_list_count--;
          if (TAILQ_EMPTY(&m->md.pv_list))
                  vm_page_flag_clear(m, PG_WRITEABLE);
          TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
          free_pv_entry(pv);
  }
  
  /*
   * 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;
  
          pv = get_pv_entry();
          if (pv == NULL)
                  panic("no pv entries: increase vm.pmap.shpgperproc");
          pv->pv_va = va;
          pv->pv_pmap = pmap;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
          TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
          m->md.pv_list_count++;
  }
  
  /*
   * 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)
  {
          pt_entry_t oldpte;
          vm_page_t m;
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          oldpte = pte_load_clear(ptq);
          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);
                  if (oldpte & PG_M) {
  #if defined(PMAP_DIAGNOSTIC)
                          if (pmap_nw_modified((pt_entry_t) oldpte)) {
                                  printf(
          "pmap_remove: modified page not writable: va: 0x%x, pte: 0x%x\n",
                                      va, oldpte);
                          }
  #endif
                          if (pmap_track_modified(va))
                                  vm_page_dirty(m);
                  }
                  if (oldpte & PG_A)
                          vm_page_flag_set(m, PG_REFERENCED);
                  pmap_remove_entry(pmap, m, va);
          }
          return (pmap_unuse_pt(pmap, va));
  }
  
  /*
   * Remove a single page from a process address space
   */
  static void
  pmap_remove_page(pmap_t pmap, vm_offset_t va)
  {
          pt_entry_t *pte;
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          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);
          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;
          int anyvalid;
  
          /*
           * Perform an unsynchronized read.  This is, however, safe.
           */
          if (pmap->pm_stats.resident_count == 0)
                  return;
  
          anyvalid = 0;
  
          vm_page_lock_queues();
          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);
                  goto out;
          }
  
          for (; sva < eva; sva = pdnxt) {
                  unsigned pdirindex;
  
                  /*
                   * Calculate index for next page table.
                   */
                  pdnxt = (sva + NBPDR) & ~PDRMASK;
                  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) {
                          pmap->pm_pdir[pdirindex] = 0;
                          pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                          anyvalid = 1;
                          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;
                          anyvalid = 1;
                          if (pmap_remove_pte(pmap, pte, sva))
                                  break;
                  }
          }
  out:
          sched_unpin();
          vm_page_unlock_queues();
          if (anyvalid)
                  pmap_invalidate_all(pmap);
          PMAP_UNLOCK(pmap);
  }
  
  /*
   *      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)
  {
          register pv_entry_t pv;
          pt_entry_t *pte, tpte;
  
  #if defined(PMAP_DIAGNOSTIC)
          /*
           * XXX This makes pmap_remove_all() illegal for non-managed pages!
           */
          if (m->flags & PG_FICTITIOUS) {
                  panic("pmap_remove_all: illegal for unmanaged page, va: 0x%x",
                      VM_PAGE_TO_PHYS(m));
          }
  #endif
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          sched_pin();
          while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                  PMAP_LOCK(pv->pv_pmap);
                  pv->pv_pmap->pm_stats.resident_count--;
                  pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
                  tpte = pte_load_clear(pte);
                  if (tpte & PG_W)
                          pv->pv_pmap->pm_stats.wired_count--;
                  if (tpte & PG_A)
                          vm_page_flag_set(m, PG_REFERENCED);
  
                  /*
                   * Update the vm_page_t clean and reference bits.
                   */
                  if (tpte & PG_M) {
  #if defined(PMAP_DIAGNOSTIC)
                          if (pmap_nw_modified((pt_entry_t) tpte)) {
                                  printf(
          "pmap_remove_all: modified page not writable: va: 0x%x, pte: 0x%x\n",
                                      pv->pv_va, tpte);
                          }
  #endif
                          if (pmap_track_modified(pv->pv_va))
                                  vm_page_dirty(m);
                  }
                  pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
                  TAILQ_REMOVE(&pv->pv_pmap->pm_pvlist, pv, pv_plist);
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                  m->md.pv_list_count--;
                  pmap_unuse_pt(pv->pv_pmap, pv->pv_va);
                  PMAP_UNLOCK(pv->pv_pmap);
                  free_pv_entry(pv);
          }
          vm_page_flag_clear(m, PG_WRITEABLE);
          sched_unpin();
  }
  
  /*
   *      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;
          int anychanged;
  
          if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
                  pmap_remove(pmap, sva, eva);
                  return;
          }
  
          if (prot & VM_PROT_WRITE)
                  return;
  
          anychanged = 0;
  
          vm_page_lock_queues();
          sched_pin();
          PMAP_LOCK(pmap);
          for (; sva < eva; sva = pdnxt) {
                  unsigned obits, pbits, pdirindex;
  
                  pdnxt = (sva + NBPDR) & ~PDRMASK;
  
                  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) {
                          pmap->pm_pdir[pdirindex] &= ~(PG_M|PG_RW);
                          anychanged = 1;
                          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 = *(u_int *)pte;
                          if (pbits & PG_MANAGED) {
                                  m = NULL;
                                  if (pbits & PG_A) {
                                          m = PHYS_TO_VM_PAGE(*pte);
                                          vm_page_flag_set(m, PG_REFERENCED);
                                          pbits &= ~PG_A;
                                  }
                                  if ((pbits & PG_M) != 0 &&
                                      pmap_track_modified(sva)) {
                                          if (m == NULL)
                                                  m = PHYS_TO_VM_PAGE(*pte);
                                          vm_page_dirty(m);
                                  }
                          }
  
                          pbits &= ~(PG_RW | PG_M);
  
                          if (pbits != obits) {
                                  if (!atomic_cmpset_int((u_int *)pte, obits,
                                      pbits))
                                          goto retry;
                                  if (obits & PG_G)
                                          pmap_invalidate_page(pmap, sva);
                                  else
                                          anychanged = 1;
                          }
                  }
          }
          sched_unpin();
          vm_page_unlock_queues();
          if (anychanged)
                  pmap_invalidate_all(pmap);
          PMAP_UNLOCK(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.
   */
  void
  pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
             boolean_t wired)
  {
          vm_paddr_t pa;
          register pt_entry_t *pte;
          vm_paddr_t opa;
          pt_entry_t origpte, newpte;
          vm_page_t mpte, om;
          boolean_t invlva;
  
          va &= PG_FRAME;
  #ifdef PMAP_DIAGNOSTIC
          if (va > VM_MAX_KERNEL_ADDRESS)
                  panic("pmap_enter: toobig");
          if ((va >= UPT_MIN_ADDRESS) && (va < UPT_MAX_ADDRESS))
                  panic("pmap_enter: invalid to pmap_enter page table pages (va: 0x%x)", va);
  #endif
  
          mpte = NULL;
  
          vm_page_lock_queues();
          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, M_WAITOK);
          }
  #if 0 && defined(PMAP_DIAGNOSTIC)
          else {
                  pd_entry_t *pdeaddr = pmap_pde(pmap, va);
                  origpte = *pdeaddr;
                  if ((origpte & PG_V) == 0) { 
                          panic("pmap_enter: invalid kernel page table page, pdir=%p, pde=%p, va=%p\n",
                                  pmap->pm_pdir[PTDPTDI], origpte, va);
                  }
          }
  #endif
  
          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\n",
                          (uintmax_t)pmap->pm_pdir[PTDPTDI], va);
          }
  
          pa = VM_PAGE_TO_PHYS(m);
          om = NULL;
          origpte = *pte;
          opa = origpte & PG_FRAME;
  
          if (origpte & PG_PS) {
                  /*
                   * Yes, I know this will truncate upper address bits for PAE,
                   * but I'm actually more interested in the lower bits
                   */
                  printf("pmap_enter: va %p, pte %p, origpte %p\n",
                      (void *)va, (void *)pte, (void *)(uintptr_t)origpte);
                  panic("pmap_enter: attempted pmap_enter on 4MB page");
          }
  
          /*
           * 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--;
  
                  /*
                   * We might be turning off write access to the page,
                   * so we go ahead and sense modify status.
                   */
                  if (origpte & PG_MANAGED) {
                          om = m;
                          pa |= PG_MANAGED;
                  }
                  goto validate;
          } 
          /*
           * 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);
                          pmap_remove_entry(pmap, om, 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->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0) {
                  pmap_insert_entry(pmap, va, m);
                  pa |= PG_MANAGED;
          }
  
          /*
           * Increment counters
           */
          if (wired)
                  pmap->pm_stats.wired_count++;
  
  validate:
          /*
           * Now validate mapping with desired protection/wiring.
           */
          newpte = (pt_entry_t)(pa | PG_V);
          if ((prot & VM_PROT_WRITE) != 0)
                  newpte |= PG_RW;
          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) {
                  if (origpte & PG_V) {
                          invlva = FALSE;
                          origpte = pte_load_store(pte, newpte | PG_A);
                          if (origpte & PG_A) {
                                  if (origpte & PG_MANAGED)
                                          vm_page_flag_set(om, PG_REFERENCED);
                                  if (opa != VM_PAGE_TO_PHYS(m))
                                          invlva = TRUE;
                          }
                          if (origpte & PG_M) {
                                  KASSERT((origpte & PG_RW),
                                      ("pmap_enter: modified page not writable:"
                                       " va: 0x%x, pte: 0x%x", va, origpte));
                                  if ((origpte & PG_MANAGED) &&
                                      pmap_track_modified(va))
                                          vm_page_dirty(om);
                                  if ((prot & VM_PROT_WRITE) == 0)
                                          invlva = TRUE;
                          }
                          if (invlva)
                                  pmap_invalidate_page(pmap, va);
                  } else
                          pte_store(pte, newpte | PG_A);
          }
          sched_unpin();
          vm_page_unlock_queues();
          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...
   */
  
  vm_page_t
  pmap_enter_quick(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;
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
          PMAP_LOCK(pmap);
  
          /*
           * In the case that a page table page is not
           * resident, we are creating it here.
           */
          if (va < VM_MAXUSER_ADDRESS) {
                  unsigned ptepindex;
                  pd_entry_t ptepa;
  
                  /*
                   * Calculate pagetable page index
                   */
                  ptepindex = va >> PDRSHIFT;
                  if (mpte && (mpte->pindex == ptepindex)) {
                          mpte->wire_count++;
                  } else {
  retry:
                          /*
                           * 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)
                                          panic("pmap_enter_quick: unexpected mapping into 4MB page");
                                  mpte = PHYS_TO_VM_PAGE(ptepa);
                                  mpte->wire_count++;
                          } else {
                                  mpte = _pmap_allocpte(pmap, ptepindex,
                                      M_NOWAIT);
                                  if (mpte == NULL) {
                                          PMAP_UNLOCK(pmap);
                                          vm_page_busy(m);
                                          vm_page_unlock_queues();
                                          VM_OBJECT_UNLOCK(m->object);
                                          VM_WAIT;
                                          VM_OBJECT_LOCK(m->object);
                                          vm_page_lock_queues();
                                          vm_page_wakeup(m);
                                          PMAP_LOCK(pmap);
                                          goto retry;
                                  }
                          }
                  }
          } 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) {
                          pmap_unwire_pte_hold(pmap, mpte);
                          mpte = NULL;
                  }
                  goto out;
          }
  
          /*
           * Enter on the PV list if part of our managed memory. Note that we
           * raise IPL while manipulating pv_table since pmap_enter can be
           * called at interrupt time.
           */
          if ((m->flags & (PG_FICTITIOUS|PG_UNMANAGED)) == 0)
                  pmap_insert_entry(pmap, va, m);
  
          /*
           * Increment counters
           */
          pmap->pm_stats.resident_count++;
  
          pa = VM_PAGE_TO_PHYS(m);
  
          /*
           * Now validate mapping with RO protection
           */
          if (m->flags & (PG_FICTITIOUS|PG_UNMANAGED))
                  pte_store(pte, pa | PG_V | PG_U);
          else
                  pte_store(pte, pa | PG_V | PG_U | PG_MANAGED);
  out:
          PMAP_UNLOCK(pmap);
          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)
  {
          vm_page_t p;
  
          VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
          KASSERT(object->type == OBJT_DEVICE,
              ("pmap_object_init_pt: non-device object"));
          if (pseflag && 
              ((addr & (NBPDR - 1)) == 0) && ((size & (NBPDR - 1)) == 0)) {
                  int i;
                  vm_page_t m[1];
                  unsigned int ptepindex;
                  int npdes;
                  pd_entry_t ptepa;
  
                  PMAP_LOCK(pmap);
                  if (pmap->pm_pdir[ptepindex = (addr >> PDRSHIFT)])
                          goto out;
                  PMAP_UNLOCK(pmap);
  retry:
                  p = vm_page_lookup(object, pindex);
                  if (p != NULL) {
                          vm_page_lock_queues();
                          if (vm_page_sleep_if_busy(p, FALSE, "init4p"))
                                  goto retry;
                  } else {
                          p = vm_page_alloc(object, pindex, VM_ALLOC_NORMAL);
                          if (p == NULL)
                                  return;
                          m[0] = p;
  
                          if (vm_pager_get_pages(object, m, 1, 0) != VM_PAGER_OK) {
                                  vm_page_lock_queues();
                                  vm_page_free(p);
                                  vm_page_unlock_queues();
                                  return;
                          }
  
                          p = vm_page_lookup(object, pindex);
                          vm_page_lock_queues();
                          vm_page_wakeup(p);
                  }
                  vm_page_unlock_queues();
  
                  ptepa = VM_PAGE_TO_PHYS(p);
                  if (ptepa & (NBPDR - 1))
                          return;
  
                  p->valid = VM_PAGE_BITS_ALL;
  
                  PMAP_LOCK(pmap);
                  pmap->pm_stats.resident_count += size >> PAGE_SHIFT;
                  npdes = size >> PDRSHIFT;
                  for(i = 0; i < npdes; i++) {
                          pde_store(&pmap->pm_pdir[ptepindex],
                              ptepa | PG_U | PG_RW | PG_V | PG_PS);
                          ptepa += NBPDR;
                          ptepindex += 1;
                  }
                  pmap_invalidate_all(pmap);
  out:
                  PMAP_UNLOCK(pmap);
          }
  }
  
  /*
   *      Routine:        pmap_change_wiring
   *      Function:       Change the wiring attribute for a map/virtual-address
   *                      pair.
   *      In/out conditions:
   *                      The mapping must already exist in the pmap.
   */
  void
  pmap_change_wiring(pmap, va, wired)
          register pmap_t pmap;
          vm_offset_t va;
          boolean_t wired;
  {
          register pt_entry_t *pte;
  
          PMAP_LOCK(pmap);
          pte = pmap_pte(pmap, va);
  
          if (wired && !pmap_pte_w(pte))
                  pmap->pm_stats.wired_count++;
          else if (!wired && pmap_pte_w(pte))
                  pmap->pm_stats.wired_count--;
  
          /*
           * Wiring is not a hardware characteristic so there is no need to
           * invalidate TLB.
           */
          pmap_pte_set_w(pte, wired);
          pmap_pte_release(pte);
          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)
  {
          vm_offset_t addr;
          vm_offset_t end_addr = src_addr + len;
          vm_offset_t pdnxt;
          vm_page_t m;
  
          if (dst_addr != src_addr)
                  return;
  
          if (!pmap_is_current(src_pmap))
                  return;
  
          vm_page_lock_queues();
          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;
                  unsigned ptepindex;
  
                  if (addr >= UPT_MIN_ADDRESS)
                          panic("pmap_copy: invalid to pmap_copy page tables");
  
                  /*
                   * Don't let optional prefaulting of pages make us go
                   * way below the low water mark of free pages or way
                   * above high water mark of used pv entries.
                   */
                  if (cnt.v_free_count < cnt.v_free_reserved ||
                      pv_entry_count > pv_entry_high_water)
                          break;
                  
                  pdnxt = (addr + NBPDR) & ~PDRMASK;
                  ptepindex = addr >> PDRSHIFT;
  
                  srcptepaddr = src_pmap->pm_pdir[ptepindex];
                  if (srcptepaddr == 0)
                          continue;
                          
                  if (srcptepaddr & PG_PS) {
                          if (dst_pmap->pm_pdir[ptepindex] == 0) {
                                  dst_pmap->pm_pdir[ptepindex] = srcptepaddr &
                                      ~PG_W;
                                  dst_pmap->pm_stats.resident_count +=
                                      NBPDR / PAGE_SIZE;
                          }
                          continue;
                  }
  
                  srcmpte = PHYS_TO_VM_PAGE(srcptepaddr);
                  if (srcmpte->wire_count == 0)
                          panic("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) {
                                  /*
                                   * We have to check after allocpte for the
                                   * pte still being around...  allocpte can
                                   * block.
                                   */
                                  dstmpte = pmap_allocpte(dst_pmap, addr,
                                      M_NOWAIT);
                                  if (dstmpte == NULL)
                                          break;
                                  dst_pte = pmap_pte_quick(dst_pmap, addr);
                                  if (*dst_pte == 0) {
                                          /*
                                           * Clear the wired, modified, and
                                           * accessed (referenced) bits
                                           * during the copy.
                                           */
                                          m = PHYS_TO_VM_PAGE(ptetemp);
                                          *dst_pte = ptetemp & ~(PG_W | PG_M |
                                              PG_A);
                                          dst_pmap->pm_stats.resident_count++;
                                          pmap_insert_entry(dst_pmap, addr, m);
                                  } else
                                          pmap_unwire_pte_hold(dst_pmap, dstmpte);
                                  if (dstmpte->wire_count >= srcmpte->wire_count)
                                          break;
                          }
                          addr += PAGE_SIZE;
                          src_pte++;
                  }
          }
          sched_unpin();
          vm_page_unlock_queues();
          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;
          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: CMAP2 busy");
          sched_pin();
          *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M;
          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: CMAP3 busy");
          sched_pin();
          *CMAP3 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M;
          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();
          invlpg((u_int)sysmaps->CADDR1);
          invlpg((u_int)sysmaps->CADDR2);
          *sysmaps->CMAP1 = PG_V | VM_PAGE_TO_PHYS(src) | PG_A;
          *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(dst) | PG_A | PG_M;
          bcopy(sysmaps->CADDR1, sysmaps->CADDR2, PAGE_SIZE);
          *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, m)
          pmap_t pmap;
          vm_page_t m;
  {
          pv_entry_t pv;
          int loops = 0;
  
          if (m->flags & PG_FICTITIOUS)
                  return FALSE;
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  if (pv->pv_pmap == pmap) {
                          return TRUE;
                  }
                  loops++;
                  if (loops >= 16)
                          break;
          }
          return (FALSE);
  }
  
  #define PMAP_REMOVE_PAGES_CURPROC_ONLY
  /*
   * 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, sva, eva)
          pmap_t pmap;
          vm_offset_t sva, eva;
  {
          pt_entry_t *pte, tpte;
          vm_page_t m;
          pv_entry_t pv, npv;
  
  #ifdef PMAP_REMOVE_PAGES_CURPROC_ONLY
          if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) {
                  printf("warning: pmap_remove_pages called with non-current pmap\n");
                  return;
          }
  #endif
          vm_page_lock_queues();
          PMAP_LOCK(pmap);
          sched_pin();
          for (pv = TAILQ_FIRST(&pmap->pm_pvlist); pv; pv = npv) {
  
                  if (pv->pv_va >= eva || pv->pv_va < sva) {
                          npv = TAILQ_NEXT(pv, pv_plist);
                          continue;
                  }
  
  #ifdef PMAP_REMOVE_PAGES_CURPROC_ONLY
                  pte = vtopte(pv->pv_va);
  #else
                  pte = pmap_pte_quick(pmap, pv->pv_va);
  #endif
                  tpte = *pte;
  
                  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) {
                          npv = TAILQ_NEXT(pv, pv_plist);
                          continue;
                  }
  
                  m = PHYS_TO_VM_PAGE(tpte);
                  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 < &vm_page_array[vm_page_array_size],
                          ("pmap_remove_pages: bad tpte %#jx", (uintmax_t)tpte));
  
                  pmap->pm_stats.resident_count--;
  
                  pte_clear(pte);
  
                  /*
                   * Update the vm_page_t clean and reference bits.
                   */
                  if (tpte & PG_M) {
                          vm_page_dirty(m);
                  }
  
                  npv = TAILQ_NEXT(pv, pv_plist);
                  TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
  
                  m->md.pv_list_count--;
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                  if (TAILQ_EMPTY(&m->md.pv_list))
                          vm_page_flag_clear(m, PG_WRITEABLE);
  
                  pmap_unuse_pt(pmap, pv->pv_va);
                  free_pv_entry(pv);
          }
          sched_unpin();
          pmap_invalidate_all(pmap);
          PMAP_UNLOCK(pmap);
          vm_page_unlock_queues();
  }
  
  /*
   *      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)
  {
          pv_entry_t pv;
          pt_entry_t *pte;
          boolean_t rv;
  
          rv = FALSE;
          if (m->flags & PG_FICTITIOUS)
                  return (rv);
  
          sched_pin();
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  /*
                   * if the bit being tested is the modified bit, then
                   * mark clean_map and ptes as never
                   * modified.
                   */
                  if (!pmap_track_modified(pv->pv_va))
                          continue;
                  PMAP_LOCK(pv->pv_pmap);
                  pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
                  rv = (*pte & PG_M) != 0;
                  PMAP_UNLOCK(pv->pv_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)
  {
          pt_entry_t *pte;
          boolean_t rv;
  
          rv = FALSE;
          PMAP_LOCK(pmap);
          if (*pmap_pde(pmap, addr)) {
                  pte = vtopte(addr);
                  rv = *pte == 0;
          }
          PMAP_UNLOCK(pmap);
          return (rv);
  }
  
  /*
   *      Clear the given bit in each of the given page's ptes.  The bit is
   *      expressed as a 32-bit mask.  Consequently, if the pte is 64 bits in
   *      size, only a bit within the least significant 32 can be cleared.
   */
  static __inline void
  pmap_clear_ptes(vm_page_t m, int bit)
  {
          register pv_entry_t pv;
          pt_entry_t pbits, *pte;
  
          if ((m->flags & PG_FICTITIOUS) ||
              (bit == PG_RW && (m->flags & PG_WRITEABLE) == 0))
                  return;
  
          sched_pin();
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          /*
           * Loop over all current mappings setting/clearing as appropos If
           * setting RO do we need to clear the VAC?
           */
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  /*
                   * don't write protect pager mappings
                   */
                  if (bit == PG_RW) {
                          if (!pmap_track_modified(pv->pv_va))
                                  continue;
                  }
  
                  PMAP_LOCK(pv->pv_pmap);
                  pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
  retry:
                  pbits = *pte;
                  if (pbits & bit) {
                          if (bit == PG_RW) {
                                  /*
                                   * 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, pbits,
                                      pbits & ~(PG_RW | PG_M)))
                                          goto retry;
                                  if (pbits & PG_M) {
                                          vm_page_dirty(m);
                                  }
                          } else {
                                  atomic_clear_int((u_int *)pte, bit);
                          }
                          pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
                  }
                  PMAP_UNLOCK(pv->pv_pmap);
          }
          if (bit == PG_RW)
                  vm_page_flag_clear(m, PG_WRITEABLE);
          sched_unpin();
  }
  
  /*
   *      pmap_page_protect:
   *
   *      Lower the permission for all mappings to a given page.
   */
  void
  pmap_page_protect(vm_page_t m, vm_prot_t prot)
  {
          if ((prot & VM_PROT_WRITE) == 0) {
                  if (prot & (VM_PROT_READ | VM_PROT_EXECUTE)) {
                          pmap_clear_ptes(m, PG_RW);
                  } else {
                          pmap_remove_all(m);
                  }
          }
  }
  
  /*
   *      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)
  {
          register pv_entry_t pv, pvf, pvn;
          pt_entry_t *pte;
          pt_entry_t v;
          int rtval = 0;
  
          if (m->flags & PG_FICTITIOUS)
                  return (rtval);
  
          sched_pin();
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          if ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
  
                  pvf = pv;
  
                  do {
                          pvn = TAILQ_NEXT(pv, pv_list);
  
                          TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
  
                          TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
  
                          if (!pmap_track_modified(pv->pv_va))
                                  continue;
  
                          PMAP_LOCK(pv->pv_pmap);
                          pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
  
                          if (pte && ((v = pte_load(pte)) & PG_A) != 0) {
                                  atomic_clear_int((u_int *)pte, PG_A);
                                  pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
  
                                  rtval++;
                                  if (rtval > 4) {
                                          PMAP_UNLOCK(pv->pv_pmap);
                                          break;
                                  }
                          }
                          PMAP_UNLOCK(pv->pv_pmap);
                  } while ((pv = pvn) != NULL && pv != pvf);
          }
          sched_unpin();
  
          return (rtval);
  }
  
  /*
   *      Clear the modify bits on the specified physical page.
   */
  void
  pmap_clear_modify(vm_page_t m)
  {
          pmap_clear_ptes(m, PG_M);
  }
  
  /*
   *      pmap_clear_reference:
   *
   *      Clear the reference bit on the specified physical page.
   */
  void
  pmap_clear_reference(vm_page_t m)
  {
          pmap_clear_ptes(m, PG_A);
  }
  
  /*
   * Miscellaneous support routines follow
   */
  
  /*
   * 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(pa, size)
          vm_paddr_t pa;
          vm_size_t size;
  {
          vm_offset_t va, tmpva, offset;
  
          offset = pa & PAGE_MASK;
          size = roundup(offset + size, PAGE_SIZE);
          pa = pa & PG_FRAME;
  
          if (pa < KERNLOAD && pa + size <= KERNLOAD)
                  va = KERNBASE + pa;
          else
                  va = kmem_alloc_nofault(kernel_map, size);
          if (!va)
                  panic("pmap_mapdev: Couldn't alloc kernel virtual memory");
  
          for (tmpva = va; size > 0; ) {
                  pmap_kenter(tmpva, pa);
                  size -= PAGE_SIZE;
                  tmpva += PAGE_SIZE;
                  pa += PAGE_SIZE;
          }
          pmap_invalidate_range(kernel_pmap, va, tmpva);
          return ((void *)(va + offset));
  }
  
  void
  pmap_unmapdev(va, size)
          vm_offset_t va;
          vm_size_t size;
  {
          vm_offset_t base, offset, tmpva;
  
          if (va >= KERNBASE && va + size <= KERNBASE + KERNLOAD)
                  return;
          base = va & PG_FRAME;
          offset = va & PAGE_MASK;
          size = roundup(offset + size, PAGE_SIZE);
          for (tmpva = base; tmpva < (base + size); tmpva += PAGE_SIZE)
                  pmap_kremove(tmpva);
          pmap_invalidate_range(kernel_pmap, va, tmpva);
          kmem_free(kernel_map, base, size);
  }
  
  /*
   * perform the pmap work for mincore
   */
  int
  pmap_mincore(pmap, addr)
          pmap_t pmap;
          vm_offset_t addr;
  {
          pt_entry_t *ptep, pte;
          vm_page_t m;
          int val = 0;
          
          PMAP_LOCK(pmap);
          ptep = pmap_pte(pmap, addr);
          pte = (ptep != NULL) ? *ptep : 0;
          pmap_pte_release(ptep);
          PMAP_UNLOCK(pmap);
  
          if (pte != 0) {
                  vm_paddr_t pa;
  
                  val = MINCORE_INCORE;
                  if ((pte & PG_MANAGED) == 0)
                          return val;
  
                  pa = pte & PG_FRAME;
  
                  m = PHYS_TO_VM_PAGE(pa);
  
                  /*
                   * Modified by us
                   */
                  if (pte & PG_M)
                          val |= MINCORE_MODIFIED|MINCORE_MODIFIED_OTHER;
                  else {
                          /*
                           * Modified by someone else
                           */
                          vm_page_lock_queues();
                          if (m->dirty || pmap_is_modified(m))
                                  val |= MINCORE_MODIFIED_OTHER;
                          vm_page_unlock_queues();
                  }
                  /*
                   * Referenced by us
                   */
                  if (pte & PG_A)
                          val |= MINCORE_REFERENCED|MINCORE_REFERENCED_OTHER;
                  else {
                          /*
                           * Referenced by someone else
                           */
                          vm_page_lock_queues();
                          if ((m->flags & PG_REFERENCED) ||
                              pmap_ts_referenced(m)) {
                                  val |= MINCORE_REFERENCED_OTHER;
                                  vm_page_flag_set(m, PG_REFERENCED);
                          }
                          vm_page_unlock_queues();
                  }
          } 
          return val;
  }
  
  void
  pmap_activate(struct thread *td)
  {
          struct proc *p = td->td_proc;
          pmap_t  pmap, oldpmap;
          u_int32_t  cr3;
  
          critical_enter();
          pmap = vmspace_pmap(td->td_proc->p_vmspace);
          oldpmap = PCPU_GET(curpmap);
  #if defined(SMP)
          atomic_clear_int(&oldpmap->pm_active, PCPU_GET(cpumask));
          atomic_set_int(&pmap->pm_active, PCPU_GET(cpumask));
  #else
          oldpmap->pm_active &= ~1;
          pmap->pm_active |= 1;
  #endif
  #ifdef PAE
          cr3 = vtophys(pmap->pm_pdpt);
  #else
          cr3 = vtophys(pmap->pm_pdir);
  #endif
          /* XXXKSE this is wrong.
           * pmap_activate is for the current thread on the current cpu
           */
          if (p->p_flag & P_SA) {
                  /* Make sure all other cr3 entries are updated. */
                  /* what if they are running?  XXXKSE (maybe abort them) */
                  FOREACH_THREAD_IN_PROC(p, td) {
                          td->td_pcb->pcb_cr3 = cr3;
                  }
          } else {
                  td->td_pcb->pcb_cr3 = cr3;
          }
          load_cr3(cr3);
          PCPU_SET(curpmap, pmap);
          critical_exit();
  }
  
  vm_offset_t
  pmap_addr_hint(vm_object_t obj, vm_offset_t addr, vm_size_t size)
  {
  
          if ((obj == NULL) || (size < NBPDR) || (obj->type != OBJT_DEVICE)) {
                  return addr;
          }
  
          addr = (addr + PDRMASK) & ~PDRMASK;
          return addr;
  }
  
  
  #if defined(PMAP_DEBUG)
  pmap_pid_dump(int pid)
  {
          pmap_t pmap;
          struct proc *p;
          int npte = 0;
          int index;
  
          sx_slock(&allproc_lock);
          LIST_FOREACH(p, &allproc, p_list) {
                  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);
                                                          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_offset_t pa);
  
  /* print address space of pmap*/
  static void
  pads(pm)
          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(pa)
          vm_paddr_t pa;
  {
          pv_entry_t pv;
          vm_page_t m;
  
          printf("pa %x", pa);
          m = PHYS_TO_VM_PAGE(pa);
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  printf(" -> pmap %p, va %x", (void *)pv->pv_pmap, pv->pv_va);
                  pads(pv->pv_pmap);
          }
          printf(" ");
  }
  #endif