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.
      *
      * 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
     * $FreeBSD: releng/5.0/sys/i386/i386/pmap.c 107882 2002-12-14 21:08:30Z 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_pmap.h"
    #include "opt_msgbuf.h"
    #include "opt_kstack_pages.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/mman.h>
    #include <sys/msgbuf.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/sx.h>
    #include <sys/user.h>
    #include <sys/vmmeter.h>
    #include <sys/sysctl.h>
    #ifdef SMP
    #include <sys/smp.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/specialreg.h>
   #if defined(SMP) || defined(APIC_IO)
   #include <machine/smp.h>
   #include <machine/apic.h>
   #include <machine/segments.h>
   #include <machine/tss.h>
   #endif /* SMP || APIC_IO */
   
   #define PMAP_KEEP_PDIRS
   #ifndef PMAP_SHPGPERPROC
   #define PMAP_SHPGPERPROC 200
   #endif
   
   #if defined(DIAGNOSTIC)
   #define PMAP_DIAGNOSTIC
   #endif
   
   #define MINPV 2048
   
   #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)?(*(int *)pte |= PG_W):(*(int *)pte &= ~PG_W))
   #define pmap_pte_set_prot(pte, v) ((*(int *)pte &= ~PG_PROT), (*(int *)pte |= (v)))
   
   /*
    * Given a map and a machine independent protection code,
    * convert to a vax protection code.
    */
   #define pte_prot(m, p)  (protection_codes[p])
   static int protection_codes[8];
   
   struct pmap kernel_pmap_store;
   LIST_HEAD(pmaplist, pmap);
   struct pmaplist allpmaps;
   
   vm_offset_t avail_start;        /* PA of first available physical page */
   vm_offset_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) */
   static boolean_t pmap_initialized = FALSE;      /* Has pmap_init completed? */
   static int pgeflag;             /* PG_G or-in */
   static int pseflag;             /* PG_PS or-in */
   
   static vm_object_t kptobj;
   
   static int nkpt;
   vm_offset_t kernel_vm_end;
   extern u_int32_t KERNend;
   
   /*
    * 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
    */
   pt_entry_t *CMAP1 = 0;
   static pt_entry_t *CMAP2, *CMAP3, *ptmmap;
   caddr_t CADDR1 = 0, ptvmmap = 0;
   static caddr_t CADDR2, CADDR3;
   static pt_entry_t *msgbufmap;
   struct msgbuf *msgbufp = 0;
   
   /*
    * Crashdump maps.
    */
   static pt_entry_t *pt_crashdumpmap;
   static caddr_t crashdumpmap;
   
   #ifdef SMP
   extern pt_entry_t *SMPpt;
   #endif
   static pt_entry_t *PMAP1 = 0;
   static pt_entry_t *PADDR1 = 0;
   
   static PMAP_INLINE void free_pv_entry(pv_entry_t pv);
   static pt_entry_t *get_ptbase(pmap_t pmap);
   static pv_entry_t get_pv_entry(void);
   static void     i386_protection_init(void);
   static __inline void    pmap_changebit(vm_page_t m, int bit, boolean_t setem);
   
   static vm_page_t pmap_enter_quick(pmap_t pmap, vm_offset_t va,
                                         vm_page_t m, vm_page_t mpte);
   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 int pmap_remove_entry(struct pmap *pmap, vm_page_t m,
                                           vm_offset_t va);
   static boolean_t pmap_testbit(vm_page_t m, int bit);
   static void pmap_insert_entry(pmap_t pmap, vm_offset_t va,
                   vm_page_t mpte, vm_page_t m);
   
   static vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va);
   
   static int pmap_release_free_page(pmap_t pmap, vm_page_t p);
   static vm_page_t _pmap_allocpte(pmap_t pmap, unsigned ptepindex);
   static pt_entry_t *pmap_pte_quick(pmap_t pmap, vm_offset_t va);
   static vm_page_t pmap_page_lookup(vm_object_t object, vm_pindex_t pindex);
   static int pmap_unuse_pt(pmap_t, vm_offset_t, vm_page_t);
   static vm_offset_t pmap_kmem_choose(vm_offset_t addr);
   static void *pmap_allocf(uma_zone_t zone, int bytes, u_int8_t *flags, int wait);
   
   static pd_entry_t pdir4mb;
   
   /*
    *      Routine:        pmap_pte
    *      Function:
    *              Extract the page table entry associated
    *              with the given map/virtual_address pair.
    */
   
   PMAP_INLINE pt_entry_t *
   pmap_pte(pmap, va)
           register pmap_t pmap;
           vm_offset_t va;
   {
           pd_entry_t *pdeaddr;
   
           if (pmap) {
                   pdeaddr = pmap_pde(pmap, va);
                   if (*pdeaddr & PG_PS)
                           return pdeaddr;
                   if (*pdeaddr) {
                           return get_ptbase(pmap) + i386_btop(va);
                   }
           }
           return (0);
   }
   
   /*
    * 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 + (NBPDR - 1)) & ~(NBPDR - 1);
   #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_offset_t firstaddr;
           vm_offset_t loadaddr;
   {
           vm_offset_t va;
           pt_entry_t *pte;
           int i;
   
           avail_start = firstaddr;
   
           /*
            * 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 protection array.
            */
           i386_protection_init();
   
           /*
            * Initialize the kernel pmap (which is statically allocated).
            */
           kernel_pmap->pm_pdir = (pd_entry_t *) (KERNBASE + (u_int)IdlePTD);
           kernel_pmap->pm_active = -1;    /* don't allow deactivation */
           TAILQ_INIT(&kernel_pmap->pm_pvlist);
           LIST_INIT(&allpmaps);
           LIST_INSERT_HEAD(&allpmaps, kernel_pmap, pm_list);
           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 = (pt_entry_t *) pmap_pte(kernel_pmap, va);
   
           /*
            * CMAP1/CMAP2 are used for zeroing and copying pages.
            * CMAP3 is used for the idle process page zeroing.
            */
           SYSMAP(caddr_t, CMAP1, CADDR1, 1)
           SYSMAP(caddr_t, CMAP2, CADDR2, 1)
           SYSMAP(caddr_t, CMAP3, CADDR3, 1)
   
           /*
            * Crashdump maps.
            */
           SYSMAP(caddr_t, pt_crashdumpmap, crashdumpmap, MAXDUMPPGS);
   
           /*
            * ptvmmap is used for reading arbitrary physical pages via /dev/mem.
            * XXX ptmmap is not used.
            */
           SYSMAP(caddr_t, ptmmap, ptvmmap, 1)
   
           /*
            * msgbufp is used to map the system message buffer.
            * XXX msgbufmap is not used.
            */
           SYSMAP(struct msgbuf *, msgbufmap, msgbufp,
                  atop(round_page(MSGBUF_SIZE)))
   
           /*
            * ptemap is used for pmap_pte_quick
            */
           SYSMAP(pt_entry_t *, PMAP1, PADDR1, 1);
   
           virtual_avail = va;
   
           *CMAP1 = *CMAP2 = 0;
           for (i = 0; i < NKPT; i++)
                   PTD[i] = 0;
   
           pgeflag = 0;
   #ifndef DISABLE_PG_G
           if (cpu_feature & CPUID_PGE)
                   pgeflag = PG_G;
   #endif
           
   /*
    * Initialize the 4MB page size flag
    */
           pseflag = 0;
   /*
    * The 4MB page version of the initial
    * kernel page mapping.
    */
           pdir4mb = 0;
   
   #ifndef DISABLE_PSE
           if (cpu_feature & CPUID_PSE) {
                   pd_entry_t ptditmp;
                   /*
                    * Note that we have enabled PSE mode
                    */
                   pseflag = PG_PS;
                   ptditmp = *(PTmap + i386_btop(KERNBASE));
                   ptditmp &= ~(NBPDR - 1);
                   ptditmp |= PG_V | PG_RW | PG_PS | PG_U | pgeflag;
                   pdir4mb = ptditmp;
           }
   #endif
   #ifndef SMP
           /*
            * Turn on PGE/PSE.  SMP does this later on since the
            * 4K page tables are required for AP boot (for now).
            * XXX fixme.
            */
           pmap_set_opt();
   #endif
   #ifdef SMP
           if (cpu_apic_address == 0)
                   panic("pmap_bootstrap: no local apic! (non-SMP hardware?)");
   
           /* local apic is mapped on last page */
           SMPpt[NPTEPG - 1] = (pt_entry_t)(PG_V | PG_RW | PG_N | pgeflag |
               (cpu_apic_address & PG_FRAME));
   #endif
           invltlb();
   }
   
   /*
    * Enable 4MB page mode for MP startup.  Turn on PG_G support.
    * BSP will run this after all the AP's have started up.
    */
   void
   pmap_set_opt(void)
   {
           pt_entry_t *pte;
           vm_offset_t va, endva;
   
           if (pgeflag && (cpu_feature & CPUID_PGE)) {
                   load_cr4(rcr4() | CR4_PGE);
                   invltlb();              /* Insurance */
           }
   #ifndef DISABLE_PSE
           if (pseflag && (cpu_feature & CPUID_PSE)) {
                   load_cr4(rcr4() | CR4_PSE);
                   invltlb();              /* Insurance */
           }
   #endif
           if (PCPU_GET(cpuid) == 0) {
   #ifndef DISABLE_PSE
                   if (pdir4mb) {
                           kernel_pmap->pm_pdir[KPTDI] = PTD[KPTDI] = pdir4mb;
                           invltlb();      /* Insurance */
                   }
   #endif
                   if (pgeflag) {
                           /* Turn on PG_G for text, data, bss pages. */
                           va = (vm_offset_t)btext;
   #ifndef DISABLE_PSE
                           if (pseflag && (cpu_feature & CPUID_PSE)) {
                                   if (va < KERNBASE + (1 << PDRSHIFT))
                                           va = KERNBASE + (1 << PDRSHIFT);
                           }
   #endif
                           endva = KERNBASE + KERNend;
                           while (va < endva) {
                                   pte = vtopte(va);
                                   if (*pte)
                                           *pte |= pgeflag;
                                   va += PAGE_SIZE;
                           }
                           invltlb();      /* Insurance */
                   }
                   /*
                    * We do not need to broadcast the invltlb here, because
                    * each AP does it the moment it is released from the boot
                    * lock.  See ap_init().
                    */
           }
   }
   
   static void *
   pmap_allocf(uma_zone_t zone, int bytes, u_int8_t *flags, int wait)
   {
           *flags = UMA_SLAB_PRIV;
           return (void *)kmem_alloc(kernel_map, bytes);
   }
   
   /*
    *      Initialize the pmap module.
    *      Called by vm_init, to initialize any structures that the pmap
    *      system needs to map virtual memory.
    *      pmap_init has been enhanced to support in a fairly consistant
    *      way, discontiguous physical memory.
    */
   void
   pmap_init(phys_start, phys_end)
           vm_offset_t phys_start, phys_end;
   {
           int i;
           int initial_pvs;
   
           /*
            * object for kernel page table pages
            */
           kptobj = vm_object_allocate(OBJT_DEFAULT, NKPDE);
   
           /*
            * Allocate memory for random pmap data structures.  Includes the
            * pv_head_table.
            */
   
           for(i = 0; i < vm_page_array_size; i++) {
                   vm_page_t m;
   
                   m = &vm_page_array[i];
                   TAILQ_INIT(&m->md.pv_list);
                   m->md.pv_list_count = 0;
           }
   
           /*
            * init the pv free list
            */
           initial_pvs = vm_page_array_size;
           if (initial_pvs < MINPV)
                   initial_pvs = MINPV;
           pvzone = uma_zcreate("PV ENTRY", sizeof (struct pv_entry), NULL, NULL, 
               NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_VM);
           uma_zone_set_allocf(pvzone, pmap_allocf);
           uma_prealloc(pvzone, initial_pvs);
   
           /*
            * Now it is safe to enable pv_table recording.
            */
           pmap_initialized = TRUE;
   }
   
   /*
    * 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.
    */
   void
   pmap_init2()
   {
           int shpgperproc = PMAP_SHPGPERPROC;
   
           TUNABLE_INT_FETCH("vm.pmap.shpgperproc", &shpgperproc);
           pv_entry_max = shpgperproc * maxproc + vm_page_array_size;
           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);
   }
   
   
   /***************************************************
    * 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 I386_CPU
   /*
    * i386 only has "invalidate everything" and no SMP to worry about.
    */
   PMAP_INLINE void
   pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
   {
   
           if (pmap == kernel_pmap || pmap->pm_active)
                   invltlb();
   }
   
   PMAP_INLINE void
   pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
   {
   
           if (pmap == kernel_pmap || pmap->pm_active)
                   invltlb();
   }
   
   PMAP_INLINE void
   pmap_invalidate_all(pmap_t pmap)
   {
   
           if (pmap == kernel_pmap || pmap->pm_active)
                   invltlb();
   }
   #else /* !I386_CPU */
   #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;
   
           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
            */
           if (pmap->pm_active == -1 || 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);
           }
           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;
   
           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
            */
           if (pmap->pm_active == -1 || 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);
           }
           critical_exit();
   }
   
   void
   pmap_invalidate_all(pmap_t pmap)
   {
           u_int cpumask;
           u_int other_cpus;
   
   #ifdef SWTCH_OPTIM_STATS
           tlb_flush_count++;
   #endif
           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
            */
           if (pmap->pm_active == -1 || 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);
           }
           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 */
   #endif /* !I386_CPU */
   
   /*
    * Return an address which is the base of the Virtual mapping of
    * all the PTEs for the given pmap. Note this doesn't say that
    * all the PTEs will be present or that the pages there are valid.
    * The PTEs are made available by the recursive mapping trick.
    * It will map in the alternate PTE space if needed.
    */
   static pt_entry_t *
   get_ptbase(pmap)
           pmap_t pmap;
   {
           pd_entry_t frame;
   
           /* are we current address space or kernel? */
           if (pmap == kernel_pmap)
                   return PTmap;
           frame = pmap->pm_pdir[PTDPTDI] & PG_FRAME;
           if (frame == (PTDpde & PG_FRAME))
                   return PTmap;
           /* otherwise, we are alternate address space */
           if (frame != (APTDpde & PG_FRAME)) {
                   APTDpde = (pd_entry_t) (frame | PG_RW | PG_V);
                   pmap_invalidate_all(kernel_pmap);       /* XXX Bandaid */
           }
           return APTmap;
   }
   
   /*
    * 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.
    */
   
   static pt_entry_t * 
   pmap_pte_quick(pmap, va)
           register pmap_t pmap;
           vm_offset_t va;
   {
           pd_entry_t pde, newpf;
           pde = pmap->pm_pdir[va >> PDRSHIFT];
           if (pde != 0) {
                   pd_entry_t frame = pmap->pm_pdir[PTDPTDI] & PG_FRAME;
                   unsigned index = i386_btop(va);
                   /* are we current address space or kernel? */
                   if (pmap == kernel_pmap || frame == (PTDpde & PG_FRAME))
                           return PTmap + index;
                   newpf = pde & PG_FRAME;
                   if (((*PMAP1) & PG_FRAME) != newpf) {
                           *PMAP1 = newpf | PG_RW | PG_V;
                           pmap_invalidate_page(kernel_pmap, (vm_offset_t)PADDR1);
                   }
                   return PADDR1 + (index & (NPTEPG - 1));
           }
           return (0);
   }
   
   /*
    *      Routine:        pmap_extract
    *      Function:
    *              Extract the physical page address associated
    *              with the given map/virtual_address pair.
    */
   vm_offset_t 
   pmap_extract(pmap, va)
           register pmap_t pmap;
           vm_offset_t va;
   {
           vm_offset_t rtval;      /* XXX FIXME */
           vm_offset_t pdirindex;
   
           if (pmap == 0)
                   return 0;
           pdirindex = va >> PDRSHIFT;
           rtval = pmap->pm_pdir[pdirindex];
           if (rtval != 0) {
                   pt_entry_t *pte;
                   if ((rtval & PG_PS) != 0) {
                           rtval &= ~(NBPDR - 1);
                           rtval |= va & (NBPDR - 1);
                           return rtval;
                   }
                   pte = get_ptbase(pmap) + i386_btop(va);
                   rtval = ((*pte & PG_FRAME) | (va & PAGE_MASK));
                   return rtval;
           }
           return 0;
   
   }
   
   /***************************************************
    * 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_offset_t pa)
   {
           pt_entry_t *pte;
   
           pte = vtopte(va);
           *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 = 0;
   }
   
   /*
    *      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_offset_t start, vm_offset_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);
   }
   
   static vm_page_t
   pmap_page_lookup(vm_object_t object, vm_pindex_t pindex)
   {
           vm_page_t m;
   
   retry:
           m = vm_page_lookup(object, pindex);
           if (m != NULL) {
                   vm_page_lock_queues();
                   if (vm_page_sleep_if_busy(m, FALSE, "pplookp"))
                           goto retry;
                   vm_page_unlock_queues();
           }
           return m;
   }
   
   #ifndef KSTACK_MAX_PAGES
   #define KSTACK_MAX_PAGES 32
   #endif
   
   /*
    * Create the kernel stack (including pcb for i386) for a new thread.
    * This routine directly affects the fork perf for a process and
    * create performance for a thread.
    */
   void
   pmap_new_thread(struct thread *td, int pages)
   {
           int i;
           vm_page_t ma[KSTACK_MAX_PAGES];
           vm_object_t ksobj;
           vm_page_t m;
           vm_offset_t ks;
   
           /* Bounds check */
           if (pages <= 1)
                   pages = KSTACK_PAGES;
           else if (pages > KSTACK_MAX_PAGES)
                   pages = KSTACK_MAX_PAGES;
   
           /*
            * allocate object for the kstack
            */
           ksobj = vm_object_allocate(OBJT_DEFAULT, pages);
           td->td_kstack_obj = ksobj;
   
           /* get a kernel virtual address for the kstack for this thread */
   #ifdef KSTACK_GUARD
           ks = kmem_alloc_nofault(kernel_map, (pages + 1) * PAGE_SIZE);
           if (ks == 0)
                   panic("pmap_new_thread: kstack allocation failed");
           if (*vtopte(ks) != 0)
                   pmap_qremove(ks, 1);
           ks += PAGE_SIZE;
           td->td_kstack = ks;
   #else
           /* get a kernel virtual address for the kstack for this thread */
           ks = kmem_alloc_nofault(kernel_map, pages * PAGE_SIZE);
           if (ks == 0)
                   panic("pmap_new_thread: kstack allocation failed");
           td->td_kstack = ks;
   #endif
           /*
            * Knowing the number of pages allocated is useful when you
            * want to deallocate them.
            */
           td->td_kstack_pages = pages;
   
           /* 
            * For the length of the stack, link in a real page of ram for each
            * page of stack.
            */
           for (i = 0; i < pages; i++) {
                   /*
                    * Get a kernel stack page
                    */
                   m = vm_page_grab(ksobj, i,
                       VM_ALLOC_NORMAL | VM_ALLOC_RETRY | VM_ALLOC_WIRED);
                   ma[i] = m;
   
                  vm_page_wakeup(m);
                  vm_page_flag_clear(m, PG_ZERO);
                  m->valid = VM_PAGE_BITS_ALL;
          }
          pmap_qenter(ks, ma, pages);
  }
  
  /*
   * Dispose the kernel stack for a thread that has exited.
   * This routine directly impacts the exit perf of a process and thread.
   */
  void
  pmap_dispose_thread(td)
          struct thread *td;
  {
          int i;
          int pages;
          vm_object_t ksobj;
          vm_offset_t ks;
          vm_page_t m;
  
          pages = td->td_kstack_pages;
          ksobj = td->td_kstack_obj;
          ks = td->td_kstack;
          pmap_qremove(ks, pages);
          for (i = 0; i < pages; i++) {
                  m = vm_page_lookup(ksobj, i);
                  if (m == NULL)
                          panic("pmap_dispose_thread: kstack already missing?");
                  vm_page_lock_queues();
                  vm_page_busy(m);
                  vm_page_unwire(m, 0);
                  vm_page_free(m);
                  vm_page_unlock_queues();
          }
          /*
           * Free the space that this stack was mapped to in the kernel
           * address map.
           */
  #ifdef KSTACK_GUARD
          kmem_free(kernel_map, ks - PAGE_SIZE, (pages + 1) * PAGE_SIZE);
  #else
          kmem_free(kernel_map, ks, pages * PAGE_SIZE);
  #endif
          vm_object_deallocate(ksobj);
  }
  
  /*
   * Set up a variable sized alternate kstack.  Though it may look MI, it may
   * need to be different on certain arches like ia64.
   */
  void
  pmap_new_altkstack(struct thread *td, int pages)
  {
          /* shuffle the original stack */
          td->td_altkstack_obj = td->td_kstack_obj;
          td->td_altkstack = td->td_kstack;
          td->td_altkstack_pages = td->td_kstack_pages;
  
          pmap_new_thread(td, pages);
  }
  
  void
  pmap_dispose_altkstack(td)
          struct thread *td;
  {
          pmap_dispose_thread(td);
  
          /* restore the original kstack */
          td->td_kstack = td->td_altkstack;
          td->td_kstack_obj = td->td_altkstack_obj;
          td->td_kstack_pages = td->td_altkstack_pages;
          td->td_altkstack = 0;
          td->td_altkstack_obj = NULL;
          td->td_altkstack_pages = 0;
  }
  
  /*
   * Allow the Kernel stack for a thread to be prejudicially paged out.
   */
  void
  pmap_swapout_thread(td)
          struct thread *td;
  {
          int i;
          int pages;
          vm_object_t ksobj;
          vm_offset_t ks;
          vm_page_t m;
  
          pages = td->td_kstack_pages;
          ksobj = td->td_kstack_obj;
          ks = td->td_kstack;
          pmap_qremove(ks, pages);
          for (i = 0; i < pages; i++) {
                  m = vm_page_lookup(ksobj, i);
                  if (m == NULL)
                          panic("pmap_swapout_thread: kstack already missing?");
                  vm_page_lock_queues();
                  vm_page_dirty(m);
                  vm_page_unwire(m, 0);
                  vm_page_unlock_queues();
          }
  }
  
  /*
   * Bring the kernel stack for a specified thread back in.
   */
  void
  pmap_swapin_thread(td)
          struct thread *td;
  {
          int i, rv;
          int pages;
          vm_page_t ma[KSTACK_MAX_PAGES];
          vm_object_t ksobj;
          vm_offset_t ks;
          vm_page_t m;
  
          pages = td->td_kstack_pages;
          ksobj = td->td_kstack_obj;
          ks = td->td_kstack;
          for (i = 0; i < pages; i++) {
                  m = vm_page_grab(ksobj, i, VM_ALLOC_NORMAL | VM_ALLOC_RETRY);
                  if (m->valid != VM_PAGE_BITS_ALL) {
                          rv = vm_pager_get_pages(ksobj, &m, 1, 0);
                          if (rv != VM_PAGER_OK)
                                  panic("pmap_swapin_thread: cannot get kstack for proc: %d\n", td->td_proc->p_pid);
                          m = vm_page_lookup(ksobj, i);
                          m->valid = VM_PAGE_BITS_ALL;
                  }
                  ma[i] = m;
                  vm_page_lock_queues();
                  vm_page_wire(m);
                  vm_page_wakeup(m);
                  vm_page_unlock_queues();
          }
          pmap_qenter(ks, ma, pages);
  }
  
  /***************************************************
   * 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 int 
  _pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m)
  {
  
          while (vm_page_sleep_if_busy(m, FALSE, "pmuwpt"))
                  vm_page_lock_queues();
  
          if (m->hold_count == 0) {
                  vm_offset_t pteva;
                  /*
                   * unmap the page table page
                   */
                  pmap->pm_pdir[m->pindex] = 0;
                  --pmap->pm_stats.resident_count;
                  if ((pmap->pm_pdir[PTDPTDI] & PG_FRAME) ==
                      (PTDpde & PG_FRAME)) {
                          /*
                           * Do a invltlb to make the invalidated mapping
                           * take effect immediately.
                           */
                          pteva = VM_MAXUSER_ADDRESS + i386_ptob(m->pindex);
                          pmap_invalidate_page(pmap, pteva);
                  }
  
                  if (pmap->pm_ptphint == m)
                          pmap->pm_ptphint = NULL;
  
                  /*
                   * If the page is finally unwired, simply free it.
                   */
                  --m->wire_count;
                  if (m->wire_count == 0) {
                          vm_page_busy(m);
                          vm_page_free_zero(m);
                          --cnt.v_wire_count;
                  }
                  return 1;
          }
          return 0;
  }
  
  static PMAP_INLINE int
  pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m)
  {
          vm_page_unhold(m);
          if (m->hold_count == 0)
                  return _pmap_unwire_pte_hold(pmap, m);
          else
                  return 0;
  }
  
  /*
   * 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, vm_page_t mpte)
  {
          unsigned ptepindex;
          if (va >= VM_MAXUSER_ADDRESS)
                  return 0;
  
          if (mpte == NULL) {
                  ptepindex = (va >> PDRSHIFT);
                  if (pmap->pm_ptphint &&
                          (pmap->pm_ptphint->pindex == ptepindex)) {
                          mpte = pmap->pm_ptphint;
                  } else {
                          while ((mpte = vm_page_lookup(pmap->pm_pteobj, ptepindex)) != NULL &&
                                 vm_page_sleep_if_busy(mpte, FALSE, "pulook"))
                                  vm_page_lock_queues();
                          pmap->pm_ptphint = mpte;
                  }
          }
  
          return pmap_unwire_pte_hold(pmap, mpte);
  }
  
  void
  pmap_pinit0(pmap)
          struct pmap *pmap;
  {
          pmap->pm_pdir =
                  (pd_entry_t *)kmem_alloc_pageable(kernel_map, PAGE_SIZE);
          pmap_kenter((vm_offset_t)pmap->pm_pdir, (vm_offset_t)IdlePTD);
  #ifndef I386_CPU
          invlpg((vm_offset_t)pmap->pm_pdir);
  #else
          invltlb();
  #endif
          pmap->pm_ptphint = NULL;
          pmap->pm_active = 0;
          TAILQ_INIT(&pmap->pm_pvlist);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
          LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
  }
  
  /*
   * 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 ptdpg;
  
          /*
           * 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_pageable(kernel_map, PAGE_SIZE);
  
          /*
           * allocate object for the ptes
           */
          if (pmap->pm_pteobj == NULL)
                  pmap->pm_pteobj = vm_object_allocate(OBJT_DEFAULT, PTDPTDI + 1);
  
          /*
           * allocate the page directory page
           */
          ptdpg = vm_page_grab(pmap->pm_pteobj, PTDPTDI,
              VM_ALLOC_NORMAL | VM_ALLOC_RETRY | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
          vm_page_flag_clear(ptdpg, PG_BUSY);
          ptdpg->valid = VM_PAGE_BITS_ALL;
  
          pmap_qenter((vm_offset_t) pmap->pm_pdir, &ptdpg, 1);
          if ((ptdpg->flags & PG_ZERO) == 0)
                  bzero(pmap->pm_pdir, PAGE_SIZE);
  
          LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
          /* Wire in kernel global address entries. */
          /* XXX copies current process, does not fill in MPPTDI */
          bcopy(PTD + KPTDI, pmap->pm_pdir + KPTDI, nkpt * PTESIZE);
  #ifdef SMP
          pmap->pm_pdir[MPPTDI] = PTD[MPPTDI];
  #endif
  
          /* install self-referential address mapping entry */
          pmap->pm_pdir[PTDPTDI] =
                  VM_PAGE_TO_PHYS(ptdpg) | PG_V | PG_RW | PG_A | PG_M;
  
          pmap->pm_active = 0;
          pmap->pm_ptphint = NULL;
          TAILQ_INIT(&pmap->pm_pvlist);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
  }
  
  /*
   * Wire in kernel global address entries.  To avoid a race condition
   * between pmap initialization and pmap_growkernel, this procedure
   * should be called after the vmspace is attached to the process
   * but before this pmap is activated.
   */
  void
  pmap_pinit2(pmap)
          struct pmap *pmap;
  {
          /* XXX: Remove this stub when no longer called */
  }
  
  static int
  pmap_release_free_page(pmap_t pmap, vm_page_t p)
  {
          pd_entry_t *pde = pmap->pm_pdir;
  
          /*
           * This code optimizes the case of freeing non-busy
           * page-table pages.  Those pages are zero now, and
           * might as well be placed directly into the zero queue.
           */
          vm_page_lock_queues();
          if (vm_page_sleep_if_busy(p, FALSE, "pmaprl"))
                  return (0);
          vm_page_busy(p);
  
          /*
           * Remove the page table page from the processes address space.
           */
          pde[p->pindex] = 0;
          pmap->pm_stats.resident_count--;
  
          if (p->hold_count)  {
                  panic("pmap_release: freeing held page table page");
          }
          /*
           * Page directory pages need to have the kernel
           * stuff cleared, so they can go into the zero queue also.
           */
          if (p->pindex == PTDPTDI) {
                  bzero(pde + KPTDI, nkpt * PTESIZE);
  #ifdef SMP
                  pde[MPPTDI] = 0;
  #endif
                  pde[APTDPTDI] = 0;
                  pmap_kremove((vm_offset_t) pmap->pm_pdir);
          }
  
          if (pmap->pm_ptphint == p)
                  pmap->pm_ptphint = NULL;
  
          p->wire_count--;
          cnt.v_wire_count--;
          vm_page_free_zero(p);
          vm_page_unlock_queues();
          return 1;
  }
  
  /*
   * this routine is called if the page table page is not
   * mapped correctly.
   */
  static vm_page_t
  _pmap_allocpte(pmap, ptepindex)
          pmap_t  pmap;
          unsigned ptepindex;
  {
          vm_offset_t pteva, ptepa;       /* XXXPA */
          vm_page_t m;
  
          /*
           * Find or fabricate a new pagetable page
           */
          m = vm_page_grab(pmap->pm_pteobj, ptepindex,
              VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
  
          KASSERT(m->queue == PQ_NONE,
                  ("_pmap_allocpte: %p->queue != PQ_NONE", m));
  
          /*
           * Increment the hold count for the page table page
           * (denoting a new mapping.)
           */
          m->hold_count++;
  
          /*
           * 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);
  
          /*
           * Set the page table hint
           */
          pmap->pm_ptphint = m;
  
          /*
           * Try to use the new mapping, but if we cannot, then
           * do it with the routine that maps the page explicitly.
           */
          if ((m->flags & PG_ZERO) == 0) {
                  if ((pmap->pm_pdir[PTDPTDI] & PG_FRAME) ==
                      (PTDpde & PG_FRAME)) {
                          pteva = VM_MAXUSER_ADDRESS + i386_ptob(ptepindex);
                          bzero((caddr_t) pteva, PAGE_SIZE);
                  } else {
                          pmap_zero_page(m);
                  }
          }
  
          m->valid = VM_PAGE_BITS_ALL;
          vm_page_flag_clear(m, PG_ZERO);
          vm_page_wakeup(m);
  
          return m;
  }
  
  static vm_page_t
  pmap_allocpte(pmap_t pmap, vm_offset_t va)
  {
          unsigned ptepindex;
          pd_entry_t ptepa;
          vm_page_t m;
  
          /*
           * Calculate pagetable page index
           */
          ptepindex = va >> PDRSHIFT;
  
          /*
           * Get the page directory entry
           */
          ptepa = (vm_offset_t) 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_invalidate_all(kernel_pmap);
          }
  
          /*
           * If the page table page is mapped, we just increment the
           * hold count, and activate it.
           */
          if (ptepa) {
                  /*
                   * In order to get the page table page, try the
                   * hint first.
                   */
                  if (pmap->pm_ptphint &&
                          (pmap->pm_ptphint->pindex == ptepindex)) {
                          m = pmap->pm_ptphint;
                  } else {
                          m = pmap_page_lookup(pmap->pm_pteobj, ptepindex);
                          pmap->pm_ptphint = m;
                  }
                  m->hold_count++;
                  return m;
          }
          /*
           * Here if the pte page isn't mapped, or if it has been deallocated.
           */
          return _pmap_allocpte(pmap, ptepindex);
  }
  
  
  /***************************************************
  * Pmap allocation/deallocation routines.
   ***************************************************/
  
  /*
   * Release any resources held by the given physical map.
   * Called when a pmap initialized by pmap_pinit is being released.
   * Should only be called if the map contains no valid mappings.
   */
  void
  pmap_release(pmap_t pmap)
  {
          vm_page_t p,n,ptdpg;
          vm_object_t object = pmap->pm_pteobj;
          int curgeneration;
  
  #if defined(DIAGNOSTIC)
          if (object->ref_count != 1)
                  panic("pmap_release: pteobj reference count != 1");
  #endif
          
          ptdpg = NULL;
          LIST_REMOVE(pmap, pm_list);
  retry:
          curgeneration = object->generation;
          for (p = TAILQ_FIRST(&object->memq); p != NULL; p = n) {
                  n = TAILQ_NEXT(p, listq);
                  if (p->pindex == PTDPTDI) {
                          ptdpg = p;
                          continue;
                  }
                  while (1) {
                          if (!pmap_release_free_page(pmap, p) &&
                                  (object->generation != curgeneration))
                                  goto retry;
                  }
          }
  
          if (ptdpg && !pmap_release_free_page(pmap, ptdpg))
                  goto retry;
  }
  
  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;
          int s;
          vm_offset_t ptppaddr;
          vm_page_t nkpg;
          pd_entry_t newpdir;
  
          s = splhigh();
          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++;
                  }
          }
          addr = roundup2(addr, PAGE_SIZE * NPTEPG);
          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);
                          continue;
                  }
  
                  /*
                   * This index is bogus, but out of the way
                   */
                  nkpg = vm_page_alloc(kptobj, nkpt,
                                       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;
  
                  LIST_FOREACH(pmap, &allpmaps, pm_list) {
                          *pmap_pde(pmap, kernel_vm_end) = newpdir;
                  }
                  kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
          }
          splx(s);
  }
  
  
  /***************************************************
   * 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_high_water &&
                  (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);
  }
  
  /*
   * If it is the first entry on the list, it is actually
   * in the header and we must copy the following entry up
   * to the header.  Otherwise we must search the list for
   * the entry.  In either case we free the now unused entry.
   */
  
  static int
  pmap_remove_entry(pmap_t pmap, vm_page_t m, vm_offset_t va)
  {
          pv_entry_t pv;
          int rtval;
          int s;
  
          s = splvm();
          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;
                  }
          }
  
          rtval = 0;
          if (pv) {
                  rtval = pmap_unuse_pt(pmap, va, pv->pv_ptem);
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                  m->md.pv_list_count--;
                  if (TAILQ_FIRST(&m->md.pv_list) == NULL)
                          vm_page_flag_clear(m, PG_WRITEABLE);
  
                  TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
                  free_pv_entry(pv);
          }
                          
          splx(s);
          return rtval;
  }
  
  /*
   * 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 mpte, vm_page_t m)
  {
  
          int s;
          pv_entry_t pv;
  
          s = splvm();
          pv = get_pv_entry();
          pv->pv_va = va;
          pv->pv_pmap = pmap;
          pv->pv_ptem = mpte;
  
          TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
          TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
          m->md.pv_list_count++;
  
          splx(s);
  }
  
  /*
   * 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;
  
          oldpte = atomic_readandclear_int(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);
                  return pmap_remove_entry(pmap, m, va);
          } else {
                  return pmap_unuse_pt(pmap, va, NULL);
          }
  
          return 0;
  }
  
  /*
   * Remove a single page from a process address space
   */
  static void
  pmap_remove_page(pmap_t pmap, vm_offset_t va)
  {
          register pt_entry_t *ptq;
  
          /*
           * if there is no pte for this address, just skip it!!!
           */
          if (*pmap_pde(pmap, va) == 0) {
                  return;
          }
  
          /*
           * get a local va for mappings for this pmap.
           */
          ptq = get_ptbase(pmap) + i386_btop(va);
          if (*ptq) {
                  (void) pmap_remove_pte(pmap, ptq, va);
                  pmap_invalidate_page(pmap, va);
          }
          return;
  }
  
  /*
   *      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)
  {
          register pt_entry_t *ptbase;
          vm_offset_t pdnxt;
          pd_entry_t ptpaddr;
          vm_offset_t sindex, eindex;
          int anyvalid;
  
          if (pmap == NULL)
                  return;
  
          if (pmap->pm_stats.resident_count == 0)
                  return;
  
          /*
           * 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);
                  return;
          }
  
          anyvalid = 0;
  
          /*
           * Get a local virtual address for the mappings that are being
           * worked with.
           */
          ptbase = get_ptbase(pmap);
  
          sindex = i386_btop(sva);
          eindex = i386_btop(eva);
  
          for (; sindex < eindex; sindex = pdnxt) {
                  unsigned pdirindex;
  
                  /*
                   * Calculate index for next page table.
                   */
                  pdnxt = ((sindex + NPTEPG) & ~(NPTEPG - 1));
                  if (pmap->pm_stats.resident_count == 0)
                          break;
  
                  pdirindex = sindex / NPDEPG;
                  ptpaddr = pmap->pm_pdir[pdirindex];
                  if ((ptpaddr & PG_PS) != 0) {
                          pmap->pm_pdir[pdirindex] = 0;
                          pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                          anyvalid++;
                          continue;
                  }
  
                  /*
                   * Weed out invalid mappings. Note: we assume that the page
                   * directory table is always allocated, and in kernel virtual.
                   */
                  if (ptpaddr == 0)
                          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 > eindex) {
                          pdnxt = eindex;
                  }
  
                  for (; sindex != pdnxt; sindex++) {
                          vm_offset_t va;
                          if (ptbase[sindex] == 0) {
                                  continue;
                          }
                          va = i386_ptob(sindex);
                          
                          anyvalid++;
                          if (pmap_remove_pte(pmap,
                                  ptbase + sindex, va))
                                  break;
                  }
          }
  
          if (anyvalid)
                  pmap_invalidate_all(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;
          int s;
  
  #if defined(PMAP_DIAGNOSTIC)
          /*
           * XXX This makes pmap_remove_all() illegal for non-managed pages!
           */
          if (!pmap_initialized || (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);
          s = splvm();
          while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                  pv->pv_pmap->pm_stats.resident_count--;
                  pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
                  tpte = atomic_readandclear_int(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, pv->pv_ptem);
                  free_pv_entry(pv);
          }
          vm_page_flag_clear(m, PG_WRITEABLE);
          splx(s);
  }
  
  /*
   *      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)
  {
          register pt_entry_t *ptbase;
          vm_offset_t pdnxt;
          pd_entry_t ptpaddr;
          vm_offset_t sindex, eindex;
          int anychanged;
  
          if (pmap == NULL)
                  return;
  
          if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
                  pmap_remove(pmap, sva, eva);
                  return;
          }
  
          if (prot & VM_PROT_WRITE)
                  return;
  
          anychanged = 0;
  
          ptbase = get_ptbase(pmap);
  
          sindex = i386_btop(sva);
          eindex = i386_btop(eva);
  
          for (; sindex < eindex; sindex = pdnxt) {
  
                  unsigned pdirindex;
  
                  pdnxt = ((sindex + NPTEPG) & ~(NPTEPG - 1));
  
                  pdirindex = sindex / NPDEPG;
                  ptpaddr = pmap->pm_pdir[pdirindex];
                  if ((ptpaddr & PG_PS) != 0) {
                          pmap->pm_pdir[pdirindex] &= ~(PG_M|PG_RW);
                          pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                          anychanged++;
                          continue;
                  }
  
                  /*
                   * Weed out invalid mappings. Note: we assume that the page
                   * directory table is always allocated, and in kernel virtual.
                   */
                  if (ptpaddr == 0)
                          continue;
  
                  if (pdnxt > eindex) {
                          pdnxt = eindex;
                  }
  
                  for (; sindex != pdnxt; sindex++) {
  
                          pt_entry_t pbits;
                          vm_page_t m;
  
                          pbits = ptbase[sindex];
  
                          if (pbits & PG_MANAGED) {
                                  m = NULL;
                                  if (pbits & PG_A) {
                                          m = PHYS_TO_VM_PAGE(pbits);
                                          vm_page_flag_set(m, PG_REFERENCED);
                                          pbits &= ~PG_A;
                                  }
                                  if (pbits & PG_M) {
                                          if (pmap_track_modified(i386_ptob(sindex))) {
                                                  if (m == NULL)
                                                          m = PHYS_TO_VM_PAGE(pbits);
                                                  vm_page_dirty(m);
                                                  pbits &= ~PG_M;
                                          }
                                  }
                          }
  
                          pbits &= ~PG_RW;
  
                          if (pbits != ptbase[sindex]) {
                                  ptbase[sindex] = pbits;
                                  anychanged = 1;
                          }
                  }
          }
          if (anychanged)
                  pmap_invalidate_all(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_offset_t pa;
          register pt_entry_t *pte;
          vm_offset_t opa;
          pt_entry_t origpte, newpte;
          vm_page_t mpte;
  
          if (pmap == NULL)
                  return;
  
          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;
          /*
           * 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);
          }
  #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(pmap, va);
  
          /*
           * Page Directory table entry not valid, we need a new PT page
           */
          if (pte == NULL) {
                  panic("pmap_enter: invalid page directory, pdir=%p, va=0x%x\n",
                          (void *)pmap->pm_pdir[PTDPTDI], va);
          }
  
          pa = VM_PAGE_TO_PHYS(m) & PG_FRAME;
          origpte = *(vm_offset_t *)pte;
          opa = origpte & PG_FRAME;
  
          if (origpte & PG_PS)
                  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--;
  
  #if defined(PMAP_DIAGNOSTIC)
                  if (pmap_nw_modified((pt_entry_t) origpte)) {
                          printf(
          "pmap_enter: modified page not writable: va: 0x%x, pte: 0x%x\n",
                              va, origpte);
                  }
  #endif
  
                  /*
                   * Remove extra pte reference
                   */
                  if (mpte)
                          mpte->hold_count--;
  
                  if ((prot & VM_PROT_WRITE) && (origpte & PG_V)) {
                          if ((origpte & PG_RW) == 0) {
                                  *pte |= PG_RW;
                                  pmap_invalidate_page(pmap, va);
                          }
                          return;
                  }
  
                  /*
                   * We might be turning off write access to the page,
                   * so we go ahead and sense modify status.
                   */
                  if (origpte & PG_MANAGED) {
                          if ((origpte & PG_M) && pmap_track_modified(va)) {
                                  vm_page_t om;
                                  om = PHYS_TO_VM_PAGE(opa);
                                  vm_page_dirty(om);
                          }
                          pa |= PG_MANAGED;
                  }
                  goto validate;
          } 
          /*
           * Mapping has changed, invalidate old range and fall through to
           * handle validating new mapping.
           */
          if (opa) {
                  int err;
                  vm_page_lock_queues();
                  err = pmap_remove_pte(pmap, pte, va);
                  vm_page_unlock_queues();
                  if (err)
                          panic("pmap_enter: pte vanished, va: 0x%x", va);
          }
  
          /*
           * 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 (pmap_initialized && 
              (m->flags & (PG_FICTITIOUS|PG_UNMANAGED)) == 0) {
                  pmap_insert_entry(pmap, va, mpte, m);
                  pa |= PG_MANAGED;
          }
  
          /*
           * Increment counters
           */
          pmap->pm_stats.resident_count++;
          if (wired)
                  pmap->pm_stats.wired_count++;
  
  validate:
          /*
           * Now validate mapping with desired protection/wiring.
           */
          newpte = (vm_offset_t) (pa | pte_prot(pmap, prot) | PG_V);
  
          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) {
                  *pte = newpte | PG_A;
                  /*if (origpte)*/ {
                          pmap_invalidate_page(pmap, va);
                  }
          }
  }
  
  /*
   * this code makes some *MAJOR* assumptions:
   * 1. Current pmap & pmap exists.
   * 2. Not wired.
   * 3. Read access.
   * 4. No page table pages.
   * 5. Tlbflush is deferred to calling procedure.
   * 6. Page IS managed.
   * but is *MUCH* faster than pmap_enter...
   */
  
  static vm_page_t
  pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_page_t mpte)
  {
          pt_entry_t *pte;
          vm_offset_t pa;
  
          /*
           * 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->hold_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");
                                  if (pmap->pm_ptphint &&
                                          (pmap->pm_ptphint->pindex == ptepindex)) {
                                          mpte = pmap->pm_ptphint;
                                  } else {
                                          mpte = pmap_page_lookup(pmap->pm_pteobj, ptepindex);
                                          pmap->pm_ptphint = mpte;
                                  }
                                  if (mpte == NULL)
                                          goto retry;
                                  mpte->hold_count++;
                          } else {
                                  mpte = _pmap_allocpte(pmap, ptepindex);
                          }
                  }
          } 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) {
                          vm_page_lock_queues();
                          pmap_unwire_pte_hold(pmap, mpte);
                          vm_page_unlock_queues();
                  }
                  return 0;
          }
  
          /*
           * 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, mpte, 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 = pa | PG_V | PG_U;
          else
                  *pte = pa | PG_V | PG_U | PG_MANAGED;
  
          return mpte;
  }
  
  /*
   * Make a temporary mapping for a physical address.  This is only intended
   * to be used for panic dumps.
   */
  void *
  pmap_kenter_temporary(vm_offset_t pa, int i)
  {
          vm_offset_t va;
  
          va = (vm_offset_t)crashdumpmap + (i * PAGE_SIZE);
          pmap_kenter(va, pa);
  #ifndef I386_CPU
          invlpg(va);
  #else
          invltlb();
  #endif
          return ((void *)crashdumpmap);
  }
  
  #define MAX_INIT_PT (96)
  /*
   * pmap_object_init_pt preloads the ptes for a given object
   * into the specified pmap.  This eliminates the blast of soft
   * faults on process startup and immediately after an mmap.
   */
  void
  pmap_object_init_pt(pmap_t pmap, vm_offset_t addr,
                      vm_object_t object, vm_pindex_t pindex,
                      vm_size_t size, int limit)
  {
          vm_offset_t tmpidx;
          int psize;
          vm_page_t p, mpte;
  
          if (pmap == NULL || object == NULL)
                  return;
  
          /*
           * This code maps large physical mmap regions into the
           * processor address space.  Note that some shortcuts
           * are taken, but the code works.
           */
          if (pseflag && (object->type == OBJT_DEVICE) &&
              ((addr & (NBPDR - 1)) == 0) && ((size & (NBPDR - 1)) == 0)) {
                  int i;
                  vm_page_t m[1];
                  unsigned int ptepindex;
                  int npdes;
                  pd_entry_t ptepa;
  
                  if (pmap->pm_pdir[ptepindex = (addr >> PDRSHIFT)])
                          return;
  
  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;
                          vm_page_unlock_queues();
                  } 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_wakeup(p);
                  }
  
                  ptepa = VM_PAGE_TO_PHYS(p);
                  if (ptepa & (NBPDR - 1)) {
                          return;
                  }
  
                  p->valid = VM_PAGE_BITS_ALL;
  
                  pmap->pm_stats.resident_count += size >> PAGE_SHIFT;
                  npdes = size >> PDRSHIFT;
                  for(i = 0; i < npdes; i++) {
                          pmap->pm_pdir[ptepindex] =
                              ptepa | PG_U | PG_RW | PG_V | PG_PS;
                          ptepa += NBPDR;
                          ptepindex += 1;
                  }
                  pmap_invalidate_all(kernel_pmap);
                  return;
          }
  
          psize = i386_btop(size);
  
          if ((object->type != OBJT_VNODE) ||
              ((limit & MAP_PREFAULT_PARTIAL) && (psize > MAX_INIT_PT) &&
               (object->resident_page_count > MAX_INIT_PT))) {
                  return;
          }
  
          if (psize + pindex > object->size) {
                  if (object->size < pindex)
                          return;
                  psize = object->size - pindex;
          }
  
          mpte = NULL;
  
          if ((p = TAILQ_FIRST(&object->memq)) != NULL) {
                  if (p->pindex < pindex) {
                          p = vm_page_splay(pindex, object->root);
                          if ((object->root = p)->pindex < pindex)
                                  p = TAILQ_NEXT(p, listq);
                  }
          }
          /*
           * Assert: the variable p is either (1) the page with the
           * least pindex greater than or equal to the parameter pindex
           * or (2) NULL.
           */
          for (;
               p != NULL && (tmpidx = p->pindex - pindex) < psize;
               p = TAILQ_NEXT(p, listq)) {
                  /*
                   * don't allow an madvise to blow away our really
                   * free pages allocating pv entries.
                   */
                  if ((limit & MAP_PREFAULT_MADVISE) &&
                      cnt.v_free_count < cnt.v_free_reserved) {
                          break;
                  }
                  vm_page_lock_queues();
                  if ((p->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL &&
                      (p->busy == 0) &&
                      (p->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) {
                          if ((p->queue - p->pc) == PQ_CACHE)
                                  vm_page_deactivate(p);
                          vm_page_busy(p);
                          vm_page_unlock_queues();
                          mpte = pmap_enter_quick(pmap, 
                                  addr + i386_ptob(tmpidx), p, mpte);
                          vm_page_lock_queues();
                          vm_page_wakeup(p);
                  }
                  vm_page_unlock_queues();
          }
          return;
  }
  
  /*
   * pmap_prefault provides a quick way of clustering
   * pagefaults into a processes address space.  It is a "cousin"
   * of pmap_object_init_pt, except it runs at page fault time instead
   * of mmap time.
   */
  #define PFBAK 4
  #define PFFOR 4
  #define PAGEORDER_SIZE (PFBAK+PFFOR)
  
  static int pmap_prefault_pageorder[] = {
          -1 * PAGE_SIZE, 1 * PAGE_SIZE,
          -2 * PAGE_SIZE, 2 * PAGE_SIZE,
          -3 * PAGE_SIZE, 3 * PAGE_SIZE,
          -4 * PAGE_SIZE, 4 * PAGE_SIZE
  };
  
  void
  pmap_prefault(pmap, addra, entry)
          pmap_t pmap;
          vm_offset_t addra;
          vm_map_entry_t entry;
  {
          int i;
          vm_offset_t starta;
          vm_offset_t addr;
          vm_pindex_t pindex;
          vm_page_t m, mpte;
          vm_object_t object;
  
          if (!curthread || (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)))
                  return;
  
          object = entry->object.vm_object;
  
          starta = addra - PFBAK * PAGE_SIZE;
          if (starta < entry->start) {
                  starta = entry->start;
          } else if (starta > addra) {
                  starta = 0;
          }
  
          mpte = NULL;
          for (i = 0; i < PAGEORDER_SIZE; i++) {
                  vm_object_t lobject;
                  pt_entry_t *pte;
  
                  addr = addra + pmap_prefault_pageorder[i];
                  if (addr > addra + (PFFOR * PAGE_SIZE))
                          addr = 0;
  
                  if (addr < starta || addr >= entry->end)
                          continue;
  
                  if ((*pmap_pde(pmap, addr)) == 0) 
                          continue;
  
                  pte = vtopte(addr);
                  if (*pte)
                          continue;
  
                  pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
                  lobject = object;
                  for (m = vm_page_lookup(lobject, pindex);
                      (!m && (lobject->type == OBJT_DEFAULT) && (lobject->backing_object));
                      lobject = lobject->backing_object) {
                          if (lobject->backing_object_offset & PAGE_MASK)
                                  break;
                          pindex += (lobject->backing_object_offset >> PAGE_SHIFT);
                          m = vm_page_lookup(lobject->backing_object, pindex);
                  }
  
                  /*
                   * give-up when a page is not in memory
                   */
                  if (m == NULL)
                          break;
                  vm_page_lock_queues();
                  if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
                          (m->busy == 0) &&
                      (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) {
  
                          if ((m->queue - m->pc) == PQ_CACHE) {
                                  vm_page_deactivate(m);
                          }
                          vm_page_busy(m);
                          vm_page_unlock_queues();
                          mpte = pmap_enter_quick(pmap, addr, m, mpte);
                          vm_page_lock_queues();
                          vm_page_wakeup(m);
                  }
                  vm_page_unlock_queues();
          }
  }
  
  /*
   *      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;
  
          if (pmap == NULL)
                  return;
  
          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);
  }
  
  
  
  /*
   *      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;
          pd_entry_t src_frame, dst_frame;
          vm_page_t m;
  
          if (dst_addr != src_addr)
                  return;
  
          src_frame = src_pmap->pm_pdir[PTDPTDI] & PG_FRAME;
          if (src_frame != (PTDpde & PG_FRAME))
                  return;
  
          dst_frame = dst_pmap->pm_pdir[PTDPTDI] & PG_FRAME;
          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\n");
  
                  /*
                   * 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 + PAGE_SIZE*NPTEPG) & ~(PAGE_SIZE*NPTEPG - 1));
                  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;
                                  dst_pmap->pm_stats.resident_count += NBPDR / PAGE_SIZE;
                          }
                          continue;
                  }
  
                  srcmpte = vm_page_lookup(src_pmap->pm_pteobj, ptepindex);
                  if ((srcmpte == NULL) ||
                      (srcmpte->hold_count == 0) || (srcmpte->flags & PG_BUSY))
                          continue;
  
                  if (pdnxt > end_addr)
                          pdnxt = end_addr;
  
                  /*
                   * Have to recheck this before every avtopte() call below
                   * in case we have blocked and something else used APTDpde.
                   */
                  if (dst_frame != (APTDpde & PG_FRAME)) {
                          APTDpde = dst_frame | PG_RW | PG_V;
                          pmap_invalidate_all(kernel_pmap); /* XXX Bandaid */
                  }
                  src_pte = vtopte(addr);
                  dst_pte = avtopte(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);
                                  if ((*dst_pte == 0) && (ptetemp = *src_pte)) {
                                          /*
                                           * Clear the modified and
                                           * accessed (referenced) bits
                                           * during the copy.
                                           */
                                          m = PHYS_TO_VM_PAGE(ptetemp);
                                          *dst_pte = ptetemp & ~(PG_M | PG_A);
                                          dst_pmap->pm_stats.resident_count++;
                                          pmap_insert_entry(dst_pmap, addr,
                                                  dstmpte, m);
                                  } else {
                                          vm_page_lock_queues();
                                          pmap_unwire_pte_hold(dst_pmap, dstmpte);
                                          vm_page_unlock_queues();
                                  }
                                  if (dstmpte->hold_count >= srcmpte->hold_count)
                                          break;
                          }
                          addr += PAGE_SIZE;
                          src_pte++;
                          dst_pte++;
                  }
          }
  }       
  
  #ifdef SMP
  
  /*
   *      pmap_zpi_switchin*()
   *
   *      These functions allow us to avoid doing IPIs alltogether in certain
   *      temporary page-mapping situations (page zeroing).  Instead to deal
   *      with being preempted and moved onto a different cpu we invalidate
   *      the page when the scheduler switches us in.  This does not occur
   *      very often so we remain relatively optimal with very little effort.
   */
  static void
  pmap_zpi_switchin12(void)
  {
          invlpg((u_int)CADDR1);
          invlpg((u_int)CADDR2);
  }
  
  static void
  pmap_zpi_switchin2(void)
  {
          invlpg((u_int)CADDR2);
  }
  
  static void
  pmap_zpi_switchin3(void)
  {
          invlpg((u_int)CADDR3);
  }
  
  #endif
  
  /*
   *      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)
  {
          vm_offset_t phys;
  
          phys = VM_PAGE_TO_PHYS(m);
          if (*CMAP2)
                  panic("pmap_zero_page: CMAP2 busy");
          *CMAP2 = PG_V | PG_RW | phys | PG_A | PG_M;
  #ifdef I386_CPU
          invltlb();
  #else
  #ifdef SMP
          curthread->td_switchin = pmap_zpi_switchin2;
  #endif
          invlpg((u_int)CADDR2);
  #endif
  #if defined(I686_CPU)
          if (cpu_class == CPUCLASS_686)
                  i686_pagezero(CADDR2);
          else
  #endif
                  bzero(CADDR2, PAGE_SIZE);
  #ifdef SMP
          curthread->td_switchin = NULL;
  #endif
          *CMAP2 = 0;
  }
  
  /*
   *      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)
  {
          vm_offset_t phys;
  
          phys = VM_PAGE_TO_PHYS(m);
          if (*CMAP2)
                  panic("pmap_zero_page: CMAP2 busy");
          *CMAP2 = PG_V | PG_RW | phys | PG_A | PG_M;
  #ifdef I386_CPU
          invltlb();
  #else
  #ifdef SMP
          curthread->td_switchin = pmap_zpi_switchin2;
  #endif
          invlpg((u_int)CADDR2);
  #endif
  #if defined(I686_CPU)
          if (cpu_class == CPUCLASS_686 && off == 0 && size == PAGE_SIZE)
                  i686_pagezero(CADDR2);
          else
  #endif
                  bzero((char *)CADDR2 + off, size);
  #ifdef SMP
          curthread->td_switchin = NULL;
  #endif
          *CMAP2 = 0;
  }
  
  /*
   *      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)
  {
          vm_offset_t phys;
  
          phys = VM_PAGE_TO_PHYS(m);
          if (*CMAP3)
                  panic("pmap_zero_page: CMAP3 busy");
          *CMAP3 = PG_V | PG_RW | phys | PG_A | PG_M;
  #ifdef I386_CPU
          invltlb();
  #else
  #ifdef SMP
          curthread->td_switchin = pmap_zpi_switchin3;
  #endif
          invlpg((u_int)CADDR3);
  #endif
  #if defined(I686_CPU)
          if (cpu_class == CPUCLASS_686)
                  i686_pagezero(CADDR3);
          else
  #endif
                  bzero(CADDR3, PAGE_SIZE);
  #ifdef SMP
          curthread->td_switchin = NULL;
  #endif
          *CMAP3 = 0;
  }
  
  /*
   *      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)
  {
  
          if (*CMAP1)
                  panic("pmap_copy_page: CMAP1 busy");
          if (*CMAP2)
                  panic("pmap_copy_page: CMAP2 busy");
          *CMAP1 = PG_V | VM_PAGE_TO_PHYS(src) | PG_A;
          *CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(dst) | PG_A | PG_M;
  #ifdef I386_CPU
          invltlb();
  #else
  #ifdef SMP
          curthread->td_switchin = pmap_zpi_switchin12;
  #endif
          invlpg((u_int)CADDR1);
          invlpg((u_int)CADDR2);
  #endif
          bcopy(CADDR1, CADDR2, PAGE_SIZE);
  #ifdef SMP
          curthread->td_switchin = NULL;
  #endif
          *CMAP1 = 0;
          *CMAP2 = 0;
  }
  
  /*
   * 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;
          int s;
  
          if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                  return FALSE;
  
          s = splvm();
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  if (pv->pv_pmap == pmap) {
                          splx(s);
                          return TRUE;
                  }
                  loops++;
                  if (loops >= 16)
                          break;
          }
          splx(s);
          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;
          int s;
  
  #ifdef PMAP_REMOVE_PAGES_CURPROC_ONLY
          if (!curthread || (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))) {
                  printf("warning: pmap_remove_pages called with non-current pmap\n");
                  return;
          }
  #endif
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          s = splvm();
          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(pv->pv_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 %08x %08x",
                      m, m->phys_addr, tpte));
  
                  KASSERT(m < &vm_page_array[vm_page_array_size],
                          ("pmap_remove_pages: bad tpte %x", tpte));
  
                  pv->pv_pmap->pm_stats.resident_count--;
  
                  *pte = 0;
  
                  /*
                   * 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(&pv->pv_pmap->pm_pvlist, pv, pv_plist);
  
                  m->md.pv_list_count--;
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                  if (TAILQ_FIRST(&m->md.pv_list) == NULL) {
                          vm_page_flag_clear(m, PG_WRITEABLE);
                  }
  
                  pmap_unuse_pt(pv->pv_pmap, pv->pv_va, pv->pv_ptem);
                  free_pv_entry(pv);
          }
          splx(s);
          pmap_invalidate_all(pmap);
  }
  
  /*
   * pmap_testbit tests bits in pte's
   * note that the testbit/changebit routines are inline,
   * and a lot of things compile-time evaluate.
   */
  static boolean_t
  pmap_testbit(m, bit)
          vm_page_t m;
          int bit;
  {
          pv_entry_t pv;
          pt_entry_t *pte;
          int s;
  
          if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                  return FALSE;
  
          if (TAILQ_FIRST(&m->md.pv_list) == NULL)
                  return FALSE;
  
          s = splvm();
  
          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 (bit & (PG_A|PG_M)) {
                          if (!pmap_track_modified(pv->pv_va))
                                  continue;
                  }
  
  #if defined(PMAP_DIAGNOSTIC)
                  if (!pv->pv_pmap) {
                          printf("Null pmap (tb) at va: 0x%x\n", pv->pv_va);
                          continue;
                  }
  #endif
                  pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
                  if (*pte & bit) {
                          splx(s);
                          return TRUE;
                  }
          }
          splx(s);
          return (FALSE);
  }
  
  /*
   * this routine is used to modify bits in ptes
   */
  static __inline void
  pmap_changebit(vm_page_t m, int bit, boolean_t setem)
  {
          register pv_entry_t pv;
          register pt_entry_t *pte;
          int s;
  
          if (!pmap_initialized || (m->flags & PG_FICTITIOUS) ||
              (!setem && bit == PG_RW && (m->flags & PG_WRITEABLE) == 0))
                  return;
  
          s = splvm();
          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 (!setem && (bit == PG_RW)) {
                          if (!pmap_track_modified(pv->pv_va))
                                  continue;
                  }
  
  #if defined(PMAP_DIAGNOSTIC)
                  if (!pv->pv_pmap) {
                          printf("Null pmap (cb) at va: 0x%x\n", pv->pv_va);
                          continue;
                  }
  #endif
  
                  pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
  
                  if (setem) {
                          *pte |= bit;
                          pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
                  } else {
                          pt_entry_t pbits = *pte;
                          if (pbits & bit) {
                                  if (bit == PG_RW) {
                                          if (pbits & PG_M) {
                                                  vm_page_dirty(m);
                                          }
                                          *pte = pbits & ~(PG_M|PG_RW);
                                  } else {
                                          *pte = pbits & ~bit;
                                  }
                                  pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
                          }
                  }
          }
          if (!setem && bit == PG_RW)
                  vm_page_flag_clear(m, PG_WRITEABLE);
          splx(s);
  }
  
  /*
   *      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_changebit(m, PG_RW, FALSE);
                  } else {
                          pmap_remove_all(m);
                  }
          }
  }
  
  vm_offset_t
  pmap_phys_address(ppn)
          int ppn;
  {
          return (i386_ptob(ppn));
  }
  
  /*
   *      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;
          int s;
          int rtval = 0;
  
          if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                  return (rtval);
  
          s = splvm();
          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;
  
                          pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
  
                          if (pte && (*pte & PG_A)) {
                                  *pte &= ~PG_A;
  
                                  pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
  
                                  rtval++;
                                  if (rtval > 4) {
                                          break;
                                  }
                          }
                  } while ((pv = pvn) != NULL && pv != pvf);
          }
          splx(s);
  
          return (rtval);
  }
  
  /*
   *      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)
  {
          return pmap_testbit(m, PG_M);
  }
  
  /*
   *      Clear the modify bits on the specified physical page.
   */
  void
  pmap_clear_modify(vm_page_t m)
  {
          pmap_changebit(m, PG_M, FALSE);
  }
  
  /*
   *      pmap_clear_reference:
   *
   *      Clear the reference bit on the specified physical page.
   */
  void
  pmap_clear_reference(vm_page_t m)
  {
          pmap_changebit(m, PG_A, FALSE);
  }
  
  /*
   * Miscellaneous support routines follow
   */
  
  static void
  i386_protection_init()
  {
          register int *kp, prot;
  
          kp = protection_codes;
          for (prot = 0; prot < 8; prot++) {
                  switch (prot) {
                  case VM_PROT_NONE | VM_PROT_NONE | VM_PROT_NONE:
                          /*
                           * Read access is also 0. There isn't any execute bit,
                           * so just make it readable.
                           */
                  case VM_PROT_READ | VM_PROT_NONE | VM_PROT_NONE:
                  case VM_PROT_READ | VM_PROT_NONE | VM_PROT_EXECUTE:
                  case VM_PROT_NONE | VM_PROT_NONE | VM_PROT_EXECUTE:
                          *kp++ = 0;
                          break;
                  case VM_PROT_NONE | VM_PROT_WRITE | VM_PROT_NONE:
                  case VM_PROT_NONE | VM_PROT_WRITE | VM_PROT_EXECUTE:
                  case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_NONE:
                  case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
                          *kp++ = PG_RW;
                          break;
                  }
          }
  }
  
  /*
   * 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_offset_t pa;
          vm_size_t size;
  {
          vm_offset_t va, tmpva, offset;
          pt_entry_t *pte;
  
          offset = pa & PAGE_MASK;
          size = roundup(offset + size, PAGE_SIZE);
  
          GIANT_REQUIRED;
  
          va = kmem_alloc_pageable(kernel_map, size);
          if (!va)
                  panic("pmap_mapdev: Couldn't alloc kernel virtual memory");
  
          pa = pa & PG_FRAME;
          for (tmpva = va; size > 0; ) {
                  pte = vtopte(tmpva);
                  *pte = pa | PG_RW | PG_V | pgeflag;
                  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;
          pt_entry_t *pte;
  
          base = va & PG_FRAME;
          offset = va & PAGE_MASK;
          size = roundup(offset + size, PAGE_SIZE);
          for (tmpva = base; tmpva < (base + size); tmpva += PAGE_SIZE) {
                  pte = vtopte(tmpva);
                  *pte = 0;
          }
          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;
          
          ptep = pmap_pte(pmap, addr);
          if (ptep == 0) {
                  return 0;
          }
  
          if ((pte = *ptep) != 0) {
                  vm_offset_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;
          u_int32_t  cr3;
  
          pmap = vmspace_pmap(td->td_proc->p_vmspace);
  #if defined(SMP)
          pmap->pm_active |= PCPU_GET(cpumask);
  #else
          pmap->pm_active |= 1;
  #endif
          cr3 = vtophys(pmap->pm_pdir);
          /* XXXKSE this is wrong.
           * pmap_activate is for the current thread on the current cpu
           */
          if (p->p_flag & P_KSES) {
                  /* 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);
  #ifdef SWTCH_OPTIM_STATS
          tlb_flush_count++;
  #endif
  }
  
  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 + (NBPDR - 1)) & ~(NBPDR - 1);
          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 < NPDEPG; 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_quick(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_offset_t va;
          pt_entry_t *ptep;
  
          if (pm == kernel_pmap)
                  return;
          for (i = 0; i < NPDEPG; 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_quick(pm, va);
                                  if (pmap_pte_v(ptep))
                                          printf("%x:%x ", va, *ptep);
                          };
  
  }
  
  void
  pmap_pvdump(pa)
          vm_offset_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