kernel - Fix i386 pmap bug

[dragonfly.git] / sys / platform / pc32 / i386 / pmap.c

/*
 * (MPSAFE)
 *
 * 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: src/sys/i386/i386/pmap.c,v 1.250.2.18 2002/03/06 22:48:53 silby Exp $
 */

/*
 * Manages physical address maps.
 *
 * In most cases we hold page table pages busy in order to manipulate them.
 */
/*
 * PMAP_DEBUG - see platform/pc32/include/pmap.h
 */

#include "opt_disable_pse.h"
#include "opt_pmap.h"
#include "opt_msgbuf.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/msgbuf.h>
#include <sys/vmmeter.h>
#include <sys/mman.h>
#include <sys/thread.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <sys/sysctl.h>
#include <sys/lock.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/vm_zone.h>

#include <sys/user.h>
#include <sys/thread2.h>
#include <sys/sysref2.h>
#include <sys/spinlock2.h>
#include <vm/vm_page2.h>

#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>
#include <machine/smp.h>
#include <machine_base/apic/apicreg.h>
#include <machine/globaldata.h>
#include <machine/pmap.h>
#include <machine/pmap_inval.h>

#define PMAP_KEEP_PDIRS
#ifndef PMAP_SHPGPERPROC
#define PMAP_SHPGPERPROC 200
#define PMAP_PVLIMIT     1400000        /* i386 kvm problems */
#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)

/*
 * Given a map and a machine independent protection code,
 * convert to a vax protection code.
 */
#define pte_prot(m, p)          \
        (protection_codes[p & (VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE)])
static int protection_codes[8];

struct pmap kernel_pmap;
static TAILQ_HEAD(,pmap)        pmap_list = TAILQ_HEAD_INITIALIZER(pmap_list);

vm_paddr_t avail_start;         /* PA of first available physical page */
vm_paddr_t avail_end;           /* PA of last available physical page */
vm_offset_t virtual_start;      /* VA of first avail page (after kernel bss) */
vm_offset_t virtual_end;        /* VA of last avail page (end of kernel AS) */
vm_offset_t virtual2_start;
vm_offset_t virtual2_end;
vm_offset_t KvaStart;           /* VA start of KVA space */
vm_offset_t KvaEnd;             /* VA end of KVA space (non-inclusive) */
vm_offset_t KvaSize;            /* max size of kernel virtual address space */
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;

/*
 * Data for the pv entry allocation mechanism
 */
static vm_zone_t pvzone;
static struct vm_zone pvzone_store;
static struct vm_object pvzone_obj;
static int pv_entry_count=0, pv_entry_max=0, pv_entry_high_water=0;
static int pmap_pagedaemon_waken = 0;
static struct pv_entry *pvinit;

/*
 * Considering all the issues I'm having with pmap caching, if breakage
 * continues to occur, and for debugging, I've added a sysctl that will
 * just do an unconditional invltlb.
 */
static int dreadful_invltlb;

SYSCTL_INT(_vm, OID_AUTO, dreadful_invltlb,
           CTLFLAG_RW, &dreadful_invltlb, 0, "Debugging sysctl to force invltlb on pmap operations");

/*
 * All those kernel PT submaps that BSD is so fond of
 */
pt_entry_t *CMAP1 = NULL, *ptmmap;
caddr_t CADDR1 = NULL, ptvmmap = NULL;
static pt_entry_t *msgbufmap;
struct msgbuf *msgbufp=NULL;

/*
 * Crashdump maps.
 */
static pt_entry_t *pt_crashdumpmap;
static caddr_t crashdumpmap;

extern pt_entry_t *SMPpt;

static PMAP_INLINE void free_pv_entry (pv_entry_t pv);
static unsigned * get_ptbase (pmap_t pmap);
static pv_entry_t get_pv_entry (void);
static void     i386_protection_init (void);
static __inline void    pmap_clearbit (vm_page_t m, int bit);

static void pmap_remove_all (vm_page_t m);
static void pmap_remove_pte (struct pmap *pmap, unsigned *ptq,
                                vm_offset_t sva, pmap_inval_info_t info);
static void pmap_remove_page (struct pmap *pmap, 
                                vm_offset_t va, pmap_inval_info_t info);
static void pmap_remove_entry (struct pmap *pmap, vm_page_t m,
                                vm_offset_t va, pmap_inval_info_t info);
static boolean_t pmap_testbit (vm_page_t m, int bit);
static void pmap_insert_entry (pmap_t pmap, pv_entry_t pv,
                                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 unsigned * 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 void pmap_unuse_pt (pmap_t, vm_offset_t, vm_page_t, pmap_inval_info_t);
static vm_offset_t pmap_kmem_choose(vm_offset_t addr);

static void pmap_hold(pmap_t pmap);
static void pmap_drop(pmap_t pmap);
static void pmap_wait(pmap_t pmap, int count);

static unsigned pdir4mb;

/*
 * 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;
}

/*
 * This function returns a pointer to the pte entry in the pmap and has
 * the side effect of potentially retaining a cached mapping of the pmap.
 *
 * The caller must hold vm_token and the returned value is only valid
 * until the caller blocks or releases the token.
 */
static
unsigned *
pmap_pte(pmap_t pmap, vm_offset_t va)
{
        unsigned *pdeaddr;

        ASSERT_LWKT_TOKEN_HELD(&vm_token);
        if (pmap) {
                pdeaddr = (unsigned *) pmap_pde(pmap, va);
                if (*pdeaddr & PG_PS)
                        return pdeaddr;
                if (*pdeaddr)
                        return get_ptbase(pmap) + i386_btop(va);
        }
        return (0);
}

/*
 * pmap_pte using the kernel_pmap
 *
 * Used for debugging, no requirements.
 */
unsigned *
pmap_kernel_pte(vm_offset_t va)
{
        unsigned *pdeaddr;

        pdeaddr = (unsigned *) pmap_pde(&kernel_pmap, va);
        if (*pdeaddr & PG_PS)
                return pdeaddr;
        if (*pdeaddr)
                return (unsigned *)vtopte(va);
        return(0);
}

/*
 * pmap_pte_quick:
 *
 * Super fast pmap_pte routine best used when scanning the pv lists.
 * This eliminates many course-grained invltlb calls.  Note that many of
 * the pv list scans are across different pmaps and it is very wasteful
 * to do an entire invltlb when checking a single mapping.
 *
 * Should only be called while in a critical section.
 *
 * The caller must hold vm_token and the returned value is only valid
 * until the caller blocks or releases the token.
 */
static
unsigned *
pmap_pte_quick(pmap_t pmap, vm_offset_t va)
{
        struct mdglobaldata *gd = mdcpu;
        unsigned pde, newpf;

        ASSERT_LWKT_TOKEN_HELD(&vm_token);
        if ((pde = (unsigned) pmap->pm_pdir[va >> PDRSHIFT]) != 0) {
                unsigned frame = (unsigned) pmap->pm_pdir[PTDPTDI] & PG_FRAME;
                unsigned index = i386_btop(va);
                /* are we current address space or kernel? */
                if ((pmap == &kernel_pmap) ||
                        (frame == (((unsigned) PTDpde) & PG_FRAME))) {
                        return (unsigned *) PTmap + index;
                }
                newpf = pde & PG_FRAME;
                if (((*(unsigned *)gd->gd_PMAP1) & PG_FRAME) != newpf) {
                        *(unsigned *)gd->gd_PMAP1 = newpf | PG_RW | PG_V;
                        cpu_invlpg(gd->gd_PADDR1);
                }
                return gd->gd_PADDR1 + (index & (NPTEPG - 1));
        }
        return (0);
}


/*
 * Bootstrap the system enough to run with virtual memory.
 *
 * On the i386 this is called after mapping has already been enabled
 * and just syncs the pmap module with what has already been done.
 * [We can't call it easily with mapping off since the kernel is not
 * mapped with PA == VA, hence we would have to relocate every address
 * from the linked base (virtual) address "KERNBASE" to the actual
 * (physical) address starting relative to 0]
 */
void
pmap_bootstrap(vm_paddr_t firstaddr, vm_paddr_t loadaddr)
{
        vm_offset_t va;
        pt_entry_t *pte;
        struct mdglobaldata *gd;
        int i;
        int pg;

        KvaStart = (vm_offset_t)VADDR(PTDPTDI, 0);
        KvaSize = (vm_offset_t)VADDR(APTDPTDI, 0) - KvaStart;
        KvaEnd  = KvaStart + KvaSize;

        avail_start = firstaddr;

        /*
         * XXX The calculation of virtual_start 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_start = (vm_offset_t) KERNBASE + firstaddr;
        virtual_start = pmap_kmem_choose(virtual_start);
        virtual_end = VADDR(KPTDI+NKPDE-1, NPTEPG-1);

        /*
         * Initialize protection array.
         */
        i386_protection_init();

        /*
         * The kernel's pmap is statically allocated so we don't have to use
         * pmap_create, which is unlikely to work correctly at this part of
         * the boot sequence (XXX and which no longer exists).
         *
         * The kernel_pmap's pm_pteobj is used only for locking and not
         * for mmu pages.
         */
        kernel_pmap.pm_pdir = (pd_entry_t *)(KERNBASE + (u_int)IdlePTD);
        kernel_pmap.pm_count = 1;
        kernel_pmap.pm_active = (cpumask_t)-1 & ~CPUMASK_LOCK;
        kernel_pmap.pm_pteobj = &kernel_object;
        TAILQ_INIT(&kernel_pmap.pm_pvlist);
        TAILQ_INIT(&kernel_pmap.pm_pvlist_free);
        spin_init(&kernel_pmap.pm_spin);
        lwkt_token_init(&kernel_pmap.pm_token, "kpmap_tok");
        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_start;
        pte = (pt_entry_t *) pmap_kernel_pte(va);

        /*
         * CMAP1/CMAP2 are used for zeroing and copying pages.
         */
        SYSMAP(caddr_t, CMAP1, CADDR1, 1)

        /*
         * Crashdump maps.
         */
        SYSMAP(caddr_t, pt_crashdumpmap, crashdumpmap, MAXDUMPPGS);

        /*
         * ptvmmap is used for reading arbitrary physical pages via
         * /dev/mem.
         */
        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)))

        virtual_start = va;

        *(int *) CMAP1 = 0;
        for (i = 0; i < NKPT; i++)
                PTD[i] = 0;

        /*
         * PG_G is terribly broken on SMP because we IPI invltlb's in some
         * cases rather then invl1pg.  Actually, I don't even know why it
         * works under UP because self-referential page table mappings
         */
#ifdef SMP
        pgeflag = 0;
#else
        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;

#if !defined(DISABLE_PSE)
        if (cpu_feature & CPUID_PSE) {
                unsigned ptditmp;
                /*
                 * Note that we have enabled PSE mode
                 */
                pseflag = PG_PS;
                ptditmp = *((unsigned *)PTmap + i386_btop(KERNBASE));
                ptditmp &= ~(NBPDR - 1);
                ptditmp |= PG_V | PG_RW | PG_PS | PG_U | pgeflag;
                pdir4mb = ptditmp;

#ifndef SMP
                /*
                 * Enable the PSE mode.  If we are SMP we can't do this
                 * now because the APs will not be able to use it when
                 * they boot up.
                 */
                load_cr4(rcr4() | CR4_PSE);

                /*
                 * We can do the mapping here for the single processor
                 * case.  We simply ignore the old page table page from
                 * now on.
                 */
                /*
                 * For SMP, we still need 4K pages to bootstrap APs,
                 * PSE will be enabled as soon as all APs are up.
                 */
                PTD[KPTDI] = (pd_entry_t)ptditmp;
                kernel_pmap.pm_pdir[KPTDI] = (pd_entry_t)ptditmp;
                cpu_invltlb();
#endif
        }
#endif

        /*
         * We need to finish setting up the globaldata page for the BSP.
         * locore has already populated the page table for the mdglobaldata
         * portion.
         */
        pg = MDGLOBALDATA_BASEALLOC_PAGES;
        gd = &CPU_prvspace[0].mdglobaldata;
        gd->gd_CMAP1 = &SMPpt[pg + 0];
        gd->gd_CMAP2 = &SMPpt[pg + 1];
        gd->gd_CMAP3 = &SMPpt[pg + 2];
        gd->gd_PMAP1 = &SMPpt[pg + 3];
        gd->gd_GDMAP1 = &PTD[APTDPTDI];
        gd->gd_CADDR1 = CPU_prvspace[0].CPAGE1;
        gd->gd_CADDR2 = CPU_prvspace[0].CPAGE2;
        gd->gd_CADDR3 = CPU_prvspace[0].CPAGE3;
        gd->gd_PADDR1 = (unsigned *)CPU_prvspace[0].PPAGE1;
        gd->gd_GDADDR1= (unsigned *)VADDR(APTDPTDI, 0);

        cpu_invltlb();
}

#ifdef SMP
/*
 * Set 4mb pdir for mp startup
 */
void
pmap_set_opt(void)
{
        if (pseflag && (cpu_feature & CPUID_PSE)) {
                load_cr4(rcr4() | CR4_PSE);
                if (pdir4mb && mycpu->gd_cpuid == 0) {  /* only on BSP */
                        kernel_pmap.pm_pdir[KPTDI] =
                            PTD[KPTDI] = (pd_entry_t)pdir4mb;
                        cpu_invltlb();
                }
        }
}
#endif

/*
 * Initialize the pmap module, called by vm_init()
 *
 * Called from the low level boot code only.
 */
void
pmap_init(void)
{
        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 = &pvzone_store;
        pvinit = (void *)kmem_alloc(&kernel_map,
                                    initial_pvs * sizeof (struct pv_entry));
        zbootinit(pvzone, "PV ENTRY", sizeof (struct pv_entry),
                  pvinit, 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.
 *
 * Called from the low level boot code only.
 */
void
pmap_init2(void)
{
        int shpgperproc = PMAP_SHPGPERPROC;
        int entry_max;

        TUNABLE_INT_FETCH("vm.pmap.shpgperproc", &shpgperproc);
        pv_entry_max = shpgperproc * maxproc + vm_page_array_size;

#ifdef PMAP_PVLIMIT
        /*
         * Horrible hack for systems with a lot of memory running i386.
         * the calculated pv_entry_max can wind up eating a ton of KVM
         * so put a cap on the number of entries if the user did not
         * change any of the values.   This saves about 44MB of KVM on
         * boxes with 3+GB of ram.
         *
         * On the flip side, this makes it more likely that some setups
         * will run out of pv entries.  Those sysads will have to bump
         * the limit up with vm.pamp.pv_entries or vm.pmap.shpgperproc.
         */
        if (shpgperproc == PMAP_SHPGPERPROC) {
                if (pv_entry_max > PMAP_PVLIMIT)
                        pv_entry_max = PMAP_PVLIMIT;
        }
#endif
        TUNABLE_INT_FETCH("vm.pmap.pv_entries", &pv_entry_max);
        pv_entry_high_water = 9 * (pv_entry_max / 10);

        /*
         * Subtract out pages already installed in the zone (hack)
         */
        entry_max = pv_entry_max - vm_page_array_size;
        if (entry_max <= 0)
                entry_max = 1;

        zinitna(pvzone, &pvzone_obj, NULL, 0, entry_max, ZONE_INTERRUPT, 1);
}


/***************************************************
 * Low level helper routines.....
 ***************************************************/

#ifdef PMAP_DEBUG

static void
test_m_maps_pv(vm_page_t m, pv_entry_t pv)
{
        pv_entry_t spv;

        crit_enter();
#ifdef PMAP_DEBUG
        KKASSERT(pv->pv_m == m);
#endif
        TAILQ_FOREACH(spv, &m->md.pv_list, pv_list) {
                if (pv == spv) {
                        crit_exit();
                        return;
                }
        }
        crit_exit();
        panic("test_m_maps_pv: failed m %p pv %p", m, pv);
}

static void
ptbase_assert(struct pmap *pmap)
{
        unsigned frame = (unsigned) pmap->pm_pdir[PTDPTDI] & PG_FRAME;

        /* are we current address space or kernel? */
        if (pmap == &kernel_pmap || frame == (((unsigned)PTDpde) & PG_FRAME))
                return;
        KKASSERT(frame == (*mdcpu->gd_GDMAP1 & PG_FRAME));
}

#else

#define test_m_maps_pv(m, pv)
#define ptbase_assert(pmap)

#endif

#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.
 *
 * No requirements.
 */
static PMAP_INLINE int
pmap_track_modified(vm_offset_t va)
{
        if ((va < clean_sva) || (va >= clean_eva)) 
                return 1;
        else
                return 0;
}

/*
 * Retrieve the mapped page table base for a particular pmap.  Use our self
 * mapping for the kernel_pmap or our current pmap.
 *
 * For foreign pmaps we use the per-cpu page table map.  Since this involves
 * installing a ptd it's actually (per-process x per-cpu).  However, we
 * still cannot depend on our mapping to survive thread switches because
 * the process might be threaded and switching to another thread for the
 * same process on the same cpu will allow that other thread to make its
 * own mapping.
 *
 * This could be a bit confusing but the jist is for something like the
 * vkernel which uses foreign pmaps all the time this represents a pretty
 * good cache that avoids unnecessary invltlb()s.
 *
 * The caller must hold vm_token and the returned value is only valid
 * until the caller blocks or releases the token.
 */
static unsigned *
get_ptbase(pmap_t pmap)
{
        unsigned frame = (unsigned) pmap->pm_pdir[PTDPTDI] & PG_FRAME;
        struct mdglobaldata *gd = mdcpu;

        ASSERT_LWKT_TOKEN_HELD(&vm_token);

        /*
         * We can use PTmap if the pmap is our current address space or
         * the kernel address space.
         */
        if (pmap == &kernel_pmap || frame == (((unsigned) PTDpde) & PG_FRAME)) {
                return (unsigned *) PTmap;
        }

        /*
         * Otherwise we use the per-cpu alternative page table map.  Each
         * cpu gets its own map.  Because of this we cannot use this map
         * from interrupts or threads which can preempt.
         *
         * Even if we already have the map cached we may still have to
         * invalidate the TLB if another cpu modified a PDE in the map.
         */
        KKASSERT(gd->mi.gd_intr_nesting_level == 0 &&
                 (gd->mi.gd_curthread->td_flags & TDF_INTTHREAD) == 0);

        if ((*gd->gd_GDMAP1 & PG_FRAME) != frame) {
                *gd->gd_GDMAP1 = frame | PG_RW | PG_V;
                pmap->pm_cached |= gd->mi.gd_cpumask;
                cpu_invltlb();
        } else if ((pmap->pm_cached & gd->mi.gd_cpumask) == 0) {
                pmap->pm_cached |= gd->mi.gd_cpumask;
                cpu_invltlb();
        } else if (dreadful_invltlb) {
                cpu_invltlb();
        }
        return ((unsigned *)gd->gd_GDADDR1);
}

/*
 * pmap_extract:
 *
 * Extract the physical page address associated with the map/VA pair.
 *
 * The caller may hold vm_token if it desires non-blocking operation.
 */
vm_paddr_t 
pmap_extract(pmap_t pmap, vm_offset_t va)
{
        vm_offset_t rtval;
        vm_offset_t pdirindex;

        lwkt_gettoken(&vm_token);
        pdirindex = va >> PDRSHIFT;
        if (pmap && (rtval = (unsigned) pmap->pm_pdir[pdirindex])) {
                unsigned *pte;
                if ((rtval & PG_PS) != 0) {
                        rtval &= ~(NBPDR - 1);
                        rtval |= va & (NBPDR - 1);
                } else {
                        pte = get_ptbase(pmap) + i386_btop(va);
                        rtval = ((*pte & PG_FRAME) | (va & PAGE_MASK));
                }
        } else {
                rtval = 0;
        }
        lwkt_reltoken(&vm_token);
        return rtval;
}

/***************************************************
 * Low level mapping routines.....
 ***************************************************/

/*
 * Map a wired VM page to a KVA, fully SMP synchronized.
 *
 * No requirements, non blocking.
 */
void 
pmap_kenter(vm_offset_t va, vm_paddr_t pa)
{
        unsigned *pte;
        unsigned npte;
        pmap_inval_info info;

        pmap_inval_init(&info);
        npte = pa | PG_RW | PG_V | pgeflag;
        pte = (unsigned *)vtopte(va);
        pmap_inval_interlock(&info, &kernel_pmap, va);
        *pte = npte;
        pmap_inval_deinterlock(&info, &kernel_pmap);
        pmap_inval_done(&info);
}

/*
 * Map a wired VM page to a KVA, synchronized on current cpu only.
 *
 * No requirements, non blocking.
 */
void
pmap_kenter_quick(vm_offset_t va, vm_paddr_t pa)
{
        unsigned *pte;
        unsigned npte;

        npte = pa | PG_RW | PG_V | pgeflag;
        pte = (unsigned *)vtopte(va);
        *pte = npte;
        cpu_invlpg((void *)va);
}

/*
 * Synchronize a previously entered VA on all cpus.
 *
 * No requirements, non blocking.
 */
void
pmap_kenter_sync(vm_offset_t va)
{
        pmap_inval_info info;

        pmap_inval_init(&info);
        pmap_inval_interlock(&info, &kernel_pmap, va);
        pmap_inval_deinterlock(&info, &kernel_pmap);
        pmap_inval_done(&info);
}

/*
 * Synchronize a previously entered VA on the current cpu only.
 *
 * No requirements, non blocking.
 */
void
pmap_kenter_sync_quick(vm_offset_t va)
{
        cpu_invlpg((void *)va);
}

/*
 * Remove a page from the kernel pagetables, fully SMP synchronized.
 *
 * No requirements, non blocking.
 */
void
pmap_kremove(vm_offset_t va)
{
        unsigned *pte;
        pmap_inval_info info;

        pmap_inval_init(&info);
        pte = (unsigned *)vtopte(va);
        pmap_inval_interlock(&info, &kernel_pmap, va);
        *pte = 0;
        pmap_inval_deinterlock(&info, &kernel_pmap);
        pmap_inval_done(&info);
}

/*
 * Remove a page from the kernel pagetables, synchronized on current cpu only.
 *
 * No requirements, non blocking.
 */
void
pmap_kremove_quick(vm_offset_t va)
{
        unsigned *pte;
        pte = (unsigned *)vtopte(va);
        *pte = 0;
        cpu_invlpg((void *)va);
}

/*
 * Adjust the permissions of a page in the kernel page table,
 * synchronized on the current cpu only.
 *
 * No requirements, non blocking.
 */
void
pmap_kmodify_rw(vm_offset_t va)
{
        atomic_set_int(vtopte(va), PG_RW);
        cpu_invlpg((void *)va);
}

/*
 * Adjust the permissions of a page in the kernel page table,
 * synchronized on the current cpu only.
 *
 * No requirements, non blocking.
 */
void
pmap_kmodify_nc(vm_offset_t va)
{
        atomic_set_int(vtopte(va), PG_N);
        cpu_invlpg((void *)va);
}

/*
 * Map a range of physical addresses into kernel virtual address space.
 *
 * No requirements, non blocking.
 */
vm_offset_t
pmap_map(vm_offset_t *virtp, vm_paddr_t start, vm_paddr_t end, int prot)
{
        vm_offset_t     sva, virt;

        sva = virt = *virtp;
        while (start < end) {
                pmap_kenter(virt, start);
                virt += PAGE_SIZE;
                start += PAGE_SIZE;
        }
        *virtp = virt;
        return (sva);
}

/*
 * Add a list of wired pages to the kva, fully SMP synchronized.
 *
 * No requirements, non blocking.
 */
void
pmap_qenter(vm_offset_t va, vm_page_t *m, int count)
{
        vm_offset_t end_va;

        end_va = va + count * PAGE_SIZE;
                
        while (va < end_va) {
                unsigned *pte;

                pte = (unsigned *)vtopte(va);
                *pte = VM_PAGE_TO_PHYS(*m) | PG_RW | PG_V | pgeflag;
                cpu_invlpg((void *)va);
                va += PAGE_SIZE;
                m++;
        }
#ifdef SMP
        smp_invltlb();  /* XXX */
#endif
}

/*
 * Remove pages from KVA, fully SMP synchronized.
 *
 * No requirements, non blocking.
 */
void
pmap_qremove(vm_offset_t va, int count)
{
        vm_offset_t end_va;

        end_va = va + count*PAGE_SIZE;

        while (va < end_va) {
                unsigned *pte;

                pte = (unsigned *)vtopte(va);
                *pte = 0;
                cpu_invlpg((void *)va);
                va += PAGE_SIZE;
        }
#ifdef SMP
        smp_invltlb();
#endif
}

/*
 * This routine works like vm_page_lookup() but also blocks as long as the
 * page is busy.  This routine does not busy the page it returns.
 *
 * The caller must hold the object.
 */
static vm_page_t
pmap_page_lookup(vm_object_t object, vm_pindex_t pindex)
{
        vm_page_t m;

        ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
        m = vm_page_lookup_busy_wait(object, pindex, FALSE, "pplookp");

        return(m);
}

/*
 * Create a new thread and optionally associate it with a (new) process.
 * NOTE! the new thread's cpu may not equal the current cpu.
 */
void
pmap_init_thread(thread_t td)
{
        /* enforce pcb placement */
        td->td_pcb = (struct pcb *)(td->td_kstack + td->td_kstack_size) - 1;
        td->td_savefpu = &td->td_pcb->pcb_save;
        td->td_sp = (char *)td->td_pcb - 16;
}

/*
 * This routine directly affects the fork perf for a process.
 */
void
pmap_init_proc(struct proc *p)
{
}

/***************************************************
 * Page table page management routines.....
 ***************************************************/

/*
 * This routine unwires page table pages, removing and freeing the page
 * tale page when the wire count drops to 0.
 *
 * The caller must hold vm_token.
 * This function can block.
 */
static int 
_pmap_unwire_pte(pmap_t pmap, vm_page_t m, pmap_inval_info_t info)
{
        /* 
         * Wait until we can busy the page ourselves.  We cannot have
         * any active flushes if we block.
         */
        vm_page_busy_wait(m, FALSE, "pmuwpt");
        KASSERT(m->queue == PQ_NONE,
                ("_pmap_unwire_pte: %p->queue != PQ_NONE", m));

        if (m->wire_count == 1) {
                /*
                 * Unmap the page table page.
                 *
                 * NOTE: We must clear pm_cached for all cpus, including
                 *       the current one, when clearing a page directory
                 *       entry.
                 */
                pmap_inval_interlock(info, pmap, -1);
                KKASSERT(pmap->pm_pdir[m->pindex]);
                pmap->pm_pdir[m->pindex] = 0;
                pmap->pm_cached = 0;
                pmap_inval_deinterlock(info, pmap);

                KKASSERT(pmap->pm_stats.resident_count > 0);
                --pmap->pm_stats.resident_count;

                if (pmap->pm_ptphint == m)
                        pmap->pm_ptphint = NULL;

                /*
                 * This was our last hold, the page had better be unwired
                 * after we decrement wire_count.
                 * 
                 * FUTURE NOTE: shared page directory page could result in
                 * multiple wire counts.
                 */
                vm_page_unwire(m, 0);
                vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);
                vm_page_flash(m);
                vm_page_free_zero(m);
                return 1;
        } else {
                KKASSERT(m->wire_count > 1);
                if (vm_page_unwire_quick(m))
                        panic("pmap_unwire_pte: Insufficient wire_count");
                vm_page_wakeup(m);
                return 0;
        }
}

/*
 * The caller must hold vm_token.
 *
 * This function can block.
 *
 * This function can race the wire_count 2->1 case because the page
 * is not busied during the unwire_quick operation.  An eventual
 * pmap_release() will catch the case.
 */
static PMAP_INLINE int
pmap_unwire_pte(pmap_t pmap, vm_page_t m, pmap_inval_info_t info)
{
        KKASSERT(m->wire_count > 0);
        if (m->wire_count > 1) {
                if (vm_page_unwire_quick(m))
                        panic("pmap_unwire_pte: Insufficient wire_count");
                return 0;
        } else {
                return _pmap_unwire_pte(pmap, m, info);
        }
}

/*
 * After removing a (user) page table entry, this routine is used to
 * conditionally free the page, and manage the hold/wire counts.
 *
 * The caller must hold vm_token.
 * This function can block regardless.
 */
static void
pmap_unuse_pt(pmap_t pmap, vm_offset_t va, vm_page_t mpte,
              pmap_inval_info_t info)
{
        unsigned ptepindex;

        ASSERT_LWKT_TOKEN_HELD(vm_object_token(pmap->pm_pteobj));

        if (va >= UPT_MIN_ADDRESS)
                return;

        if (mpte == NULL) {
                ptepindex = (va >> PDRSHIFT);
                if ((mpte = pmap->pm_ptphint) != NULL &&
                    mpte->pindex == ptepindex &&
                    (mpte->flags & PG_BUSY) == 0) {
                        ; /* use mpte */
                } else {
                        mpte = pmap_page_lookup(pmap->pm_pteobj, ptepindex);
                        pmap->pm_ptphint = mpte;
                        vm_page_wakeup(mpte);
                }
        }
        pmap_unwire_pte(pmap, mpte, info);
}

/*
 * Initialize pmap0/vmspace0.  This pmap is not added to pmap_list because
 * it, and IdlePTD, represents the template used to update all other pmaps.
 *
 * On architectures where the kernel pmap is not integrated into the user
 * process pmap, this pmap represents the process pmap, not the kernel pmap.
 * kernel_pmap should be used to directly access the kernel_pmap.
 *
 * No requirements.
 */
void
pmap_pinit0(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);
        pmap->pm_count = 1;
        pmap->pm_active = 0;
        pmap->pm_cached = 0;
        pmap->pm_ptphint = NULL;
        TAILQ_INIT(&pmap->pm_pvlist);
        TAILQ_INIT(&pmap->pm_pvlist_free);
        spin_init(&pmap->pm_spin);
        lwkt_token_init(&pmap->pm_token, "pmap_tok");
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
}

/*
 * Initialize a preallocated and zeroed pmap structure,
 * such as one in a vmspace structure.
 *
 * No requirements.
 */
void
pmap_pinit(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 an object for the ptes
         */
        if (pmap->pm_pteobj == NULL)
                pmap->pm_pteobj = vm_object_allocate(OBJT_DEFAULT, PTDPTDI + 1);

        /*
         * Allocate the page directory page, unless we already have
         * one cached.  If we used the cached page the wire_count will
         * already be set appropriately.
         */
        if ((ptdpg = pmap->pm_pdirm) == NULL) {
                ptdpg = vm_page_grab(pmap->pm_pteobj, PTDPTDI,
                                     VM_ALLOC_NORMAL | VM_ALLOC_RETRY |
                                     VM_ALLOC_ZERO);
                pmap->pm_pdirm = ptdpg;
                vm_page_flag_clear(ptdpg, PG_MAPPED);
                vm_page_wire(ptdpg);
                KKASSERT(ptdpg->valid == VM_PAGE_BITS_ALL);
                pmap_kenter((vm_offset_t)pmap->pm_pdir, VM_PAGE_TO_PHYS(ptdpg));
                vm_page_wakeup(ptdpg);
        }
        pmap->pm_pdir[MPPTDI] = PTD[MPPTDI];

        /* install self-referential address mapping entry */
        *(unsigned *) (pmap->pm_pdir + PTDPTDI) =
                VM_PAGE_TO_PHYS(ptdpg) | PG_V | PG_RW | PG_A | PG_M;

        pmap->pm_count = 1;
        pmap->pm_active = 0;
        pmap->pm_cached = 0;
        pmap->pm_ptphint = NULL;
        TAILQ_INIT(&pmap->pm_pvlist);
        TAILQ_INIT(&pmap->pm_pvlist_free);
        spin_init(&pmap->pm_spin);
        lwkt_token_init(&pmap->pm_token, "pmap_tok");
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
        pmap->pm_stats.resident_count = 1;
}

/*
 * Clean up a pmap structure so it can be physically freed.  This routine
 * is called by the vmspace dtor function.  A great deal of pmap data is
 * left passively mapped to improve vmspace management so we have a bit
 * of cleanup work to do here.
 *
 * No requirements.
 */
void
pmap_puninit(pmap_t pmap)
{
        vm_page_t p;

        pmap_wait(pmap, -1);
        KKASSERT(pmap->pm_active == 0);
        if ((p = pmap->pm_pdirm) != NULL) {
                KKASSERT(pmap->pm_pdir != NULL);
                pmap_kremove((vm_offset_t)pmap->pm_pdir);
                vm_page_busy_wait(p, FALSE, "pgpun");
                vm_page_unwire(p, 0);
                vm_page_free_zero(p);
                pmap->pm_pdirm = NULL;
        }
        if (pmap->pm_pdir) {
                kmem_free(&kernel_map, (vm_offset_t)pmap->pm_pdir, PAGE_SIZE);
                pmap->pm_pdir = NULL;
        }
        if (pmap->pm_pteobj) {
                vm_object_deallocate(pmap->pm_pteobj);
                pmap->pm_pteobj = NULL;
        }
}

/*
 * Wire in kernel global address entries.  To avoid a race condition
 * between pmap initialization and pmap_growkernel, this procedure
 * adds the pmap to the master list (which growkernel scans to update),
 * then copies the template.
 *
 * No requirements.
 */
void
pmap_pinit2(struct pmap *pmap)
{
        /*
         * XXX copies current process, does not fill in MPPTDI
         */
        spin_lock(&pmap_spin);
        TAILQ_INSERT_TAIL(&pmap_list, pmap, pm_pmnode);
        bcopy(PTD + KPTDI, pmap->pm_pdir + KPTDI, nkpt * PTESIZE);
        spin_unlock(&pmap_spin);
}

/*
 * Attempt to release and free a vm_page in a pmap.  Returns 1 on success,
 * 0 on failure (if the procedure had to sleep).
 *
 * When asked to remove the page directory page itself, we actually just
 * leave it cached so we do not have to incur the SMP inval overhead of
 * removing the kernel mapping.  pmap_puninit() will take care of it.
 *
 * The caller must hold vm_token.
 * This function can block regardless.
 */
static int
pmap_release_free_page(struct pmap *pmap, vm_page_t p)
{
        unsigned *pde = (unsigned *) 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.
         */
        if (vm_page_busy_try(p, FALSE)) {
                vm_page_sleep_busy(p, FALSE, "pmaprl");
                return 0;
        }

        KKASSERT(pmap->pm_stats.resident_count > 0);
        KKASSERT(pde[p->pindex]);

        /*
         * page table page's wire_count must be 1.  Caller is the pmap
         * termination code which holds the pm_pteobj, there is a race
         * if someone else is trying to hold the VM object in order to
         * clean up a wire_count.
         */
        if (p->wire_count != 1)  {
                if (pmap->pm_pteobj->hold_count <= 1)
                        panic("pmap_release: freeing wired page table page");
                kprintf("pmap_release_free_page: unwire race detected\n");
                vm_page_wakeup(p);
                tsleep(p, 0, "pmapx", 1);
                return 0;
        }

        /*
         * Remove the page table page from the processes address space.
         */
        pmap->pm_cached = 0;
        pde[p->pindex] = 0;
        --pmap->pm_stats.resident_count;
        if (pmap->pm_ptphint && (pmap->pm_ptphint->pindex == p->pindex))
                pmap->pm_ptphint = NULL;

        /*
         * We leave the page directory page cached, wired, and mapped in
         * the pmap until the dtor function (pmap_puninit()) gets called.
         * However, still clean it up so we can set PG_ZERO.
         *
         * The pmap has already been removed from the pmap_list in the
         * PTDPTDI case.
         */
        if (p->pindex == PTDPTDI) {
                bzero(pde + KPTDI, nkpt * PTESIZE);
                bzero(pde + MPPTDI, (NPDEPG - MPPTDI) * PTESIZE);
                vm_page_flag_set(p, PG_ZERO);
                vm_page_wakeup(p);
        } else {
                /*
                 * This case can occur if a pmap_unwire_pte() loses a race
                 * while the page is unbusied.
                 */
                /*panic("pmap_release: page should already be gone %p", p);*/
                vm_page_flag_clear(p, PG_MAPPED);
                vm_page_unwire(p, 0);
                vm_page_free_zero(p);
        }
        return 1;
}

/*
 * This routine is called if the page table page is not mapped correctly.
 *
 * The caller must hold vm_token.
 */
static vm_page_t
_pmap_allocpte(pmap_t pmap, unsigned ptepindex)
{
        vm_offset_t ptepa;
        vm_page_t m;

        /*
         * Find or fabricate a new pagetable page.  Setting VM_ALLOC_ZERO
         * will zero any new page and mark it valid.
         */
        m = vm_page_grab(pmap->pm_pteobj, ptepindex,
                         VM_ALLOC_NORMAL | VM_ALLOC_ZERO | VM_ALLOC_RETRY);

        KASSERT(m->queue == PQ_NONE,
                ("_pmap_allocpte: %p->queue != PQ_NONE", m));

        /*
         * Increment the wire count for the page we will be returning to
         * the caller.
         */
        vm_page_wire(m);

        /*
         * It is possible that someone else got in and mapped by the page
         * directory page while we were blocked, if so just unbusy and
         * return the wired page.
         */
        if ((ptepa = pmap->pm_pdir[ptepindex]) != 0) {
                KKASSERT((ptepa & PG_FRAME) == VM_PAGE_TO_PHYS(m));
                vm_page_wakeup(m);
                return(m);
        }

        /*
         * Map the pagetable page into the process address space, if
         * it isn't already there.
         *
         * NOTE: For safety clear pm_cached for all cpus including the
         *       current one when adding a PDE to the map.
         */
        ++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);
        pmap->pm_cached = 0;

        /*
         * Set the page table hint
         */
        pmap->pm_ptphint = m;
        vm_page_flag_set(m, PG_MAPPED);
        vm_page_wakeup(m);

        return m;
}

/*
 * Allocate a page table entry for a va.
 *
 * The caller must hold vm_token.
 */
static vm_page_t
pmap_allocpte(pmap_t pmap, vm_offset_t va)
{
        unsigned ptepindex;
        vm_offset_t ptepa;
        vm_page_t mpte;

        ASSERT_LWKT_TOKEN_HELD(vm_object_token(pmap->pm_pteobj));

        /*
         * 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;
                smp_invltlb();
                cpu_invltlb();
        }

        /*
         * If the page table page is mapped, we just increment the
         * wire count, and activate it.
         */
        if (ptepa) {
                /*
                 * In order to get the page table page, try the
                 * hint first.
                 */
                if ((mpte = pmap->pm_ptphint) != NULL &&
                    (mpte->pindex == ptepindex) &&
                    (mpte->flags & PG_BUSY) == 0) {
                        vm_page_wire_quick(mpte);
                } else {
                        mpte = pmap_page_lookup(pmap->pm_pteobj, ptepindex);
                        pmap->pm_ptphint = mpte;
                        vm_page_wire_quick(mpte);
                        vm_page_wakeup(mpte);
                }
                return mpte;
        }
        /*
         * 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.
 *
 * Caller must hold pmap->pm_token
 */
static int pmap_release_callback(struct vm_page *p, void *data);

void
pmap_release(struct pmap *pmap)
{
        vm_object_t object = pmap->pm_pteobj;
        struct rb_vm_page_scan_info info;

        KASSERT(pmap->pm_active == 0,
                ("pmap still active! %08x", pmap->pm_active));
#if defined(DIAGNOSTIC)
        if (object->ref_count != 1)
                panic("pmap_release: pteobj reference count != 1");
#endif
        
        info.pmap = pmap;
        info.object = object;

        spin_lock(&pmap_spin);
        TAILQ_REMOVE(&pmap_list, pmap, pm_pmnode);
        spin_unlock(&pmap_spin);

        vm_object_hold(object);
        /*lwkt_gettoken(&vm_token);*/
        do {
                info.error = 0;
                info.mpte = NULL;
                info.limit = object->generation;

                vm_page_rb_tree_RB_SCAN(&object->rb_memq, NULL, 
                                        pmap_release_callback, &info);
                if (info.error == 0 && info.mpte) {
                        if (!pmap_release_free_page(pmap, info.mpte))
                                info.error = 1;
                }
        } while (info.error);
        /*lwkt_reltoken(&vm_token);*/
        vm_object_drop(object);

        pmap->pm_cached = 0;
}

/*
 * The caller must hold vm_token.
 */
static int
pmap_release_callback(struct vm_page *p, void *data)
{
        struct rb_vm_page_scan_info *info = data;

        if (p->pindex == PTDPTDI) {
                info->mpte = p;
                return(0);
        }
        if (!pmap_release_free_page(info->pmap, p)) {
                info->error = 1;
                return(-1);
        }
        if (info->object->generation != info->limit) {
                info->error = 1;
                return(-1);
        }
        return(0);
}

/*
 * Grow the number of kernel page table entries, if needed.
 *
 * No requirements.
 */
void
pmap_growkernel(vm_offset_t kstart, vm_offset_t kend)
{
        vm_offset_t addr = kend;
        struct pmap *pmap;
        vm_offset_t ptppaddr;
        vm_page_t nkpg;
        pd_entry_t newpdir;

        vm_object_hold(kptobj);
        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 = (addr + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
        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_NORMAL |
                                                   VM_ALLOC_SYSTEM |
                                                   VM_ALLOC_INTERRUPT);
                if (nkpg == NULL)
                        panic("pmap_growkernel: no memory to grow kernel");

                vm_page_wire(nkpg);
                ptppaddr = VM_PAGE_TO_PHYS(nkpg);
                pmap_zero_page(ptppaddr);
                newpdir = (pd_entry_t) (ptppaddr | PG_V | PG_RW | PG_A | PG_M);
                pdir_pde(PTD, kernel_vm_end) = newpdir;
                *pmap_pde(&kernel_pmap, kernel_vm_end) = newpdir;
                nkpt++;

                /*
                 * This update must be interlocked with pmap_pinit2.
                 */
                spin_lock(&pmap_spin);
                TAILQ_FOREACH(pmap, &pmap_list, pm_pmnode) {
                        *pmap_pde(pmap, kernel_vm_end) = newpdir;
                }
                spin_unlock(&pmap_spin);
                kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) &
                                ~(PAGE_SIZE * NPTEPG - 1);
        }
        vm_object_drop(kptobj);
}

/*
 * Add a reference to the specified pmap.
 *
 * No requirements.
 */
void
pmap_reference(pmap_t pmap)
{
        if (pmap) {
                lwkt_gettoken(&vm_token);
                ++pmap->pm_count;
                lwkt_reltoken(&vm_token);
        }
}

/*
 * vm_token must be held
 */
static
void
pmap_hold(pmap_t pmap)
{
        ++pmap->pm_count;
}

/*
 * vm_token must be held
 */
static
void
pmap_drop(pmap_t pmap)
{
        --pmap->pm_count;
        if (pmap->pm_count == (int)0x80000000)
                wakeup(pmap);
}

static
void
pmap_wait(pmap_t pmap, int count)
{
        lwkt_gettoken(&vm_token);
        pmap->pm_count += count;
        if (pmap->pm_count & 0x7FFFFFFF) {
                while (pmap->pm_count & 0x7FFFFFFF) {
                        pmap->pm_count |= 0x80000000;
                        tsleep(pmap, 0, "pmapd", 0);
                        pmap->pm_count &= ~0x80000000;
                        kprintf("pmap_wait: race averted\n");
                }
        }
        lwkt_reltoken(&vm_token);
}

/***************************************************
 * page management routines.
 ***************************************************/

/*
 * free the pv_entry back to the free list.  This function may be
 * called from an interrupt.
 *
 * The caller must hold vm_token.
 */
static PMAP_INLINE void
free_pv_entry(pv_entry_t pv)
{
        struct mdglobaldata *gd;

#ifdef PMAP_DEBUG
        KKASSERT(pv->pv_m != NULL);
        pv->pv_m = NULL;
#endif
        gd = mdcpu;
        pv_entry_count--;
        if (gd->gd_freepv == NULL)
                gd->gd_freepv = pv;
        else
                zfree(pvzone, pv);
}

/*
 * get a new pv_entry, allocating a block from the system
 * when needed.  This function may be called from an interrupt thread.
 *
 * THIS FUNCTION CAN BLOCK ON THE ZALLOC TOKEN, serialization of other
 * tokens (aka vm_token) to be temporarily lost.
 *
 * The caller must hold vm_token.
 */
static pv_entry_t
get_pv_entry(void)
{
        struct mdglobaldata *gd;
        pv_entry_t pv;

        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);
        }
        gd = mdcpu;
        if ((pv = gd->gd_freepv) != NULL)
                gd->gd_freepv = NULL;
        else
                pv = zalloc(pvzone);
        return pv;
}

/*
 * This routine is very drastic, but can save the system
 * in a pinch.
 *
 * No requirements.
 */
void
pmap_collect(void)
{
        int i;
        vm_page_t m;
        static int warningdone=0;

        if (pmap_pagedaemon_waken == 0)
                return;
        lwkt_gettoken(&vm_token);
        pmap_pagedaemon_waken = 0;

        if (warningdone < 5) {
                kprintf("pmap_collect: collecting pv entries -- "
                        "suggest increasing PMAP_SHPGPERPROC\n");
                warningdone++;
        }

        for (i = 0; i < vm_page_array_size; i++) {
                m = &vm_page_array[i];
                if (m->wire_count || m->hold_count)
                        continue;
                if (vm_page_busy_try(m, TRUE) == 0) {
                        if (m->wire_count == 0 && m->hold_count == 0) {
                                pmap_remove_all(m);
                        }
                        vm_page_wakeup(m);
                }
        }
        lwkt_reltoken(&vm_token);
}
        

/*
 * Remove the pv entry and unwire the page table page related to the
 * pte the caller has cleared from the page table.
 *
 * The caller must hold vm_token.
 */
static void
pmap_remove_entry(struct pmap *pmap, vm_page_t m, 
                  vm_offset_t va, pmap_inval_info_t info)
{
        pv_entry_t pv;

        /*
         * Cannot block
         */
        ASSERT_LWKT_TOKEN_HELD(&vm_token);
        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) {
#ifdef PMAP_DEBUG
                        KKASSERT(pv->pv_pmap == pmap);
#endif
                        if (va == pv->pv_va)
                                break;
                }
        }
        KKASSERT(pv);

        /*
         * Cannot block
         */
        test_m_maps_pv(m, pv);
        TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
        m->md.pv_list_count--;
        if (m->object)
                atomic_add_int(&m->object->agg_pv_list_count, -1);
        if (TAILQ_EMPTY(&m->md.pv_list))
                vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);
        TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
        ++pmap->pm_generation;

        /*
         * This can block.
         */
        vm_object_hold(pmap->pm_pteobj);
        pmap_unuse_pt(pmap, va, pv->pv_ptem, info);
        vm_object_drop(pmap->pm_pteobj);
        free_pv_entry(pv);
}

/*
 * Create a pv entry for page at pa for (pmap, va).
 *
 * The caller must hold vm_token.
 */
static void
pmap_insert_entry(pmap_t pmap, pv_entry_t pv, vm_offset_t va,
                  vm_page_t mpte, vm_page_t m)
{
#ifdef PMAP_DEBUG
        KKASSERT(pv->pv_m == NULL);
        pv->pv_m = m;
#endif
        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);
        ++pmap->pm_generation;
        m->md.pv_list_count++;
        if (m->object)
                atomic_add_int(&m->object->agg_pv_list_count, 1);
}

/*
 * pmap_remove_pte: do the things to unmap a page in a process.
 *
 * The caller must hold vm_token.
 *
 * WARNING! As with most other pmap functions this one can block, so
 *          callers using temporary page table mappings must reload
 *          them.
 */
static void
pmap_remove_pte(struct pmap *pmap, unsigned *ptq, vm_offset_t va,
                pmap_inval_info_t info)
{
        unsigned oldpte;
        vm_page_t m;

        ptbase_assert(pmap);
        pmap_inval_interlock(info, pmap, va);
        ptbase_assert(pmap);
        oldpte = loadandclear(ptq);
        if (oldpte & PG_W)
                pmap->pm_stats.wired_count -= 1;
        pmap_inval_deinterlock(info, pmap);
        KKASSERT(oldpte & PG_V);
        /*
         * Machines that don't support invlpg, also don't support
         * PG_G.  XXX PG_G is disabled for SMP so don't worry about
         * the SMP case.
         */
        if (oldpte & PG_G)
                cpu_invlpg((void *)va);
        KKASSERT(pmap->pm_stats.resident_count > 0);
        --pmap->pm_stats.resident_count;
        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)) {
                                kprintf("pmap_remove: modified page not "
                                        "writable: va: %p, pte: 0x%lx\n",
                                        (void *)va, (long)oldpte);
                        }
#endif
                        if (pmap_track_modified(va))
                                vm_page_dirty(m);
                }
                if (oldpte & PG_A)
                        vm_page_flag_set(m, PG_REFERENCED);
                pmap_remove_entry(pmap, m, va, info);
        } else {
                pmap_unuse_pt(pmap, va, NULL, info);
        }
}

/*
 * Remove a single page from a process address space.
 *
 * The caller must hold vm_token.
 */
static void
pmap_remove_page(struct pmap *pmap, vm_offset_t va, pmap_inval_info_t info)
{
        unsigned *ptq;

        /*
         * If there is no pte for this address, just skip it!!!  Otherwise
         * get a local va for mappings for this pmap and remove the entry.
         */
        if (*pmap_pde(pmap, va) != 0) {
                ptq = get_ptbase(pmap) + i386_btop(va);
                if (*ptq) {
                        pmap_remove_pte(pmap, ptq, va, info);
                        /* ptq invalid */
                }
        }
}

/*
 * 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.
 *
 * No requirements.
 */
void
pmap_remove(struct pmap *pmap, vm_offset_t sva, vm_offset_t eva)
{
        unsigned *ptbase;
        vm_offset_t pdnxt;
        vm_offset_t ptpaddr;
        vm_offset_t sindex, eindex;
        struct pmap_inval_info info;

        if (pmap == NULL)
                return;

        vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);
        if (pmap->pm_stats.resident_count == 0) {
                lwkt_reltoken(&vm_token);
                vm_object_drop(pmap->pm_pteobj);
                return;
        }

        pmap_inval_init(&info);

        /*
         * special handling of removing one page.  a very
         * common operation and easy to short circuit some
         * code.
         */
        if (((sva + PAGE_SIZE) == eva) && 
                (((unsigned) pmap->pm_pdir[(sva >> PDRSHIFT)] & PG_PS) == 0)) {
                pmap_remove_page(pmap, sva, &info);
                pmap_inval_done(&info);
                lwkt_reltoken(&vm_token);
                vm_object_drop(pmap->pm_pteobj);
                return;
        }

        /*
         * Get a local virtual address for the mappings that are being
         * worked with.
         */
        sindex = i386_btop(sva);
        eindex = i386_btop(eva);

        while (sindex < eindex) {
                unsigned pdirindex;

                /*
                 * Stop scanning if no pages are left
                 */
                if (pmap->pm_stats.resident_count == 0)
                        break;

                /*
                 * Calculate index for next page table, limited by eindex.
                 */
                pdnxt = ((sindex + NPTEPG) & ~(NPTEPG - 1));
                if (pdnxt > eindex)
                        pdnxt = eindex;

                pdirindex = sindex / NPDEPG;
                ptpaddr = (unsigned)pmap->pm_pdir[pdirindex];
                if (ptpaddr & PG_PS) {
                        pmap_inval_interlock(&info, pmap, -1);
                        pmap->pm_pdir[pdirindex] = 0;
                        pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                        pmap->pm_cached = 0;
                        pmap_inval_deinterlock(&info, pmap);
                        sindex = pdnxt;
                        continue;
                }

                /*
                 * Weed out invalid mappings. Note: we assume that the page
                 * directory table is always allocated, and in kernel virtual.
                 */
                if (ptpaddr == 0) {
                        sindex = pdnxt;
                        continue;
                }

                /*
                 * Sub-scan the page table page.  pmap_remove_pte() can
                 * block on us, invalidating ptbase, so we must reload
                 * ptbase and we must also check whether the page directory
                 * page is still present.
                 */
                while (sindex < pdnxt) {
                        vm_offset_t va;

                        ptbase = get_ptbase(pmap);
                        if (ptbase[sindex]) {
                                va = i386_ptob(sindex);
                                pmap_remove_pte(pmap, ptbase + sindex,
                                                va, &info);
                        }
                        if (pmap->pm_pdir[pdirindex] == 0 ||
                            (pmap->pm_pdir[pdirindex] & PG_PS)) {
                                break;
                        }
                        ++sindex;
                }
        }
        pmap_inval_done(&info);
        lwkt_reltoken(&vm_token);
        vm_object_drop(pmap->pm_pteobj);
}

/*
 * Removes this physical page from all physical maps in which it resides.
 * Reflects back modify bits to the pager.
 *
 * vm_token must be held by caller.
 */
static void
pmap_remove_all(vm_page_t m)
{
        struct pmap_inval_info info;
        unsigned *pte, tpte;
        pv_entry_t pv;
        pmap_t pmap;

        if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                return;
        if (TAILQ_EMPTY(&m->md.pv_list))
                return;

        pmap_inval_init(&info);
        while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                pmap = pv->pv_pmap;
                KKASSERT(pmap->pm_stats.resident_count > 0);
                pmap_hold(pmap);
                vm_object_hold(pmap->pm_pteobj);

                if (pv != TAILQ_FIRST(&m->md.pv_list)) {
                        vm_object_drop(pmap->pm_pteobj);
                        pmap_drop(pmap);
                        continue;
                }

                --pmap->pm_stats.resident_count;
                pte = pmap_pte_quick(pmap, pv->pv_va);
                pmap_inval_interlock(&info, pmap, pv->pv_va);
                tpte = loadandclear(pte);
                if (tpte & PG_W)
                        pmap->pm_stats.wired_count--;
                pmap_inval_deinterlock(&info, pmap);
                if (tpte & PG_A)
                        vm_page_flag_set(m, PG_REFERENCED);
                KKASSERT(PHYS_TO_VM_PAGE(tpte) == m);

                /*
                 * 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)) {
                                kprintf("pmap_remove_all: modified page "
                                        "not writable: va: %p, pte: 0x%lx\n",
                                        (void *)pv->pv_va, (long)tpte);
                        }
#endif
                        if (pmap_track_modified(pv->pv_va))
                                vm_page_dirty(m);
                }
#ifdef PMAP_DEBUG
                KKASSERT(pv->pv_m == m);
#endif
                KKASSERT(pv == TAILQ_FIRST(&m->md.pv_list));
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
                ++pmap->pm_generation;
                m->md.pv_list_count--;
                if (m->object)
                        atomic_add_int(&m->object->agg_pv_list_count, -1);
                if (TAILQ_EMPTY(&m->md.pv_list))
                        vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);
                pmap_unuse_pt(pmap, pv->pv_va, pv->pv_ptem, &info);
                vm_object_drop(pmap->pm_pteobj);
                free_pv_entry(pv);
                pmap_drop(pmap);
        }
        KKASSERT((m->flags & (PG_MAPPED|PG_WRITEABLE)) == 0);
        pmap_inval_done(&info);
}

/*
 * Set the physical protection on the specified range of this map
 * as requested.
 *
 * No requirements.
 */
void
pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
{
        unsigned *ptbase;
        vm_offset_t pdnxt, ptpaddr;
        vm_pindex_t sindex, eindex;
        pmap_inval_info info;

        if (pmap == NULL)
                return;

        if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
                pmap_remove(pmap, sva, eva);
                return;
        }

        if (prot & VM_PROT_WRITE)
                return;

        lwkt_gettoken(&vm_token);
        pmap_inval_init(&info);

        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;
                if (((ptpaddr = (unsigned) pmap->pm_pdir[pdirindex]) & PG_PS) != 0) {
                        pmap_inval_interlock(&info, pmap, -1);
                        pmap->pm_pdir[pdirindex] &= ~(PG_M|PG_RW);
                        pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                        pmap_inval_deinterlock(&info, pmap);
                        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++) {
                        unsigned pbits;
                        unsigned cbits;
                        vm_page_t m;

                        /*
                         * XXX non-optimal.
                         */
                        pmap_inval_interlock(&info, pmap, i386_ptob(sindex));
again:
                        pbits = ptbase[sindex];
                        cbits = pbits;

                        if (pbits & PG_MANAGED) {
                                m = NULL;
                                if (pbits & PG_A) {
                                        m = PHYS_TO_VM_PAGE(pbits);
                                        vm_page_flag_set(m, PG_REFERENCED);
                                        cbits &= ~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);
                                                cbits &= ~PG_M;
                                        }
                                }
                        }
                        cbits &= ~PG_RW;
                        if (pbits != cbits &&
                            !atomic_cmpset_int(ptbase + sindex, pbits, cbits)) {
                                goto again;
                        }
                        pmap_inval_deinterlock(&info, pmap);
                }
        }
        pmap_inval_done(&info);
        lwkt_reltoken(&vm_token);
}

/*
 * 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
 * cannot be reclaimed.
 *
 * No requirements.
 */
void
pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
           boolean_t wired, vm_map_entry_t entry __unused)
{
        vm_paddr_t pa;
        unsigned *pte;
        vm_paddr_t opa;
        vm_offset_t origpte, newpte;
        vm_page_t mpte;
        pmap_inval_info info;
        pv_entry_t pv;

        if (pmap == NULL)
                return;

        va &= PG_FRAME;
#ifdef PMAP_DIAGNOSTIC
        if (va >= KvaEnd)
                panic("pmap_enter: toobig");
        if ((va >= UPT_MIN_ADDRESS) && (va < UPT_MAX_ADDRESS)) {
                panic("pmap_enter: invalid to pmap_enter page "
                      "table pages (va: %p)", (void *)va);
        }
#endif
        if (va < UPT_MAX_ADDRESS && pmap == &kernel_pmap) {
                kprintf("Warning: pmap_enter called on UVA with kernel_pmap\n");
                print_backtrace(-1);
        }
        if (va >= UPT_MAX_ADDRESS && pmap != &kernel_pmap) {
                kprintf("Warning: pmap_enter called on KVA without kernel_pmap\n");
                print_backtrace(-1);
        }

        vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);

        /*
         * This can block, get it before we do anything important.
         */
        if (pmap_initialized &&
            (m->flags & (PG_FICTITIOUS|PG_UNMANAGED)) == 0) {
                pv = get_pv_entry();
        } else {
                pv = NULL;
        }

        /*
         * In the case that a page table page is not
         * resident, we are creating it here.
         */
        if (va < UPT_MIN_ADDRESS)
                mpte = pmap_allocpte(pmap, va);
        else
                mpte = NULL;

        if ((prot & VM_PROT_NOSYNC) == 0)
                pmap_inval_init(&info);
        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=0x%lx, va=%p",
                     (long)pmap->pm_pdir[PTDPTDI], (void *)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)) {
                        kprintf("pmap_enter: modified page not "
                                "writable: va: %p, pte: 0x%lx\n",
                                (void *)va, (long )origpte);
                }
#endif

                /*
                 * 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;
                        KKASSERT(m->flags & PG_MAPPED);
                }
                goto validate;
        } 
        /*
         * Mapping has changed, invalidate old range and fall through to
         * handle validating new mapping.
         *
         * Since we have a ref on the page directory page pmap_pte()
         * will always return non-NULL.
         *
         * NOTE: pmap_remove_pte() can block and cause the temporary ptbase
         *       to get wiped.  reload the ptbase.  I'm not sure if it is
         *       also possible to race another pmap_enter() but check for
         *       that case too.
         */
        while (opa) {
                KKASSERT((origpte & PG_FRAME) ==
                         (*(vm_offset_t *)pte & PG_FRAME));
                if (prot & VM_PROT_NOSYNC) {
                        prot &= ~VM_PROT_NOSYNC;
                        pmap_inval_init(&info);
                }
                pmap_remove_pte(pmap, pte, va, &info);
                pte = pmap_pte(pmap, va);
                origpte = *(vm_offset_t *)pte;
                opa = origpte & PG_FRAME;
                if (opa) {
                        kprintf("pmap_enter: Warning, raced pmap %p va %p\n",
                                pmap, (void *)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, pv, va, mpte, m);
                pv = NULL;
                ptbase_assert(pmap);
                pa |= PG_MANAGED;
                vm_page_flag_set(m, PG_MAPPED);
        }

        /*
         * Increment counters
         */
        ++pmap->pm_stats.resident_count;
        if (wired)
                pmap->pm_stats.wired_count++;
        KKASSERT(*pte == 0);

validate:
        /*
         * Now validate mapping with desired protection/wiring.
         */
        ptbase_assert(pmap);
        newpte = (vm_offset_t) (pa | pte_prot(pmap, prot) | PG_V);

        if (wired)
                newpte |= PG_W;
        if (va < UPT_MIN_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 the pte is already present we have
         * to get rid of the extra wire-count on mpte we had obtained
         * above.
         *
         * mpte has a new wire_count, which also serves to prevent the
         * page table page from getting ripped out while we work.  If we
         * are modifying an existing pte instead of installing a new one
         * we have to drop it.
         */
        if ((origpte & ~(PG_M|PG_A)) != newpte) {
                if (prot & VM_PROT_NOSYNC)
                        cpu_invlpg((void *)va);
                else
                        pmap_inval_interlock(&info, pmap, va);
                ptbase_assert(pmap);

                if (*pte) {
                        KKASSERT((*pte & PG_FRAME) == (newpte & PG_FRAME));
                        if (mpte && vm_page_unwire_quick(mpte))
                                panic("pmap_enter: Insufficient wire_count");
                }

                *pte = newpte | PG_A;
                if ((prot & VM_PROT_NOSYNC) == 0)
                        pmap_inval_deinterlock(&info, pmap);
                if (newpte & PG_RW)
                        vm_page_flag_set(m, PG_WRITEABLE);
        } else {
                if (*pte) {
                        KKASSERT((*pte & PG_FRAME) == (newpte & PG_FRAME));
                        if (mpte && vm_page_unwire_quick(mpte))
                                panic("pmap_enter: Insufficient wire_count");
                }
        }

        /*
         * NOTE: mpte invalid after this point if we block.
         */
        KKASSERT((newpte & PG_MANAGED) == 0 || (m->flags & PG_MAPPED));
        if ((prot & VM_PROT_NOSYNC) == 0)
                pmap_inval_done(&info);
        if (pv)
                free_pv_entry(pv);
        lwkt_reltoken(&vm_token);
        vm_object_drop(pmap->pm_pteobj);
}

/*
 * This code works like pmap_enter() but assumes VM_PROT_READ and not-wired.
 * This code also assumes that the pmap has no pre-existing entry for this
 * VA.
 *
 * This code currently may only be used on user pmaps, not kernel_pmap.
 *
 * No requirements.
 */
void
pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m)
{
        unsigned *pte;
        vm_paddr_t pa;
        vm_page_t mpte;
        unsigned ptepindex;
        vm_offset_t ptepa;
        pmap_inval_info info;
        pv_entry_t pv;

        vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);

        /*
         * This can block, get it before we do anything important.
         */
        if (pmap_initialized &&
            (m->flags & (PG_FICTITIOUS|PG_UNMANAGED)) == 0) {
                pv = get_pv_entry();
        } else {
                pv = NULL;
        }

        pmap_inval_init(&info);

        if (va < UPT_MAX_ADDRESS && pmap == &kernel_pmap) {
                kprintf("Warning: pmap_enter_quick called on UVA with kernel_pmap\n");
                print_backtrace(-1);
        }
        if (va >= UPT_MAX_ADDRESS && pmap != &kernel_pmap) {
                kprintf("Warning: pmap_enter_quick called on KVA without kernel_pmap\n");
                print_backtrace(-1);
        }

        KKASSERT(va < UPT_MIN_ADDRESS); /* assert used on user pmaps only */

        /*
         * Calculate the page table page (mpte), allocating it if necessary.
         *
         * A held page table page (mpte), or NULL, is passed onto the
         * section following.
         */
        if (va < UPT_MIN_ADDRESS) {
                /*
                 * Calculate pagetable page index
                 */
                ptepindex = va >> PDRSHIFT;

                do {
                        /*
                         * Get the page directory entry
                         */
                        ptepa = (vm_offset_t) pmap->pm_pdir[ptepindex];

                        /*
                         * If the page table page is mapped, we just increment
                         * the wire count, and activate it.
                         */
                        if (ptepa) {
                                if (ptepa & PG_PS)
                                        panic("pmap_enter_quick: unexpected mapping into 4MB page");
                                if ((mpte = pmap->pm_ptphint) != NULL &&
                                    (mpte->pindex == ptepindex) &&
                                    (mpte->flags & PG_BUSY) == 0) {
                                        vm_page_wire_quick(mpte);
                                } else {
                                        mpte = pmap_page_lookup(pmap->pm_pteobj,
                                                                ptepindex);
                                        pmap->pm_ptphint = mpte;
                                        vm_page_wire_quick(mpte);
                                        vm_page_wakeup(mpte);
                                }
                        } else {
                                mpte = _pmap_allocpte(pmap, ptepindex);
                        }
                } while (mpte == NULL);
        } else {
                mpte = NULL;
                /* this code path is not yet used */
        }

        /*
         * With a valid (and held) page directory page, we can just use
         * vtopte() to get to the pte.  If the pte is already present
         * we do not disturb it.
         */
        pte = (unsigned *)vtopte(va);
        if (*pte) {
                KKASSERT(*pte & PG_V);
                pa = VM_PAGE_TO_PHYS(m);
                KKASSERT(((*pte ^ pa) & PG_FRAME) == 0);
                pmap_inval_done(&info);
                if (mpte)
                        pmap_unwire_pte(pmap, mpte, &info);
                if (pv) {
                        free_pv_entry(pv);
                        /* pv = NULL; */
                }
                lwkt_reltoken(&vm_token);
                vm_object_drop(pmap->pm_pteobj);
                return;
        }

        /*
         * Enter on the PV list if part of our managed memory
         */
        if (pmap_initialized &&
            (m->flags & (PG_FICTITIOUS|PG_UNMANAGED)) == 0) {
                pmap_insert_entry(pmap, pv, va, mpte, m);
                pv = NULL;
                vm_page_flag_set(m, PG_MAPPED);
        }

        /*
         * 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;
/*      pmap_inval_add(&info, pmap, va); shouldn't be needed inval->valid */
        pmap_inval_done(&info);
        if (pv) {
                free_pv_entry(pv);
                /* pv = NULL; */
        }
        lwkt_reltoken(&vm_token);
        vm_object_drop(pmap->pm_pteobj);
}

/*
 * Make a temporary mapping for a physical address.  This is only intended
 * to be used for panic dumps.
 *
 * The caller is responsible for calling smp_invltlb().
 *
 * No requirements.
 */
void *
pmap_kenter_temporary(vm_paddr_t pa, long i)
{
        pmap_kenter_quick((vm_offset_t)crashdumpmap + (i * PAGE_SIZE), pa);
        return ((void *)crashdumpmap);
}

#define MAX_INIT_PT (96)

/*
 * This routine 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.
 *
 * No requirements.
 */
static int pmap_object_init_pt_callback(vm_page_t p, void *data);

void
pmap_object_init_pt(pmap_t pmap, vm_offset_t addr, vm_prot_t prot,
                    vm_object_t object, vm_pindex_t pindex, 
                    vm_size_t size, int limit)
{
        struct rb_vm_page_scan_info info;
        struct lwp *lp;
        int psize;

        /*
         * We can't preinit if read access isn't set or there is no pmap
         * or object.
         */
        if ((prot & VM_PROT_READ) == 0 || pmap == NULL || object == NULL)
                return;

        /*
         * We can't preinit if the pmap is not the current pmap
         */
        lp = curthread->td_lwp;
        if (lp == NULL || pmap != vmspace_pmap(lp->lwp_vmspace))
                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;
        }

        if (psize == 0)
                return;

        /*
         * Use a red-black scan to traverse the requested range and load
         * any valid pages found into the pmap.
         *
         * We cannot safely scan the object's memq unless we are in a
         * critical section since interrupts can remove pages from objects.
         */
        info.start_pindex = pindex;
        info.end_pindex = pindex + psize - 1;
        info.limit = limit;
        info.mpte = NULL;
        info.addr = addr;
        info.pmap = pmap;

        vm_object_hold(object);
        vm_page_rb_tree_RB_SCAN(&object->rb_memq, rb_vm_page_scancmp,
                                pmap_object_init_pt_callback, &info);
        vm_object_drop(object);
}

/*
 * The caller must hold vm_token.
 */
static
int
pmap_object_init_pt_callback(vm_page_t p, void *data)
{
        struct rb_vm_page_scan_info *info = data;
        vm_pindex_t rel_index;
        /*
         * don't allow an madvise to blow away our really
         * free pages allocating pv entries.
         */
        if ((info->limit & MAP_PREFAULT_MADVISE) &&
                vmstats.v_free_count < vmstats.v_free_reserved) {
                    return(-1);
        }

        /*
         * Ignore list markers and ignore pages we cannot instantly
         * busy (while holding the object token).
         */
        if (p->flags & PG_MARKER)
                return 0;
        if (vm_page_busy_try(p, TRUE))
                return 0;
        if (((p->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
            (p->flags & PG_FICTITIOUS) == 0) {
                if ((p->queue - p->pc) == PQ_CACHE)
                        vm_page_deactivate(p);
                rel_index = p->pindex - info->start_pindex;
                pmap_enter_quick(info->pmap,
                                 info->addr + i386_ptob(rel_index), p);
        }
        vm_page_wakeup(p);
        return(0);
}

/*
 * Return TRUE if the pmap is in shape to trivially
 * pre-fault the specified address.
 *
 * Returns FALSE if it would be non-trivial or if a
 * pte is already loaded into the slot.
 *
 * No requirements.
 */
int
pmap_prefault_ok(pmap_t pmap, vm_offset_t addr)
{
        unsigned *pte;
        int ret;

        lwkt_gettoken(&vm_token);
        if ((*pmap_pde(pmap, addr)) == 0) {
                ret = 0;
        } else {
                pte = (unsigned *) vtopte(addr);
                ret = (*pte) ? 0 : 1;
        }
        lwkt_reltoken(&vm_token);
        return(ret);
}

/*
 * Change the wiring attribute for a map/virtual-adderss pair.  The mapping
 * must already exist.
 *
 * No requirements.
 */
void
pmap_change_wiring(pmap_t pmap, vm_offset_t va, boolean_t wired,
                   vm_map_entry_t entry __unused)
{
        unsigned *pte;

        if (pmap == NULL)
                return;

        lwkt_gettoken(&vm_token);
        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.  However, in an SMP environment we must use
         * a locked bus cycle to update the pte (if we are not using 
         * the pmap_inval_*() API that is)... it's ok to do this for simple
         * wiring changes.
         */
#ifdef SMP
        if (wired)
                atomic_set_int(pte, PG_W);
        else
                atomic_clear_int(pte, PG_W);
#else
        if (wired)
                atomic_set_int_nonlocked(pte, PG_W);
        else
                atomic_clear_int_nonlocked(pte, PG_W);
#endif
        lwkt_reltoken(&vm_token);
}

/*
 * 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.
 *
 * No requirements.
 */
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)
{
        /* does nothing */
}       

/*
 * Zero the specified PA by mapping the page into KVM and clearing its
 * contents.
 *
 * No requirements.
 */
void
pmap_zero_page(vm_paddr_t phys)
{
        struct mdglobaldata *gd = mdcpu;

        crit_enter();
        if (*(int *)gd->gd_CMAP3)
                panic("pmap_zero_page: CMAP3 busy");
        *(int *)gd->gd_CMAP3 =
                    PG_V | PG_RW | (phys & PG_FRAME) | PG_A | PG_M;
        cpu_invlpg(gd->gd_CADDR3);
        bzero(gd->gd_CADDR3, PAGE_SIZE);
        *(int *) gd->gd_CMAP3 = 0;
        crit_exit();
}

/*
 * Assert that a page is empty, panic if it isn't.
 *
 * No requirements.
 */
void
pmap_page_assertzero(vm_paddr_t phys)
{
        struct mdglobaldata *gd = mdcpu;
        int i;

        crit_enter();
        if (*(int *)gd->gd_CMAP3)
                panic("pmap_zero_page: CMAP3 busy");
        *(int *)gd->gd_CMAP3 =
                    PG_V | PG_RW | (phys & PG_FRAME) | PG_A | PG_M;
        cpu_invlpg(gd->gd_CADDR3);
        for (i = 0; i < PAGE_SIZE; i += 4) {
            if (*(int *)((char *)gd->gd_CADDR3 + i) != 0) {
                panic("pmap_page_assertzero() @ %p not zero!",
                    (void *)gd->gd_CADDR3);
            }
        }
        *(int *) gd->gd_CMAP3 = 0;
        crit_exit();
}

/*
 * Zero part of a physical page by mapping it into memory and clearing
 * its contents with bzero.
 *
 * off and size may not cover an area beyond a single hardware page.
 *
 * No requirements.
 */
void
pmap_zero_page_area(vm_paddr_t phys, int off, int size)
{
        struct mdglobaldata *gd = mdcpu;

        crit_enter();
        if (*(int *) gd->gd_CMAP3)
                panic("pmap_zero_page: CMAP3 busy");
        *(int *) gd->gd_CMAP3 = PG_V | PG_RW | (phys & PG_FRAME) | PG_A | PG_M;
        cpu_invlpg(gd->gd_CADDR3);
        bzero((char *)gd->gd_CADDR3 + off, size);
        *(int *) gd->gd_CMAP3 = 0;
        crit_exit();
}

/*
 * Copy the physical page from the source PA to the target PA.
 * This function may be called from an interrupt.  No locking
 * is required.
 *
 * No requirements.
 */
void
pmap_copy_page(vm_paddr_t src, vm_paddr_t dst)
{
        struct mdglobaldata *gd = mdcpu;

        crit_enter();
        if (*(int *) gd->gd_CMAP1)
                panic("pmap_copy_page: CMAP1 busy");
        if (*(int *) gd->gd_CMAP2)
                panic("pmap_copy_page: CMAP2 busy");

        *(int *) gd->gd_CMAP1 = PG_V | (src & PG_FRAME) | PG_A;
        *(int *) gd->gd_CMAP2 = PG_V | PG_RW | (dst & PG_FRAME) | PG_A | PG_M;

        cpu_invlpg(gd->gd_CADDR1);
        cpu_invlpg(gd->gd_CADDR2);

        bcopy(gd->gd_CADDR1, gd->gd_CADDR2, PAGE_SIZE);

        *(int *) gd->gd_CMAP1 = 0;
        *(int *) gd->gd_CMAP2 = 0;
        crit_exit();
}

/*
 * Copy the physical page from the source PA to the target PA.
 * This function may be called from an interrupt.  No locking
 * is required.
 *
 * No requirements.
 */
void
pmap_copy_page_frag(vm_paddr_t src, vm_paddr_t dst, size_t bytes)
{
        struct mdglobaldata *gd = mdcpu;

        crit_enter();
        if (*(int *) gd->gd_CMAP1)
                panic("pmap_copy_page: CMAP1 busy");
        if (*(int *) gd->gd_CMAP2)
                panic("pmap_copy_page: CMAP2 busy");

        *(int *) gd->gd_CMAP1 = PG_V | (src & PG_FRAME) | PG_A;
        *(int *) gd->gd_CMAP2 = PG_V | PG_RW | (dst & PG_FRAME) | PG_A | PG_M;

        cpu_invlpg(gd->gd_CADDR1);
        cpu_invlpg(gd->gd_CADDR2);

        bcopy((char *)gd->gd_CADDR1 + (src & PAGE_MASK),
              (char *)gd->gd_CADDR2 + (dst & PAGE_MASK),
              bytes);

        *(int *) gd->gd_CMAP1 = 0;
        *(int *) gd->gd_CMAP2 = 0;
        crit_exit();
}

/*
 * 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.
 *
 * No requirements.
 */
boolean_t
pmap_page_exists_quick(pmap_t pmap, vm_page_t m)
{
        pv_entry_t pv;
        int loops = 0;

        if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                return FALSE;

        lwkt_gettoken(&vm_token);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                if (pv->pv_pmap == pmap) {
                        lwkt_reltoken(&vm_token);
                        return TRUE;
                }
                loops++;
                if (loops >= 16)
                        break;
        }
        lwkt_reltoken(&vm_token);
        return (FALSE);
}

/*
 * 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.
 *
 * No requirements.
 */
void
pmap_remove_pages(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        struct lwp *lp;
        unsigned *pte, tpte;
        pv_entry_t pv, npv;
        vm_page_t m;
        pmap_inval_info info;
        int iscurrentpmap;
        int32_t save_generation;

        lp = curthread->td_lwp;
        if (lp && pmap == vmspace_pmap(lp->lwp_vmspace))
                iscurrentpmap = 1;
        else
                iscurrentpmap = 0;

        if (pmap->pm_pteobj)
                vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);
        pmap_inval_init(&info);

        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;
                }

                KKASSERT(pmap == pv->pv_pmap);

                if (iscurrentpmap)
                        pte = (unsigned *)vtopte(pv->pv_va);
                else
                        pte = pmap_pte_quick(pmap, pv->pv_va);
                KKASSERT(*pte);
                pmap_inval_interlock(&info, pmap, pv->pv_va);

                /*
                 * We cannot remove wired pages from a process' mapping
                 * at this time
                 */
                if (*pte & PG_W) {
                        pmap_inval_deinterlock(&info, pmap);
                        npv = TAILQ_NEXT(pv, pv_plist);
                        continue;
                }
                KKASSERT(*pte);
                tpte = loadandclear(pte);
                pmap_inval_deinterlock(&info, pmap);

                m = PHYS_TO_VM_PAGE(tpte);
                test_m_maps_pv(m, pv);

                KASSERT(m < &vm_page_array[vm_page_array_size],
                        ("pmap_remove_pages: bad tpte %x", tpte));

                KKASSERT(pmap->pm_stats.resident_count > 0);
                --pmap->pm_stats.resident_count;

                /*
                 * Update the vm_page_t clean and reference bits.
                 */
                if (tpte & PG_M) {
                        vm_page_dirty(m);
                }

                npv = TAILQ_NEXT(pv, pv_plist);
#ifdef PMAP_DEBUG
                KKASSERT(pv->pv_m == m);
                KKASSERT(pv->pv_pmap == pmap);
#endif
                TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
                save_generation = ++pmap->pm_generation;

                m->md.pv_list_count--;
                if (m->object)
                        atomic_add_int(&m->object->agg_pv_list_count, -1);
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                if (TAILQ_EMPTY(&m->md.pv_list))
                        vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);

                pmap_unuse_pt(pmap, pv->pv_va, pv->pv_ptem, &info);
                free_pv_entry(pv);

                /*
                 * Restart the scan if we blocked during the unuse or free
                 * calls and other removals were made.
                 */
                if (save_generation != pmap->pm_generation) {
                        kprintf("Warning: pmap_remove_pages race-A avoided\n");
                        npv = TAILQ_FIRST(&pmap->pm_pvlist);
                }
        }
        pmap_inval_done(&info);
        lwkt_reltoken(&vm_token);
        if (pmap->pm_pteobj)
                vm_object_drop(pmap->pm_pteobj);
}

/*
 * pmap_testbit tests bits in pte's
 * note that the testbit/clearbit routines are inline,
 * and a lot of things compile-time evaluate.
 *
 * The caller must hold vm_token.
 */
static boolean_t
pmap_testbit(vm_page_t m, int bit)
{
        pv_entry_t pv;
        unsigned *pte;

        if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                return FALSE;

        if (TAILQ_FIRST(&m->md.pv_list) == NULL)
                return FALSE;

        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) {
                        kprintf("Null pmap (tb) at va: %p\n",
                                (void *)pv->pv_va);
                        continue;
                }
#endif
                pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
                if (*pte & bit) {
                        return TRUE;
                }
        }
        return (FALSE);
}

/*
 * This routine is used to modify bits in ptes
 *
 * The caller must hold vm_token.
 */
static __inline void
pmap_clearbit(vm_page_t m, int bit)
{
        struct pmap_inval_info info;
        pv_entry_t pv;
        unsigned *pte;
        unsigned pbits;

        if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                return;

        pmap_inval_init(&info);

        /*
         * Loop over all current mappings setting/clearing as appropos If
         * setting RO do we need to clear the VAC?
         */
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                /*
                 * don't write protect pager mappings
                 */
                if (bit == PG_RW) {
                        if (!pmap_track_modified(pv->pv_va))
                                continue;
                }

#if defined(PMAP_DIAGNOSTIC)
                if (!pv->pv_pmap) {
                        kprintf("Null pmap (cb) at va: %p\n",
                                (void *)pv->pv_va);
                        continue;
                }
#endif

                /*
                 * Careful here.  We can use a locked bus instruction to
                 * clear PG_A or PG_M safely but we need to synchronize
                 * with the target cpus when we mess with PG_RW.
                 *
                 * We do not have to force synchronization when clearing
                 * PG_M even for PTEs generated via virtual memory maps,
                 * because the virtual kernel will invalidate the pmap
                 * entry when/if it needs to resynchronize the Modify bit.
                 */
                if (bit & PG_RW)
                        pmap_inval_interlock(&info, pv->pv_pmap, pv->pv_va);
                pte = pmap_pte_quick(pv->pv_pmap, pv->pv_va);
again:
                pbits = *pte;
                if (pbits & bit) {
                        if (bit == PG_RW) {
                                if (pbits & PG_M) {
                                        vm_page_dirty(m);
                                        atomic_clear_int(pte, PG_M|PG_RW);
                                } else {
                                        /*
                                         * The cpu may be trying to set PG_M
                                         * simultaniously with our clearing
                                         * of PG_RW.
                                         */
                                        if (!atomic_cmpset_int(pte, pbits,
                                                               pbits & ~PG_RW))
                                                goto again;
                                }
                        } else if (bit == PG_M) {
                                /*
                                 * We could also clear PG_RW here to force
                                 * a fault on write to redetect PG_M for
                                 * virtual kernels, but it isn't necessary
                                 * since virtual kernels invalidate the pte 
                                 * when they clear the VPTE_M bit in their
                                 * virtual page tables.
                                 */
                                atomic_clear_int(pte, PG_M);
                        } else {
                                atomic_clear_int(pte, bit);
                        }
                }
                if (bit & PG_RW)
                        pmap_inval_deinterlock(&info, pv->pv_pmap);
        }
        pmap_inval_done(&info);
}

/*
 * Lower the permission for all mappings to a given page.
 *
 * No requirements.
 */
void
pmap_page_protect(vm_page_t m, vm_prot_t prot)
{
        if ((prot & VM_PROT_WRITE) == 0) {
                lwkt_gettoken(&vm_token);
                if (prot & (VM_PROT_READ | VM_PROT_EXECUTE)) {
                        pmap_clearbit(m, PG_RW);
                        vm_page_flag_clear(m, PG_WRITEABLE);
                } else {
                        pmap_remove_all(m);
                }
                lwkt_reltoken(&vm_token);
        }
}

/*
 * Return the physical address given a physical page index.
 *
 * No requirements.
 */
vm_paddr_t
pmap_phys_address(vm_pindex_t ppn)
{
        return (i386_ptob(ppn));
}

/*
 * 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.
 *
 * No requirements.
 */
int
pmap_ts_referenced(vm_page_t m)
{
        pv_entry_t pv, pvf, pvn;
        unsigned *pte;
        int rtval = 0;

        if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                return (rtval);

        lwkt_gettoken(&vm_token);

        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)) {
#ifdef SMP
                                atomic_clear_int(pte, PG_A);
#else
                                atomic_clear_int_nonlocked(pte, PG_A);
#endif
                                rtval++;
                                if (rtval > 4) {
                                        break;
                                }
                        }
                } while ((pv = pvn) != NULL && pv != pvf);
        }

        lwkt_reltoken(&vm_token);

        return (rtval);
}

/*
 * Return whether or not the specified physical page was modified
 * in any physical maps.
 *
 * No requirements.
 */
boolean_t
pmap_is_modified(vm_page_t m)
{
        boolean_t res;

        lwkt_gettoken(&vm_token);
        res = pmap_testbit(m, PG_M);
        lwkt_reltoken(&vm_token);
        return (res);
}

/*
 * Clear the modify bits on the specified physical page.
 *
 * No requirements.
 */
void
pmap_clear_modify(vm_page_t m)
{
        lwkt_gettoken(&vm_token);
        pmap_clearbit(m, PG_M);
        lwkt_reltoken(&vm_token);
}

/*
 * Clear the reference bit on the specified physical page.
 *
 * No requirements.
 */
void
pmap_clear_reference(vm_page_t m)
{
        lwkt_gettoken(&vm_token);
        pmap_clearbit(m, PG_A);
        lwkt_reltoken(&vm_token);
}

/*
 * Miscellaneous support routines follow
 *
 * Called from the low level boot code only.
 */
static void
i386_protection_init(void)
{
        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.
 *
 * NOTE: we can't use pgeflag unless we invalidate the pages one at
 * a time.
 *
 * No requirements.
 */
void *
pmap_mapdev(vm_paddr_t pa, vm_size_t size)
{
        vm_offset_t va, tmpva, offset;
        unsigned *pte;

        offset = pa & PAGE_MASK;
        size = roundup(offset + size, PAGE_SIZE);

        va = kmem_alloc_nofault(&kernel_map, size, PAGE_SIZE);
        if (!va)
                panic("pmap_mapdev: Couldn't alloc kernel virtual memory");

        pa = pa & PG_FRAME;
        for (tmpva = va; size > 0;) {
                pte = (unsigned *)vtopte(tmpva);
                *pte = pa | PG_RW | PG_V; /* | pgeflag; */
                size -= PAGE_SIZE;
                tmpva += PAGE_SIZE;
                pa += PAGE_SIZE;
        }
        smp_invltlb();
        cpu_invltlb();

        return ((void *)(va + offset));
}

void *
pmap_mapdev_uncacheable(vm_paddr_t pa, vm_size_t size)
{
        vm_offset_t va, tmpva, offset;
        unsigned *pte;

        offset = pa & PAGE_MASK;
        size = roundup(offset + size, PAGE_SIZE);

        va = kmem_alloc_nofault(&kernel_map, size, PAGE_SIZE);
        if (va == 0) {
                panic("pmap_mapdev_uncacheable: "
                    "Couldn't alloc kernel virtual memory");
        }

        pa = pa & PG_FRAME;
        for (tmpva = va; size > 0;) {
                pte = (unsigned *)vtopte(tmpva);
                *pte = pa | PG_RW | PG_V | PG_N; /* | pgeflag; */
                size -= PAGE_SIZE;
                tmpva += PAGE_SIZE;
                pa += PAGE_SIZE;
        }
        smp_invltlb();
        cpu_invltlb();

        return ((void *)(va + offset));
}

/*
 * No requirements.
 */
void
pmap_unmapdev(vm_offset_t va, vm_size_t size)
{
        vm_offset_t base, offset;

        base = va & PG_FRAME;
        offset = va & PAGE_MASK;
        size = roundup(offset + size, PAGE_SIZE);
        pmap_qremove(va, size >> PAGE_SHIFT);
        kmem_free(&kernel_map, base, size);
}

/*
 * Perform the pmap work for mincore
 *
 * The caller must hold vm_token if the caller wishes a stable result,
 * and even in that case some bits can change due to third party accesses
 * to the pmap.
 *
 * No requirements.
 */
int
pmap_mincore(pmap_t pmap, vm_offset_t addr)
{
        unsigned *ptep, pte;
        vm_page_t m;
        int val = 0;

        lwkt_gettoken(&vm_token);
        ptep = pmap_pte(pmap, addr);

        if (ptep && (pte = *ptep) != 0) {
                vm_offset_t pa;

                val = MINCORE_INCORE;
                if ((pte & PG_MANAGED) == 0)
                        goto done;

                pa = pte & PG_FRAME;

                m = PHYS_TO_VM_PAGE(pa);

                if (pte & PG_M) {
                        /*
                         * Modified by us
                         */
                        val |= MINCORE_MODIFIED|MINCORE_MODIFIED_OTHER;
                } else if (m->dirty || pmap_is_modified(m)) {
                        /*
                         * Modified by someone else
                         */
                        val |= MINCORE_MODIFIED_OTHER;
                }

                if (pte & PG_A) {
                        /*
                         * Referenced by us
                         */
                        val |= MINCORE_REFERENCED|MINCORE_REFERENCED_OTHER;
                } else if ((m->flags & PG_REFERENCED) ||
                           pmap_ts_referenced(m)) {
                        /*
                         * Referenced by someone else
                         */
                        val |= MINCORE_REFERENCED_OTHER;
                        vm_page_flag_set(m, PG_REFERENCED);
                }
        } 
done:
        lwkt_reltoken(&vm_token);
        return val;
}

/*
 * Replace p->p_vmspace with a new one.  If adjrefs is non-zero the new
 * vmspace will be ref'd and the old one will be deref'd.
 *
 * cr3 will be reloaded if any lwp is the current lwp.
 *
 * Only called with new VM spaces.
 * The process must have only a single thread.
 * The process must hold the vmspace->vm_map.token for oldvm and newvm
 * No other requirements.
 */
void
pmap_replacevm(struct proc *p, struct vmspace *newvm, int adjrefs)
{
        struct vmspace *oldvm;
        struct lwp *lp;

        oldvm = p->p_vmspace;
        if (oldvm != newvm) {
                if (adjrefs)
                        sysref_get(&newvm->vm_sysref);
                p->p_vmspace = newvm;
                KKASSERT(p->p_nthreads == 1);
                lp = RB_ROOT(&p->p_lwp_tree);
                pmap_setlwpvm(lp, newvm);
                if (adjrefs) 
                        sysref_put(&oldvm->vm_sysref);
        }
}

/*
 * Set the vmspace for a LWP.  The vmspace is almost universally set the
 * same as the process vmspace, but virtual kernels need to swap out contexts
 * on a per-lwp basis.
 *
 * Always called with a lp under the caller's direct control, either
 * unscheduled or the current lwp.
 *
 * No requirements.
 */
void
pmap_setlwpvm(struct lwp *lp, struct vmspace *newvm)
{
        struct vmspace *oldvm;
        struct pmap *pmap;

        oldvm = lp->lwp_vmspace;

        if (oldvm != newvm) {
                lp->lwp_vmspace = newvm;
                if (curthread->td_lwp == lp) {
                        pmap = vmspace_pmap(newvm);
#if defined(SMP)
                        atomic_set_cpumask(&pmap->pm_active, mycpu->gd_cpumask);
                        if (pmap->pm_active & CPUMASK_LOCK)
                                pmap_interlock_wait(newvm);
#else
                        pmap->pm_active |= 1;
#endif
#if defined(SWTCH_OPTIM_STATS)
                        tlb_flush_count++;
#endif
                        curthread->td_pcb->pcb_cr3 = vtophys(pmap->pm_pdir);
                        load_cr3(curthread->td_pcb->pcb_cr3);
                        pmap = vmspace_pmap(oldvm);
#if defined(SMP)
                        atomic_clear_cpumask(&pmap->pm_active,
                                             mycpu->gd_cpumask);
#else
                        pmap->pm_active &= ~(cpumask_t)1;
#endif
                }
        }
}

#ifdef SMP
/*
 * Called when switching to a locked pmap, used to interlock against pmaps
 * undergoing modifications to prevent us from activating the MMU for the
 * target pmap until all such modifications have completed.  We have to do
 * this because the thread making the modifications has already set up its
 * SMP synchronization mask.
 *
 * No requirements.
 */
void
pmap_interlock_wait(struct vmspace *vm)
{
        struct pmap *pmap = &vm->vm_pmap;

        if (pmap->pm_active & CPUMASK_LOCK) {
                crit_enter();
                DEBUG_PUSH_INFO("pmap_interlock_wait");
                while (pmap->pm_active & CPUMASK_LOCK) {
                        cpu_ccfence();
                        lwkt_process_ipiq();
                }
                DEBUG_POP_INFO();
                crit_exit();
        }
}

#endif

/*
 * Return a page-directory alignment hint for device mappings which will
 * allow the use of super-pages for the mapping.
 *
 * No requirements.
 */
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;
}

/*
 * Return whether the PGE flag is supported globally.
 *
 * No requirements.
 */
int
pmap_get_pgeflag(void)
{
        return pgeflag;
}

/*
 * Used by kmalloc/kfree, page already exists at va
 */
vm_page_t
pmap_kvtom(vm_offset_t va)
{
        return(PHYS_TO_VM_PAGE(*vtopte(va) & PG_FRAME));
}

void
pmap_object_init(vm_object_t object)
{
        /* empty */
}

void
pmap_object_free(vm_object_t object)
{
        /* empty */
}