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

     /*
      * Copyright (c) 1991 Regents of the University of California.
      * All rights reserved.
      * Copyright (c) 1994 John S. Dyson
      * All rights reserved.
      * Copyright (c) 1994 David Greenman
      * All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
     * the Systems Programming Group of the University of Utah Computer
     * Science Department and William Jolitz of UUNET Technologies Inc.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 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
     *      from: src/sys/i386/i386/pmap.c,v 1.250.2.8 2000/11/21 00:09:14 ps
     *      JNPR: pmap.c,v 1.11.2.1 2007/08/16 11:51:06 girish
     */
    
    /*
     *      Manages physical address maps.
     *
     *      In addition to hardware address maps, this
     *      module is called upon to provide software-use-only
     *      maps which may or may not be stored in the same
     *      form as hardware maps.  These pseudo-maps are
     *      used to store intermediate results from copy
     *      operations to and from address spaces.
     *
     *      Since the information managed by this module is
     *      also stored by the logical address mapping module,
     *      this module may throw away valid virtual-to-physical
     *      mappings at almost any time.  However, invalidations
     *      of virtual-to-physical mappings must be done as
     *      requested.
     *
     *      In order to cope with hardware architectures which
     *      make virtual-to-physical map invalidates expensive,
     *      this module may delay invalidate or reduced protection
     *      operations until such time as they are actually
     *      necessary.  This module is given full information as
     *      to which processors are currently using which maps,
     *      and to when physical maps must be made correct.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/9.2/sys/mips/mips/pmap.c 251897 2013-06-18 05:21:40Z scottl $");
    
    #include "opt_ddb.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    #include <sys/msgbuf.h>
    #include <sys/vmmeter.h>
    #include <sys/mman.h>
    #include <sys/smp.h>
    #ifdef DDB
    #include <ddb/ddb.h>
    #endif
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_phys.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_page.h>
    #include <vm/vm_map.h>
    #include <vm/vm_object.h>
    #include <vm/vm_extern.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_pager.h>
    #include <vm/uma.h>
    #include <sys/pcpu.h>
    #include <sys/sched.h>
    #ifdef SMP
   #include <sys/smp.h>
   #endif
   
   #include <machine/cache.h>
   #include <machine/md_var.h>
   #include <machine/tlb.h>
   
   #undef PMAP_DEBUG
   
   #ifndef PMAP_SHPGPERPROC
   #define PMAP_SHPGPERPROC 200
   #endif
   
   #if !defined(DIAGNOSTIC)
   #define PMAP_INLINE __inline
   #else
   #define PMAP_INLINE
   #endif
   
   /*
    * Get PDEs and PTEs for user/kernel address space
    */
   #define pmap_seg_index(v)       (((v) >> SEGSHIFT) & (NPDEPG - 1))
   #define pmap_pde_index(v)       (((v) >> PDRSHIFT) & (NPDEPG - 1))
   #define pmap_pte_index(v)       (((v) >> PAGE_SHIFT) & (NPTEPG - 1))
   #define pmap_pde_pindex(v)      ((v) >> PDRSHIFT)
   
   #ifdef __mips_n64
   #define NUPDE                   (NPDEPG * NPDEPG)
   #define NUSERPGTBLS             (NUPDE + NPDEPG)
   #else
   #define NUPDE                   (NPDEPG)
   #define NUSERPGTBLS             (NUPDE)
   #endif
   
   #define is_kernel_pmap(x)       ((x) == kernel_pmap)
   
   struct pmap kernel_pmap_store;
   pd_entry_t *kernel_segmap;
   
   vm_offset_t virtual_avail;      /* VA of first avail page (after kernel bss) */
   vm_offset_t virtual_end;        /* VA of last avail page (end of kernel AS) */
   
   static int nkpt;
   unsigned pmap_max_asid;         /* max ASID supported by the system */
   
   #define PMAP_ASID_RESERVED      0
   
   vm_offset_t kernel_vm_end = VM_MIN_KERNEL_ADDRESS;
   
   static void pmap_asid_alloc(pmap_t pmap);
   
   /*
    * Data for the pv entry allocation mechanism
    */
   static uma_zone_t pvzone;
   static struct vm_object pvzone_obj;
   static int pv_entry_count = 0, pv_entry_max = 0, pv_entry_high_water = 0;
   
   static PMAP_INLINE void free_pv_entry(pv_entry_t pv);
   static pv_entry_t get_pv_entry(pmap_t locked_pmap);
   static void pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va);
   static pv_entry_t pmap_pvh_remove(struct md_page *pvh, pmap_t pmap,
       vm_offset_t va);
   static __inline void pmap_changebit(vm_page_t m, int bit, boolean_t setem);
   static vm_page_t pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va,
       vm_page_t m, vm_prot_t prot, vm_page_t mpte);
   static int pmap_remove_pte(struct pmap *pmap, pt_entry_t *ptq, vm_offset_t va);
   static void pmap_remove_page(struct pmap *pmap, vm_offset_t va);
   static void pmap_remove_entry(struct pmap *pmap, vm_page_t m, vm_offset_t va);
   static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_page_t mpte,
       vm_offset_t va, vm_page_t m);
   static void pmap_update_page(pmap_t pmap, vm_offset_t va, pt_entry_t pte);
   static void pmap_invalidate_all(pmap_t pmap);
   static void pmap_invalidate_page(pmap_t pmap, vm_offset_t va);
   static void _pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m);
   
   static vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va, int flags);
   static vm_page_t _pmap_allocpte(pmap_t pmap, unsigned ptepindex, int flags);
   static int pmap_unuse_pt(pmap_t, vm_offset_t, vm_page_t);
   static pt_entry_t init_pte_prot(vm_offset_t va, vm_page_t m, vm_prot_t prot);
   
   #ifdef SMP
   static void pmap_invalidate_page_action(void *arg);
   static void pmap_invalidate_all_action(void *arg);
   static void pmap_update_page_action(void *arg);
   #endif
   
   #ifndef __mips_n64
   /*
    * This structure is for high memory (memory above 512Meg in 32 bit) support.
    * The highmem area does not have a KSEG0 mapping, and we need a mechanism to
    * do temporary per-CPU mappings for pmap_zero_page, pmap_copy_page etc.
    *
    * At bootup, we reserve 2 virtual pages per CPU for mapping highmem pages. To 
    * access a highmem physical address on a CPU, we map the physical address to
    * the reserved virtual address for the CPU in the kernel pagetable.  This is 
    * done with interrupts disabled(although a spinlock and sched_pin would be 
    * sufficient).
    */
   struct local_sysmaps {
           vm_offset_t     base;
           uint32_t        saved_intr;
           uint16_t        valid1, valid2;
   };
   static struct local_sysmaps sysmap_lmem[MAXCPU];
   
   static __inline void
   pmap_alloc_lmem_map(void)
   {
           int i;
   
           for (i = 0; i < MAXCPU; i++) {
                   sysmap_lmem[i].base = virtual_avail;
                   virtual_avail += PAGE_SIZE * 2;
                   sysmap_lmem[i].valid1 = sysmap_lmem[i].valid2 = 0;
           }
   }
   
   static __inline vm_offset_t
   pmap_lmem_map1(vm_paddr_t phys)
   {
           struct local_sysmaps *sysm;
           pt_entry_t *pte, npte;
           vm_offset_t va;
           uint32_t intr;
           int cpu;
   
           intr = intr_disable();
           cpu = PCPU_GET(cpuid);
           sysm = &sysmap_lmem[cpu];
           sysm->saved_intr = intr;
           va = sysm->base;
           npte = TLBLO_PA_TO_PFN(phys) |
               PTE_D | PTE_V | PTE_G | PTE_W | PTE_C_CACHE;
           pte = pmap_pte(kernel_pmap, va);
           *pte = npte;
           sysm->valid1 = 1;
           return (va);
   }
   
   static __inline vm_offset_t
   pmap_lmem_map2(vm_paddr_t phys1, vm_paddr_t phys2)
   {
           struct local_sysmaps *sysm;
           pt_entry_t *pte, npte;
           vm_offset_t va1, va2;
           uint32_t intr;
           int cpu;
   
           intr = intr_disable();
           cpu = PCPU_GET(cpuid);
           sysm = &sysmap_lmem[cpu];
           sysm->saved_intr = intr;
           va1 = sysm->base;
           va2 = sysm->base + PAGE_SIZE;
           npte = TLBLO_PA_TO_PFN(phys1) |
               PTE_D | PTE_V | PTE_G | PTE_W | PTE_C_CACHE;
           pte = pmap_pte(kernel_pmap, va1);
           *pte = npte;
           npte =  TLBLO_PA_TO_PFN(phys2) |
               PTE_D | PTE_V | PTE_G | PTE_W | PTE_C_CACHE;
           pte = pmap_pte(kernel_pmap, va2);
           *pte = npte;
           sysm->valid1 = 1;
           sysm->valid2 = 1;
           return (va1);
   }
   
   static __inline void
   pmap_lmem_unmap(void)
   {
           struct local_sysmaps *sysm;
           pt_entry_t *pte;
           int cpu;
   
           cpu = PCPU_GET(cpuid);
           sysm = &sysmap_lmem[cpu];
           pte = pmap_pte(kernel_pmap, sysm->base);
           *pte = PTE_G;
           tlb_invalidate_address(kernel_pmap, sysm->base);
           sysm->valid1 = 0;
           if (sysm->valid2) {
                   pte = pmap_pte(kernel_pmap, sysm->base + PAGE_SIZE);
                   *pte = PTE_G;
                   tlb_invalidate_address(kernel_pmap, sysm->base + PAGE_SIZE);
                   sysm->valid2 = 0;
           }
           intr_restore(sysm->saved_intr);
   }
   #else  /* __mips_n64 */
   
   static __inline void
   pmap_alloc_lmem_map(void)
   {
   }
   
   static __inline vm_offset_t
   pmap_lmem_map1(vm_paddr_t phys)
   {
   
           return (0);
   }
   
   static __inline vm_offset_t
   pmap_lmem_map2(vm_paddr_t phys1, vm_paddr_t phys2)
   {
   
           return (0);
   }
   
   static __inline vm_offset_t 
   pmap_lmem_unmap(void)
   {
   
           return (0);
   }
   #endif /* !__mips_n64 */
   
   /*
    * Page table entry lookup routines.
    */
   static __inline pd_entry_t *
   pmap_segmap(pmap_t pmap, vm_offset_t va)
   {
   
           return (&pmap->pm_segtab[pmap_seg_index(va)]);
   }
   
   #ifdef __mips_n64
   static __inline pd_entry_t *
   pmap_pdpe_to_pde(pd_entry_t *pdpe, vm_offset_t va)
   {
           pd_entry_t *pde;
   
           pde = (pd_entry_t *)*pdpe;
           return (&pde[pmap_pde_index(va)]);
   }
   
   static __inline pd_entry_t *
   pmap_pde(pmap_t pmap, vm_offset_t va)
   {
           pd_entry_t *pdpe;
   
           pdpe = pmap_segmap(pmap, va);
           if (pdpe == NULL || *pdpe == NULL)
                   return (NULL);
   
           return (pmap_pdpe_to_pde(pdpe, va));
   }
   #else
   static __inline pd_entry_t *
   pmap_pdpe_to_pde(pd_entry_t *pdpe, vm_offset_t va)
   {
   
           return (pdpe);
   }
   
   static __inline 
   pd_entry_t *pmap_pde(pmap_t pmap, vm_offset_t va)
   {
   
           return (pmap_segmap(pmap, va));
   }
   #endif
   
   static __inline pt_entry_t *
   pmap_pde_to_pte(pd_entry_t *pde, vm_offset_t va)
   {
           pt_entry_t *pte;
   
           pte = (pt_entry_t *)*pde;
           return (&pte[pmap_pte_index(va)]);
   }
   
   pt_entry_t *
   pmap_pte(pmap_t pmap, vm_offset_t va)
   {
           pd_entry_t *pde;
   
           pde = pmap_pde(pmap, va);
           if (pde == NULL || *pde == NULL)
                   return (NULL);
   
           return (pmap_pde_to_pte(pde, va));
   }
   
   vm_offset_t
   pmap_steal_memory(vm_size_t size)
   {
           vm_paddr_t bank_size, pa;
           vm_offset_t va;
   
           size = round_page(size);
           bank_size = phys_avail[1] - phys_avail[0];
           while (size > bank_size) {
                   int i;
   
                   for (i = 0; phys_avail[i + 2]; i += 2) {
                           phys_avail[i] = phys_avail[i + 2];
                           phys_avail[i + 1] = phys_avail[i + 3];
                   }
                   phys_avail[i] = 0;
                   phys_avail[i + 1] = 0;
                   if (!phys_avail[0])
                           panic("pmap_steal_memory: out of memory");
                   bank_size = phys_avail[1] - phys_avail[0];
           }
   
           pa = phys_avail[0];
           phys_avail[0] += size;
           if (MIPS_DIRECT_MAPPABLE(pa) == 0)
                   panic("Out of memory below 512Meg?");
           va = MIPS_PHYS_TO_DIRECT(pa);
           bzero((caddr_t)va, size);
           return (va);
   }
   
   /*
    * Bootstrap the system enough to run with virtual memory.  This
    * assumes that the phys_avail array has been initialized.
    */
   static void 
   pmap_create_kernel_pagetable(void)
   {
           int i, j;
           vm_offset_t ptaddr;
           pt_entry_t *pte;
   #ifdef __mips_n64
           pd_entry_t *pde;
           vm_offset_t pdaddr;
           int npt, npde;
   #endif
   
           /*
            * Allocate segment table for the kernel
            */
           kernel_segmap = (pd_entry_t *)pmap_steal_memory(PAGE_SIZE);
   
           /*
            * Allocate second level page tables for the kernel
            */
   #ifdef __mips_n64
           npde = howmany(NKPT, NPDEPG);
           pdaddr = pmap_steal_memory(PAGE_SIZE * npde);
   #endif
           nkpt = NKPT;
           ptaddr = pmap_steal_memory(PAGE_SIZE * nkpt);
   
           /*
            * The R[4-7]?00 stores only one copy of the Global bit in the
            * translation lookaside buffer for each 2 page entry. Thus invalid
            * entrys must have the Global bit set so when Entry LO and Entry HI
            * G bits are anded together they will produce a global bit to store
            * in the tlb.
            */
           for (i = 0, pte = (pt_entry_t *)ptaddr; i < (nkpt * NPTEPG); i++, pte++)
                   *pte = PTE_G;
   
   #ifdef __mips_n64
           for (i = 0,  npt = nkpt; npt > 0; i++) {
                   kernel_segmap[i] = (pd_entry_t)(pdaddr + i * PAGE_SIZE);
                   pde = (pd_entry_t *)kernel_segmap[i];
   
                   for (j = 0; j < NPDEPG && npt > 0; j++, npt--)
                           pde[j] = (pd_entry_t)(ptaddr + (i * NPDEPG + j) * PAGE_SIZE);
           }
   #else
           for (i = 0, j = pmap_seg_index(VM_MIN_KERNEL_ADDRESS); i < nkpt; i++, j++)
                   kernel_segmap[j] = (pd_entry_t)(ptaddr + (i * PAGE_SIZE));
   #endif
   
           PMAP_LOCK_INIT(kernel_pmap);
           kernel_pmap->pm_segtab = kernel_segmap;
           CPU_FILL(&kernel_pmap->pm_active);
           TAILQ_INIT(&kernel_pmap->pm_pvlist);
           kernel_pmap->pm_asid[0].asid = PMAP_ASID_RESERVED;
           kernel_pmap->pm_asid[0].gen = 0;
           kernel_vm_end += nkpt * NPTEPG * PAGE_SIZE;
   }
   
   void
   pmap_bootstrap(void)
   {
           int i;
           int need_local_mappings = 0; 
   
           /* Sort. */
   again:
           for (i = 0; phys_avail[i + 1] != 0; i += 2) {
                   /*
                    * Keep the memory aligned on page boundary.
                    */
                   phys_avail[i] = round_page(phys_avail[i]);
                   phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
   
                   if (i < 2)
                           continue;
                   if (phys_avail[i - 2] > phys_avail[i]) {
                           vm_paddr_t ptemp[2];
   
                           ptemp[0] = phys_avail[i + 0];
                           ptemp[1] = phys_avail[i + 1];
   
                           phys_avail[i + 0] = phys_avail[i - 2];
                           phys_avail[i + 1] = phys_avail[i - 1];
   
                           phys_avail[i - 2] = ptemp[0];
                           phys_avail[i - 1] = ptemp[1];
                           goto again;
                   }
           }
   
           /*
            * In 32 bit, we may have memory which cannot be mapped directly.
            * This memory will need temporary mapping before it can be
            * accessed.
            */
           if (!MIPS_DIRECT_MAPPABLE(phys_avail[i - 1] - 1))
                   need_local_mappings = 1;
   
           /*
            * Copy the phys_avail[] array before we start stealing memory from it.
            */
           for (i = 0; phys_avail[i + 1] != 0; i += 2) {
                   physmem_desc[i] = phys_avail[i];
                   physmem_desc[i + 1] = phys_avail[i + 1];
           }
   
           Maxmem = atop(phys_avail[i - 1]);
   
           if (bootverbose) {
                   printf("Physical memory chunk(s):\n");
                   for (i = 0; phys_avail[i + 1] != 0; i += 2) {
                           vm_paddr_t size;
   
                           size = phys_avail[i + 1] - phys_avail[i];
                           printf("%#08jx - %#08jx, %ju bytes (%ju pages)\n",
                               (uintmax_t) phys_avail[i],
                               (uintmax_t) phys_avail[i + 1] - 1,
                               (uintmax_t) size, (uintmax_t) size / PAGE_SIZE);
                   }
                   printf("Maxmem is 0x%0jx\n", ptoa((uintmax_t)Maxmem));
           }
           /*
            * Steal the message buffer from the beginning of memory.
            */
           msgbufp = (struct msgbuf *)pmap_steal_memory(msgbufsize);
           msgbufinit(msgbufp, msgbufsize);
   
           /*
            * Steal thread0 kstack.
            */
           kstack0 = pmap_steal_memory(KSTACK_PAGES << PAGE_SHIFT);
   
           virtual_avail = VM_MIN_KERNEL_ADDRESS;
           virtual_end = VM_MAX_KERNEL_ADDRESS;
   
   #ifdef SMP
           /*
            * Steal some virtual address space to map the pcpu area.
            */
           virtual_avail = roundup2(virtual_avail, PAGE_SIZE * 2);
           pcpup = (struct pcpu *)virtual_avail;
           virtual_avail += PAGE_SIZE * 2;
   
           /*
            * Initialize the wired TLB entry mapping the pcpu region for
            * the BSP at 'pcpup'. Up until this point we were operating
            * with the 'pcpup' for the BSP pointing to a virtual address
            * in KSEG0 so there was no need for a TLB mapping.
            */
           mips_pcpu_tlb_init(PCPU_ADDR(0));
   
           if (bootverbose)
                   printf("pcpu is available at virtual address %p.\n", pcpup);
   #endif
   
           if (need_local_mappings)
                   pmap_alloc_lmem_map();
           pmap_create_kernel_pagetable();
           pmap_max_asid = VMNUM_PIDS;
           mips_wr_entryhi(0);
           mips_wr_pagemask(0);
   }
   
   /*
    * Initialize a vm_page's machine-dependent fields.
    */
   void
   pmap_page_init(vm_page_t m)
   {
   
           TAILQ_INIT(&m->md.pv_list);
           m->md.pv_list_count = 0;
           m->md.pv_flags = 0;
   }
   
   /*
    *      Initialize the pmap module.
    *      Called by vm_init, to initialize any structures that the pmap
    *      system needs to map virtual memory.
    *      pmap_init has been enhanced to support in a fairly consistant
    *      way, discontiguous physical memory.
    */
   void
   pmap_init(void)
   {
   
           /*
            * Initialize the address space (zone) for the pv entries.  Set a
            * high water mark so that the system can recover from excessive
            * numbers of pv entries.
            */
           pvzone = uma_zcreate("PV ENTRY", sizeof(struct pv_entry), NULL, NULL,
               NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_VM | UMA_ZONE_NOFREE);
           pv_entry_max = PMAP_SHPGPERPROC * maxproc + cnt.v_page_count;
           pv_entry_high_water = 9 * (pv_entry_max / 10);
           uma_zone_set_obj(pvzone, &pvzone_obj, pv_entry_max);
   }
   
   /***************************************************
    * Low level helper routines.....
    ***************************************************/
   
   static __inline void
   pmap_invalidate_all_local(pmap_t pmap)
   {
           u_int cpuid;
   
           cpuid = PCPU_GET(cpuid);
   
           if (pmap == kernel_pmap) {
                   tlb_invalidate_all();
                   return;
           }
           if (CPU_ISSET(cpuid, &pmap->pm_active))
                   tlb_invalidate_all_user(pmap);
           else
                   pmap->pm_asid[cpuid].gen = 0;
   }
   
   #ifdef SMP
   static void
   pmap_invalidate_all(pmap_t pmap)
   {
   
           smp_rendezvous(0, pmap_invalidate_all_action, 0, pmap);
   }
   
   static void
   pmap_invalidate_all_action(void *arg)
   {
   
           pmap_invalidate_all_local((pmap_t)arg);
   }
   #else
   static void
   pmap_invalidate_all(pmap_t pmap)
   {
   
           pmap_invalidate_all_local(pmap);
   }
   #endif
   
   static __inline void
   pmap_invalidate_page_local(pmap_t pmap, vm_offset_t va)
   {
           u_int cpuid;
   
           cpuid = PCPU_GET(cpuid);
   
           if (is_kernel_pmap(pmap)) {
                   tlb_invalidate_address(pmap, va);
                   return;
           }
           if (pmap->pm_asid[cpuid].gen != PCPU_GET(asid_generation))
                   return;
           else if (!CPU_ISSET(cpuid, &pmap->pm_active)) {
                   pmap->pm_asid[cpuid].gen = 0;
                   return;
           }
           tlb_invalidate_address(pmap, va);
   }
   
   #ifdef SMP
   struct pmap_invalidate_page_arg {
           pmap_t pmap;
           vm_offset_t va;
   };
   
   static void
   pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
   {
           struct pmap_invalidate_page_arg arg;
   
           arg.pmap = pmap;
           arg.va = va;
           smp_rendezvous(0, pmap_invalidate_page_action, 0, &arg);
   }
   
   static void
   pmap_invalidate_page_action(void *arg)
   {
           struct pmap_invalidate_page_arg *p = arg;
   
           pmap_invalidate_page_local(p->pmap, p->va);
   }
   #else
   static void
   pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
   {
   
           pmap_invalidate_page_local(pmap, va);
   }
   #endif
   
   static __inline void
   pmap_update_page_local(pmap_t pmap, vm_offset_t va, pt_entry_t pte)
   {
           u_int cpuid;
   
           cpuid = PCPU_GET(cpuid);
   
           if (is_kernel_pmap(pmap)) {
                   tlb_update(pmap, va, pte);
                   return;
           }
           if (pmap->pm_asid[cpuid].gen != PCPU_GET(asid_generation))
                   return;
           else if (!CPU_ISSET(cpuid, &pmap->pm_active)) {
                   pmap->pm_asid[cpuid].gen = 0;
                   return;
           }
           tlb_update(pmap, va, pte);
   }
   
   #ifdef SMP
   struct pmap_update_page_arg {
           pmap_t pmap;
           vm_offset_t va;
           pt_entry_t pte;
   };
   
   static void
   pmap_update_page(pmap_t pmap, vm_offset_t va, pt_entry_t pte)
   {
           struct pmap_update_page_arg arg;
   
           arg.pmap = pmap;
           arg.va = va;
           arg.pte = pte;
           smp_rendezvous(0, pmap_update_page_action, 0, &arg);
   }
   
   static void
   pmap_update_page_action(void *arg)
   {
           struct pmap_update_page_arg *p = arg;
   
           pmap_update_page_local(p->pmap, p->va, p->pte);
   }
   #else
   static void
   pmap_update_page(pmap_t pmap, vm_offset_t va, pt_entry_t pte)
   {
   
           pmap_update_page_local(pmap, va, pte);
   }
   #endif
   
   /*
    *      Routine:        pmap_extract
    *      Function:
    *              Extract the physical page address associated
    *              with the given map/virtual_address pair.
    */
   vm_paddr_t
   pmap_extract(pmap_t pmap, vm_offset_t va)
   {
           pt_entry_t *pte;
           vm_offset_t retval = 0;
   
           PMAP_LOCK(pmap);
           pte = pmap_pte(pmap, va);
           if (pte) {
                   retval = TLBLO_PTE_TO_PA(*pte) | (va & PAGE_MASK);
           }
           PMAP_UNLOCK(pmap);
           return (retval);
   }
   
   /*
    *      Routine:        pmap_extract_and_hold
    *      Function:
    *              Atomically extract and hold the physical page
    *              with the given pmap and virtual address pair
    *              if that mapping permits the given protection.
    */
   vm_page_t
   pmap_extract_and_hold(pmap_t pmap, vm_offset_t va, vm_prot_t prot)
   {
           pt_entry_t pte;
           vm_page_t m;
           vm_paddr_t pa;
   
           m = NULL;
           pa = 0;
           PMAP_LOCK(pmap);
   retry:
           pte = *pmap_pte(pmap, va);
           if (pte != 0 && pte_test(&pte, PTE_V) &&
               (pte_test(&pte, PTE_D) || (prot & VM_PROT_WRITE) == 0)) {
                   if (vm_page_pa_tryrelock(pmap, TLBLO_PTE_TO_PA(pte), &pa))
                           goto retry;
   
                   m = PHYS_TO_VM_PAGE(TLBLO_PTE_TO_PA(pte));
                   vm_page_hold(m);
           }
           PA_UNLOCK_COND(pa);
           PMAP_UNLOCK(pmap);
           return (m);
   }
   
   /***************************************************
    * Low level mapping routines.....
    ***************************************************/
   
   /*
    * add a wired page to the kva
    */
   void
   pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int attr)
   {
           pt_entry_t *pte;
           pt_entry_t opte, npte;
   
   #ifdef PMAP_DEBUG
           printf("pmap_kenter:  va: %p -> pa: %p\n", (void *)va, (void *)pa);
   #endif
   
           pte = pmap_pte(kernel_pmap, va);
           opte = *pte;
           npte = TLBLO_PA_TO_PFN(pa) | attr | PTE_D | PTE_V | PTE_G;
           *pte = npte;
           if (pte_test(&opte, PTE_V) && opte != npte)
                   pmap_update_page(kernel_pmap, va, npte);
   }
   
   void
   pmap_kenter(vm_offset_t va, vm_paddr_t pa)
   {
   
           KASSERT(is_cacheable_mem(pa),
                   ("pmap_kenter: memory at 0x%lx is not cacheable", (u_long)pa));
   
           pmap_kenter_attr(va, pa, PTE_C_CACHE);
   }
   
   /*
    * remove a page from the kernel pagetables
    */
    /* PMAP_INLINE */ void
   pmap_kremove(vm_offset_t va)
   {
           pt_entry_t *pte;
   
           /*
            * Write back all caches from the page being destroyed
            */
           mips_dcache_wbinv_range_index(va, PAGE_SIZE);
   
           pte = pmap_pte(kernel_pmap, va);
           *pte = PTE_G;
           pmap_invalidate_page(kernel_pmap, va);
   }
   
   /*
    *      Used to map a range of physical addresses into kernel
    *      virtual address space.
    *
    *      The value passed in '*virt' is a suggested virtual address for
    *      the mapping. Architectures which can support a direct-mapped
    *      physical to virtual region can return the appropriate address
    *      within that region, leaving '*virt' unchanged. Other
    *      architectures should map the pages starting at '*virt' and
    *      update '*virt' with the first usable address after the mapped
    *      region.
    *
    *      Use XKPHYS for 64 bit, and KSEG0 where possible for 32 bit.
    */
   vm_offset_t
   pmap_map(vm_offset_t *virt, vm_paddr_t start, vm_paddr_t end, int prot)
   {
           vm_offset_t va, sva;
   
           if (MIPS_DIRECT_MAPPABLE(end - 1))
                   return (MIPS_PHYS_TO_DIRECT(start));
   
           va = sva = *virt;
           while (start < end) {
                   pmap_kenter(va, start);
                   va += PAGE_SIZE;
                   start += PAGE_SIZE;
           }
           *virt = va;
           return (sva);
   }
   
   /*
    * Add a list of wired pages to the kva
    * this routine is only used for temporary
    * kernel mappings that do not need to have
    * page modification or references recorded.
    * Note that old mappings are simply written
    * over.  The page *must* be wired.
    */
   void
   pmap_qenter(vm_offset_t va, vm_page_t *m, int count)
   {
           int i;
           vm_offset_t origva = va;
   
           for (i = 0; i < count; i++) {
                   pmap_flush_pvcache(m[i]);
                   pmap_kenter(va, VM_PAGE_TO_PHYS(m[i]));
                   va += PAGE_SIZE;
           }
   
           mips_dcache_wbinv_range_index(origva, PAGE_SIZE*count);
   }
   
   /*
    * this routine jerks page mappings from the
    * kernel -- it is meant only for temporary mappings.
    */
   void
   pmap_qremove(vm_offset_t va, int count)
   {
           /*
            * No need to wb/inv caches here, 
            *   pmap_kremove will do it for us
            */
   
           while (count-- > 0) {
                   pmap_kremove(va);
                   va += PAGE_SIZE;
           }
   }
   
   /***************************************************
    * Page table page management routines.....
    ***************************************************/
   
   /*
    * Decrements a page table page's wire count, which is used to record the
    * number of valid page table entries within the page.  If the wire count
    * drops to zero, then the page table page is unmapped.  Returns TRUE if the
    * page table page was unmapped and FALSE otherwise.
    */
   static PMAP_INLINE boolean_t
   pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m)
   {
   
           --m->wire_count;
           if (m->wire_count == 0) {
                   _pmap_unwire_ptp(pmap, va, m);
                   return (TRUE);
           } else
                   return (FALSE);
   }
   
   static void
   _pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m)
   {
           pd_entry_t *pde;
   
           PMAP_LOCK_ASSERT(pmap, MA_OWNED);
           /*
            * unmap the page table page
            */
   #ifdef __mips_n64
           if (m->pindex < NUPDE)
                   pde = pmap_pde(pmap, va);
           else
                   pde = pmap_segmap(pmap, va);
   #else
           pde = pmap_pde(pmap, va);
   #endif
           *pde = 0;
           pmap->pm_stats.resident_count--;
   
   #ifdef __mips_n64
           if (m->pindex < NUPDE) {
                   pd_entry_t *pdp;
                   vm_page_t pdpg;
   
                   /*
                    * Recursively decrement next level pagetable refcount
                    */
                  pdp = (pd_entry_t *)*pmap_segmap(pmap, va);
                  pdpg = PHYS_TO_VM_PAGE(MIPS_DIRECT_TO_PHYS(pdp));
                  pmap_unwire_ptp(pmap, va, pdpg);
          }
  #endif
          if (pmap->pm_ptphint == m)
                  pmap->pm_ptphint = NULL;
  
          /*
           * If the page is finally unwired, simply free it.
           */
          vm_page_free_zero(m);
          atomic_subtract_int(&cnt.v_wire_count, 1);
  }
  
  /*
   * After removing a page table entry, this routine is used to
   * conditionally free the page, and manage the hold/wire counts.
   */
  static int
  pmap_unuse_pt(pmap_t pmap, vm_offset_t va, vm_page_t mpte)
  {
          unsigned ptepindex;
          pd_entry_t pteva;
  
          if (va >= VM_MAXUSER_ADDRESS)
                  return (0);
  
          if (mpte == NULL) {
                  ptepindex = pmap_pde_pindex(va);
                  if (pmap->pm_ptphint &&
                      (pmap->pm_ptphint->pindex == ptepindex)) {
                          mpte = pmap->pm_ptphint;
                  } else {
                          pteva = *pmap_pde(pmap, va);
                          mpte = PHYS_TO_VM_PAGE(MIPS_DIRECT_TO_PHYS(pteva));
                          pmap->pm_ptphint = mpte;
                  }
          }
          return (pmap_unwire_ptp(pmap, va, mpte));
  }
  
  void
  pmap_pinit0(pmap_t pmap)
  {
          int i;
  
          PMAP_LOCK_INIT(pmap);
          pmap->pm_segtab = kernel_segmap;
          CPU_ZERO(&pmap->pm_active);
          pmap->pm_ptphint = NULL;
          for (i = 0; i < MAXCPU; i++) {
                  pmap->pm_asid[i].asid = PMAP_ASID_RESERVED;
                  pmap->pm_asid[i].gen = 0;
          }
          PCPU_SET(curpmap, pmap);
          TAILQ_INIT(&pmap->pm_pvlist);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
  }
  
  void
  pmap_grow_direct_page_cache()
  {
  
  #ifdef __mips_n64
          vm_contig_grow_cache(3, 0, MIPS_XKPHYS_LARGEST_PHYS);
  #else
          vm_contig_grow_cache(3, 0, MIPS_KSEG0_LARGEST_PHYS);
  #endif
  }
  
  vm_page_t
  pmap_alloc_direct_page(unsigned int index, int req)
  {
          vm_page_t m;
  
          m = vm_page_alloc_freelist(VM_FREELIST_DIRECT, req);
          if (m == NULL)
                  return (NULL);
  
          if ((m->flags & PG_ZERO) == 0)
                  pmap_zero_page(m);
  
          m->pindex = index;
          atomic_add_int(&cnt.v_wire_count, 1);
          m->wire_count = 1;
          return (m);
  }
  
  /*
   * Initialize a preallocated and zeroed pmap structure,
   * such as one in a vmspace structure.
   */
  int
  pmap_pinit(pmap_t pmap)
  {
          vm_offset_t ptdva;
          vm_page_t ptdpg;
          int i;
  
          PMAP_LOCK_INIT(pmap);
  
          /*
           * allocate the page directory page
           */
          while ((ptdpg = pmap_alloc_direct_page(NUSERPGTBLS, VM_ALLOC_NORMAL)) == NULL)
                 pmap_grow_direct_page_cache();
  
          ptdva = MIPS_PHYS_TO_DIRECT(VM_PAGE_TO_PHYS(ptdpg));
          pmap->pm_segtab = (pd_entry_t *)ptdva;
          CPU_ZERO(&pmap->pm_active);
          pmap->pm_ptphint = NULL;
          for (i = 0; i < MAXCPU; i++) {
                  pmap->pm_asid[i].asid = PMAP_ASID_RESERVED;
                  pmap->pm_asid[i].gen = 0;
          }
          TAILQ_INIT(&pmap->pm_pvlist);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
  
          return (1);
  }
  
  /*
   * this routine is called if the page table page is not
   * mapped correctly.
   */
  static vm_page_t
  _pmap_allocpte(pmap_t pmap, unsigned ptepindex, int flags)
  {
          vm_offset_t pageva;
          vm_page_t m;
  
          KASSERT((flags & (M_NOWAIT | M_WAITOK)) == M_NOWAIT ||
              (flags & (M_NOWAIT | M_WAITOK)) == M_WAITOK,
              ("_pmap_allocpte: flags is neither M_NOWAIT nor M_WAITOK"));
  
          /*
           * Find or fabricate a new pagetable page
           */
          if ((m = pmap_alloc_direct_page(ptepindex, VM_ALLOC_NORMAL)) == NULL) {
                  if (flags & M_WAITOK) {
                          PMAP_UNLOCK(pmap);
                          vm_page_unlock_queues();
                          pmap_grow_direct_page_cache();
                          vm_page_lock_queues();
                          PMAP_LOCK(pmap);
                  }
  
                  /*
                   * Indicate the need to retry.  While waiting, the page
                   * table page may have been allocated.
                   */
                  return (NULL);
          }
  
          /*
           * Map the pagetable page into the process address space, if it
           * isn't already there.
           */
          pageva = MIPS_PHYS_TO_DIRECT(VM_PAGE_TO_PHYS(m));
  
  #ifdef __mips_n64
          if (ptepindex >= NUPDE) {
                  pmap->pm_segtab[ptepindex - NUPDE] = (pd_entry_t)pageva;
          } else {
                  pd_entry_t *pdep, *pde;
                  int segindex = ptepindex >> (SEGSHIFT - PDRSHIFT);
                  int pdeindex = ptepindex & (NPDEPG - 1);
                  vm_page_t pg;
                  
                  pdep = &pmap->pm_segtab[segindex];
                  if (*pdep == NULL) { 
                          /* recurse for allocating page dir */
                          if (_pmap_allocpte(pmap, NUPDE + segindex, 
                              flags) == NULL) {
                                  /* alloc failed, release current */
                                  --m->wire_count;
                                  atomic_subtract_int(&cnt.v_wire_count, 1);
                                  vm_page_free_zero(m);
                                  return (NULL);
                          }
                  } else {
                          pg = PHYS_TO_VM_PAGE(MIPS_DIRECT_TO_PHYS(*pdep));
                          pg->wire_count++;
                  }
                  /* Next level entry */
                  pde = (pd_entry_t *)*pdep;
                  pde[pdeindex] = (pd_entry_t)pageva;
                  pmap->pm_ptphint = m;
          }
  #else
          pmap->pm_segtab[ptepindex] = (pd_entry_t)pageva;
  #endif
          pmap->pm_stats.resident_count++;
  
          /*
           * Set the page table hint
           */
          pmap->pm_ptphint = m;
          return (m);
  }
  
  static vm_page_t
  pmap_allocpte(pmap_t pmap, vm_offset_t va, int flags)
  {
          unsigned ptepindex;
          pd_entry_t *pde;
          vm_page_t m;
  
          KASSERT((flags & (M_NOWAIT | M_WAITOK)) == M_NOWAIT ||
              (flags & (M_NOWAIT | M_WAITOK)) == M_WAITOK,
              ("pmap_allocpte: flags is neither M_NOWAIT nor M_WAITOK"));
  
          /*
           * Calculate pagetable page index
           */
          ptepindex = pmap_pde_pindex(va);
  retry:
          /*
           * Get the page directory entry
           */
          pde = pmap_pde(pmap, va);
  
          /*
           * If the page table page is mapped, we just increment the hold
           * count, and activate it.
           */
          if (pde != NULL && *pde != NULL) {
                  /*
                   * In order to get the page table page, try the hint first.
                   */
                  if (pmap->pm_ptphint &&
                      (pmap->pm_ptphint->pindex == ptepindex)) {
                          m = pmap->pm_ptphint;
                  } else {
                          m = PHYS_TO_VM_PAGE(MIPS_DIRECT_TO_PHYS(*pde));
                          pmap->pm_ptphint = m;
                  }
                  m->wire_count++;
          } else {
                  /*
                   * Here if the pte page isn't mapped, or if it has been
                   * deallocated.
                   */
                  m = _pmap_allocpte(pmap, ptepindex, flags);
                  if (m == NULL && (flags & M_WAITOK))
                          goto retry;
          }
          return (m);
  }
  
  
  /***************************************************
  * Pmap allocation/deallocation routines.
   ***************************************************/
  /*
   *  Revision 1.397
   *  - Merged pmap_release and pmap_release_free_page.  When pmap_release is
   *    called only the page directory page(s) can be left in the pmap pte
   *    object, since all page table pages will have been freed by
   *    pmap_remove_pages and pmap_remove.  In addition, there can only be one
   *    reference to the pmap and the page directory is wired, so the page(s)
   *    can never be busy.  So all there is to do is clear the magic mappings
   *    from the page directory and free the page(s).
   */
  
  
  /*
   * Release any resources held by the given physical map.
   * Called when a pmap initialized by pmap_pinit is being released.
   * Should only be called if the map contains no valid mappings.
   */
  void
  pmap_release(pmap_t pmap)
  {
          vm_offset_t ptdva;
          vm_page_t ptdpg;
  
          KASSERT(pmap->pm_stats.resident_count == 0,
              ("pmap_release: pmap resident count %ld != 0",
              pmap->pm_stats.resident_count));
  
          ptdva = (vm_offset_t)pmap->pm_segtab;
          ptdpg = PHYS_TO_VM_PAGE(MIPS_DIRECT_TO_PHYS(ptdva));
  
          ptdpg->wire_count--;
          atomic_subtract_int(&cnt.v_wire_count, 1);
          vm_page_free_zero(ptdpg);
          PMAP_LOCK_DESTROY(pmap);
  }
  
  /*
   * grow the number of kernel page table entries, if needed
   */
  void
  pmap_growkernel(vm_offset_t addr)
  {
          vm_page_t nkpg;
          pd_entry_t *pde, *pdpe;
          pt_entry_t *pte;
          int i;
  
          mtx_assert(&kernel_map->system_mtx, MA_OWNED);
          addr = roundup2(addr, NBSEG);
          if (addr - 1 >= kernel_map->max_offset)
                  addr = kernel_map->max_offset;
          while (kernel_vm_end < addr) {
                  pdpe = pmap_segmap(kernel_pmap, kernel_vm_end);
  #ifdef __mips_n64
                  if (*pdpe == 0) {
                          /* new intermediate page table entry */
                          nkpg = pmap_alloc_direct_page(nkpt, VM_ALLOC_INTERRUPT);
                          if (nkpg == NULL)
                                  panic("pmap_growkernel: no memory to grow kernel");
                          *pdpe = (pd_entry_t)MIPS_PHYS_TO_DIRECT(VM_PAGE_TO_PHYS(nkpg));
                          continue; /* try again */
                  }
  #endif
                  pde = pmap_pdpe_to_pde(pdpe, kernel_vm_end);
                  if (*pde != 0) {
                          kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                          if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                                  kernel_vm_end = kernel_map->max_offset;
                                  break;
                          }
                          continue;
                  }
  
                  /*
                   * This index is bogus, but out of the way
                   */
                  nkpg = pmap_alloc_direct_page(nkpt, VM_ALLOC_INTERRUPT);
                  if (!nkpg)
                          panic("pmap_growkernel: no memory to grow kernel");
                  nkpt++;
                  *pde = (pd_entry_t)MIPS_PHYS_TO_DIRECT(VM_PAGE_TO_PHYS(nkpg));
  
                  /*
                   * The R[4-7]?00 stores only one copy of the Global bit in
                   * the translation lookaside buffer for each 2 page entry.
                   * Thus invalid entrys must have the Global bit set so when
                   * Entry LO and Entry HI G bits are anded together they will
                   * produce a global bit to store in the tlb.
                   */
                  pte = (pt_entry_t *)*pde;
                  for (i = 0; i < NPTEPG; i++)
                          pte[i] = PTE_G;
  
                  kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                  if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                          kernel_vm_end = kernel_map->max_offset;
                          break;
                  }
          }
  }
  
  /***************************************************
  * page management routines.
   ***************************************************/
  
  /*
   * free the pv_entry back to the free list
   */
  static PMAP_INLINE void
  free_pv_entry(pv_entry_t pv)
  {
  
          pv_entry_count--;
          uma_zfree(pvzone, pv);
  }
  
  /*
   * get a new pv_entry, allocating a block from the system
   * when needed.
   * the memory allocation is performed bypassing the malloc code
   * because of the possibility of allocations at interrupt time.
   */
  static pv_entry_t
  get_pv_entry(pmap_t locked_pmap)
  {
          static const struct timeval printinterval = { 60, 0 };
          static struct timeval lastprint;
          struct vpgqueues *vpq;
          pt_entry_t *pte, oldpte;
          pmap_t pmap;
          pv_entry_t allocated_pv, next_pv, pv;
          vm_offset_t va;
          vm_page_t m;
  
          PMAP_LOCK_ASSERT(locked_pmap, MA_OWNED);
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          allocated_pv = uma_zalloc(pvzone, M_NOWAIT);
          if (allocated_pv != NULL) {
                  pv_entry_count++;
                  if (pv_entry_count > pv_entry_high_water)
                          pagedaemon_wakeup();
                  else
                          return (allocated_pv);
          }
          /*
           * Reclaim pv entries: At first, destroy mappings to inactive
           * pages.  After that, if a pv entry is still needed, destroy
           * mappings to active pages.
           */
          if (ratecheck(&lastprint, &printinterval))
                  printf("Approaching the limit on PV entries, "
                      "increase the vm.pmap.shpgperproc tunable.\n");
          vpq = &vm_page_queues[PQ_INACTIVE];
  retry:
          TAILQ_FOREACH(m, &vpq->pl, pageq) {
                  if ((m->flags & PG_MARKER) != 0 || m->hold_count || m->busy)
                          continue;
                  TAILQ_FOREACH_SAFE(pv, &m->md.pv_list, pv_list, next_pv) {
                          va = pv->pv_va;
                          pmap = pv->pv_pmap;
                          /* Avoid deadlock and lock recursion. */
                          if (pmap > locked_pmap)
                                  PMAP_LOCK(pmap);
                          else if (pmap != locked_pmap && !PMAP_TRYLOCK(pmap))
                                  continue;
                          pmap->pm_stats.resident_count--;
                          pte = pmap_pte(pmap, va);
                          KASSERT(pte != NULL, ("pte"));
                          oldpte = *pte;
                          if (is_kernel_pmap(pmap))
                                  *pte = PTE_G;
                          else
                                  *pte = 0;
                          KASSERT(!pte_test(&oldpte, PTE_W),
                              ("wired pte for unwired page"));
                          if (m->md.pv_flags & PV_TABLE_REF)
                                  vm_page_aflag_set(m, PGA_REFERENCED);
                          if (pte_test(&oldpte, PTE_D))
                                  vm_page_dirty(m);
                          pmap_invalidate_page(pmap, va);
                          TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
                          m->md.pv_list_count--;
                          TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                          pmap_unuse_pt(pmap, va, pv->pv_ptem);
                          if (pmap != locked_pmap)
                                  PMAP_UNLOCK(pmap);
                          if (allocated_pv == NULL)
                                  allocated_pv = pv;
                          else
                                  free_pv_entry(pv);
                  }
                  if (TAILQ_EMPTY(&m->md.pv_list)) {
                          vm_page_aflag_clear(m, PGA_WRITEABLE);
                          m->md.pv_flags &= ~(PV_TABLE_REF | PV_TABLE_MOD);
                  }
          }
          if (allocated_pv == NULL) {
                  if (vpq == &vm_page_queues[PQ_INACTIVE]) {
                          vpq = &vm_page_queues[PQ_ACTIVE];
                          goto retry;
                  }
                  panic("get_pv_entry: increase the vm.pmap.shpgperproc tunable");
          }
          return (allocated_pv);
  }
  
  /*
   *  Revision 1.370
   *
   *  Move pmap_collect() out of the machine-dependent code, rename it
   *  to reflect its new location, and add page queue and flag locking.
   *
   *  Notes: (1) alpha, i386, and ia64 had identical implementations
   *  of pmap_collect() in terms of machine-independent interfaces;
   *  (2) sparc64 doesn't require it; (3) powerpc had it as a TODO.
   *
   *  MIPS implementation was identical to alpha [Junos 8.2]
   */
  
  /*
   * If it is the first entry on the list, it is actually
   * in the header and we must copy the following entry up
   * to the header.  Otherwise we must search the list for
   * the entry.  In either case we free the now unused entry.
   */
  
  static pv_entry_t
  pmap_pvh_remove(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
  {
          pv_entry_t pv;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          if (pvh->pv_list_count < pmap->pm_stats.resident_count) {
                  TAILQ_FOREACH(pv, &pvh->pv_list, pv_list) {
                          if (pmap == pv->pv_pmap && va == pv->pv_va)
                                  break;
                  }
          } else {
                  TAILQ_FOREACH(pv, &pmap->pm_pvlist, pv_plist) {
                          if (va == pv->pv_va)
                                  break;
                  }
          }
          if (pv != NULL) {
                  TAILQ_REMOVE(&pvh->pv_list, pv, pv_list);
                  pvh->pv_list_count--;
                  TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
          }
          return (pv);
  }
  
  static void
  pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
  {
          pv_entry_t pv;
  
          pv = pmap_pvh_remove(pvh, pmap, va);
          KASSERT(pv != NULL, ("pmap_pvh_free: pv not found, pa %lx va %lx",
               (u_long)VM_PAGE_TO_PHYS(member2struct(vm_page, md, pvh)),
               (u_long)va));
          free_pv_entry(pv);
  }
  
  static void
  pmap_remove_entry(pmap_t pmap, vm_page_t m, vm_offset_t va)
  {
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          pmap_pvh_free(&m->md, pmap, va);
          if (TAILQ_EMPTY(&m->md.pv_list))
                  vm_page_aflag_clear(m, PGA_WRITEABLE);
  }
  
  /*
   * Conditionally create a pv entry.
   */
  static boolean_t
  pmap_try_insert_pv_entry(pmap_t pmap, vm_page_t mpte, vm_offset_t va,
      vm_page_t m)
  {
          pv_entry_t pv;
  
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          if (pv_entry_count < pv_entry_high_water && 
              (pv = uma_zalloc(pvzone, M_NOWAIT)) != NULL) {
                  pv_entry_count++;
                  pv->pv_va = va;
                  pv->pv_pmap = pmap;
                  pv->pv_ptem = mpte;
                  TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
                  TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
                  m->md.pv_list_count++;
                  return (TRUE);
          } else
                  return (FALSE);
  }
  
  /*
   * pmap_remove_pte: do the things to unmap a page in a process
   */
  static int
  pmap_remove_pte(struct pmap *pmap, pt_entry_t *ptq, vm_offset_t va)
  {
          pt_entry_t oldpte;
          vm_page_t m;
          vm_paddr_t pa;
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
  
          oldpte = *ptq;
          if (is_kernel_pmap(pmap))
                  *ptq = PTE_G;
          else
                  *ptq = 0;
  
          if (pte_test(&oldpte, PTE_W))
                  pmap->pm_stats.wired_count -= 1;
  
          pmap->pm_stats.resident_count -= 1;
          pa = TLBLO_PTE_TO_PA(oldpte);
  
          if (page_is_managed(pa)) {
                  m = PHYS_TO_VM_PAGE(pa);
                  if (pte_test(&oldpte, PTE_D)) {
                          KASSERT(!pte_test(&oldpte, PTE_RO),
                              ("%s: modified page not writable: va: %p, pte: %#jx",
                              __func__, (void *)va, (uintmax_t)oldpte));
                          vm_page_dirty(m);
                  }
                  if (m->md.pv_flags & PV_TABLE_REF)
                          vm_page_aflag_set(m, PGA_REFERENCED);
                  m->md.pv_flags &= ~(PV_TABLE_REF | PV_TABLE_MOD);
  
                  pmap_remove_entry(pmap, m, va);
          }
          return (pmap_unuse_pt(pmap, va, NULL));
  }
  
  /*
   * Remove a single page from a process address space
   */
  static void
  pmap_remove_page(struct pmap *pmap, vm_offset_t va)
  {
          pt_entry_t *ptq;
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
          ptq = pmap_pte(pmap, va);
  
          /*
           * if there is no pte for this address, just skip it!!!
           */
          if (!ptq || !pte_test(ptq, PTE_V)) {
                  return;
          }
  
          /*
           * Write back all caches from the page being destroyed
           */
          mips_dcache_wbinv_range_index(va, PAGE_SIZE);
  
          /*
           * get a local va for mappings for this pmap.
           */
          (void)pmap_remove_pte(pmap, ptq, va);
          pmap_invalidate_page(pmap, va);
  
          return;
  }
  
  /*
   *      Remove the given range of addresses from the specified map.
   *
   *      It is assumed that the start and end are properly
   *      rounded to the page size.
   */
  void
  pmap_remove(struct pmap *pmap, vm_offset_t sva, vm_offset_t eva)
  {
          vm_offset_t va_next;
          pd_entry_t *pde, *pdpe;
          pt_entry_t *pte;
  
          if (pmap == NULL)
                  return;
  
          if (pmap->pm_stats.resident_count == 0)
                  return;
  
          vm_page_lock_queues();
          PMAP_LOCK(pmap);
  
          /*
           * special handling of removing one page.  a very common operation
           * and easy to short circuit some code.
           */
          if ((sva + PAGE_SIZE) == eva) {
                  pmap_remove_page(pmap, sva);
                  goto out;
          }
          for (; sva < eva; sva = va_next) {
                  pdpe = pmap_segmap(pmap, sva);
  #ifdef __mips_n64
                  if (*pdpe == 0) {
                          va_next = (sva + NBSEG) & ~SEGMASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
  #endif
                  va_next = (sva + NBPDR) & ~PDRMASK;
                  if (va_next < sva)
                          va_next = eva;
  
                  pde = pmap_pdpe_to_pde(pdpe, sva);
                  if (*pde == 0)
                          continue;
                  if (va_next > eva)
                          va_next = eva;
                  for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; 
                      pte++, sva += PAGE_SIZE) {
                          pmap_remove_page(pmap, sva);
                  }
          }
  out:
          vm_page_unlock_queues();
          PMAP_UNLOCK(pmap);
  }
  
  /*
   *      Routine:        pmap_remove_all
   *      Function:
   *              Removes this physical page from
   *              all physical maps in which it resides.
   *              Reflects back modify bits to the pager.
   *
   *      Notes:
   *              Original versions of this routine were very
   *              inefficient because they iteratively called
   *              pmap_remove (slow...)
   */
  
  void
  pmap_remove_all(vm_page_t m)
  {
          pv_entry_t pv;
          pt_entry_t *pte, tpte;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_remove_all: page %p is not managed", m));
          vm_page_lock_queues();
  
          if (m->md.pv_flags & PV_TABLE_REF)
                  vm_page_aflag_set(m, PGA_REFERENCED);
  
          while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                  PMAP_LOCK(pv->pv_pmap);
  
                  /*
                   * If it's last mapping writeback all caches from 
                   * the page being destroyed
                   */
                  if (m->md.pv_list_count == 1) 
                          mips_dcache_wbinv_range_index(pv->pv_va, PAGE_SIZE);
  
                  pv->pv_pmap->pm_stats.resident_count--;
  
                  pte = pmap_pte(pv->pv_pmap, pv->pv_va);
  
                  tpte = *pte;
                  if (is_kernel_pmap(pv->pv_pmap))
                          *pte = PTE_G;
                  else
                          *pte = 0;
  
                  if (pte_test(&tpte, PTE_W))
                          pv->pv_pmap->pm_stats.wired_count--;
  
                  /*
                   * Update the vm_page_t clean and reference bits.
                   */
                  if (pte_test(&tpte, PTE_D)) {
                          KASSERT(!pte_test(&tpte, PTE_RO),
                              ("%s: modified page not writable: va: %p, pte: %#jx",
                              __func__, (void *)pv->pv_va, (uintmax_t)tpte));
                          vm_page_dirty(m);
                  }
                  pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
  
                  TAILQ_REMOVE(&pv->pv_pmap->pm_pvlist, pv, pv_plist);
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                  m->md.pv_list_count--;
                  pmap_unuse_pt(pv->pv_pmap, pv->pv_va, pv->pv_ptem);
                  PMAP_UNLOCK(pv->pv_pmap);
                  free_pv_entry(pv);
          }
  
          vm_page_aflag_clear(m, PGA_WRITEABLE);
          m->md.pv_flags &= ~(PV_TABLE_REF | PV_TABLE_MOD);
          vm_page_unlock_queues();
  }
  
  /*
   *      Set the physical protection on the
   *      specified range of this map as requested.
   */
  void
  pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
  {
          pt_entry_t *pte;
          pd_entry_t *pde, *pdpe;
          vm_offset_t va_next;
  
          if (pmap == NULL)
                  return;
  
          if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
                  pmap_remove(pmap, sva, eva);
                  return;
          }
          if (prot & VM_PROT_WRITE)
                  return;
  
          vm_page_lock_queues();
          PMAP_LOCK(pmap);
          for (; sva < eva; sva = va_next) {
                  pt_entry_t pbits;
                  vm_page_t m;
                  vm_paddr_t pa;
  
                  pdpe = pmap_segmap(pmap, sva);
  #ifdef __mips_n64
                  if (*pdpe == 0) {
                          va_next = (sva + NBSEG) & ~SEGMASK;
                          if (va_next < sva)
                                  va_next = eva;
                          continue;
                  }
  #endif
                  va_next = (sva + NBPDR) & ~PDRMASK;
                  if (va_next < sva)
                          va_next = eva;
  
                  pde = pmap_pdpe_to_pde(pdpe, sva);
                  if (pde == NULL || *pde == NULL)
                          continue;
                  if (va_next > eva)
                          va_next = eva;
  
                  for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
                       sva += PAGE_SIZE) {
  
                          /* Skip invalid PTEs */
                          if (!pte_test(pte, PTE_V))
                                  continue;
                          pbits = *pte;
                          pa = TLBLO_PTE_TO_PA(pbits);
                          if (page_is_managed(pa) && pte_test(&pbits, PTE_D)) {
                                  m = PHYS_TO_VM_PAGE(pa);
                                  vm_page_dirty(m);
                                  m->md.pv_flags &= ~PV_TABLE_MOD;
                          }
                          pte_clear(&pbits, PTE_D);
                          pte_set(&pbits, PTE_RO);
                          
                          if (pbits != *pte) {
                                  *pte = pbits;
                                  pmap_update_page(pmap, sva, pbits);
                          }
                  }
          }
          vm_page_unlock_queues();
          PMAP_UNLOCK(pmap);
  }
  
  /*
   *      Insert the given physical page (p) at
   *      the specified virtual address (v) in the
   *      target physical map with the protection requested.
   *
   *      If specified, the page will be wired down, meaning
   *      that the related pte can not be reclaimed.
   *
   *      NB:  This is the only routine which MAY NOT lazy-evaluate
   *      or lose information.  That is, this routine must actually
   *      insert this page into the given map NOW.
   */
  void
  pmap_enter(pmap_t pmap, vm_offset_t va, vm_prot_t access, vm_page_t m,
      vm_prot_t prot, boolean_t wired)
  {
          vm_paddr_t pa, opa;
          pt_entry_t *pte;
          pt_entry_t origpte, newpte;
          pv_entry_t pv;
          vm_page_t mpte, om;
          pt_entry_t rw = 0;
  
          if (pmap == NULL)
                  return;
  
          va &= ~PAGE_MASK;
          KASSERT(va <= VM_MAX_KERNEL_ADDRESS, ("pmap_enter: toobig"));
          KASSERT((m->oflags & (VPO_UNMANAGED | VPO_BUSY)) != 0,
              ("pmap_enter: page %p is not busy", m));
  
          mpte = NULL;
  
          vm_page_lock_queues();
          PMAP_LOCK(pmap);
  
          /*
           * In the case that a page table page is not resident, we are
           * creating it here.
           */
          if (va < VM_MAXUSER_ADDRESS) {
                  mpte = pmap_allocpte(pmap, va, M_WAITOK);
          }
          pte = pmap_pte(pmap, va);
  
          /*
           * Page Directory table entry not valid, we need a new PT page
           */
          if (pte == NULL) {
                  panic("pmap_enter: invalid page directory, pdir=%p, va=%p",
                      (void *)pmap->pm_segtab, (void *)va);
          }
          pa = VM_PAGE_TO_PHYS(m);
          om = NULL;
          origpte = *pte;
          opa = TLBLO_PTE_TO_PA(origpte);
  
          /*
           * Mapping has not changed, must be protection or wiring change.
           */
          if (pte_test(&origpte, PTE_V) && 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 && !pte_test(&origpte, PTE_W))
                          pmap->pm_stats.wired_count++;
                  else if (!wired && pte_test(&origpte, PTE_W))
                          pmap->pm_stats.wired_count--;
  
                  KASSERT(!pte_test(&origpte, PTE_D | PTE_RO),
                      ("%s: modified page not writable: va: %p, pte: %#jx",
                      __func__, (void *)va, (uintmax_t)origpte));
  
                  /*
                   * Remove extra pte reference
                   */
                  if (mpte)
                          mpte->wire_count--;
  
                  if (page_is_managed(opa)) {
                          om = m;
                  }
                  goto validate;
          }
  
          pv = NULL;
  
          /*
           * Mapping has changed, invalidate old range and fall through to
           * handle validating new mapping.
           */
          if (opa) {
                  if (pte_test(&origpte, PTE_W))
                          pmap->pm_stats.wired_count--;
  
                  if (page_is_managed(opa)) {
                          om = PHYS_TO_VM_PAGE(opa);
                          pv = pmap_pvh_remove(&om->md, pmap, va);
                  }
                  if (mpte != NULL) {
                          mpte->wire_count--;
                          KASSERT(mpte->wire_count > 0,
                              ("pmap_enter: missing reference to page table page,"
                              " va: %p", (void *)va));
                  }
          } else
                  pmap->pm_stats.resident_count++;
  
          /*
           * Enter on the PV list if part of our managed memory. Note that we
           * raise IPL while manipulating pv_table since pmap_enter can be
           * called at interrupt time.
           */
          if ((m->oflags & VPO_UNMANAGED) == 0) {
                  KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva,
                      ("pmap_enter: managed mapping within the clean submap"));
                  if (pv == NULL)
                          pv = get_pv_entry(pmap);
                  pv->pv_va = va;
                  pv->pv_pmap = pmap;
                  pv->pv_ptem = mpte;
                  TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
                  TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
                  m->md.pv_list_count++;
          } else if (pv != NULL)
                  free_pv_entry(pv);
  
          /*
           * Increment counters
           */
          if (wired)
                  pmap->pm_stats.wired_count++;
  
  validate:
          if ((access & VM_PROT_WRITE) != 0)
                  m->md.pv_flags |= PV_TABLE_MOD | PV_TABLE_REF;
          rw = init_pte_prot(va, m, prot);
  
  #ifdef PMAP_DEBUG
          printf("pmap_enter:  va: %p -> pa: %p\n", (void *)va, (void *)pa);
  #endif
          /*
           * Now validate mapping with desired protection/wiring.
           */
          newpte = TLBLO_PA_TO_PFN(pa) | rw | PTE_V;
  
          if (is_cacheable_mem(pa))
                  newpte |= PTE_C_CACHE;
          else
                  newpte |= PTE_C_UNCACHED;
  
          if (wired)
                  newpte |= PTE_W;
  
          if (is_kernel_pmap(pmap))
                   newpte |= PTE_G;
  
          /*
           * if the mapping or permission bits are different, we need to
           * update the pte.
           */
          if (origpte != newpte) {
                  if (pte_test(&origpte, PTE_V)) {
                          *pte = newpte;
                          if (page_is_managed(opa) && (opa != pa)) {
                                  if (om->md.pv_flags & PV_TABLE_REF)
                                          vm_page_aflag_set(om, PGA_REFERENCED);
                                  om->md.pv_flags &=
                                      ~(PV_TABLE_REF | PV_TABLE_MOD);
                          }
                          if (pte_test(&origpte, PTE_D)) {
                                  KASSERT(!pte_test(&origpte, PTE_RO),
                                      ("pmap_enter: modified page not writable:"
                                      " va: %p, pte: %#jx", (void *)va, (uintmax_t)origpte));
                                  if (page_is_managed(opa))
                                          vm_page_dirty(om);
                          }
                          if (page_is_managed(opa) &&
                              TAILQ_EMPTY(&om->md.pv_list))
                                  vm_page_aflag_clear(om, PGA_WRITEABLE);
                  } else {
                          *pte = newpte;
                  }
          }
          pmap_update_page(pmap, va, newpte);
  
          /*
           * Sync I & D caches for executable pages.  Do this only if the
           * target pmap belongs to the current process.  Otherwise, an
           * unresolvable TLB miss may occur.
           */
          if (!is_kernel_pmap(pmap) && (pmap == &curproc->p_vmspace->vm_pmap) &&
              (prot & VM_PROT_EXECUTE)) {
                  mips_icache_sync_range(va, PAGE_SIZE);
                  mips_dcache_wbinv_range(va, PAGE_SIZE);
          }
          vm_page_unlock_queues();
          PMAP_UNLOCK(pmap);
  }
  
  /*
   * this code makes some *MAJOR* assumptions:
   * 1. Current pmap & pmap exists.
   * 2. Not wired.
   * 3. Read access.
   * 4. No page table pages.
   * but is *MUCH* faster than pmap_enter...
   */
  
  void
  pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
  {
  
          vm_page_lock_queues();
          PMAP_LOCK(pmap);
          (void)pmap_enter_quick_locked(pmap, va, m, prot, NULL);
          vm_page_unlock_queues();
          PMAP_UNLOCK(pmap);
  }
  
  static vm_page_t
  pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, vm_page_t m,
      vm_prot_t prot, vm_page_t mpte)
  {
          pt_entry_t *pte;
          vm_paddr_t pa;
  
          KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
              (m->oflags & VPO_UNMANAGED) != 0,
              ("pmap_enter_quick_locked: managed mapping within the clean submap"));
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          PMAP_LOCK_ASSERT(pmap, MA_OWNED);
  
          /*
           * In the case that a page table page is not resident, we are
           * creating it here.
           */
          if (va < VM_MAXUSER_ADDRESS) {
                  pd_entry_t *pde;
                  unsigned ptepindex;
  
                  /*
                   * Calculate pagetable page index
                   */
                  ptepindex = pmap_pde_pindex(va);
                  if (mpte && (mpte->pindex == ptepindex)) {
                          mpte->wire_count++;
                  } else {
                          /*
                           * Get the page directory entry
                           */
                          pde = pmap_pde(pmap, va);
  
                          /*
                           * If the page table page is mapped, we just
                           * increment the hold count, and activate it.
                           */
                          if (pde && *pde != 0) {
                                  if (pmap->pm_ptphint &&
                                      (pmap->pm_ptphint->pindex == ptepindex)) {
                                          mpte = pmap->pm_ptphint;
                                  } else {
                                          mpte = PHYS_TO_VM_PAGE(
                                                  MIPS_DIRECT_TO_PHYS(*pde));
                                          pmap->pm_ptphint = mpte;
                                  }
                                  mpte->wire_count++;
                          } else {
                                  mpte = _pmap_allocpte(pmap, ptepindex,
                                      M_NOWAIT);
                                  if (mpte == NULL)
                                          return (mpte);
                          }
                  }
          } else {
                  mpte = NULL;
          }
  
          pte = pmap_pte(pmap, va);
          if (pte_test(pte, PTE_V)) {
                  if (mpte != NULL) {
                          mpte->wire_count--;
                          mpte = NULL;
                  }
                  return (mpte);
          }
  
          /*
           * Enter on the PV list if part of our managed memory.
           */
          if ((m->oflags & VPO_UNMANAGED) == 0 &&
              !pmap_try_insert_pv_entry(pmap, mpte, va, m)) {
                  if (mpte != NULL) {
                          pmap_unwire_ptp(pmap, va, mpte);
                          mpte = NULL;
                  }
                  return (mpte);
          }
  
          /*
           * Increment counters
           */
          pmap->pm_stats.resident_count++;
  
          pa = VM_PAGE_TO_PHYS(m);
  
          /*
           * Now validate mapping with RO protection
           */
          *pte = TLBLO_PA_TO_PFN(pa) | PTE_V;
  
          if (is_cacheable_mem(pa))
                  *pte |= PTE_C_CACHE;
          else
                  *pte |= PTE_C_UNCACHED;
  
          if (is_kernel_pmap(pmap))
                  *pte |= PTE_G;
          else {
                  *pte |= PTE_RO;
                  /*
                   * Sync I & D caches.  Do this only if the target pmap
                   * belongs to the current process.  Otherwise, an
                   * unresolvable TLB miss may occur. */
                  if (pmap == &curproc->p_vmspace->vm_pmap) {
                          va &= ~PAGE_MASK;
                          mips_icache_sync_range(va, PAGE_SIZE);
                          mips_dcache_wbinv_range(va, PAGE_SIZE);
                  }
          }
          return (mpte);
  }
  
  /*
   * Make a temporary mapping for a physical address.  This is only intended
   * to be used for panic dumps.
   *
   * Use XKPHYS for 64 bit, and KSEG0 where possible for 32 bit.
   */
  void *
  pmap_kenter_temporary(vm_paddr_t pa, int i)
  {
          vm_offset_t va;
  
          if (i != 0)
                  printf("%s: ERROR!!! More than one page of virtual address mapping not supported\n",
                      __func__);
  
          if (MIPS_DIRECT_MAPPABLE(pa)) {
                  va = MIPS_PHYS_TO_DIRECT(pa);
          } else {
  #ifndef __mips_n64    /* XXX : to be converted to new style */
                  int cpu;
                  register_t intr;
                  struct local_sysmaps *sysm;
                  pt_entry_t *pte, npte;
  
                  /* If this is used other than for dumps, we may need to leave
                   * interrupts disasbled on return. If crash dumps don't work when
                   * we get to this point, we might want to consider this (leaving things
                   * disabled as a starting point ;-)
                   */
                  intr = intr_disable();
                  cpu = PCPU_GET(cpuid);
                  sysm = &sysmap_lmem[cpu];
                  /* Since this is for the debugger, no locks or any other fun */
                  npte = TLBLO_PA_TO_PFN(pa) | PTE_D | PTE_V | PTE_G | PTE_W | PTE_C_CACHE;
                  pte = pmap_pte(kernel_pmap, sysm->base);
                  *pte = npte;
                  sysm->valid1 = 1;
                  pmap_update_page(kernel_pmap, sysm->base, npte);
                  va = sysm->base;
                  intr_restore(intr);
  #endif
          }
          return ((void *)va);
  }
  
  void
  pmap_kenter_temporary_free(vm_paddr_t pa)
  {
  #ifndef __mips_n64    /* XXX : to be converted to new style */
          int cpu;
          register_t intr;
          struct local_sysmaps *sysm;
  #endif
  
          if (MIPS_DIRECT_MAPPABLE(pa)) {
                  /* nothing to do for this case */
                  return;
          }
  #ifndef __mips_n64    /* XXX : to be converted to new style */
          cpu = PCPU_GET(cpuid);
          sysm = &sysmap_lmem[cpu];
          if (sysm->valid1) {
                  pt_entry_t *pte;
  
                  intr = intr_disable();
                  pte = pmap_pte(kernel_pmap, sysm->base);
                  *pte = PTE_G;
                  pmap_invalidate_page(kernel_pmap, sysm->base);
                  intr_restore(intr);
                  sysm->valid1 = 0;
          }
  #endif
  }
  
  /*
   * Moved the code to Machine Independent
   *       vm_map_pmap_enter()
   */
  
  /*
   * Maps a sequence of resident pages belonging to the same object.
   * The sequence begins with the given page m_start.  This page is
   * mapped at the given virtual address start.  Each subsequent page is
   * mapped at a virtual address that is offset from start by the same
   * amount as the page is offset from m_start within the object.  The
   * last page in the sequence is the page with the largest offset from
   * m_start that can be mapped at a virtual address less than the given
   * virtual address end.  Not every virtual page between start and end
   * is mapped; only those for which a resident page exists with the
   * corresponding offset from m_start are mapped.
   */
  void
  pmap_enter_object(pmap_t pmap, vm_offset_t start, vm_offset_t end,
      vm_page_t m_start, vm_prot_t prot)
  {
          vm_page_t m, mpte;
          vm_pindex_t diff, psize;
  
          VM_OBJECT_LOCK_ASSERT(m_start->object, MA_OWNED);
          psize = atop(end - start);
          mpte = NULL;
          m = m_start;
          vm_page_lock_queues();
          PMAP_LOCK(pmap);
          while (m != NULL && (diff = m->pindex - m_start->pindex) < psize) {
                  mpte = pmap_enter_quick_locked(pmap, start + ptoa(diff), m,
                      prot, mpte);
                  m = TAILQ_NEXT(m, listq);
          }
          vm_page_unlock_queues();
          PMAP_UNLOCK(pmap);
  }
  
  /*
   * pmap_object_init_pt preloads the ptes for a given object
   * into the specified pmap.  This eliminates the blast of soft
   * faults on process startup and immediately after an mmap.
   */
  void
  pmap_object_init_pt(pmap_t pmap, vm_offset_t addr,
      vm_object_t object, vm_pindex_t pindex, vm_size_t size)
  {
          VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
          KASSERT(object->type == OBJT_DEVICE || object->type == OBJT_SG,
              ("pmap_object_init_pt: non-device object"));
  }
  
  /*
   *      Routine:        pmap_change_wiring
   *      Function:       Change the wiring attribute for a map/virtual-address
   *                      pair.
   *      In/out conditions:
   *                      The mapping must already exist in the pmap.
   */
  void
  pmap_change_wiring(pmap_t pmap, vm_offset_t va, boolean_t wired)
  {
          pt_entry_t *pte;
  
          if (pmap == NULL)
                  return;
  
          PMAP_LOCK(pmap);
          pte = pmap_pte(pmap, va);
  
          if (wired && !pte_test(pte, PTE_W))
                  pmap->pm_stats.wired_count++;
          else if (!wired && pte_test(pte, PTE_W))
                  pmap->pm_stats.wired_count--;
  
          /*
           * Wiring is not a hardware characteristic so there is no need to
           * invalidate TLB.
           */
          if (wired)
                  pte_set(pte, PTE_W);
          else
                  pte_clear(pte, PTE_W);
          PMAP_UNLOCK(pmap);
  }
  
  /*
   *      Copy the range specified by src_addr/len
   *      from the source map to the range dst_addr/len
   *      in the destination map.
   *
   *      This routine is only advisory and need not do anything.
   */
  
  void
  pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr,
      vm_size_t len, vm_offset_t src_addr)
  {
  }
  
  /*
   *      pmap_zero_page zeros the specified hardware page by mapping
   *      the page into KVM and using bzero to clear its contents.
   *
   *      Use XKPHYS for 64 bit, and KSEG0 where possible for 32 bit.
   */
  void
  pmap_zero_page(vm_page_t m)
  {
          vm_offset_t va;
          vm_paddr_t phys = VM_PAGE_TO_PHYS(m);
  
          if (MIPS_DIRECT_MAPPABLE(phys)) {
                  va = MIPS_PHYS_TO_DIRECT(phys);
                  bzero((caddr_t)va, PAGE_SIZE);
                  mips_dcache_wbinv_range(va, PAGE_SIZE);
          } else {
                  va = pmap_lmem_map1(phys);
                  bzero((caddr_t)va, PAGE_SIZE);
                  mips_dcache_wbinv_range(va, PAGE_SIZE);
                  pmap_lmem_unmap();
          }
  }
  
  /*
   *      pmap_zero_page_area zeros the specified hardware page by mapping
   *      the page into KVM and using bzero to clear its contents.
   *
   *      off and size may not cover an area beyond a single hardware page.
   */
  void
  pmap_zero_page_area(vm_page_t m, int off, int size)
  {
          vm_offset_t va;
          vm_paddr_t phys = VM_PAGE_TO_PHYS(m);
  
          if (MIPS_DIRECT_MAPPABLE(phys)) {
                  va = MIPS_PHYS_TO_DIRECT(phys);
                  bzero((char *)(caddr_t)va + off, size);
                  mips_dcache_wbinv_range(va + off, size);
          } else {
                  va = pmap_lmem_map1(phys);
                  bzero((char *)va + off, size);
                  mips_dcache_wbinv_range(va + off, size);
                  pmap_lmem_unmap();
          }
  }
  
  void
  pmap_zero_page_idle(vm_page_t m)
  {
          vm_offset_t va;
          vm_paddr_t phys = VM_PAGE_TO_PHYS(m);
  
          if (MIPS_DIRECT_MAPPABLE(phys)) {
                  va = MIPS_PHYS_TO_DIRECT(phys);
                  bzero((caddr_t)va, PAGE_SIZE);
                  mips_dcache_wbinv_range(va, PAGE_SIZE);
          } else {
                  va = pmap_lmem_map1(phys);
                  bzero((caddr_t)va, PAGE_SIZE);
                  mips_dcache_wbinv_range(va, PAGE_SIZE);
                  pmap_lmem_unmap();
          }
  }
  
  /*
   *      pmap_copy_page copies the specified (machine independent)
   *      page by mapping the page into virtual memory and using
   *      bcopy to copy the page, one machine dependent page at a
   *      time.
   *
   *      Use XKPHYS for 64 bit, and KSEG0 where possible for 32 bit.
   */
  void
  pmap_copy_page(vm_page_t src, vm_page_t dst)
  {
          vm_offset_t va_src, va_dst;
          vm_paddr_t phys_src = VM_PAGE_TO_PHYS(src);
          vm_paddr_t phys_dst = VM_PAGE_TO_PHYS(dst);
  
          if (MIPS_DIRECT_MAPPABLE(phys_src) && MIPS_DIRECT_MAPPABLE(phys_dst)) {
                  /* easy case, all can be accessed via KSEG0 */
                  /*
                   * Flush all caches for VA that are mapped to this page
                   * to make sure that data in SDRAM is up to date
                   */
                  pmap_flush_pvcache(src);
                  mips_dcache_wbinv_range_index(
                      MIPS_PHYS_TO_DIRECT(phys_dst), PAGE_SIZE);
                  va_src = MIPS_PHYS_TO_DIRECT(phys_src);
                  va_dst = MIPS_PHYS_TO_DIRECT(phys_dst);
                  bcopy((caddr_t)va_src, (caddr_t)va_dst, PAGE_SIZE);
                  mips_dcache_wbinv_range(va_dst, PAGE_SIZE);
          } else {
                  va_src = pmap_lmem_map2(phys_src, phys_dst);
                  va_dst = va_src + PAGE_SIZE;
                  bcopy((void *)va_src, (void *)va_dst, PAGE_SIZE);
                  mips_dcache_wbinv_range(va_dst, PAGE_SIZE);
                  pmap_lmem_unmap();
          }
  }
  
  int unmapped_buf_allowed;
  
  void
  pmap_copy_pages(vm_page_t ma[], vm_offset_t a_offset, vm_page_t mb[],
      vm_offset_t b_offset, int xfersize)
  {
          char *a_cp, *b_cp;
          vm_page_t a_m, b_m;
          vm_offset_t a_pg_offset, b_pg_offset;
          vm_paddr_t a_phys, b_phys;
          int cnt;
  
          while (xfersize > 0) {
                  a_pg_offset = a_offset & PAGE_MASK;
                  cnt = min(xfersize, PAGE_SIZE - a_pg_offset);
                  a_m = ma[a_offset >> PAGE_SHIFT];
                  a_phys = VM_PAGE_TO_PHYS(a_m);
                  b_pg_offset = b_offset & PAGE_MASK;
                  cnt = min(cnt, PAGE_SIZE - b_pg_offset);
                  b_m = mb[b_offset >> PAGE_SHIFT];
                  b_phys = VM_PAGE_TO_PHYS(b_m);
                  if (MIPS_DIRECT_MAPPABLE(a_phys) &&
                      MIPS_DIRECT_MAPPABLE(b_phys)) {
                          pmap_flush_pvcache(a_m);
                          mips_dcache_wbinv_range_index(
                              MIPS_PHYS_TO_DIRECT(b_phys), PAGE_SIZE);
                          a_cp = (char *)MIPS_PHYS_TO_DIRECT(a_phys) +
                              a_pg_offset;
                          b_cp = (char *)MIPS_PHYS_TO_DIRECT(b_phys) +
                              b_pg_offset;
                          bcopy(a_cp, b_cp, cnt);
                          mips_dcache_wbinv_range((vm_offset_t)b_cp, cnt);
                  } else {
                          a_cp = (char *)pmap_lmem_map2(a_phys, b_phys);
                          b_cp = (char *)a_cp + PAGE_SIZE;
                          a_cp += a_pg_offset;
                          b_cp += b_pg_offset;
                          bcopy(a_cp, b_cp, cnt);
                          mips_dcache_wbinv_range((vm_offset_t)b_cp, cnt);
                          pmap_lmem_unmap();
                  }
                  a_offset += cnt;
                  b_offset += cnt;
                  xfersize -= cnt;
          }
  }
  
  /*
   * Returns true if the pmap's pv is one of the first
   * 16 pvs linked to from this page.  This count may
   * be changed upwards or downwards in the future; it
   * is only necessary that true be returned for a small
   * subset of pmaps for proper page aging.
   */
  boolean_t
  pmap_page_exists_quick(pmap_t pmap, vm_page_t m)
  {
          pv_entry_t pv;
          int loops = 0;
          boolean_t rv;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_page_exists_quick: page %p is not managed", m));
          rv = FALSE;
          vm_page_lock_queues();
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  if (pv->pv_pmap == pmap) {
                          rv = TRUE;
                          break;
                  }
                  loops++;
                  if (loops >= 16)
                          break;
          }
          vm_page_unlock_queues();
          return (rv);
  }
  
  /*
   * Remove all pages from specified address space
   * this aids process exit speeds.  Also, this code
   * is special cased for current process only, but
   * can have the more generic (and slightly slower)
   * mode enabled.  This is much faster than pmap_remove
   * in the case of running down an entire address space.
   */
  void
  pmap_remove_pages(pmap_t pmap)
  {
          pt_entry_t *pte, tpte;
          pv_entry_t pv, npv;
          vm_page_t m;
  
          if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) {
                  printf("warning: pmap_remove_pages called with non-current pmap\n");
                  return;
          }
          vm_page_lock_queues();
          PMAP_LOCK(pmap);
          for (pv = TAILQ_FIRST(&pmap->pm_pvlist); pv != NULL; pv = npv) {
  
                  pte = pmap_pte(pv->pv_pmap, pv->pv_va);
                  if (!pte_test(pte, PTE_V))
                          panic("pmap_remove_pages: page on pm_pvlist has no pte");
                  tpte = *pte;
  
  /*
   * We cannot remove wired pages from a process' mapping at this time
   */
                  if (pte_test(&tpte, PTE_W)) {
                          npv = TAILQ_NEXT(pv, pv_plist);
                          continue;
                  }
                  *pte = is_kernel_pmap(pmap) ? PTE_G : 0;
  
                  m = PHYS_TO_VM_PAGE(TLBLO_PTE_TO_PA(tpte));
                  KASSERT(m != NULL,
                      ("pmap_remove_pages: bad tpte %#jx", (uintmax_t)tpte));
  
                  pv->pv_pmap->pm_stats.resident_count--;
  
                  /*
                   * Update the vm_page_t clean and reference bits.
                   */
                  if (pte_test(&tpte, PTE_D)) {
                          vm_page_dirty(m);
                  }
                  npv = TAILQ_NEXT(pv, pv_plist);
                  TAILQ_REMOVE(&pv->pv_pmap->pm_pvlist, pv, pv_plist);
  
                  m->md.pv_list_count--;
                  TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                  if (TAILQ_FIRST(&m->md.pv_list) == NULL) {
                          vm_page_aflag_clear(m, PGA_WRITEABLE);
                  }
                  pmap_unuse_pt(pv->pv_pmap, pv->pv_va, pv->pv_ptem);
                  free_pv_entry(pv);
          }
          pmap_invalidate_all(pmap);
          PMAP_UNLOCK(pmap);
          vm_page_unlock_queues();
  }
  
  /*
   * pmap_testbit tests bits in pte's
   * note that the testbit/changebit routines are inline,
   * and a lot of things compile-time evaluate.
   */
  static boolean_t
  pmap_testbit(vm_page_t m, int bit)
  {
          pv_entry_t pv;
          pt_entry_t *pte;
          boolean_t rv = FALSE;
  
          if (m->oflags & VPO_UNMANAGED)
                  return (rv);
  
          if (TAILQ_FIRST(&m->md.pv_list) == NULL)
                  return (rv);
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  PMAP_LOCK(pv->pv_pmap);
                  pte = pmap_pte(pv->pv_pmap, pv->pv_va);
                  rv = pte_test(pte, bit);
                  PMAP_UNLOCK(pv->pv_pmap);
                  if (rv)
                          break;
          }
          return (rv);
  }
  
  /*
   * this routine is used to clear dirty bits in ptes
   */
  static __inline void
  pmap_changebit(vm_page_t m, int bit, boolean_t setem)
  {
          pv_entry_t pv;
          pt_entry_t *pte;
  
          if (m->oflags & VPO_UNMANAGED)
                  return;
  
          mtx_assert(&vm_page_queue_mtx, MA_OWNED);
          /*
           * Loop over all current mappings setting/clearing as appropos If
           * setting RO do we need to clear the VAC?
           */
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  PMAP_LOCK(pv->pv_pmap);
                  pte = pmap_pte(pv->pv_pmap, pv->pv_va);
                  if (setem) {
                          *pte |= bit;
                          pmap_update_page(pv->pv_pmap, pv->pv_va, *pte);
                  } else {
                          pt_entry_t pbits = *pte;
  
                          if (pbits & bit) {
                                  if (bit == PTE_D) {
                                          if (pbits & PTE_D)
                                                  vm_page_dirty(m);
                                          *pte = (pbits & ~PTE_D) | PTE_RO;
                                  } else {
                                          *pte = pbits & ~bit;
                                  }
                                  pmap_update_page(pv->pv_pmap, pv->pv_va, *pte);
                          }
                  }
                  PMAP_UNLOCK(pv->pv_pmap);
          }
          if (!setem && bit == PTE_D)
                  vm_page_aflag_clear(m, PGA_WRITEABLE);
  }
  
  /*
   *      pmap_page_wired_mappings:
   *
   *      Return the number of managed mappings to the given physical page
   *      that are wired.
   */
  int
  pmap_page_wired_mappings(vm_page_t m)
  {
          pv_entry_t pv;
          pmap_t pmap;
          pt_entry_t *pte;
          int count;
  
          count = 0;
          if ((m->oflags & VPO_UNMANAGED) != 0)
                  return (count);
          vm_page_lock_queues();
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                  pmap = pv->pv_pmap;
                  PMAP_LOCK(pmap);
                  pte = pmap_pte(pmap, pv->pv_va);
                  if (pte_test(pte, PTE_W))
                          count++;
                  PMAP_UNLOCK(pmap);
          }
          vm_page_unlock_queues();
          return (count);
  }
  
  /*
   * Clear the write and modified bits in each of the given page's mappings.
   */
  void
  pmap_remove_write(vm_page_t m)
  {
          pv_entry_t pv, npv;
          vm_offset_t va;
          pt_entry_t *pte;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_remove_write: page %p is not managed", m));
  
          /*
           * If the page is not VPO_BUSY, then PGA_WRITEABLE cannot be set by
           * another thread while the object is locked.  Thus, if PGA_WRITEABLE
           * is clear, no page table entries need updating.
           */
          VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
          if ((m->oflags & VPO_BUSY) == 0 &&
              (m->aflags & PGA_WRITEABLE) == 0)
                  return;
  
          /*
           * Loop over all current mappings setting/clearing as appropos.
           */
          vm_page_lock_queues();
          for (pv = TAILQ_FIRST(&m->md.pv_list); pv; pv = npv) {
                  npv = TAILQ_NEXT(pv, pv_plist);
                  pte = pmap_pte(pv->pv_pmap, pv->pv_va);
                  if (pte == NULL || !pte_test(pte, PTE_V))
                          panic("page on pm_pvlist has no pte");
  
                  va = pv->pv_va;
                  pmap_protect(pv->pv_pmap, va, va + PAGE_SIZE,
                      VM_PROT_READ | VM_PROT_EXECUTE);
          }
          vm_page_aflag_clear(m, PGA_WRITEABLE);
          vm_page_unlock_queues();
  }
  
  /*
   *      pmap_ts_referenced:
   *
   *      Return the count of reference bits for a page, clearing all of them.
   */
  int
  pmap_ts_referenced(vm_page_t m)
  {
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_ts_referenced: page %p is not managed", m));
          if (m->md.pv_flags & PV_TABLE_REF) {
                  vm_page_lock_queues();
                  m->md.pv_flags &= ~PV_TABLE_REF;
                  vm_page_unlock_queues();
                  return (1);
          }
          return (0);
  }
  
  /*
   *      pmap_is_modified:
   *
   *      Return whether or not the specified physical page was modified
   *      in any physical maps.
   */
  boolean_t
  pmap_is_modified(vm_page_t m)
  {
          boolean_t rv;
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_is_modified: page %p is not managed", m));
  
          /*
           * If the page is not VPO_BUSY, then PGA_WRITEABLE cannot be
           * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
           * is clear, no PTEs can have PTE_D set.
           */
          VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
          if ((m->oflags & VPO_BUSY) == 0 &&
              (m->aflags & PGA_WRITEABLE) == 0)
                  return (FALSE);
          vm_page_lock_queues();
          if (m->md.pv_flags & PV_TABLE_MOD)
                  rv = TRUE;
          else
                  rv = pmap_testbit(m, PTE_D);
          vm_page_unlock_queues();
          return (rv);
  }
  
  /* N/C */
  
  /*
   *      pmap_is_prefaultable:
   *
   *      Return whether or not the specified virtual address is elgible
   *      for prefault.
   */
  boolean_t
  pmap_is_prefaultable(pmap_t pmap, vm_offset_t addr)
  {
          pd_entry_t *pde;
          pt_entry_t *pte;
          boolean_t rv;
  
          rv = FALSE;
          PMAP_LOCK(pmap);
          pde = pmap_pde(pmap, addr);
          if (pde != NULL && *pde != 0) {
                  pte = pmap_pde_to_pte(pde, addr);
                  rv = (*pte == 0);
          }
          PMAP_UNLOCK(pmap);
          return (rv);
  }
  
  /*
   *      Clear the modify bits on the specified physical page.
   */
  void
  pmap_clear_modify(vm_page_t m)
  {
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_clear_modify: page %p is not managed", m));
          VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
          KASSERT((m->oflags & VPO_BUSY) == 0,
              ("pmap_clear_modify: page %p is busy", m));
  
          /*
           * If the page is not PGA_WRITEABLE, then no PTEs can have PTE_D set.
           * If the object containing the page is locked and the page is not
           * VPO_BUSY, then PGA_WRITEABLE cannot be concurrently set.
           */
          if ((m->aflags & PGA_WRITEABLE) == 0)
                  return;
          vm_page_lock_queues();
          if (m->md.pv_flags & PV_TABLE_MOD) {
                  pmap_changebit(m, PTE_D, FALSE);
                  m->md.pv_flags &= ~PV_TABLE_MOD;
          }
          vm_page_unlock_queues();
  }
  
  /*
   *      pmap_is_referenced:
   *
   *      Return whether or not the specified physical page was referenced
   *      in any physical maps.
   */
  boolean_t
  pmap_is_referenced(vm_page_t m)
  {
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_is_referenced: page %p is not managed", m));
          return ((m->md.pv_flags & PV_TABLE_REF) != 0);
  }
  
  /*
   *      pmap_clear_reference:
   *
   *      Clear the reference bit on the specified physical page.
   */
  void
  pmap_clear_reference(vm_page_t m)
  {
  
          KASSERT((m->oflags & VPO_UNMANAGED) == 0,
              ("pmap_clear_reference: page %p is not managed", m));
          vm_page_lock_queues();
          if (m->md.pv_flags & PV_TABLE_REF) {
                  m->md.pv_flags &= ~PV_TABLE_REF;
          }
          vm_page_unlock_queues();
  }
  
  /*
   * Miscellaneous support routines follow
   */
  
  /*
   * Map a set of physical memory pages into the kernel virtual
   * address space. Return a pointer to where it is mapped. This
   * routine is intended to be used for mapping device memory,
   * NOT real memory.
   */
  
  /*
   * 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.
   *
   * Use XKPHYS uncached for 64 bit, and KSEG1 where possible for 32 bit.
   */
  void *
  pmap_mapdev(vm_paddr_t pa, vm_size_t size)
  {
          vm_offset_t va, tmpva, offset;
  
          /* 
           * KSEG1 maps only first 512M of phys address space. For 
           * pa > 0x20000000 we should make proper mapping * using pmap_kenter.
           */
          if (MIPS_DIRECT_MAPPABLE(pa + size - 1))
                  return ((void *)MIPS_PHYS_TO_DIRECT_UNCACHED(pa));
          else {
                  offset = pa & PAGE_MASK;
                  size = roundup(size + offset, PAGE_SIZE);
          
                  va = kmem_alloc_nofault(kernel_map, size);
                  if (!va)
                          panic("pmap_mapdev: Couldn't alloc kernel virtual memory");
                  pa = trunc_page(pa);
                  for (tmpva = va; size > 0;) {
                          pmap_kenter_attr(tmpva, pa, PTE_C_UNCACHED);
                          size -= PAGE_SIZE;
                          tmpva += PAGE_SIZE;
                          pa += PAGE_SIZE;
                  }
          }
  
          return ((void *)(va + offset));
  }
  
  void
  pmap_unmapdev(vm_offset_t va, vm_size_t size)
  {
  #ifndef __mips_n64
          vm_offset_t base, offset;
  
          /* If the address is within KSEG1 then there is nothing to do */
          if (va >= MIPS_KSEG1_START && va <= MIPS_KSEG1_END)
                  return;
  
          base = trunc_page(va);
          offset = va & PAGE_MASK;
          size = roundup(size + offset, PAGE_SIZE);
          kmem_free(kernel_map, base, size);
  #endif
  }
  
  /*
   * perform the pmap work for mincore
   */
  int
  pmap_mincore(pmap_t pmap, vm_offset_t addr, vm_paddr_t *locked_pa)
  {
          pt_entry_t *ptep, pte;
          vm_paddr_t pa;
          vm_page_t m;
          int val;
          boolean_t managed;
  
          PMAP_LOCK(pmap);
  retry:
          ptep = pmap_pte(pmap, addr);
          pte = (ptep != NULL) ? *ptep : 0;
          if (!pte_test(&pte, PTE_V)) {
                  val = 0;
                  goto out;
          }
          val = MINCORE_INCORE;
          if (pte_test(&pte, PTE_D))
                  val |= MINCORE_MODIFIED | MINCORE_MODIFIED_OTHER;
          pa = TLBLO_PTE_TO_PA(pte);
          managed = page_is_managed(pa);
          if (managed) {
                  /*
                   * This may falsely report the given address as
                   * MINCORE_REFERENCED.  Unfortunately, due to the lack of
                   * per-PTE reference information, it is impossible to
                   * determine if the address is MINCORE_REFERENCED.  
                   */
                  m = PHYS_TO_VM_PAGE(pa);
                  if ((m->aflags & PGA_REFERENCED) != 0)
                          val |= MINCORE_REFERENCED | MINCORE_REFERENCED_OTHER;
          }
          if ((val & (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER)) !=
              (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER) && managed) {
                  /* Ensure that "PHYS_TO_VM_PAGE(pa)->object" doesn't change. */
                  if (vm_page_pa_tryrelock(pmap, pa, locked_pa))
                          goto retry;
          } else
  out:
                  PA_UNLOCK_COND(*locked_pa);
          PMAP_UNLOCK(pmap);
          return (val);
  }
  
  void
  pmap_activate(struct thread *td)
  {
          pmap_t pmap, oldpmap;
          struct proc *p = td->td_proc;
          u_int cpuid;
  
          critical_enter();
  
          pmap = vmspace_pmap(p->p_vmspace);
          oldpmap = PCPU_GET(curpmap);
          cpuid = PCPU_GET(cpuid);
  
          if (oldpmap)
                  CPU_CLR_ATOMIC(cpuid, &oldpmap->pm_active);
          CPU_SET_ATOMIC(cpuid, &pmap->pm_active);
          pmap_asid_alloc(pmap);
          if (td == curthread) {
                  PCPU_SET(segbase, pmap->pm_segtab);
                  mips_wr_entryhi(pmap->pm_asid[cpuid].asid);
          }
  
          PCPU_SET(curpmap, pmap);
          critical_exit();
  }
  
  void
  pmap_sync_icache(pmap_t pm, vm_offset_t va, vm_size_t sz)
  {
  }
  
  /*
   *      Increase the starting virtual address of the given mapping if a
   *      different alignment might result in more superpage mappings.
   */
  void
  pmap_align_superpage(vm_object_t object, vm_ooffset_t offset,
      vm_offset_t *addr, vm_size_t size)
  {
          vm_offset_t superpage_offset;
  
          if (size < NBSEG)
                  return;
          if (object != NULL && (object->flags & OBJ_COLORED) != 0)
                  offset += ptoa(object->pg_color);
          superpage_offset = offset & SEGMASK;
          if (size - ((NBSEG - superpage_offset) & SEGMASK) < NBSEG ||
              (*addr & SEGMASK) == superpage_offset)
                  return;
          if ((*addr & SEGMASK) < superpage_offset)
                  *addr = (*addr & ~SEGMASK) + superpage_offset;
          else
                  *addr = ((*addr + SEGMASK) & ~SEGMASK) + superpage_offset;
  }
  
  /*
   *      Increase the starting virtual address of the given mapping so
   *      that it is aligned to not be the second page in a TLB entry.
   *      This routine assumes that the length is appropriately-sized so
   *      that the allocation does not share a TLB entry at all if required.
   */
  void
  pmap_align_tlb(vm_offset_t *addr)
  {
          if ((*addr & PAGE_SIZE) == 0)
                  return;
          *addr += PAGE_SIZE;
          return;
  }
  
  #ifdef DDB
  DB_SHOW_COMMAND(ptable, ddb_pid_dump)
  {
          pmap_t pmap;
          struct thread *td = NULL;
          struct proc *p;
          int i, j, k;
          vm_paddr_t pa;
          vm_offset_t va;
  
          if (have_addr) {
                  td = db_lookup_thread(addr, TRUE);
                  if (td == NULL) {
                          db_printf("Invalid pid or tid");
                          return;
                  }
                  p = td->td_proc;
                  if (p->p_vmspace == NULL) {
                          db_printf("No vmspace for process");
                          return;
                  }
                          pmap = vmspace_pmap(p->p_vmspace);
          } else
                  pmap = kernel_pmap;
  
          db_printf("pmap:%p segtab:%p asid:%x generation:%x\n",
              pmap, pmap->pm_segtab, pmap->pm_asid[0].asid,
              pmap->pm_asid[0].gen);
          for (i = 0; i < NPDEPG; i++) {
                  pd_entry_t *pdpe;
                  pt_entry_t *pde;
                  pt_entry_t pte;
  
                  pdpe = (pd_entry_t *)pmap->pm_segtab[i];
                  if (pdpe == NULL)
                          continue;
                  db_printf("[%4d] %p\n", i, pdpe);
  #ifdef __mips_n64
                  for (j = 0; j < NPDEPG; j++) {
                          pde = (pt_entry_t *)pdpe[j];
                          if (pde == NULL)
                                  continue;
                          db_printf("\t[%4d] %p\n", j, pde);
  #else
                  {
                          j = 0;
                          pde =  (pt_entry_t *)pdpe;
  #endif
                          for (k = 0; k < NPTEPG; k++) {
                                  pte = pde[k];
                                  if (pte == 0 || !pte_test(&pte, PTE_V))
                                          continue;
                                  pa = TLBLO_PTE_TO_PA(pte);
                                  va = ((u_long)i << SEGSHIFT) | (j << PDRSHIFT) | (k << PAGE_SHIFT);
                                  db_printf("\t\t[%04d] va: %p pte: %8jx pa:%jx\n",
                                         k, (void *)va, (uintmax_t)pte, (uintmax_t)pa);
                          }
                  }
          }
  }
  #endif
  
  #if defined(DEBUG)
  
  static void pads(pmap_t pm);
  void pmap_pvdump(vm_offset_t pa);
  
  /* print address space of pmap*/
  static void
  pads(pmap_t pm)
  {
          unsigned va, i, j;
          pt_entry_t *ptep;
  
          if (pm == kernel_pmap)
                  return;
          for (i = 0; i < NPTEPG; i++)
                  if (pm->pm_segtab[i])
                          for (j = 0; j < NPTEPG; j++) {
                                  va = (i << SEGSHIFT) + (j << PAGE_SHIFT);
                                  if (pm == kernel_pmap && va < KERNBASE)
                                          continue;
                                  if (pm != kernel_pmap &&
                                      va >= VM_MAXUSER_ADDRESS)
                                          continue;
                                  ptep = pmap_pte(pm, va);
                                  if (pte_test(ptep, PTE_V))
                                          printf("%x:%x ", va, *(int *)ptep);
                          }
  
  }
  
  void
  pmap_pvdump(vm_offset_t pa)
  {
          register pv_entry_t pv;
          vm_page_t m;
  
          printf("pa %x", pa);
          m = PHYS_TO_VM_PAGE(pa);
          for (pv = TAILQ_FIRST(&m->md.pv_list); pv;
              pv = TAILQ_NEXT(pv, pv_list)) {
                  printf(" -> pmap %p, va %x", (void *)pv->pv_pmap, pv->pv_va);
                  pads(pv->pv_pmap);
          }
          printf(" ");
  }
  
  /* N/C */
  #endif
  
  
  /*
   * Allocate TLB address space tag (called ASID or TLBPID) and return it.
   * It takes almost as much or more time to search the TLB for a
   * specific ASID and flush those entries as it does to flush the entire TLB.
   * Therefore, when we allocate a new ASID, we just take the next number. When
   * we run out of numbers, we flush the TLB, increment the generation count
   * and start over. ASID zero is reserved for kernel use.
   */
  static void
  pmap_asid_alloc(pmap)
          pmap_t pmap;
  {
          if (pmap->pm_asid[PCPU_GET(cpuid)].asid != PMAP_ASID_RESERVED &&
              pmap->pm_asid[PCPU_GET(cpuid)].gen == PCPU_GET(asid_generation));
          else {
                  if (PCPU_GET(next_asid) == pmap_max_asid) {
                          tlb_invalidate_all_user(NULL);
                          PCPU_SET(asid_generation,
                              (PCPU_GET(asid_generation) + 1) & ASIDGEN_MASK);
                          if (PCPU_GET(asid_generation) == 0) {
                                  PCPU_SET(asid_generation, 1);
                          }
                          PCPU_SET(next_asid, 1); /* 0 means invalid */
                  }
                  pmap->pm_asid[PCPU_GET(cpuid)].asid = PCPU_GET(next_asid);
                  pmap->pm_asid[PCPU_GET(cpuid)].gen = PCPU_GET(asid_generation);
                  PCPU_SET(next_asid, PCPU_GET(next_asid) + 1);
          }
  }
  
  int
  page_is_managed(vm_paddr_t pa)
  {
          vm_offset_t pgnum = atop(pa);
  
          if (pgnum >= first_page) {
                  vm_page_t m;
  
                  m = PHYS_TO_VM_PAGE(pa);
                  if (m == NULL)
                          return (0);
                  if ((m->oflags & VPO_UNMANAGED) == 0)
                          return (1);
          }
          return (0);
  }
  
  static pt_entry_t
  init_pte_prot(vm_offset_t va, vm_page_t m, vm_prot_t prot)
  {
          pt_entry_t rw;
  
          if (!(prot & VM_PROT_WRITE))
                  rw =  PTE_V | PTE_RO | PTE_C_CACHE;
          else if ((m->oflags & VPO_UNMANAGED) == 0) {
                  if ((m->md.pv_flags & PV_TABLE_MOD) != 0)
                          rw =  PTE_V | PTE_D | PTE_C_CACHE;
                  else
                          rw = PTE_V | PTE_C_CACHE;
                  vm_page_aflag_set(m, PGA_WRITEABLE);
          } else
                  /* Needn't emulate a modified bit for unmanaged pages. */
                  rw =  PTE_V | PTE_D | PTE_C_CACHE;
          return (rw);
  }
  
  /*
   * pmap_emulate_modified : do dirty bit emulation
   *
   * On SMP, update just the local TLB, other CPUs will update their
   * TLBs from PTE lazily, if they get the exception.
   * Returns 0 in case of sucess, 1 if the page is read only and we
   * need to fault.
   */
  int
  pmap_emulate_modified(pmap_t pmap, vm_offset_t va)
  {
          vm_page_t m;
          pt_entry_t *pte;
          vm_paddr_t pa;
  
          PMAP_LOCK(pmap);
          pte = pmap_pte(pmap, va);
          if (pte == NULL)
                  panic("pmap_emulate_modified: can't find PTE");
  #ifdef SMP
          /* It is possible that some other CPU changed m-bit */
          if (!pte_test(pte, PTE_V) || pte_test(pte, PTE_D)) {
                  pmap_update_page_local(pmap, va, *pte);
                  PMAP_UNLOCK(pmap);
                  return (0);
          }
  #else
          if (!pte_test(pte, PTE_V) || pte_test(pte, PTE_D))
                  panic("pmap_emulate_modified: invalid pte");
  #endif
          if (pte_test(pte, PTE_RO)) {
                  /* write to read only page in the kernel */
                  PMAP_UNLOCK(pmap);
                  return (1);
          }
          pte_set(pte, PTE_D);
          pmap_update_page_local(pmap, va, *pte);
          pa = TLBLO_PTE_TO_PA(*pte);
          if (!page_is_managed(pa))
                  panic("pmap_emulate_modified: unmanaged page");
          m = PHYS_TO_VM_PAGE(pa);
          m->md.pv_flags |= (PV_TABLE_REF | PV_TABLE_MOD);
          PMAP_UNLOCK(pmap);
          return (0);
  }
  
  /*
   *      Routine:        pmap_kextract
   *      Function:
   *              Extract the physical page address associated
   *              virtual address.
   */
   /* PMAP_INLINE */ vm_offset_t
  pmap_kextract(vm_offset_t va)
  {
          int mapped;
  
          /*
           * First, the direct-mapped regions.
           */
  #if defined(__mips_n64)
          if (va >= MIPS_XKPHYS_START && va < MIPS_XKPHYS_END)
                  return (MIPS_XKPHYS_TO_PHYS(va));
  #endif
          if (va >= MIPS_KSEG0_START && va < MIPS_KSEG0_END)
                  return (MIPS_KSEG0_TO_PHYS(va));
  
          if (va >= MIPS_KSEG1_START && va < MIPS_KSEG1_END)
                  return (MIPS_KSEG1_TO_PHYS(va));
  
          /*
           * User virtual addresses.
           */
          if (va < VM_MAXUSER_ADDRESS) {
                  pt_entry_t *ptep;
  
                  if (curproc && curproc->p_vmspace) {
                          ptep = pmap_pte(&curproc->p_vmspace->vm_pmap, va);
                          if (ptep) {
                                  return (TLBLO_PTE_TO_PA(*ptep) |
                                      (va & PAGE_MASK));
                          }
                          return (0);
                  }
          }
  
          /*
           * Should be kernel virtual here, otherwise fail
           */
          mapped = (va >= MIPS_KSEG2_START || va < MIPS_KSEG2_END);
  #if defined(__mips_n64)
          mapped = mapped || (va >= MIPS_XKSEG_START || va < MIPS_XKSEG_END);
  #endif 
          /*
           * Kernel virtual.
           */
  
          if (mapped) {
                  pt_entry_t *ptep;
  
                  /* Is the kernel pmap initialized? */
                  if (!CPU_EMPTY(&kernel_pmap->pm_active)) {
                          /* It's inside the virtual address range */
                          ptep = pmap_pte(kernel_pmap, va);
                          if (ptep) {
                                  return (TLBLO_PTE_TO_PA(*ptep) |
                                      (va & PAGE_MASK));
                          }
                  }
                  return (0);
          }
  
          panic("%s for unknown address space %p.", __func__, (void *)va);
  }
  
  
  void 
  pmap_flush_pvcache(vm_page_t m)
  {
          pv_entry_t pv;
  
          if (m != NULL) {
                  for (pv = TAILQ_FIRST(&m->md.pv_list); pv;
                      pv = TAILQ_NEXT(pv, pv_list)) {
                          mips_dcache_wbinv_range_index(pv->pv_va, PAGE_SIZE);
                  }
          }
  }