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

     /* From: $NetBSD: pmap.c,v 1.148 2004/04/03 04:35:48 bsh Exp $ */
     /*-
      * Copyright 2004 Olivier Houchard.
      * Copyright 2003 Wasabi Systems, Inc.
      * All rights reserved.
      *
      * Written by Steve C. Woodford for Wasabi Systems, Inc.
      *
      * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed for the NetBSD Project by
     *      Wasabi Systems, Inc.
     * 4. The name of Wasabi Systems, Inc. may not be used to endorse
     *    or promote products derived from this software without specific prior
     *    written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``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 WASABI SYSTEMS, INC
     * 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.
     */
    
    /*-
     * Copyright (c) 2002-2003 Wasabi Systems, Inc.
     * Copyright (c) 2001 Richard Earnshaw
     * Copyright (c) 2001-2002 Christopher Gilbert
     * All rights reserved.
     *
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. The name of the company nor the name of the author may be used to
     *    endorse or promote products derived from this software without specific
     *    prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     * IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
     * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    /*-
     * Copyright (c) 1999 The NetBSD Foundation, Inc.
     * All rights reserved.
     *
     * This code is derived from software contributed to The NetBSD Foundation
     * by Charles M. Hannum.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *        This product includes software developed by the NetBSD
     *        Foundation, Inc. and its contributors.
     * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
     */
   
   /*-
    * Copyright (c) 1994-1998 Mark Brinicombe.
    * Copyright (c) 1994 Brini.
    * All rights reserved.
    *
    * This code is derived from software written for Brini by Mark Brinicombe
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met:
    * 1. Redistributions of source code must retain the above copyright
    *    notice, this list of conditions and the following disclaimer.
    * 2. Redistributions in binary form must reproduce the above copyright
    *    notice, this list of conditions and the following disclaimer in the
    *    documentation and/or other materials provided with the distribution.
    * 3. All advertising materials mentioning features or use of this software
    *    must display the following acknowledgement:
    *      This product includes software developed by Mark Brinicombe.
    * 4. The name of the author may not be used to endorse or promote products
    *    derived from this software without specific prior written permission.
    *
    * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
    * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
    * IN NO EVENT SHALL THE AUTHOR 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
    *
    * RiscBSD kernel project
    *
    * pmap.c
    *
    * Machine dependant vm stuff
    *
    * Created      : 20/09/94
    */
   
   /*
    * Special compilation symbols
    * PMAP_DEBUG           - Build in pmap_debug_level code
    */
   /* Include header files */
   
   #include "opt_vm.h"
   
   #include <sys/cdefs.h>
   __FBSDID("$FreeBSD: releng/6.2/sys/arm/arm/pmap.c 159889 2006-06-23 17:41:02Z cognet $");
   #include <sys/param.h>
   #include <sys/systm.h>
   #include <sys/kernel.h>
   #include <sys/proc.h>
   #include <sys/malloc.h>
   #include <sys/msgbuf.h>
   #include <sys/vmmeter.h>
   #include <sys/mman.h>
   #include <sys/smp.h>
   #include <sys/sx.h>
   #include <sys/sched.h>
   
   #include <vm/vm.h>
   #include <vm/uma.h>
   #include <vm/pmap.h>
   #include <vm/vm_kern.h>
   #include <vm/vm_object.h>
   #include <vm/vm_map.h>
   #include <vm/vm_page.h>
   #include <vm/vm_pageout.h>
   #include <vm/vm_extern.h>
   #include <sys/lock.h>
   #include <sys/mutex.h>
   #include <machine/md_var.h>
   #include <machine/vmparam.h>
   #include <machine/cpu.h>
   #include <machine/cpufunc.h>
   #include <machine/pcb.h>
   
   #ifdef PMAP_DEBUG
   #define PDEBUG(_lev_,_stat_) \
           if (pmap_debug_level >= (_lev_)) \
                   ((_stat_))
   #define dprintf printf
   
   int pmap_debug_level = 0;
   #define PMAP_INLINE 
   #else   /* PMAP_DEBUG */
   #define PDEBUG(_lev_,_stat_) /* Nothing */
   #define dprintf(x, arg...)
   #define PMAP_INLINE __inline
   #endif  /* PMAP_DEBUG */
   
   extern struct pv_addr systempage;
   /*
    * Internal function prototypes
    */
   static void pmap_free_pv_entry (pv_entry_t);
   static pv_entry_t pmap_get_pv_entry(void);
   
   static void             pmap_vac_me_harder(struct vm_page *, pmap_t,
       vm_offset_t);
   static void             pmap_vac_me_kpmap(struct vm_page *, pmap_t, 
       vm_offset_t);
   static void             pmap_vac_me_user(struct vm_page *, pmap_t, vm_offset_t);
   static void             pmap_alloc_l1(pmap_t);
   static void             pmap_free_l1(pmap_t);
   static void             pmap_use_l1(pmap_t);
   
   static int              pmap_clearbit(struct vm_page *, u_int);
   
   static struct l2_bucket *pmap_get_l2_bucket(pmap_t, vm_offset_t);
   static struct l2_bucket *pmap_alloc_l2_bucket(pmap_t, vm_offset_t);
   static void             pmap_free_l2_bucket(pmap_t, struct l2_bucket *, u_int);
   static vm_offset_t      kernel_pt_lookup(vm_paddr_t);
   
   static MALLOC_DEFINE(M_VMPMAP, "pmap", "PMAP L1");
   
   vm_offset_t avail_end;          /* PA of last available physical page */
   vm_offset_t virtual_avail;      /* VA of first avail page (after kernel bss) */
   vm_offset_t virtual_end;        /* VA of last avail page (end of kernel AS) */
   vm_offset_t pmap_curmaxkvaddr;
   
   extern void *end;
   vm_offset_t kernel_vm_end = 0;
   
   struct pmap kernel_pmap_store;
   pmap_t kernel_pmap;
   
   static pt_entry_t *csrc_pte, *cdst_pte;
   static vm_offset_t csrcp, cdstp;
   static struct mtx cmtx;
   
   static void             pmap_init_l1(struct l1_ttable *, pd_entry_t *);
   /*
    * These routines are called when the CPU type is identified to set up
    * the PTE prototypes, cache modes, etc.
    *
    * The variables are always here, just in case LKMs need to reference
    * them (though, they shouldn't).
    */
   
   pt_entry_t      pte_l1_s_cache_mode;
   pt_entry_t      pte_l1_s_cache_mode_pt;
   pt_entry_t      pte_l1_s_cache_mask;
   
   pt_entry_t      pte_l2_l_cache_mode;
   pt_entry_t      pte_l2_l_cache_mode_pt;
   pt_entry_t      pte_l2_l_cache_mask;
   
   pt_entry_t      pte_l2_s_cache_mode;
   pt_entry_t      pte_l2_s_cache_mode_pt;
   pt_entry_t      pte_l2_s_cache_mask;
   
   pt_entry_t      pte_l2_s_prot_u;
   pt_entry_t      pte_l2_s_prot_w;
   pt_entry_t      pte_l2_s_prot_mask;
   
   pt_entry_t      pte_l1_s_proto;
   pt_entry_t      pte_l1_c_proto;
   pt_entry_t      pte_l2_s_proto;
   
   void            (*pmap_copy_page_func)(vm_paddr_t, vm_paddr_t);
   void            (*pmap_zero_page_func)(vm_paddr_t, int, int);
   /*
    * Which pmap is currently 'live' in the cache
    *
    * XXXSCW: Fix for SMP ...
    */
   union pmap_cache_state *pmap_cache_state;
   
   LIST_HEAD(pmaplist, pmap);
   struct pmaplist allpmaps;
   
   /* static pt_entry_t *msgbufmap;*/
   struct msgbuf *msgbufp = 0;
   
   extern void bcopy_page(vm_offset_t, vm_offset_t);
   extern void bzero_page(vm_offset_t);
   
   char *_tmppt;
   
   /*
    * Metadata for L1 translation tables.
    */
   struct l1_ttable {
           /* Entry on the L1 Table list */
           SLIST_ENTRY(l1_ttable) l1_link;
   
           /* Entry on the L1 Least Recently Used list */
           TAILQ_ENTRY(l1_ttable) l1_lru;
   
           /* Track how many domains are allocated from this L1 */
           volatile u_int l1_domain_use_count;
   
           /*
            * A free-list of domain numbers for this L1.
            * We avoid using ffs() and a bitmap to track domains since ffs()
            * is slow on ARM.
            */
           u_int8_t l1_domain_first;
           u_int8_t l1_domain_free[PMAP_DOMAINS];
   
           /* Physical address of this L1 page table */
           vm_paddr_t l1_physaddr;
   
           /* KVA of this L1 page table */
           pd_entry_t *l1_kva;
   };
   
   /*
    * Convert a virtual address into its L1 table index. That is, the
    * index used to locate the L2 descriptor table pointer in an L1 table.
    * This is basically used to index l1->l1_kva[].
    *
    * Each L2 descriptor table represents 1MB of VA space.
    */
   #define L1_IDX(va)              (((vm_offset_t)(va)) >> L1_S_SHIFT)
   
   /*
    * L1 Page Tables are tracked using a Least Recently Used list.
    *  - New L1s are allocated from the HEAD.
    *  - Freed L1s are added to the TAIl.
    *  - Recently accessed L1s (where an 'access' is some change to one of
    *    the userland pmaps which owns this L1) are moved to the TAIL.
    */
   static TAILQ_HEAD(, l1_ttable) l1_lru_list;
   /*
    * A list of all L1 tables
    */
   static SLIST_HEAD(, l1_ttable) l1_list;
   static struct mtx l1_lru_lock;
   
   /*
    * The l2_dtable tracks L2_BUCKET_SIZE worth of L1 slots.
    *
    * This is normally 16MB worth L2 page descriptors for any given pmap.
    * Reference counts are maintained for L2 descriptors so they can be
    * freed when empty.
    */
   struct l2_dtable {
           /* The number of L2 page descriptors allocated to this l2_dtable */
           u_int l2_occupancy;
   
           /* List of L2 page descriptors */
           struct l2_bucket {
                   pt_entry_t *l2b_kva;    /* KVA of L2 Descriptor Table */
                   vm_paddr_t l2b_phys;    /* Physical address of same */
                   u_short l2b_l1idx;      /* This L2 table's L1 index */
                   u_short l2b_occupancy;  /* How many active descriptors */
           } l2_bucket[L2_BUCKET_SIZE];
   };
   
   /* pmap_kenter_internal flags */
   #define KENTER_CACHE    0x1
   #define KENTER_USER     0x2
   
   /*
    * Given an L1 table index, calculate the corresponding l2_dtable index
    * and bucket index within the l2_dtable.
    */
   #define L2_IDX(l1idx)           (((l1idx) >> L2_BUCKET_LOG2) & \
                                    (L2_SIZE - 1))
   #define L2_BUCKET(l1idx)        ((l1idx) & (L2_BUCKET_SIZE - 1))
   
   /*
    * Given a virtual address, this macro returns the
    * virtual address required to drop into the next L2 bucket.
    */
   #define L2_NEXT_BUCKET(va)      (((va) & L1_S_FRAME) + L1_S_SIZE)
   
   /*
    * L2 allocation.
    */
   #define pmap_alloc_l2_dtable()          \
                   (void*)uma_zalloc(l2table_zone, M_NOWAIT)
   #define pmap_free_l2_dtable(l2)         \
                   uma_zfree(l2table_zone, l2)
   
   /*
    * We try to map the page tables write-through, if possible.  However, not
    * all CPUs have a write-through cache mode, so on those we have to sync
    * the cache when we frob page tables.
    *
    * We try to evaluate this at compile time, if possible.  However, it's
    * not always possible to do that, hence this run-time var.
    */
   int     pmap_needs_pte_sync;
   
   /*
    * Macro to determine if a mapping might be resident in the
    * instruction cache and/or TLB
    */
   #define PV_BEEN_EXECD(f)  (((f) & (PVF_REF | PVF_EXEC)) == (PVF_REF | PVF_EXEC))
   
   /*
    * Macro to determine if a mapping might be resident in the
    * data cache and/or TLB
    */
   #define PV_BEEN_REFD(f)   (((f) & PVF_REF) != 0)
   
   /*
    * Data for the pv entry allocation mechanism
    */
   #define MINPV   2048
   
   #ifndef PMAP_SHPGPERPROC
   #define PMAP_SHPGPERPROC 200
   #endif
   
   #define pmap_is_current(pm)     ((pm) == pmap_kernel() || \
               curproc->p_vmspace->vm_map.pmap == (pm))
   static uma_zone_t pvzone;
   uma_zone_t l2zone;
   static uma_zone_t l2table_zone;
   static vm_offset_t pmap_kernel_l2dtable_kva;
   static vm_offset_t pmap_kernel_l2ptp_kva;
   static vm_paddr_t pmap_kernel_l2ptp_phys;
   static struct vm_object pvzone_obj;
   static struct vm_object l2zone_obj;
   static int pv_entry_count=0, pv_entry_max=0, pv_entry_high_water=0;
   int pmap_pagedaemon_waken = 0;
   
   /*
    * This list exists for the benefit of pmap_map_chunk().  It keeps track
    * of the kernel L2 tables during bootstrap, so that pmap_map_chunk() can
    * find them as necessary.
    *
    * Note that the data on this list MUST remain valid after initarm() returns,
    * as pmap_bootstrap() uses it to contruct L2 table metadata.
    */
   SLIST_HEAD(, pv_addr) kernel_pt_list = SLIST_HEAD_INITIALIZER(kernel_pt_list);
   
   static void
   pmap_init_l1(struct l1_ttable *l1, pd_entry_t *l1pt)
   {
           int i;
   
           l1->l1_kva = l1pt;
           l1->l1_domain_use_count = 0;
           l1->l1_domain_first = 0;
   
           for (i = 0; i < PMAP_DOMAINS; i++)
                   l1->l1_domain_free[i] = i + 1;
   
           /*
            * Copy the kernel's L1 entries to each new L1.
            */
           if (l1pt != pmap_kernel()->pm_l1->l1_kva)
                   memcpy(l1pt, pmap_kernel()->pm_l1->l1_kva, L1_TABLE_SIZE);
   
           if ((l1->l1_physaddr = pmap_extract(pmap_kernel(), (vm_offset_t)l1pt)) == 0)
                   panic("pmap_init_l1: can't get PA of L1 at %p", l1pt);
           SLIST_INSERT_HEAD(&l1_list, l1, l1_link);
           TAILQ_INSERT_TAIL(&l1_lru_list, l1, l1_lru);
   }
   
   static vm_offset_t
   kernel_pt_lookup(vm_paddr_t pa)
   {
           struct pv_addr *pv;
   
           SLIST_FOREACH(pv, &kernel_pt_list, pv_list) {
   #ifndef ARM32_NEW_VM_LAYOUT
                   if (pv->pv_pa == (pa & ~PAGE_MASK)) {
                           return (pv->pv_va | (pa & PAGE_MASK));
                           }
   #else
                   if (pv->pv_pa == pa)
                           return (pv->pv_va);
   #endif
           }
           return (0);
   }
   
   #if (ARM_MMU_GENERIC + ARM_MMU_SA1) != 0
   void
   pmap_pte_init_generic(void)
   {
   
           pte_l1_s_cache_mode = L1_S_B|L1_S_C;
           pte_l1_s_cache_mask = L1_S_CACHE_MASK_generic;
   
           pte_l2_l_cache_mode = L2_B|L2_C;
           pte_l2_l_cache_mask = L2_L_CACHE_MASK_generic;
   
           pte_l2_s_cache_mode = L2_B|L2_C;
           pte_l2_s_cache_mask = L2_S_CACHE_MASK_generic;
   
           /*
            * If we have a write-through cache, set B and C.  If
            * we have a write-back cache, then we assume setting
            * only C will make those pages write-through.
            */
           if (cpufuncs.cf_dcache_wb_range == (void *) cpufunc_nullop) {
                   pte_l1_s_cache_mode_pt = L1_S_B|L1_S_C;
                   pte_l2_l_cache_mode_pt = L2_B|L2_C;
                   pte_l2_s_cache_mode_pt = L2_B|L2_C;
           } else {
                   pte_l1_s_cache_mode_pt = L1_S_C;
                   pte_l2_l_cache_mode_pt = L2_C;
                   pte_l2_s_cache_mode_pt = L2_C;
           }
   
           pte_l2_s_prot_u = L2_S_PROT_U_generic;
           pte_l2_s_prot_w = L2_S_PROT_W_generic;
           pte_l2_s_prot_mask = L2_S_PROT_MASK_generic;
   
           pte_l1_s_proto = L1_S_PROTO_generic;
           pte_l1_c_proto = L1_C_PROTO_generic;
           pte_l2_s_proto = L2_S_PROTO_generic;
   
           pmap_copy_page_func = pmap_copy_page_generic;
           pmap_zero_page_func = pmap_zero_page_generic;
   }
   
   #if defined(CPU_ARM8)
   void
   pmap_pte_init_arm8(void)
   {
   
           /*
            * ARM8 is compatible with generic, but we need to use
            * the page tables uncached.
            */
           pmap_pte_init_generic();
   
           pte_l1_s_cache_mode_pt = 0;
           pte_l2_l_cache_mode_pt = 0;
           pte_l2_s_cache_mode_pt = 0;
   }
   #endif /* CPU_ARM8 */
   
   #if defined(CPU_ARM9) && defined(ARM9_CACHE_WRITE_THROUGH)
   void
   pmap_pte_init_arm9(void)
   {
   
           /*
            * ARM9 is compatible with generic, but we want to use
            * write-through caching for now.
            */
           pmap_pte_init_generic();
   
           pte_l1_s_cache_mode = L1_S_C;
           pte_l2_l_cache_mode = L2_C;
           pte_l2_s_cache_mode = L2_C;
   
           pte_l1_s_cache_mode_pt = L1_S_C;
           pte_l2_l_cache_mode_pt = L2_C;
           pte_l2_s_cache_mode_pt = L2_C;
   }
   #endif /* CPU_ARM9 */
   #endif /* (ARM_MMU_GENERIC + ARM_MMU_SA1) != 0 */
   
   #if defined(CPU_ARM10)
   void
   pmap_pte_init_arm10(void)
   {
   
           /*
            * ARM10 is compatible with generic, but we want to use
            * write-through caching for now.
            */
           pmap_pte_init_generic();
   
           pte_l1_s_cache_mode = L1_S_B | L1_S_C;
           pte_l2_l_cache_mode = L2_B | L2_C;
           pte_l2_s_cache_mode = L2_B | L2_C;
   
           pte_l1_s_cache_mode_pt = L1_S_C;
           pte_l2_l_cache_mode_pt = L2_C;
           pte_l2_s_cache_mode_pt = L2_C;
   
   }
   #endif /* CPU_ARM10 */
   
   #if  ARM_MMU_SA1 == 1
   void
   pmap_pte_init_sa1(void)
   {
   
           /*
            * The StrongARM SA-1 cache does not have a write-through
            * mode.  So, do the generic initialization, then reset
            * the page table cache mode to B=1,C=1, and note that
            * the PTEs need to be sync'd.
            */
           pmap_pte_init_generic();
   
           pte_l1_s_cache_mode_pt = L1_S_B|L1_S_C;
           pte_l2_l_cache_mode_pt = L2_B|L2_C;
           pte_l2_s_cache_mode_pt = L2_B|L2_C;
   
           pmap_needs_pte_sync = 1;
   }
   #endif /* ARM_MMU_SA1 == 1*/
   
   #if ARM_MMU_XSCALE == 1
   #if (ARM_NMMUS > 1)
   static u_int xscale_use_minidata;
   #endif
   
   void
   pmap_pte_init_xscale(void)
   {
           uint32_t auxctl;
           int write_through = 0;
   
           pte_l1_s_cache_mode = L1_S_B|L1_S_C|L1_S_XSCALE_P;
           pte_l1_s_cache_mask = L1_S_CACHE_MASK_xscale;
   
           pte_l2_l_cache_mode = L2_B|L2_C;
           pte_l2_l_cache_mask = L2_L_CACHE_MASK_xscale;
   
           pte_l2_s_cache_mode = L2_B|L2_C;
           pte_l2_s_cache_mask = L2_S_CACHE_MASK_xscale;
   
           pte_l1_s_cache_mode_pt = L1_S_C;
           pte_l2_l_cache_mode_pt = L2_C;
           pte_l2_s_cache_mode_pt = L2_C;
   #ifdef XSCALE_CACHE_READ_WRITE_ALLOCATE
           /*
            * The XScale core has an enhanced mode where writes that
            * miss the cache cause a cache line to be allocated.  This
            * is significantly faster than the traditional, write-through
            * behavior of this case.
            */
           pte_l1_s_cache_mode |= L1_S_XSCALE_TEX(TEX_XSCALE_X);
           pte_l2_l_cache_mode |= L2_XSCALE_L_TEX(TEX_XSCALE_X);
           pte_l2_s_cache_mode |= L2_XSCALE_T_TEX(TEX_XSCALE_X);
   #endif /* XSCALE_CACHE_READ_WRITE_ALLOCATE */
   #ifdef XSCALE_CACHE_WRITE_THROUGH
           /*
            * Some versions of the XScale core have various bugs in
            * their cache units, the work-around for which is to run
            * the cache in write-through mode.  Unfortunately, this
            * has a major (negative) impact on performance.  So, we
            * go ahead and run fast-and-loose, in the hopes that we
            * don't line up the planets in a way that will trip the
            * bugs.
            *
            * However, we give you the option to be slow-but-correct.
            */
           write_through = 1;
   #elif defined(XSCALE_CACHE_WRITE_BACK)
           /* force write back cache mode */
           write_through = 0;
   #elif defined(CPU_XSCALE_PXA2X0)
           /*
            * Intel PXA2[15]0 processors are known to have a bug in
            * write-back cache on revision 4 and earlier (stepping
            * A[01] and B[012]).  Fixed for C0 and later.
            */
           {
                   uint32_t id, type;
   
                   id = cpufunc_id();
                   type = id & ~(CPU_ID_XSCALE_COREREV_MASK|CPU_ID_REVISION_MASK);
   
                   if (type == CPU_ID_PXA250 || type == CPU_ID_PXA210) {
                           if ((id & CPU_ID_REVISION_MASK) < 5) {
                                   /* write through for stepping A0-1 and B0-2 */
                                   write_through = 1;
                           }
                   }
           }
   #endif /* XSCALE_CACHE_WRITE_THROUGH */
   
           if (write_through) {
                   pte_l1_s_cache_mode = L1_S_C;
                   pte_l2_l_cache_mode = L2_C;
                   pte_l2_s_cache_mode = L2_C;
           }
   
   #if (ARM_NMMUS > 1)
           xscale_use_minidata = 1;
   #endif
   
           pte_l2_s_prot_u = L2_S_PROT_U_xscale;
           pte_l2_s_prot_w = L2_S_PROT_W_xscale;
           pte_l2_s_prot_mask = L2_S_PROT_MASK_xscale;
   
           pte_l1_s_proto = L1_S_PROTO_xscale;
           pte_l1_c_proto = L1_C_PROTO_xscale;
           pte_l2_s_proto = L2_S_PROTO_xscale;
   
           pmap_copy_page_func = pmap_copy_page_xscale;
           pmap_zero_page_func = pmap_zero_page_xscale;
   
           /*
            * Disable ECC protection of page table access, for now.
            */
           __asm __volatile("mrc p15, 0, %0, c1, c0, 1" : "=r" (auxctl));
           auxctl &= ~XSCALE_AUXCTL_P;
           __asm __volatile("mcr p15, 0, %0, c1, c0, 1" : : "r" (auxctl));
   }
   
   /*
    * xscale_setup_minidata:
    *
    *      Set up the mini-data cache clean area.  We require the
    *      caller to allocate the right amount of physically and
    *      virtually contiguous space.
    */
   extern vm_offset_t xscale_minidata_clean_addr;
   extern vm_size_t xscale_minidata_clean_size; /* already initialized */
   void
   xscale_setup_minidata(vm_offset_t l1pt, vm_offset_t va, vm_paddr_t pa)
   {
           pd_entry_t *pde = (pd_entry_t *) l1pt;
           pt_entry_t *pte;
           vm_size_t size;
           uint32_t auxctl;
   
           xscale_minidata_clean_addr = va;
   
           /* Round it to page size. */
           size = (xscale_minidata_clean_size + L2_S_OFFSET) & L2_S_FRAME;
   
           for (; size != 0;
                va += L2_S_SIZE, pa += L2_S_SIZE, size -= L2_S_SIZE) {
   #ifndef ARM32_NEW_VM_LAYOUT
                   pte = (pt_entry_t *)
                       kernel_pt_lookup(pde[va >> L1_S_SHIFT] & L2_S_FRAME);
   #else
                   pte = (pt_entry_t *) kernel_pt_lookup(
                       pde[L1_IDX(va)] & L1_C_ADDR_MASK);
   #endif
                   if (pte == NULL)
                           panic("xscale_setup_minidata: can't find L2 table for "
                               "VA 0x%08x", (u_int32_t) va);
   #ifndef ARM32_NEW_VM_LAYOUT
                   pte[(va >> PAGE_SHIFT) & 0x3ff] =
   #else
                   pte[l2pte_index(va)] =
   #endif
                       L2_S_PROTO | pa | L2_S_PROT(PTE_KERNEL, VM_PROT_READ) |
                       L2_C | L2_XSCALE_T_TEX(TEX_XSCALE_X);
           }
   
           /*
            * Configure the mini-data cache for write-back with
            * read/write-allocate.
            *
            * NOTE: In order to reconfigure the mini-data cache, we must
            * make sure it contains no valid data!  In order to do that,
            * we must issue a global data cache invalidate command!
            *
            * WE ASSUME WE ARE RUNNING UN-CACHED WHEN THIS ROUTINE IS CALLED!
            * THIS IS VERY IMPORTANT!
            */
   
           /* Invalidate data and mini-data. */
           __asm __volatile("mcr p15, 0, %0, c7, c6, 0" : : "r" (0));
           __asm __volatile("mrc p15, 0, %0, c1, c0, 1" : "=r" (auxctl));
           auxctl = (auxctl & ~XSCALE_AUXCTL_MD_MASK) | XSCALE_AUXCTL_MD_WB_RWA;
           __asm __volatile("mcr p15, 0, %0, c1, c0, 1" : : "r" (auxctl));
   }
   #endif
   
   /*
    * Allocate an L1 translation table for the specified pmap.
    * This is called at pmap creation time.
    */
   static void
   pmap_alloc_l1(pmap_t pm)
   {
           struct l1_ttable *l1;
           u_int8_t domain;
   
           /*
            * Remove the L1 at the head of the LRU list
            */
           mtx_lock(&l1_lru_lock);
           l1 = TAILQ_FIRST(&l1_lru_list);
           TAILQ_REMOVE(&l1_lru_list, l1, l1_lru);
   
           /*
            * Pick the first available domain number, and update
            * the link to the next number.
            */
           domain = l1->l1_domain_first;
           l1->l1_domain_first = l1->l1_domain_free[domain];
   
           /*
            * If there are still free domain numbers in this L1,
            * put it back on the TAIL of the LRU list.
            */
           if (++l1->l1_domain_use_count < PMAP_DOMAINS)
                   TAILQ_INSERT_TAIL(&l1_lru_list, l1, l1_lru);
   
           mtx_unlock(&l1_lru_lock);
   
           /*
            * Fix up the relevant bits in the pmap structure
            */
           pm->pm_l1 = l1;
           pm->pm_domain = domain;
   }
   
   /*
    * Free an L1 translation table.
    * This is called at pmap destruction time.
    */
   static void
   pmap_free_l1(pmap_t pm)
   {
           struct l1_ttable *l1 = pm->pm_l1;
   
           mtx_lock(&l1_lru_lock);
   
           /*
            * If this L1 is currently on the LRU list, remove it.
            */
           if (l1->l1_domain_use_count < PMAP_DOMAINS)
                   TAILQ_REMOVE(&l1_lru_list, l1, l1_lru);
   
           /*
            * Free up the domain number which was allocated to the pmap
            */
           l1->l1_domain_free[pm->pm_domain] = l1->l1_domain_first;
           l1->l1_domain_first = pm->pm_domain;
           l1->l1_domain_use_count--;
   
           /*
            * The L1 now must have at least 1 free domain, so add
            * it back to the LRU list. If the use count is zero,
            * put it at the head of the list, otherwise it goes
            * to the tail.
            */
           if (l1->l1_domain_use_count == 0) {
                   TAILQ_INSERT_HEAD(&l1_lru_list, l1, l1_lru);
           }       else
                   TAILQ_INSERT_TAIL(&l1_lru_list, l1, l1_lru);
   
           mtx_unlock(&l1_lru_lock);
   }
   
   static PMAP_INLINE void
   pmap_use_l1(pmap_t pm)
   {
           struct l1_ttable *l1;
   
           /*
            * Do nothing if we're in interrupt context.
            * Access to an L1 by the kernel pmap must not affect
            * the LRU list.
            */
           if (pm == pmap_kernel())
                   return;
   
           l1 = pm->pm_l1;
   
           /*
            * If the L1 is not currently on the LRU list, just return
            */
           if (l1->l1_domain_use_count == PMAP_DOMAINS)
                   return;
   
           mtx_lock(&l1_lru_lock);
   
           /*
            * Check the use count again, now that we've acquired the lock
            */
           if (l1->l1_domain_use_count == PMAP_DOMAINS) {
                   mtx_unlock(&l1_lru_lock);
                   return;
           }
   
           /*
            * Move the L1 to the back of the LRU list
            */
           TAILQ_REMOVE(&l1_lru_list, l1, l1_lru);
           TAILQ_INSERT_TAIL(&l1_lru_list, l1, l1_lru);
   
           mtx_unlock(&l1_lru_lock);
   }
   
   
   /*
    * Returns a pointer to the L2 bucket associated with the specified pmap
    * and VA, or NULL if no L2 bucket exists for the address.
    */
   static PMAP_INLINE struct l2_bucket *
   pmap_get_l2_bucket(pmap_t pm, vm_offset_t va)
   {
           struct l2_dtable *l2;
           struct l2_bucket *l2b;
           u_short l1idx;
   
           l1idx = L1_IDX(va);
   
           if ((l2 = pm->pm_l2[L2_IDX(l1idx)]) == NULL ||
               (l2b = &l2->l2_bucket[L2_BUCKET(l1idx)])->l2b_kva == NULL)
                   return (NULL);
   
           return (l2b);
   }
   
   /*
    * Returns a pointer to the L2 bucket associated with the specified pmap
    * and VA.
    *
    * If no L2 bucket exists, perform the necessary allocations to put an L2
    * bucket/page table in place.
    *
    * Note that if a new L2 bucket/page was allocated, the caller *must*
    * increment the bucket occupancy counter appropriately *before* 
    * releasing the pmap's lock to ensure no other thread or cpu deallocates
    * the bucket/page in the meantime.
    */
   static struct l2_bucket *
   pmap_alloc_l2_bucket(pmap_t pm, vm_offset_t va)
   {
           struct l2_dtable *l2;
           struct l2_bucket *l2b;
           u_short l1idx;
   
           l1idx = L1_IDX(va);
   
           mtx_assert(&vm_page_queue_mtx, MA_OWNED);
           if ((l2 = pm->pm_l2[L2_IDX(l1idx)]) == NULL) {
                   /*
                    * No mapping at this address, as there is
                    * no entry in the L1 table.
                    * Need to allocate a new l2_dtable.
                    */
   again_l2table:
                   vm_page_unlock_queues();
                   if ((l2 = pmap_alloc_l2_dtable()) == NULL) {
                           vm_page_lock_queues();
                           return (NULL);
                   }
                   vm_page_lock_queues();
                   if (pm->pm_l2[L2_IDX(l1idx)] != NULL) {
                           vm_page_unlock_queues();
                           uma_zfree(l2table_zone, l2);
                           vm_page_lock_queues();
                           l2 = pm->pm_l2[L2_IDX(l1idx)];
                           if (l2 == NULL)
                                   goto again_l2table;
                           /*
                            * Someone already allocated the l2_dtable while
                            * we were doing the same.
                            */
                   } else {
                           bzero(l2, sizeof(*l2));
                           /*
                            * Link it into the parent pmap
                            */
                           pm->pm_l2[L2_IDX(l1idx)] = l2;
                   }
           } 
           
           l2b = &l2->l2_bucket[L2_BUCKET(l1idx)];
           
           /*
            * Fetch pointer to the L2 page table associated with the address.
            */
           if (l2b->l2b_kva == NULL) {
                   pt_entry_t *ptep;
                   
                   /*
                    * No L2 page table has been allocated. Chances are, this
                    * is because we just allocated the l2_dtable, above.
                    */
   again_ptep:
                   vm_page_unlock_queues();
                   ptep = (void*)uma_zalloc(l2zone, M_NOWAIT);
                   vm_page_lock_queues();
                   if (l2b->l2b_kva != 0) {
                           /* We lost the race. */
                           vm_page_unlock_queues();
                           uma_zfree(l2zone, ptep);
                           vm_page_lock_queues();
                           if (l2b->l2b_kva == 0)
                                   goto again_ptep;
                           return (l2b);
                   }
                   l2b->l2b_phys = vtophys(ptep);
                   if (ptep == NULL) {
                           /*
                            * Oops, no more L2 page tables available at this
                            * time. We may need to deallocate the l2_dtable
                            * if we allocated a new one above.
                            */
                           if (l2->l2_occupancy == 0) {
                                   pm->pm_l2[L2_IDX(l1idx)] = NULL;
                                   pmap_free_l2_dtable(l2);
                           }
                           return (NULL);
                   }
                   
                   l2->l2_occupancy++;
                   l2b->l2b_kva = ptep;
                   l2b->l2b_l1idx = l1idx;
           }
           
          return (l2b);   
  }
  
  static PMAP_INLINE void
  #ifndef PMAP_INCLUDE_PTE_SYNC
  pmap_free_l2_ptp(pt_entry_t *l2)
  #else
  pmap_free_l2_ptp(boolean_t need_sync, pt_entry_t *l2)
  #endif
  {
  #ifdef PMAP_INCLUDE_PTE_SYNC
          /*
           * Note: With a write-back cache, we may need to sync this
           * L2 table before re-using it.
           * This is because it may have belonged to a non-current
           * pmap, in which case the cache syncs would have been
           * skipped when the pages were being unmapped. If the
           * L2 table were then to be immediately re-allocated to
           * the *current* pmap, it may well contain stale mappings
           * which have not yet been cleared by a cache write-back
           * and so would still be visible to the mmu.
           */
          if (need_sync)
                  PTE_SYNC_RANGE(l2, L2_TABLE_SIZE_REAL / sizeof(pt_entry_t));
  #endif
          uma_zfree(l2zone, l2);
  }
  /*
   * One or more mappings in the specified L2 descriptor table have just been
   * invalidated.
   *
   * Garbage collect the metadata and descriptor table itself if necessary.
   *
   * The pmap lock must be acquired when this is called (not necessary
   * for the kernel pmap).
   */
  static void
  pmap_free_l2_bucket(pmap_t pm, struct l2_bucket *l2b, u_int count)
  {
          struct l2_dtable *l2;
          pd_entry_t *pl1pd, l1pd;
          pt_entry_t *ptep;
          u_short l1idx;
  
  
          /*
           * Update the bucket's reference count according to how many
           * PTEs the caller has just invalidated.
           */
          l2b->l2b_occupancy -= count;
  
          /*
           * Note:
           *
           * Level 2 page tables allocated to the kernel pmap are never freed
           * as that would require checking all Level 1 page tables and
           * removing any references to the Level 2 page table. See also the
           * comment elsewhere about never freeing bootstrap L2 descriptors.
           *
           * We make do with just invalidating the mapping in the L2 table.
           *
           * This isn't really a big deal in practice and, in fact, leads
           * to a performance win over time as we don't need to continually
           * alloc/free.
           */
          if (l2b->l2b_occupancy > 0 || pm == pmap_kernel())
                  return;
  
          /*
           * There are no more valid mappings in this level 2 page table.
           * Go ahead and NULL-out the pointer in the bucket, then
           * free the page table.
           */
          l1idx = l2b->l2b_l1idx;
          ptep = l2b->l2b_kva;
          l2b->l2b_kva = NULL;
  
          pl1pd = &pm->pm_l1->l1_kva[l1idx];
  
          /*
           * If the L1 slot matches the pmap's domain
           * number, then invalidate it.
           */
          l1pd = *pl1pd & (L1_TYPE_MASK | L1_C_DOM_MASK);
          if (l1pd == (L1_C_DOM(pm->pm_domain) | L1_TYPE_C)) {
                  *pl1pd = 0;
                  PTE_SYNC(pl1pd);
          }
  
          /*
           * Release the L2 descriptor table back to the pool cache.
           */
  #ifndef PMAP_INCLUDE_PTE_SYNC
          pmap_free_l2_ptp(ptep);
  #else
          pmap_free_l2_ptp(!pmap_is_current(pm), ptep);
  #endif
  
          /*
           * Update the reference count in the associated l2_dtable
           */
          l2 = pm->pm_l2[L2_IDX(l1idx)];
          if (--l2->l2_occupancy > 0)
                  return;
  
          /*
           * There are no more valid mappings in any of the Level 1
           * slots managed by this l2_dtable. Go ahead and NULL-out
           * the pointer in the parent pmap and free the l2_dtable.
           */
          pm->pm_l2[L2_IDX(l1idx)] = NULL;
          pmap_free_l2_dtable(l2);
  }
  
  /*
   * Pool cache constructors for L2 descriptor tables, metadata and pmap
   * structures.
   */
  static int
  pmap_l2ptp_ctor(void *mem, int size, void *arg, int flags)
  {
  #ifndef PMAP_INCLUDE_PTE_SYNC
          struct l2_bucket *l2b;
          pt_entry_t *ptep, pte;
  #ifdef ARM_USE_SMALL_ALLOC
          pd_entry_t *pde;
  #endif
          vm_offset_t va = (vm_offset_t)mem & ~PAGE_MASK;
  
          /*
           * The mappings for these page tables were initially made using
           * pmap_kenter() by the pool subsystem. Therefore, the cache-
           * mode will not be right for page table mappings. To avoid
           * polluting the pmap_kenter() code with a special case for
           * page tables, we simply fix up the cache-mode here if it's not
           * correct.
           */
  #ifdef ARM_USE_SMALL_ALLOC
          pde = &kernel_pmap->pm_l1->l1_kva[L1_IDX(va)];
          if (!l1pte_section_p(*pde)) {
  #endif
                  l2b = pmap_get_l2_bucket(pmap_kernel(), va);
                  ptep = &l2b->l2b_kva[l2pte_index(va)];
                  pte = *ptep;
  
                  if ((pte & L2_S_CACHE_MASK) != pte_l2_s_cache_mode_pt) {
                          /*
                           * Page tables must have the cache-mode set to 
                           * Write-Thru.
                           */
                          *ptep = (pte & ~L2_S_CACHE_MASK) | pte_l2_s_cache_mode_pt;
                          PTE_SYNC(ptep);
                          cpu_tlb_flushD_SE(va);
                          cpu_cpwait();
                  }
                  
  #ifdef ARM_USE_SMALL_ALLOC
          }
  #endif
  #endif
          memset(mem, 0, L2_TABLE_SIZE_REAL);
          PTE_SYNC_RANGE(mem, L2_TABLE_SIZE_REAL / sizeof(pt_entry_t));
          return (0);
  }
  
  /*
   * A bunch of routines to conditionally flush the caches/TLB depending
   * on whether the specified pmap actually needs to be flushed at any
   * given time.
   */
  static PMAP_INLINE void
  pmap_tlb_flushID_SE(pmap_t pm, vm_offset_t va)
  {
  
          if (pmap_is_current(pm))
                  cpu_tlb_flushID_SE(va);
  }
  
  static PMAP_INLINE void
  pmap_tlb_flushD_SE(pmap_t pm, vm_offset_t va)
  {
  
          if (pmap_is_current(pm))
                  cpu_tlb_flushD_SE(va);
  }
  
  static PMAP_INLINE void
  pmap_tlb_flushID(pmap_t pm)
  {
  
          if (pmap_is_current(pm))
                  cpu_tlb_flushID();
  }
  static PMAP_INLINE void
  pmap_tlb_flushD(pmap_t pm)
  {
  
          if (pmap_is_current(pm))
                  cpu_tlb_flushD();
  }
  
  static PMAP_INLINE void
  pmap_idcache_wbinv_range(pmap_t pm, vm_offset_t va, vm_size_t len)
  {
  
          if (pmap_is_current(pm))
                  cpu_idcache_wbinv_range(va, len);
  }
  
  static PMAP_INLINE void
  pmap_dcache_wb_range(pmap_t pm, vm_offset_t va, vm_size_t len,
      boolean_t do_inv, boolean_t rd_only)
  {
  
          if (pmap_is_current(pm)) {
                  if (do_inv) {
                          if (rd_only)
                                  cpu_dcache_inv_range(va, len);
                          else
                                  cpu_dcache_wbinv_range(va, len);
                  } else
                  if (!rd_only)
                          cpu_dcache_wb_range(va, len);
          }
  }
  
  static PMAP_INLINE void
  pmap_idcache_wbinv_all(pmap_t pm)
  {
  
          if (pmap_is_current(pm))
                  cpu_idcache_wbinv_all();
  }
  
  static PMAP_INLINE void
  pmap_dcache_wbinv_all(pmap_t pm)
  {
  
          if (pmap_is_current(pm))
                  cpu_dcache_wbinv_all();
  }
  
  /*
   * this routine defines the region(s) of memory that should
   * not be tested for the modified bit.
   */
  static PMAP_INLINE int
  pmap_track_modified(vm_offset_t va)
  {
          if ((va < kmi.clean_sva) || (va >= kmi.clean_eva)) 
                  return 1;
          else
                  return 0;
  }
  /*
   * PTE_SYNC_CURRENT:
   *
   *     Make sure the pte is written out to RAM.
   *     We need to do this for one of two cases:
   *       - We're dealing with the kernel pmap
   *       - There is no pmap active in the cache/tlb.
   *       - The specified pmap is 'active' in the cache/tlb.
   */
  #ifdef PMAP_INCLUDE_PTE_SYNC
  #define PTE_SYNC_CURRENT(pm, ptep)      \
  do {                                    \
          if (PMAP_NEEDS_PTE_SYNC &&      \
              pmap_is_current(pm))        \
                  PTE_SYNC(ptep);         \
  } while (/*CONSTCOND*/0)
  #else
  #define PTE_SYNC_CURRENT(pm, ptep)      /* nothing */
  #endif
  
  /*
   * Since we have a virtually indexed cache, we may need to inhibit caching if
   * there is more than one mapping and at least one of them is writable.
   * Since we purge the cache on every context switch, we only need to check for
   * other mappings within the same pmap, or kernel_pmap.
   * This function is also called when a page is unmapped, to possibly reenable
   * caching on any remaining mappings.
   *
   * The code implements the following logic, where:
   *
   * KW = # of kernel read/write pages
   * KR = # of kernel read only pages
   * UW = # of user read/write pages
   * UR = # of user read only pages
   * 
   * KC = kernel mapping is cacheable
   * UC = user mapping is cacheable
   *
   *               KW=0,KR=0  KW=0,KR>0  KW=1,KR=0  KW>1,KR>=0
   *             +---------------------------------------------
   * UW=0,UR=0   | ---        KC=1       KC=1       KC=0
   * UW=0,UR>0   | UC=1       KC=1,UC=1  KC=0,UC=0  KC=0,UC=0
   * UW=1,UR=0   | UC=1       KC=0,UC=0  KC=0,UC=0  KC=0,UC=0
   * UW>1,UR>=0  | UC=0       KC=0,UC=0  KC=0,UC=0  KC=0,UC=0
   */
  
  static const int pmap_vac_flags[4][4] = {
          {-1,            0,              0,              PVF_KNC},
          {0,             0,              PVF_NC,         PVF_NC},
          {0,             PVF_NC,         PVF_NC,         PVF_NC},
          {PVF_UNC,       PVF_NC,         PVF_NC,         PVF_NC}
  };
  
  static PMAP_INLINE int
  pmap_get_vac_flags(const struct vm_page *pg)
  {
          int kidx, uidx;
  
          kidx = 0;
          if (pg->md.kro_mappings || pg->md.krw_mappings > 1)
                  kidx |= 1;
          if (pg->md.krw_mappings)
                  kidx |= 2;
  
          uidx = 0;
          if (pg->md.uro_mappings || pg->md.urw_mappings > 1)
                  uidx |= 1;
          if (pg->md.urw_mappings)
                  uidx |= 2;
  
          return (pmap_vac_flags[uidx][kidx]);
  }
  
  static __inline void
  pmap_vac_me_harder(struct vm_page *pg, pmap_t pm, vm_offset_t va)
  {
          int nattr;
  
          nattr = pmap_get_vac_flags(pg);
  
          if (nattr < 0) {
                  pg->md.pvh_attrs &= ~PVF_NC;
                  return;
          }
  
          if (nattr == 0 && (pg->md.pvh_attrs & PVF_NC) == 0) {
                  return;
          }
  
          if (pm == pmap_kernel())
                  pmap_vac_me_kpmap(pg, pm, va);
          else
                  pmap_vac_me_user(pg, pm, va);
  
          pg->md.pvh_attrs = (pg->md.pvh_attrs & ~PVF_NC) | nattr;
  }
  
  static void
  pmap_vac_me_kpmap(struct vm_page *pg, pmap_t pm, vm_offset_t va)
  {
          u_int u_cacheable, u_entries;
          struct pv_entry *pv;
          pmap_t last_pmap = pm;
  
          /* 
           * Pass one, see if there are both kernel and user pmaps for
           * this page.  Calculate whether there are user-writable or
           * kernel-writable pages.
           */
          u_cacheable = 0;
          TAILQ_FOREACH(pv, &pg->md.pv_list, pv_list) {
                  if (pv->pv_pmap != pm && (pv->pv_flags & PVF_NC) == 0)
                          u_cacheable++;
          }
  
          u_entries = pg->md.urw_mappings + pg->md.uro_mappings;
  
          /* 
           * We know we have just been updating a kernel entry, so if
           * all user pages are already cacheable, then there is nothing
           * further to do.
           */
          if (pg->md.k_mappings == 0 && u_cacheable == u_entries)
                  return;
  
          if (u_entries) {
                  /* 
                   * Scan over the list again, for each entry, if it
                   * might not be set correctly, call pmap_vac_me_user
                   * to recalculate the settings.
                   */
                  TAILQ_FOREACH(pv, &pg->md.pv_list, pv_list) {
                          /* 
                           * We know kernel mappings will get set
                           * correctly in other calls.  We also know
                           * that if the pmap is the same as last_pmap
                           * then we've just handled this entry.
                           */
                          if (pv->pv_pmap == pm || pv->pv_pmap == last_pmap)
                                  continue;
  
                          /* 
                           * If there are kernel entries and this page
                           * is writable but non-cacheable, then we can
                           * skip this entry also.  
                           */
                          if (pg->md.k_mappings &&
                              (pv->pv_flags & (PVF_NC | PVF_WRITE)) ==
                              (PVF_NC | PVF_WRITE))
                                  continue;
  
                          /* 
                           * Similarly if there are no kernel-writable 
                           * entries and the page is already 
                           * read-only/cacheable.
                           */
                          if (pg->md.krw_mappings == 0 &&
                              (pv->pv_flags & (PVF_NC | PVF_WRITE)) == 0)
                                  continue;
  
                          /* 
                           * For some of the remaining cases, we know
                           * that we must recalculate, but for others we
                           * can't tell if they are correct or not, so
                           * we recalculate anyway.
                           */
                          pmap_vac_me_user(pg, (last_pmap = pv->pv_pmap), 0);
                  }
  
                  if (pg->md.k_mappings == 0)
                          return;
          }
  
          pmap_vac_me_user(pg, pm, va);
  }
  
  static void
  pmap_vac_me_user(struct vm_page *pg, pmap_t pm, vm_offset_t va)
  {
          pmap_t kpmap = pmap_kernel();
          struct pv_entry *pv, *npv;
          struct l2_bucket *l2b;
          pt_entry_t *ptep, pte;
          u_int entries = 0;
          u_int writable = 0;
          u_int cacheable_entries = 0;
          u_int kern_cacheable = 0;
          u_int other_writable = 0;
  
          /*
           * Count mappings and writable mappings in this pmap.
           * Include kernel mappings as part of our own.
           * Keep a pointer to the first one.
           */
          npv = TAILQ_FIRST(&pg->md.pv_list);
          TAILQ_FOREACH(pv, &pg->md.pv_list, pv_list) {
                  /* Count mappings in the same pmap */
                  if (pm == pv->pv_pmap || kpmap == pv->pv_pmap) {
                          if (entries++ == 0)
                                  npv = pv;
  
                          /* Cacheable mappings */
                          if ((pv->pv_flags & PVF_NC) == 0) {
                                  cacheable_entries++;
                                  if (kpmap == pv->pv_pmap)
                                          kern_cacheable++;
                          }
  
                          /* Writable mappings */
                          if (pv->pv_flags & PVF_WRITE)
                                  ++writable;
                  } else
                  if (pv->pv_flags & PVF_WRITE)
                          other_writable = 1;
          }
  
          /*
           * Enable or disable caching as necessary.
           * Note: the first entry might be part of the kernel pmap,
           * so we can't assume this is indicative of the state of the
           * other (maybe non-kpmap) entries.
           */
          if ((entries > 1 && writable) ||
              (entries > 0 && pm == kpmap && other_writable)) {
                  if (cacheable_entries == 0)
                          return;
  
                  for (pv = npv; pv; pv = TAILQ_NEXT(pv, pv_list)) {
                          if ((pm != pv->pv_pmap && kpmap != pv->pv_pmap) ||
                              (pv->pv_flags & PVF_NC))
                                  continue;
  
                          pv->pv_flags |= PVF_NC;
  
                          l2b = pmap_get_l2_bucket(pv->pv_pmap, pv->pv_va);
                          ptep = &l2b->l2b_kva[l2pte_index(pv->pv_va)];
                          pte = *ptep & ~L2_S_CACHE_MASK;
  
                          if ((va != pv->pv_va || pm != pv->pv_pmap) &&
                              l2pte_valid(pte)) {
                                  if (PV_BEEN_EXECD(pv->pv_flags)) {
                                          pmap_idcache_wbinv_range(pv->pv_pmap,
                                              pv->pv_va, PAGE_SIZE);
                                          pmap_tlb_flushID_SE(pv->pv_pmap,
                                              pv->pv_va);
                                  } else
                                  if (PV_BEEN_REFD(pv->pv_flags)) {
                                          pmap_dcache_wb_range(pv->pv_pmap,
                                              pv->pv_va, PAGE_SIZE, TRUE,
                                              (pv->pv_flags & PVF_WRITE) == 0);
                                          pmap_tlb_flushD_SE(pv->pv_pmap,
                                              pv->pv_va);
                                  }
                          }
  
                          *ptep = pte;
                          PTE_SYNC_CURRENT(pv->pv_pmap, ptep);
                  }
                  cpu_cpwait();
          } else
          if (entries > cacheable_entries) {
                  /*
                   * Turn cacheing back on for some pages.  If it is a kernel
                   * page, only do so if there are no other writable pages.
                   */
                  for (pv = npv; pv; pv = TAILQ_NEXT(pv, pv_list)) {
                          if (!(pv->pv_flags & PVF_NC) || (pm != pv->pv_pmap &&
                              (kpmap != pv->pv_pmap || other_writable)))
                                  continue;
  
                          pv->pv_flags &= ~PVF_NC;
  
                          l2b = pmap_get_l2_bucket(pv->pv_pmap, pv->pv_va);
                          ptep = &l2b->l2b_kva[l2pte_index(pv->pv_va)];
                          pte = (*ptep & ~L2_S_CACHE_MASK) | pte_l2_s_cache_mode;
  
                          if (l2pte_valid(pte)) {
                                  if (PV_BEEN_EXECD(pv->pv_flags)) {
                                          pmap_tlb_flushID_SE(pv->pv_pmap,
                                              pv->pv_va);
                                  } else
                                  if (PV_BEEN_REFD(pv->pv_flags)) {
                                          pmap_tlb_flushD_SE(pv->pv_pmap,
                                              pv->pv_va);
                                  }
                          }
  
                          *ptep = pte;
                          PTE_SYNC_CURRENT(pv->pv_pmap, ptep);
                  }
          }
  }
  
  /*
   * Modify pte bits for all ptes corresponding to the given physical address.
   * We use `maskbits' rather than `clearbits' because we're always passing
   * constants and the latter would require an extra inversion at run-time.
   */
  static int 
  pmap_clearbit(struct vm_page *pg, u_int maskbits)
  {
          struct l2_bucket *l2b;
          struct pv_entry *pv;
          pt_entry_t *ptep, npte, opte;
          pmap_t pm;
          vm_offset_t va;
          u_int oflags;
          int count = 0;
  #if 0
          PMAP_HEAD_TO_MAP_LOCK();
          simple_lock(&pg->mdpage.pvh_slock);
  #endif
  
          /*
           * Clear saved attributes (modify, reference)
           */
          pg->md.pvh_attrs &= ~(maskbits & (PVF_MOD | PVF_REF));
  
          if (TAILQ_EMPTY(&pg->md.pv_list)) {
  #if 0
                  simple_unlock(&pg->mdpage.pvh_slock);
                  PMAP_HEAD_TO_MAP_UNLOCK();
  #endif
                  return (0);
          }
  
          /*
           * Loop over all current mappings setting/clearing as appropos
           */
          TAILQ_FOREACH(pv, &pg->md.pv_list, pv_list) {
                  va = pv->pv_va;
                  pm = pv->pv_pmap;
                  oflags = pv->pv_flags;
                  pv->pv_flags &= ~maskbits;
  
  #if 0
                  pmap_acquire_pmap_lock(pm);
  #endif
  
                  l2b = pmap_get_l2_bucket(pm, va);
  
                  ptep = &l2b->l2b_kva[l2pte_index(va)];
                  npte = opte = *ptep;
  
                  if (maskbits & (PVF_WRITE|PVF_MOD) &&
                      !pmap_track_modified(pv->pv_va)) {
                          if ((pv->pv_flags & PVF_NC)) {
                                  /* 
                                   * Entry is not cacheable:
                                   *
                                   * Don't turn caching on again if this is a 
                                   * modified emulation. This would be
                                   * inconsitent with the settings created by
                                   * pmap_vac_me_harder(). Otherwise, it's safe
                                   * to re-enable cacheing.
                                   *
                                   * There's no need to call pmap_vac_me_harder()
                                   * here: all pages are losing their write
                                   * permission.
                                   */
                                  if (maskbits & PVF_WRITE) {
                                          npte |= pte_l2_s_cache_mode;
                                          pv->pv_flags &= ~PVF_NC;
                                  }
                          } else
                          if (opte & L2_S_PROT_W) {
                                  vm_page_dirty(pg);
                                  /* 
                                   * Entry is writable/cacheable: check if pmap
                                   * is current if it is flush it, otherwise it
                                   * won't be in the cache
                                   */
                                  if (PV_BEEN_EXECD(oflags))
                                          pmap_idcache_wbinv_range(pm, pv->pv_va,
                                              PAGE_SIZE);
                                  else
                                  if (PV_BEEN_REFD(oflags))
                                          pmap_dcache_wb_range(pm, pv->pv_va,
                                              PAGE_SIZE,
                                              (maskbits & PVF_REF) ? TRUE : FALSE,
                                              FALSE);
                          }
  
                          /* make the pte read only */
                          npte &= ~L2_S_PROT_W;
  
                          if (maskbits & PVF_WRITE) {
                                  /*
                                   * Keep alias accounting up to date
                                   */
                                  if (pv->pv_pmap == pmap_kernel()) {
                                          if (oflags & PVF_WRITE) {
                                                  pg->md.krw_mappings--;
                                                  pg->md.kro_mappings++;
                                          }
                                  } else
                                  if (oflags & PVF_WRITE) {
                                          pg->md.urw_mappings--;
                                          pg->md.uro_mappings++;
                                  }
                          }
                  }
  
                  if (maskbits & PVF_REF && !pmap_track_modified(pv->pv_va)) {
                          if ((pv->pv_flags & PVF_NC) == 0 &&
                              (maskbits & (PVF_WRITE|PVF_MOD)) == 0) {
                                  /*
                                   * Check npte here; we may have already
                                   * done the wbinv above, and the validity
                                   * of the PTE is the same for opte and
                                   * npte.
                                   */
                                  if (npte & L2_S_PROT_W) {
                                          if (PV_BEEN_EXECD(oflags))
                                                  pmap_idcache_wbinv_range(pm,
                                                      pv->pv_va, PAGE_SIZE);
                                          else
                                          if (PV_BEEN_REFD(oflags))
                                                  pmap_dcache_wb_range(pm,
                                                      pv->pv_va, PAGE_SIZE,
                                                      TRUE, FALSE);
                                  } else
                                  if ((npte & L2_TYPE_MASK) != L2_TYPE_INV) {
                                          /* XXXJRT need idcache_inv_range */
                                          if (PV_BEEN_EXECD(oflags))
                                                  pmap_idcache_wbinv_range(pm,
                                                      pv->pv_va, PAGE_SIZE);
                                          else
                                          if (PV_BEEN_REFD(oflags))
                                                  pmap_dcache_wb_range(pm,
                                                      pv->pv_va, PAGE_SIZE,
                                                      TRUE, TRUE);
                                  }
                          }
  
                          /*
                           * Make the PTE invalid so that we will take a
                           * page fault the next time the mapping is
                           * referenced.
                           */
                          npte &= ~L2_TYPE_MASK;
                          npte |= L2_TYPE_INV;
                  }
  
                  if (npte != opte) {
                          count++;
                          *ptep = npte;
                          PTE_SYNC(ptep);
                          /* Flush the TLB entry if a current pmap. */
                          if (PV_BEEN_EXECD(oflags))
                                  pmap_tlb_flushID_SE(pm, pv->pv_va);
                          else
                          if (PV_BEEN_REFD(oflags))
                                  pmap_tlb_flushD_SE(pm, pv->pv_va);
                  }
  
  #if 0
                  pmap_release_pmap_lock(pm);
  #endif
  
          }
  
  #if 0
          simple_unlock(&pg->mdpage.pvh_slock);
          PMAP_HEAD_TO_MAP_UNLOCK();
  #endif
          if (maskbits & PVF_WRITE)
                  vm_page_flag_clear(pg, PG_WRITEABLE);
          return (count);
  }
  
  /*
   * main pv_entry manipulation functions:
   *   pmap_enter_pv: enter a mapping onto a vm_page list
   *   pmap_remove_pv: remove a mappiing from a vm_page list
   *
   * NOTE: pmap_enter_pv expects to lock the pvh itself
   *       pmap_remove_pv expects te caller to lock the pvh before calling
   */
  
  /*
   * pmap_enter_pv: enter a mapping onto a vm_page lst
   *
   * => caller should hold the proper lock on pmap_main_lock
   * => caller should have pmap locked
   * => we will gain the lock on the vm_page and allocate the new pv_entry
   * => caller should adjust ptp's wire_count before calling
   * => caller should not adjust pmap's wire_count
   */
  static void
  pmap_enter_pv(struct vm_page *pg, struct pv_entry *pve, pmap_t pm,
      vm_offset_t va, u_int flags)
  {
  
  
          pve->pv_pmap = pm;
          pve->pv_va = va;
          pve->pv_flags = flags;
  
  #if 0
          mtx_lock(&pg->md.pvh_mtx);
  #endif
          TAILQ_INSERT_HEAD(&pg->md.pv_list, pve, pv_list);
          TAILQ_INSERT_HEAD(&pm->pm_pvlist, pve, pv_plist);
          pg->md.pvh_attrs |= flags & (PVF_REF | PVF_MOD);
          if (pm == pmap_kernel()) {
                  if (flags & PVF_WRITE)
                          pg->md.krw_mappings++;
                  else
                          pg->md.kro_mappings++;
          } 
          if (flags & PVF_WRITE)
                  pg->md.urw_mappings++;
          else
                  pg->md.uro_mappings++;
          pg->md.pv_list_count++;
  #if 0
          mtx_unlock(&pg->md.pvh_mtx);
  #endif
          if (pve->pv_flags & PVF_WIRED)
                  ++pm->pm_stats.wired_count;
          vm_page_flag_set(pg, PG_REFERENCED);
  }
  
  /*
   *
   * pmap_find_pv: Find a pv entry
   *
   * => caller should hold lock on vm_page
   */
  static PMAP_INLINE struct pv_entry *
  pmap_find_pv(struct vm_page *pg, pmap_t pm, vm_offset_t va)
  {
          struct pv_entry *pv;
  
          TAILQ_FOREACH(pv, &pg->md.pv_list, pv_list)
              if (pm == pv->pv_pmap && va == pv->pv_va)
                      break;
          return (pv);
  }
  
  /*
   * vector_page_setprot:
   *
   *      Manipulate the protection of the vector page.
   */
  void
  vector_page_setprot(int prot)
  {
          struct l2_bucket *l2b;
          pt_entry_t *ptep;
  
          l2b = pmap_get_l2_bucket(pmap_kernel(), vector_page);
  
          ptep = &l2b->l2b_kva[l2pte_index(vector_page)];
  
          *ptep = (*ptep & ~L1_S_PROT_MASK) | L2_S_PROT(PTE_KERNEL, prot);
          PTE_SYNC(ptep);
          cpu_tlb_flushD_SE(vector_page);
          cpu_cpwait();
  }
  
  /*
   * pmap_remove_pv: try to remove a mapping from a pv_list
   *
   * => caller should hold proper lock on pmap_main_lock
   * => pmap should be locked
   * => caller should hold lock on vm_page [so that attrs can be adjusted]
   * => caller should adjust ptp's wire_count and free PTP if needed
   * => caller should NOT adjust pmap's wire_count
   * => we return the removed pve
   */
  
  static void
  pmap_nuke_pv(struct vm_page *pg, pmap_t pm, struct pv_entry *pve)
  {
  
          TAILQ_REMOVE(&pg->md.pv_list, pve, pv_list);
          TAILQ_REMOVE(&pm->pm_pvlist, pve, pv_plist);
          if (pve->pv_flags & PVF_WIRED)
                  --pm->pm_stats.wired_count;
          pg->md.pv_list_count--;
          if (pg->md.pvh_attrs & PVF_MOD)
                  vm_page_dirty(pg);
          if (pm == pmap_kernel()) {
                  if (pve->pv_flags & PVF_WRITE)
                          pg->md.krw_mappings--;
                  else
                          pg->md.kro_mappings--;
          } else
                  if (pve->pv_flags & PVF_WRITE)
                          pg->md.urw_mappings--;
                  else
                          pg->md.uro_mappings--;
          if (TAILQ_FIRST(&pg->md.pv_list) == NULL ||
              (pg->md.krw_mappings == 0 && pg->md.urw_mappings == 0)) {
                  pg->md.pvh_attrs &= ~PVF_MOD;
                  if (TAILQ_FIRST(&pg->md.pv_list) == NULL)
                          pg->md.pvh_attrs &= ~PVF_REF;
                  vm_page_flag_clear(pg, PG_WRITEABLE);
          }
          if (TAILQ_FIRST(&pg->md.pv_list))
                  vm_page_flag_set(pg, PG_REFERENCED);
          if (pve->pv_flags & PVF_WRITE)
                  pmap_vac_me_harder(pg, pm, 0);
  }
  
  static struct pv_entry *
  pmap_remove_pv(struct vm_page *pg, pmap_t pm, vm_offset_t va)
  {
          struct pv_entry *pve;
  
          pve = TAILQ_FIRST(&pg->md.pv_list);
  
          while (pve) {
                  if (pve->pv_pmap == pm && pve->pv_va == va) {   /* match? */
                          pmap_nuke_pv(pg, pm, pve);
                          break;
                  }
                  pve = TAILQ_NEXT(pve, pv_list);
          }
  
          return(pve);                            /* return removed pve */
  }
  /*
   *
   * pmap_modify_pv: Update pv flags
   *
   * => caller should hold lock on vm_page [so that attrs can be adjusted]
   * => caller should NOT adjust pmap's wire_count
   * => caller must call pmap_vac_me_harder() if writable status of a page
   *    may have changed.
   * => we return the old flags
   * 
   * Modify a physical-virtual mapping in the pv table
   */
  static u_int
  pmap_modify_pv(struct vm_page *pg, pmap_t pm, vm_offset_t va,
      u_int clr_mask, u_int set_mask)
  {
          struct pv_entry *npv;
          u_int flags, oflags;
  
          if ((npv = pmap_find_pv(pg, pm, va)) == NULL)
                  return (0);
  
          /*
           * There is at least one VA mapping this page.
           */
  
          if (clr_mask & (PVF_REF | PVF_MOD))
                  pg->md.pvh_attrs |= set_mask & (PVF_REF | PVF_MOD);
  
          oflags = npv->pv_flags;
          npv->pv_flags = flags = (oflags & ~clr_mask) | set_mask;
  
          if ((flags ^ oflags) & PVF_WIRED) {
                  if (flags & PVF_WIRED)
                          ++pm->pm_stats.wired_count;
                  else
                          --pm->pm_stats.wired_count;
          }
  
          if ((flags ^ oflags) & PVF_WRITE) {
                  if (pm == pmap_kernel()) {
                          if (flags & PVF_WRITE) {
                                  pg->md.krw_mappings++;
                                  pg->md.kro_mappings--;
                          } else {
                                  pg->md.kro_mappings++;
                                  pg->md.krw_mappings--;
                          }
                  } else
                  if (flags & PVF_WRITE) {
                          pg->md.urw_mappings++;
                          pg->md.uro_mappings--;
                  } else {
                          pg->md.uro_mappings++;
                          pg->md.urw_mappings--;
                  }
                  if (pg->md.krw_mappings == 0 && pg->md.urw_mappings == 0) {
                          pg->md.pvh_attrs &= ~PVF_MOD;
                          vm_page_flag_clear(pg, PG_WRITEABLE);
                  }
                  pmap_vac_me_harder(pg, pm, 0);
          }
  
          return (oflags);
  }
  
  /* Function to set the debug level of the pmap code */
  #ifdef PMAP_DEBUG
  void
  pmap_debug(int level)
  {
          pmap_debug_level = level;
          dprintf("pmap_debug: level=%d\n", pmap_debug_level);
  }
  #endif  /* PMAP_DEBUG */
  
  void
  pmap_pinit0(struct pmap *pmap)
  {
          PDEBUG(1, printf("pmap_pinit0: pmap = %08x\n", (u_int32_t) pmap));
  
          dprintf("pmap_pinit0: pmap = %08x, pm_pdir = %08x\n",
                  (u_int32_t) pmap, (u_int32_t) pmap->pm_pdir);
          bcopy(kernel_pmap, pmap, sizeof(*pmap));
  }
  
  /*
   *      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;
  }
  
  /*
   *      Initialize the pmap module.
   *      Called by vm_init, to initialize any structures that the pmap
   *      system needs to map virtual memory.
   */
  void
  pmap_init(void)
  {
  
          PDEBUG(1, printf("pmap_init: phys_start = %08x\n"));
  
          /*
           * init the pv free list
           */
          pvzone = uma_zcreate("PV ENTRY", sizeof (struct pv_entry), NULL, NULL, 
              NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_VM | UMA_ZONE_NOFREE);
          uma_prealloc(pvzone, MINPV);
          /*
           * Now it is safe to enable pv_table recording.
           */
          PDEBUG(1, printf("pmap_init: done!\n"));
  
  }
  
  int
  pmap_fault_fixup(pmap_t pm, vm_offset_t va, vm_prot_t ftype, int user)
  {
          struct l2_dtable *l2;
          struct l2_bucket *l2b;
          pd_entry_t *pl1pd, l1pd;
          pt_entry_t *ptep, pte;
          vm_paddr_t pa;
          u_int l1idx;
          int rv = 0;
  
  #if 0
          PMAP_MAP_TO_HEAD_LOCK();
          pmap_acquire_pmap_lock(pm);
  #endif
          l1idx = L1_IDX(va);
  
          /*
           * If there is no l2_dtable for this address, then the process
           * has no business accessing it.
           *
           * Note: This will catch userland processes trying to access
           * kernel addresses.
           */
          l2 = pm->pm_l2[L2_IDX(l1idx)];
          if (l2 == NULL)
                  goto out;
  
          /*
           * Likewise if there is no L2 descriptor table
           */
          l2b = &l2->l2_bucket[L2_BUCKET(l1idx)];
          if (l2b->l2b_kva == NULL)
                  goto out;
  
          /*
           * Check the PTE itself.
           */
          ptep = &l2b->l2b_kva[l2pte_index(va)];
          pte = *ptep;
          if (pte == 0)
                  goto out;
  
          /*
           * Catch a userland access to the vector page mapped at 0x0
           */
          if (user && (pte & L2_S_PROT_U) == 0)
                  goto out;
          if (va == vector_page)
                  goto out;
  
          pa = l2pte_pa(pte);
  
          if ((ftype & VM_PROT_WRITE) && (pte & L2_S_PROT_W) == 0) {
                  /*
                   * This looks like a good candidate for "page modified"
                   * emulation...
                   */
                  struct pv_entry *pv;
                  struct vm_page *pg;
  
                  /* Extract the physical address of the page */
                  if ((pg = PHYS_TO_VM_PAGE(pa)) == NULL) {
                          goto out;
                  }
                  /* Get the current flags for this page. */
  
                  pv = pmap_find_pv(pg, pm, va);
                  if (pv == NULL) {
                          goto out;
                  }
  
                  /*
                   * Do the flags say this page is writable? If not then it
                   * is a genuine write fault. If yes then the write fault is
                   * our fault as we did not reflect the write access in the
                   * PTE. Now we know a write has occurred we can correct this
                   * and also set the modified bit
                   */
                  if ((pv->pv_flags & PVF_WRITE) == 0) {
                          goto out;
                  }
  
                  if (pmap_track_modified(pv->pv_va)) {
                          pg->md.pvh_attrs |= PVF_REF | PVF_MOD;
                          vm_page_dirty(pg);
                  }
                  pv->pv_flags |= PVF_REF | PVF_MOD;
  
                  /* 
                   * Re-enable write permissions for the page.  No need to call
                   * pmap_vac_me_harder(), since this is just a
                   * modified-emulation fault, and the PVF_WRITE bit isn't
                   * changing. We've already set the cacheable bits based on
                   * the assumption that we can write to this page.
                   */
                  *ptep = (pte & ~L2_TYPE_MASK) | L2_S_PROTO | L2_S_PROT_W;
                  PTE_SYNC(ptep);
                  rv = 1;
          } else
          if ((pte & L2_TYPE_MASK) == L2_TYPE_INV) {
                  /*
                   * This looks like a good candidate for "page referenced"
                   * emulation.
                   */
                  struct pv_entry *pv;
                  struct vm_page *pg;
  
                  /* Extract the physical address of the page */
                  vm_page_lock_queues();
                  if ((pg = PHYS_TO_VM_PAGE(pa)) == NULL) {
                          vm_page_unlock_queues();
                          goto out;
                  }
                  /* Get the current flags for this page. */
  
                  pv = pmap_find_pv(pg, pm, va);
                  if (pv == NULL) {
                          vm_page_unlock_queues();
                          goto out;
                  }
  
                  pg->md.pvh_attrs |= PVF_REF;
                  pv->pv_flags |= PVF_REF;
  
  
                  *ptep = (pte & ~L2_TYPE_MASK) | L2_S_PROTO;
                  PTE_SYNC(ptep);
                  rv = 1;
                  vm_page_unlock_queues();
          }
  
          /*
           * We know there is a valid mapping here, so simply
           * fix up the L1 if necessary.
           */
          pl1pd = &pm->pm_l1->l1_kva[l1idx];
          l1pd = l2b->l2b_phys | L1_C_DOM(pm->pm_domain) | L1_C_PROTO;
          if (*pl1pd != l1pd) {
                  *pl1pd = l1pd;
                  PTE_SYNC(pl1pd);
                  rv = 1;
          }
  
  #ifdef CPU_SA110
          /*
           * There are bugs in the rev K SA110.  This is a check for one
           * of them.
           */
          if (rv == 0 && curcpu()->ci_arm_cputype == CPU_ID_SA110 &&
              curcpu()->ci_arm_cpurev < 3) {
                  /* Always current pmap */
                  if (l2pte_valid(pte)) {
                          extern int kernel_debug;
                          if (kernel_debug & 1) {
                                  struct proc *p = curlwp->l_proc;
                                  printf("prefetch_abort: page is already "
                                      "mapped - pte=%p *pte=%08x\n", ptep, pte);
                                  printf("prefetch_abort: pc=%08lx proc=%p "
                                      "process=%s\n", va, p, p->p_comm);
                                  printf("prefetch_abort: far=%08x fs=%x\n",
                                      cpu_faultaddress(), cpu_faultstatus());
                          }
  #ifdef DDB
                          if (kernel_debug & 2)
                                  Debugger();
  #endif
                          rv = 1;
                  }
          }
  #endif /* CPU_SA110 */
  
  #ifdef DEBUG
          /*
           * If 'rv == 0' at this point, it generally indicates that there is a
           * stale TLB entry for the faulting address. This happens when two or
           * more processes are sharing an L1. Since we don't flush the TLB on
           * a context switch between such processes, we can take domain faults
           * for mappings which exist at the same VA in both processes. EVEN IF
           * WE'VE RECENTLY FIXED UP THE CORRESPONDING L1 in pmap_enter(), for
           * example.
           *
           * This is extremely likely to happen if pmap_enter() updated the L1
           * entry for a recently entered mapping. In this case, the TLB is
           * flushed for the new mapping, but there may still be TLB entries for
           * other mappings belonging to other processes in the 1MB range
           * covered by the L1 entry.
           *
           * Since 'rv == 0', we know that the L1 already contains the correct
           * value, so the fault must be due to a stale TLB entry.
           *
           * Since we always need to flush the TLB anyway in the case where we
           * fixed up the L1, or frobbed the L2 PTE, we effectively deal with
           * stale TLB entries dynamically.
           *
           * However, the above condition can ONLY happen if the current L1 is
           * being shared. If it happens when the L1 is unshared, it indicates
           * that other parts of the pmap are not doing their job WRT managing
           * the TLB.
           */
          if (rv == 0 && pm->pm_l1->l1_domain_use_count == 1) {
                  extern int last_fault_code;
                  printf("fixup: pm %p, va 0x%lx, ftype %d - nothing to do!\n",
                      pm, va, ftype);
                  printf("fixup: l2 %p, l2b %p, ptep %p, pl1pd %p\n",
                      l2, l2b, ptep, pl1pd);
                  printf("fixup: pte 0x%x, l1pd 0x%x, last code 0x%x\n",
                      pte, l1pd, last_fault_code);
  #ifdef DDB
                  Debugger();
  #endif
          }
  #endif
  
          cpu_tlb_flushID_SE(va);
          cpu_cpwait();
  
          rv = 1;
  
  out:
  #if 0
          pmap_release_pmap_lock(pm);
          PMAP_MAP_TO_HEAD_UNLOCK();
  #endif
          return (rv);
  }
  
  /*
   * Initialize the address space (zone) for the pv_entries.  Set a
   * high water mark so that the system can recover from excessive
   * numbers of pv entries.
   */
  void
  pmap_init2()
  {
          int shpgperproc = PMAP_SHPGPERPROC;
          struct l2_bucket *l2b;
          struct l1_ttable *l1;
          pd_entry_t *pl1pt;
          pt_entry_t *ptep, pte;
          vm_offset_t va, eva;
          u_int loop, needed;
          
          TUNABLE_INT_FETCH("vm.pmap.shpgperproc", &shpgperproc);
          
          pv_entry_max = shpgperproc * maxproc + vm_page_array_size;
          pv_entry_high_water = 9 * (pv_entry_max / 10);
          l2zone = uma_zcreate("L2 Table", L2_TABLE_SIZE_REAL, pmap_l2ptp_ctor,
              NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_VM | UMA_ZONE_NOFREE);
          uma_prealloc(l2zone, 4096);
          l2table_zone = uma_zcreate("L2 Table", sizeof(struct l2_dtable),
              NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
              UMA_ZONE_VM | UMA_ZONE_NOFREE);
          uma_prealloc(l2table_zone, 1024);
  
          uma_zone_set_obj(pvzone, &pvzone_obj, pv_entry_max);
          uma_zone_set_obj(l2zone, &l2zone_obj, pv_entry_max);
  
          needed = (maxproc / PMAP_DOMAINS) + ((maxproc % PMAP_DOMAINS) ? 1 : 0);
          needed -= 1;
          l1 = malloc(sizeof(*l1) * needed, M_VMPMAP, M_WAITOK);
  
          for (loop = 0; loop < needed; loop++, l1++) {
                  /* Allocate a L1 page table */
                  va = (vm_offset_t)contigmalloc(L1_TABLE_SIZE, M_VMPMAP, 0, 0x0,
                      0xffffffff, L1_TABLE_SIZE, 0);
  
                  if (va == 0)
                          panic("Cannot allocate L1 KVM");
  
                  eva = va + L1_TABLE_SIZE;
                  pl1pt = (pd_entry_t *)va;
                  
                  while (va < eva) {
                                  l2b = pmap_get_l2_bucket(pmap_kernel(), va);
                                  ptep = &l2b->l2b_kva[l2pte_index(va)];
                                  pte = *ptep;
                                  pte = (pte & ~L2_S_CACHE_MASK) | pte_l2_s_cache_mode_pt;
                                  *ptep = pte;
                                  PTE_SYNC(ptep);
                                  cpu_tlb_flushD_SE(va);
                                  
                                  va += PAGE_SIZE;
                  }
                  pmap_init_l1(l1, pl1pt);
          }
  
  
  #ifdef DEBUG
          printf("pmap_postinit: Allocated %d static L1 descriptor tables\n",
              needed);
  #endif
  }
  
  /*
   * This is used to stuff certain critical values into the PCB where they
   * can be accessed quickly from cpu_switch() et al.
   */
  void
  pmap_set_pcb_pagedir(pmap_t pm, struct pcb *pcb)
  {
          struct l2_bucket *l2b;
  
          pcb->pcb_pagedir = pm->pm_l1->l1_physaddr;
          pcb->pcb_dacr = (DOMAIN_CLIENT << (PMAP_DOMAIN_KERNEL * 2)) |
              (DOMAIN_CLIENT << (pm->pm_domain * 2));
  
          if (vector_page < KERNBASE) {
                  pcb->pcb_pl1vec = &pm->pm_l1->l1_kva[L1_IDX(vector_page)];
                  l2b = pmap_get_l2_bucket(pm, vector_page);
                  pcb->pcb_l1vec = l2b->l2b_phys | L1_C_PROTO |
                      L1_C_DOM(pm->pm_domain) | L1_C_DOM(PMAP_DOMAIN_KERNEL);
          } else
                  pcb->pcb_pl1vec = NULL;
  }
  
  void
  pmap_activate(struct thread *td)
  {
          pmap_t pm;
          struct pcb *pcb;
          int s;
  
          pm = vmspace_pmap(td->td_proc->p_vmspace);
          pcb = td->td_pcb;
  
          critical_enter();
          pmap_set_pcb_pagedir(pm, pcb);
  
          if (td == curthread) {
                  u_int cur_dacr, cur_ttb;
  
                  __asm __volatile("mrc p15, 0, %0, c2, c0, 0" : "=r"(cur_ttb));
                  __asm __volatile("mrc p15, 0, %0, c3, c0, 0" : "=r"(cur_dacr));
  
                  cur_ttb &= ~(L1_TABLE_SIZE - 1);
  
                  if (cur_ttb == (u_int)pcb->pcb_pagedir &&
                      cur_dacr == pcb->pcb_dacr) {
                          /*
                           * No need to switch address spaces.
                           */
                          critical_exit();
                          return;
                  }
  
  
                  /*
                   * We MUST, I repeat, MUST fix up the L1 entry corresponding
                   * to 'vector_page' in the incoming L1 table before switching
                   * to it otherwise subsequent interrupts/exceptions (including
                   * domain faults!) will jump into hyperspace.
                   */
                  if (pcb->pcb_pl1vec) {
  
                          *pcb->pcb_pl1vec = pcb->pcb_l1vec;
                          /*
                           * Don't need to PTE_SYNC() at this point since
                           * cpu_setttb() is about to flush both the cache
                           * and the TLB.
                           */
                  }
  
                  cpu_domains(pcb->pcb_dacr);
                  cpu_setttb(pcb->pcb_pagedir);
  
                  splx(s);
          }
          critical_exit();
  }
  
  static int
  pmap_set_pt_cache_mode(pd_entry_t *kl1, vm_offset_t va)
  {
          pd_entry_t *pdep, pde;
          pt_entry_t *ptep, pte;
          vm_offset_t pa;
          int rv = 0;
  
          /*
           * Make sure the descriptor itself has the correct cache mode
           */
          pdep = &kl1[L1_IDX(va)];
          pde = *pdep;
  
          if (l1pte_section_p(pde)) {
                  if ((pde & L1_S_CACHE_MASK) != pte_l1_s_cache_mode_pt) {
                          *pdep = (pde & ~L1_S_CACHE_MASK) |
                              pte_l1_s_cache_mode_pt;
                          PTE_SYNC(pdep);
                          cpu_dcache_wbinv_range((vm_offset_t)pdep,
                              sizeof(*pdep));
                          rv = 1;
                  }
          } else {
                  pa = (vm_paddr_t)(pde & L1_C_ADDR_MASK);
                  ptep = (pt_entry_t *)kernel_pt_lookup(pa);
                  if (ptep == NULL)
                          panic("pmap_bootstrap: No L2 for L2 @ va %p\n", ptep);
  
                  ptep = &ptep[l2pte_index(va)];
                  pte = *ptep;
                  if ((pte & L2_S_CACHE_MASK) != pte_l2_s_cache_mode_pt) {
                          *ptep = (pte & ~L2_S_CACHE_MASK) |
                              pte_l2_s_cache_mode_pt;
                          PTE_SYNC(ptep);
                          cpu_dcache_wbinv_range((vm_offset_t)ptep,
                              sizeof(*ptep));
                          rv = 1;
                  }
          }
  
          return (rv);
  }
  
  static void
  pmap_alloc_specials(vm_offset_t *availp, int pages, vm_offset_t *vap, 
      pt_entry_t **ptep)
  {
          vm_offset_t va = *availp;
          struct l2_bucket *l2b;
  
          if (ptep) {
                  l2b = pmap_get_l2_bucket(pmap_kernel(), va);
                  if (l2b == NULL)
                          panic("pmap_alloc_specials: no l2b for 0x%x", va);
  
                  *ptep = &l2b->l2b_kva[l2pte_index(va)];
          }
  
          *vap = va;
          *availp = va + (PAGE_SIZE * pages);
  }
  
  /*
   *      Bootstrap the system enough to run with virtual memory.
   *
   *      On the arm this is called after mapping has already been enabled
   *      and just syncs the pmap module with what has already been done.
   *      [We can't call it easily with mapping off since the kernel is not
   *      mapped with PA == VA, hence we would have to relocate every address
   *      from the linked base (virtual) address "KERNBASE" to the actual
   *      (physical) address starting relative to 0]
   */
  #define PMAP_STATIC_L2_SIZE 16
  #ifdef ARM_USE_SMALL_ALLOC
  extern struct mtx smallalloc_mtx;
  extern vm_offset_t alloc_curaddr;
  extern vm_offset_t alloc_firstaddr;
  #endif
  
  void
  pmap_bootstrap(vm_offset_t firstaddr, vm_offset_t lastaddr, struct pv_addr *l1pt)
  {
          static struct l1_ttable static_l1;
          static struct l2_dtable static_l2[PMAP_STATIC_L2_SIZE];
          struct l1_ttable *l1 = &static_l1;
          struct l2_dtable *l2;
          struct l2_bucket *l2b;
          pd_entry_t pde;
          pd_entry_t *kernel_l1pt = (pd_entry_t *)l1pt->pv_va;
          pt_entry_t *ptep;
          vm_paddr_t pa;
          vm_offset_t va;
          vm_size_t size;
          int l1idx, l2idx, l2next = 0;
  
          PDEBUG(1, printf("firstaddr = %08x, loadaddr = %08x\n",
              firstaddr, loadaddr));
          
          virtual_avail = firstaddr;
          kernel_pmap = &kernel_pmap_store;
          kernel_pmap->pm_l1 = l1;
          
          /*
           * Scan the L1 translation table created by initarm() and create
           * the required metadata for all valid mappings found in it.
           */
          for (l1idx = 0; l1idx < (L1_TABLE_SIZE / sizeof(pd_entry_t)); l1idx++) {
                  pde = kernel_l1pt[l1idx];
  
                  /*
                   * We're only interested in Coarse mappings.
                   * pmap_extract() can deal with section mappings without
                   * recourse to checking L2 metadata.
                   */
                  if ((pde & L1_TYPE_MASK) != L1_TYPE_C)
                          continue;
  
                  /*
                   * Lookup the KVA of this L2 descriptor table
                   */
                  pa = (vm_paddr_t)(pde & L1_C_ADDR_MASK);
                  ptep = (pt_entry_t *)kernel_pt_lookup(pa);
                  
                  if (ptep == NULL) {
                          panic("pmap_bootstrap: No L2 for va 0x%x, pa 0x%lx",
                              (u_int)l1idx << L1_S_SHIFT, (long unsigned int)pa);
                  }
  
                  /*
                   * Fetch the associated L2 metadata structure.
                   * Allocate a new one if necessary.
                   */
                  if ((l2 = kernel_pmap->pm_l2[L2_IDX(l1idx)]) == NULL) {
                          if (l2next == PMAP_STATIC_L2_SIZE)
                                  panic("pmap_bootstrap: out of static L2s");
                          kernel_pmap->pm_l2[L2_IDX(l1idx)] = l2 = 
                              &static_l2[l2next++];
                  }
  
                  /*
                   * One more L1 slot tracked...
                   */
                  l2->l2_occupancy++;
  
                  /*
                   * Fill in the details of the L2 descriptor in the
                   * appropriate bucket.
                   */
                  l2b = &l2->l2_bucket[L2_BUCKET(l1idx)];
                  l2b->l2b_kva = ptep;
                  l2b->l2b_phys = pa;
                  l2b->l2b_l1idx = l1idx;
  
                  /*
                   * Establish an initial occupancy count for this descriptor
                   */
                  for (l2idx = 0;
                      l2idx < (L2_TABLE_SIZE_REAL / sizeof(pt_entry_t));
                      l2idx++) {
                          if ((ptep[l2idx] & L2_TYPE_MASK) != L2_TYPE_INV) {
                                  l2b->l2b_occupancy++;
                          }
                  }
  
                  /*
                   * Make sure the descriptor itself has the correct cache mode.
                   * If not, fix it, but whine about the problem. Port-meisters
                   * should consider this a clue to fix up their initarm()
                   * function. :)
                   */
                  if (pmap_set_pt_cache_mode(kernel_l1pt, (vm_offset_t)ptep)) {
                          printf("pmap_bootstrap: WARNING! wrong cache mode for "
                              "L2 pte @ %p\n", ptep);
                  }
          }
  
          
          /*
           * Ensure the primary (kernel) L1 has the correct cache mode for
           * a page table. Bitch if it is not correctly set.
           */
          for (va = (vm_offset_t)kernel_l1pt;
              va < ((vm_offset_t)kernel_l1pt + L1_TABLE_SIZE); va += PAGE_SIZE) {
                  if (pmap_set_pt_cache_mode(kernel_l1pt, va))
                          printf("pmap_bootstrap: WARNING! wrong cache mode for "
                              "primary L1 @ 0x%x\n", va);
          }
  
          cpu_dcache_wbinv_all();
          cpu_tlb_flushID();
          cpu_cpwait();
  
          kernel_pmap->pm_active = -1;
          kernel_pmap->pm_domain = PMAP_DOMAIN_KERNEL;
          LIST_INIT(&allpmaps);
          TAILQ_INIT(&kernel_pmap->pm_pvlist);
          LIST_INSERT_HEAD(&allpmaps, kernel_pmap, pm_list);
          
          /*
           * Reserve some special page table entries/VA space for temporary
           * mapping of pages.
           */
  #define SYSMAP(c, p, v, n)                                              \
      v = (c)va; va += ((n)*PAGE_SIZE); p = pte; pte += (n);
      
          pmap_alloc_specials(&virtual_avail, 1, &csrcp, &csrc_pte);
          pmap_set_pt_cache_mode(kernel_l1pt, (vm_offset_t)csrc_pte);
          pmap_alloc_specials(&virtual_avail, 1, &cdstp, &cdst_pte);
          pmap_set_pt_cache_mode(kernel_l1pt, (vm_offset_t)cdst_pte);
          size = ((lastaddr - pmap_curmaxkvaddr) + L1_S_OFFSET) / L1_S_SIZE;
          pmap_alloc_specials(&virtual_avail,
              round_page(size * L2_TABLE_SIZE_REAL) / PAGE_SIZE,
              &pmap_kernel_l2ptp_kva, NULL);
          
          size = (size + (L2_BUCKET_SIZE - 1)) / L2_BUCKET_SIZE;
          pmap_alloc_specials(&virtual_avail,
              round_page(size * sizeof(struct l2_dtable)) / PAGE_SIZE,
              &pmap_kernel_l2dtable_kva, NULL);
  
          pmap_alloc_specials(&virtual_avail,
              1, (vm_offset_t*)&_tmppt, NULL);
          SLIST_INIT(&l1_list);
          TAILQ_INIT(&l1_lru_list);
          mtx_init(&l1_lru_lock, "l1 list lock", NULL, MTX_DEF);
          pmap_init_l1(l1, kernel_l1pt);
          cpu_dcache_wbinv_all();
  
          virtual_avail = round_page(virtual_avail);
          virtual_end = lastaddr;
          kernel_vm_end = pmap_curmaxkvaddr;
          arm_nocache_startaddr = lastaddr;
          mtx_init(&cmtx, "TMP mappins mtx", NULL, MTX_DEF);
  #ifdef ARM_USE_SMALL_ALLOC
          mtx_init(&smallalloc_mtx, "Small alloc page list", NULL, MTX_DEF);
          alloc_firstaddr = alloc_curaddr = arm_nocache_startaddr +
              ARM_NOCACHE_KVA_SIZE;
  #endif
  }
  
  /***************************************************
   * Pmap allocation/deallocation routines.
   ***************************************************/
  
  /*
   * Release any resources held by the given physical map.
   * Called when a pmap initialized by pmap_pinit is being released.
   * Should only be called if the map contains no valid mappings.
   */
  void
  pmap_release(pmap_t pmap)
  {
          struct pcb *pcb;
          
          pmap_idcache_wbinv_all(pmap);
          pmap_tlb_flushID(pmap);
          cpu_cpwait();
          LIST_REMOVE(pmap, pm_list);
          if (vector_page < KERNBASE) {
                  struct pcb *curpcb = PCPU_GET(curpcb);
                  pcb = thread0.td_pcb;
                  if (pmap_is_current(pmap)) {
                          /*
                           * Frob the L1 entry corresponding to the vector
                           * page so that it contains the kernel pmap's domain
                           * number. This will ensure pmap_remove() does not
                           * pull the current vector page out from under us.
                           */
                          critical_enter();
                          *pcb->pcb_pl1vec = pcb->pcb_l1vec;
                          cpu_domains(pcb->pcb_dacr);
                          cpu_setttb(pcb->pcb_pagedir);
                          critical_exit();
                  }
                  pmap_remove(pmap, vector_page, vector_page + PAGE_SIZE);
                  /*
                   * Make sure cpu_switch(), et al, DTRT. This is safe to do
                   * since this process has no remaining mappings of its own.
                   */
                  curpcb->pcb_pl1vec = pcb->pcb_pl1vec;
                  curpcb->pcb_l1vec = pcb->pcb_l1vec;
                  curpcb->pcb_dacr = pcb->pcb_dacr;
                  curpcb->pcb_pagedir = pcb->pcb_pagedir;
  
          }
          pmap_free_l1(pmap);
          
          dprintf("pmap_release()\n");
  }
  
  
  
  /*
   * Helper function for pmap_grow_l2_bucket()
   */
  static __inline int
  pmap_grow_map(vm_offset_t va, pt_entry_t cache_mode, vm_paddr_t *pap)
  {
          struct l2_bucket *l2b;
          pt_entry_t *ptep;
          vm_paddr_t pa;
          struct vm_page *pg;
          
          pg = vm_page_alloc(NULL, 0, VM_ALLOC_NOOBJ | VM_ALLOC_WIRED);
          if (pg == NULL)
                  return (1);
          pa = VM_PAGE_TO_PHYS(pg);
  
          if (pap)
                  *pap = pa;
  
          l2b = pmap_get_l2_bucket(pmap_kernel(), va);
  
          ptep = &l2b->l2b_kva[l2pte_index(va)];
          *ptep = L2_S_PROTO | pa | cache_mode |
              L2_S_PROT(PTE_KERNEL, VM_PROT_READ | VM_PROT_WRITE);
          PTE_SYNC(ptep);
          return (0);
  }
  
  /*
   * This is the same as pmap_alloc_l2_bucket(), except that it is only
   * used by pmap_growkernel().
   */
  static __inline struct l2_bucket *
  pmap_grow_l2_bucket(pmap_t pm, vm_offset_t va)
  {
          struct l2_dtable *l2;
          struct l2_bucket *l2b;
          struct l1_ttable *l1;
          pd_entry_t *pl1pd;
          u_short l1idx;
          vm_offset_t nva;
  
          l1idx = L1_IDX(va);
  
          if ((l2 = pm->pm_l2[L2_IDX(l1idx)]) == NULL) {
                  /*
                   * No mapping at this address, as there is
                   * no entry in the L1 table.
                   * Need to allocate a new l2_dtable.
                   */
                  nva = pmap_kernel_l2dtable_kva;
                  if ((nva & PAGE_MASK) == 0) {
                          /*
                           * Need to allocate a backing page
                           */
                          if (pmap_grow_map(nva, pte_l2_s_cache_mode, NULL))
                                  return (NULL);
                  }
  
                  l2 = (struct l2_dtable *)nva;
                  nva += sizeof(struct l2_dtable);
  
                  if ((nva & PAGE_MASK) < (pmap_kernel_l2dtable_kva & 
                      PAGE_MASK)) {
                          /*
                           * The new l2_dtable straddles a page boundary.
                           * Map in another page to cover it.
                           */
                          if (pmap_grow_map(nva, pte_l2_s_cache_mode, NULL))
                                  return (NULL);
                  }
  
                  pmap_kernel_l2dtable_kva = nva;
  
                  /*
                   * Link it into the parent pmap
                   */
                  pm->pm_l2[L2_IDX(l1idx)] = l2;
                  memset(l2, 0, sizeof(*l2));
          }
  
          l2b = &l2->l2_bucket[L2_BUCKET(l1idx)];
  
          /*
           * Fetch pointer to the L2 page table associated with the address.
           */
          if (l2b->l2b_kva == NULL) {
                  pt_entry_t *ptep;
  
                  /*
                   * No L2 page table has been allocated. Chances are, this
                   * is because we just allocated the l2_dtable, above.
                   */
                  nva = pmap_kernel_l2ptp_kva;
                  ptep = (pt_entry_t *)nva;
                  if ((nva & PAGE_MASK) == 0) {
                          /*
                           * Need to allocate a backing page
                           */
                          if (pmap_grow_map(nva, pte_l2_s_cache_mode_pt,
                              &pmap_kernel_l2ptp_phys))
                                  return (NULL);
                          PTE_SYNC_RANGE(ptep, PAGE_SIZE / sizeof(pt_entry_t));
                  }
  
                  memset(ptep, 0, L2_TABLE_SIZE_REAL);
                  l2->l2_occupancy++;
                  l2b->l2b_kva = ptep;
                  l2b->l2b_l1idx = l1idx;
                  l2b->l2b_phys = pmap_kernel_l2ptp_phys;
  
                  pmap_kernel_l2ptp_kva += L2_TABLE_SIZE_REAL;
                  pmap_kernel_l2ptp_phys += L2_TABLE_SIZE_REAL;
          }
  
          /* Distribute new L1 entry to all other L1s */
          SLIST_FOREACH(l1, &l1_list, l1_link) {
                          pl1pd = &l1->l1_kva[L1_IDX(va)];
                          *pl1pd = l2b->l2b_phys | L1_C_DOM(PMAP_DOMAIN_KERNEL) |
                              L1_C_PROTO;
                          PTE_SYNC(pl1pd);
          }
  
          return (l2b);
  }
  
  
  /*
   * grow the number of kernel page table entries, if needed
   */
  void
  pmap_growkernel(vm_offset_t addr)
  {
          pmap_t kpm = pmap_kernel();
          int s;
  
          if (addr <= pmap_curmaxkvaddr)
                  return;         /* we are OK */
  
          /*
           * whoops!   we need to add kernel PTPs
           */
  
          s = splhigh();  /* to be safe */
  
          /* Map 1MB at a time */
          for (; pmap_curmaxkvaddr < addr; pmap_curmaxkvaddr += L1_S_SIZE)
                  pmap_grow_l2_bucket(kpm, pmap_curmaxkvaddr);
  
          /*
           * flush out the cache, expensive but growkernel will happen so
           * rarely
           */
          cpu_dcache_wbinv_all();
          cpu_tlb_flushD();
          cpu_cpwait();
          kernel_vm_end = pmap_curmaxkvaddr;
  
  }
  
  
  /*
   *      pmap_page_protect:
   *
   *      Lower the permission for all mappings to a given page.
   */
  void
  pmap_page_protect(vm_page_t m, vm_prot_t prot)
  {
          switch(prot) {
          case VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE:
          case VM_PROT_READ|VM_PROT_WRITE:
                  return;
  
          case VM_PROT_READ:
          case VM_PROT_READ|VM_PROT_EXECUTE:
                  pmap_clearbit(m, PVF_WRITE);
                  break;
  
          default:
                  pmap_remove_all(m);
                  break;
          }
  
  }
  
  
  /*
   * 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, vm_offset_t sva, vm_offset_t eva)
  {
          struct pv_entry *pv, *npv;
          struct l2_bucket *l2b = NULL;
          vm_page_t m;
          pt_entry_t *pt;
          
          vm_page_lock_queues();
          for (pv = TAILQ_FIRST(&pmap->pm_pvlist); pv; pv = npv) {
                  if (pv->pv_va >= eva || pv->pv_va < sva) {
                          npv = TAILQ_NEXT(pv, pv_plist);
                          continue;
                  }
                  if (pv->pv_flags & PVF_WIRED) {
                          /* The page is wired, cannot remove it now. */
                          npv = TAILQ_NEXT(pv, pv_plist);
                          continue;
                  }
                  pmap->pm_stats.resident_count--;
                  l2b = pmap_get_l2_bucket(pmap, pv->pv_va);
                  KASSERT(l2b != NULL, ("No L2 bucket in pmap_remove_pages"));
                  pt = &l2b->l2b_kva[l2pte_index(pv->pv_va)];
                  m = PHYS_TO_VM_PAGE(*pt & L2_ADDR_MASK);
                  *pt = 0;
                  PTE_SYNC(pt);
                  npv = TAILQ_NEXT(pv, pv_plist);
                  pmap_nuke_pv(m, pmap, pv);
                  pmap_free_pv_entry(pv);
          }
          vm_page_unlock_queues();
          cpu_idcache_wbinv_all();
          cpu_tlb_flushID();
          cpu_cpwait();
  }
  
  
  /***************************************************
   * Low level mapping routines.....
   ***************************************************/
  
  /* Map a section into the KVA. */
  
  void
  pmap_kenter_section(vm_offset_t va, vm_offset_t pa, int flags)
  {
          pd_entry_t pd = L1_S_PROTO | pa | L1_S_PROT(PTE_KERNEL,
              VM_PROT_READ|VM_PROT_WRITE) | L1_S_DOM(PMAP_DOMAIN_KERNEL);
          struct l1_ttable *l1;
  
          KASSERT(((va | pa) & L1_S_OFFSET) == 0,
              ("Not a valid section mapping"));
          if (flags & SECTION_CACHE)
                  pd |= pte_l1_s_cache_mode;
          else if (flags & SECTION_PT)
                  pd |= pte_l1_s_cache_mode_pt;
          SLIST_FOREACH(l1, &l1_list, l1_link) {
                  l1->l1_kva[L1_IDX(va)] = pd;
                  PTE_SYNC(&l1->l1_kva[L1_IDX(va)]);
          }
  }
  
  /*
   * add a wired page to the kva
   * note that in order for the mapping to take effect -- you
   * should do a invltlb after doing the pmap_kenter...
   */
  static PMAP_INLINE void
  pmap_kenter_internal(vm_offset_t va, vm_offset_t pa, int flags)
  {
          struct l2_bucket *l2b;
          pt_entry_t *pte;
          pt_entry_t opte;
          PDEBUG(1, printf("pmap_kenter: va = %08x, pa = %08x\n",
              (uint32_t) va, (uint32_t) pa));
  
  
          l2b = pmap_get_l2_bucket(pmap_kernel(), va);
          if (l2b == NULL)
                  l2b = pmap_grow_l2_bucket(pmap_kernel(), va);
          KASSERT(l2b != NULL, ("No L2 Bucket"));
          pte = &l2b->l2b_kva[l2pte_index(va)];
          opte = *pte;
          PDEBUG(1, printf("pmap_kenter: pte = %08x, opte = %08x, npte = %08x\n",
              (uint32_t) pte, opte, *pte));
          if (l2pte_valid(opte)) {
                  cpu_dcache_wbinv_range(va, PAGE_SIZE);
                  cpu_tlb_flushD_SE(va);
                  cpu_cpwait();
          } else {
                  if (opte == 0)
                          l2b->l2b_occupancy++;
          }
          *pte = L2_S_PROTO | pa | L2_S_PROT(PTE_KERNEL, 
              VM_PROT_READ | VM_PROT_WRITE);
          if (flags & KENTER_CACHE)
                  *pte |= pte_l2_s_cache_mode;
          if (flags & KENTER_USER)
                  *pte |= L2_S_PROT_U;
          PTE_SYNC(pte);
  }
  
  void
  pmap_kenter(vm_offset_t va, vm_paddr_t pa)
  {
          pmap_kenter_internal(va, pa, KENTER_CACHE);
  }
  
  void
  pmap_kenter_nocache(vm_offset_t va, vm_paddr_t pa)
  {
          pmap_kenter_internal(va, pa, 0);
  }
  
  void
  pmap_kenter_user(vm_offset_t va, vm_paddr_t pa)
  {
  
          pmap_kenter_internal(va, pa, KENTER_CACHE|KENTER_USER);
          /*
           * Call pmap_fault_fixup now, to make sure we'll have no exception
           * at the first use of the new address, or bad things will happen,
           * as we use one of these addresses in the exception handlers.
           */
          pmap_fault_fixup(pmap_kernel(), va, VM_PROT_READ|VM_PROT_WRITE, 1);
  }
  
  /*
   * remove a page rom the kernel pagetables
   */
  PMAP_INLINE void
  pmap_kremove(vm_offset_t va)
  {
          struct l2_bucket *l2b;
          pt_entry_t *pte, opte;
                  
          l2b = pmap_get_l2_bucket(pmap_kernel(), va);
          if (!l2b)
                  return;
          KASSERT(l2b != NULL, ("No L2 Bucket"));
          pte = &l2b->l2b_kva[l2pte_index(va)];
          opte = *pte;
          if (l2pte_valid(opte)) {
                  cpu_dcache_wbinv_range(va, PAGE_SIZE);
                  cpu_tlb_flushD_SE(va);
                  cpu_cpwait();
                  *pte = 0;
          }
  }
  
  
  /*
   *      Used to map a range of physical addresses into kernel
   *      virtual address space.
   *
   *      The value passed in '*virt' is a suggested virtual address for
   *      the mapping. Architectures which can support a direct-mapped
   *      physical to virtual region can return the appropriate address
   *      within that region, leaving '*virt' unchanged. Other
   *      architectures should map the pages starting at '*virt' and
   *      update '*virt' with the first usable address after the mapped
   *      region.
   */
  vm_offset_t
  pmap_map(vm_offset_t *virt, vm_offset_t start, vm_offset_t end, int prot)
  {
          vm_offset_t sva = *virt;
          vm_offset_t va = sva;
  
          PDEBUG(1, printf("pmap_map: virt = %08x, start = %08x, end = %08x, "
              "prot = %d\n", (uint32_t) *virt, (uint32_t) start, (uint32_t) end,
              prot));
              
          while (start < end) {
                  pmap_kenter(va, start);
                  va += PAGE_SIZE;
                  start += PAGE_SIZE;
          }
          *virt = va;
          return (sva);
  }
  
  static void
  pmap_wb_page(vm_page_t m, boolean_t do_inv)
  {
          struct pv_entry *pv;
  
          TAILQ_FOREACH(pv, &m->md.pv_list, pv_list)
              pmap_dcache_wb_range(pv->pv_pmap, pv->pv_va, PAGE_SIZE, do_inv,
                  (pv->pv_flags & PVF_WRITE) == 0);
  }
  
  /*
   * 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;
  
          for (i = 0; i < count; i++) {
                  pmap_wb_page(m[i], TRUE);
                  pmap_kenter_internal(va, VM_PAGE_TO_PHYS(m[i]), 
                      KENTER_CACHE);
                  va += PAGE_SIZE;
          }
  }
  
  
  /*
   * this routine jerks page mappings from the
   * kernel -- it is meant only for temporary mappings.
   */
  void
  pmap_qremove(vm_offset_t va, int count)
  {
          vm_paddr_t pa;
          int i;
  
          for (i = 0; i < count; i++) {
                  pa = vtophys(va);
                  if (pa) {
                          pmap_wb_page(PHYS_TO_VM_PAGE(pa), TRUE);
                          pmap_kremove(va);
                  }
                  va += PAGE_SIZE;
          }
  }
  
  
  /*
   * 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,
              ("pmap_object_init_pt: non-device object"));
  }
  
  
  /*
   *      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;
  
          if (!pmap_get_pde_pte(pmap, addr, &pde, &pte))
                  return (FALSE);
          KASSERT(pte != NULL, ("Valid mapping but no pte ?"));
          if (*pte == 0)
                  return (TRUE);
          return (FALSE);
  }
  
  /*
   * Fetch pointers to the PDE/PTE for the given pmap/VA pair.
   * Returns TRUE if the mapping exists, else FALSE.
   *
   * NOTE: This function is only used by a couple of arm-specific modules.
   * It is not safe to take any pmap locks here, since we could be right
   * in the middle of debugging the pmap anyway...
   *
   * It is possible for this routine to return FALSE even though a valid
   * mapping does exist. This is because we don't lock, so the metadata
   * state may be inconsistent.
   *
   * NOTE: We can return a NULL *ptp in the case where the L1 pde is
   * a "section" mapping.
   */
  boolean_t
  pmap_get_pde_pte(pmap_t pm, vm_offset_t va, pd_entry_t **pdp, pt_entry_t **ptp)
  {
          struct l2_dtable *l2;
          pd_entry_t *pl1pd, l1pd;
          pt_entry_t *ptep;
          u_short l1idx;
  
          if (pm->pm_l1 == NULL)
                  return (FALSE);
  
          l1idx = L1_IDX(va);
          *pdp = pl1pd = &pm->pm_l1->l1_kva[l1idx];
          l1pd = *pl1pd;
  
          if (l1pte_section_p(l1pd)) {
                  *ptp = NULL;
                  return (TRUE);
          }
  
          if (pm->pm_l2 == NULL)
                  return (FALSE);
  
          l2 = pm->pm_l2[L2_IDX(l1idx)];
  
          if (l2 == NULL ||
              (ptep = l2->l2_bucket[L2_BUCKET(l1idx)].l2b_kva) == NULL) {
                  return (FALSE);
          }
  
          *ptp = &ptep[l2pte_index(va)];
          return (TRUE);
  }
  
  /*
   *      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 *ptep, pte;
          struct l2_bucket *l2b;
          boolean_t flush = FALSE;
          pmap_t curpm;
          int flags = 0;
  
  #if defined(PMAP_DEBUG)
          /*
           * XXX this makes pmap_page_protect(NONE) illegal for non-managed
           * pages!
           */
          if (m->flags & PG_FICTITIOUS) {
                  panic("pmap_page_protect: illegal for unmanaged page, va: 0x%x", VM_PAGE_TO_PHYS(m));
          }
  #endif
  
          if (TAILQ_EMPTY(&m->md.pv_list))
                  return;
          curpm = vmspace_pmap(curproc->p_vmspace);
          while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                  if (flush == FALSE && (pv->pv_pmap == curpm ||
                      pv->pv_pmap == pmap_kernel()))
                          flush = TRUE;
                  l2b = pmap_get_l2_bucket(pv->pv_pmap, pv->pv_va);
                  KASSERT(l2b != NULL, ("No l2 bucket"));
                  ptep = &l2b->l2b_kva[l2pte_index(pv->pv_va)];
                  pte = *ptep;
                  *ptep = 0;
                  PTE_SYNC_CURRENT(pv->pv_pmap, ptep);
                  pmap_free_l2_bucket(pv->pv_pmap, l2b, 1);
                  if (pv->pv_flags & PVF_WIRED)
                          pv->pv_pmap->pm_stats.wired_count--;
                  pv->pv_pmap->pm_stats.resident_count--;
                  flags |= pv->pv_flags;
                  pmap_nuke_pv(m, pv->pv_pmap, pv);
                  pmap_free_pv_entry(pv);
          }
  
          if (flush) {
                  if (PV_BEEN_EXECD(flags))
                          pmap_tlb_flushID(curpm);
                  else
                          pmap_tlb_flushD(curpm);
          }
  }
  
  
  /*
   *      Set the physical protection on the
   *      specified range of this map as requested.
   */
  void
  pmap_protect(pmap_t pm, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
  {
          struct l2_bucket *l2b;
          pt_entry_t *ptep, pte;
          vm_offset_t next_bucket;
          u_int flags;
          int flush;
  
          if ((prot & VM_PROT_READ) == 0) {
                  mtx_lock(&Giant);
                  pmap_remove(pm, sva, eva);
                  mtx_unlock(&Giant);
                  return;
          }
  
          if (prot & VM_PROT_WRITE) {
                  /*
                   * If this is a read->write transition, just ignore it and let
                   * vm_fault() take care of it later.
                   */
                  return;
          }
  
          mtx_lock(&Giant);
  
          /*
           * OK, at this point, we know we're doing write-protect operation.
           * If the pmap is active, write-back the range.
           */
          pmap_dcache_wb_range(pm, sva, eva - sva, FALSE, FALSE);
  
          flush = ((eva - sva) >= (PAGE_SIZE * 4)) ? 0 : -1;
          flags = 0;
  
          vm_page_lock_queues();
          while (sva < eva) {
                  next_bucket = L2_NEXT_BUCKET(sva);
                  if (next_bucket > eva)
                          next_bucket = eva;
  
                  l2b = pmap_get_l2_bucket(pm, sva);
                  if (l2b == NULL) {
                          sva = next_bucket;
                          continue;
                  }
  
                  ptep = &l2b->l2b_kva[l2pte_index(sva)];
  
                  while (sva < next_bucket) {
                          if ((pte = *ptep) != 0 && (pte & L2_S_PROT_W) != 0) {
                                  struct vm_page *pg;
                                  u_int f;
  
                                  pg = PHYS_TO_VM_PAGE(l2pte_pa(pte));
                                  pte &= ~L2_S_PROT_W;
                                  *ptep = pte;
                                  PTE_SYNC(ptep);
  
                                  if (pg != NULL) {
                                          f = pmap_modify_pv(pg, pm, sva,
                                              PVF_WRITE, 0);
                                          pmap_vac_me_harder(pg, pm, sva);
                                          if (pmap_track_modified(sva))
                                                  vm_page_dirty(pg);
                                  } else
                                          f = PVF_REF | PVF_EXEC;
  
                                  if (flush >= 0) {
                                          flush++;
                                          flags |= f;
                                  } else
                                  if (PV_BEEN_EXECD(f))
                                          pmap_tlb_flushID_SE(pm, sva);
                                  else
                                  if (PV_BEEN_REFD(f))
                                          pmap_tlb_flushD_SE(pm, sva);
                          }
  
                          sva += PAGE_SIZE;
                          ptep++;
                  }
          }
  
  
          if (flush) {
                  if (PV_BEEN_EXECD(flags))
                          pmap_tlb_flushID(pm);
                  else
                  if (PV_BEEN_REFD(flags))
                          pmap_tlb_flushD(pm);
          }
          vm_page_unlock_queues();
  
          mtx_unlock(&Giant);
  }
  
  
  /*
   *      Insert the given physical page (p) at
   *      the specified virtual address (v) in the
   *      target physical map with the protection requested.
   *
   *      If specified, the page will be wired down, meaning
   *      that the related pte can not be reclaimed.
   *
   *      NB:  This is the only routine which MAY NOT lazy-evaluate
   *      or lose information.  That is, this routine must actually
   *      insert this page into the given map NOW.
   */
  
  void
  pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
      boolean_t wired)
  {
          struct l2_bucket *l2b = NULL;
          struct vm_page *opg;
          struct pv_entry *pve = NULL;
          pt_entry_t *ptep, npte, opte;
          u_int nflags;
          u_int oflags;
          vm_paddr_t pa;
  
          vm_page_lock_queues();
          if (va == vector_page) {
                  pa = systempage.pv_pa;
                  m = NULL;
          } else
                  pa = VM_PAGE_TO_PHYS(m);
          nflags = 0;
          if (prot & VM_PROT_WRITE)
                  nflags |= PVF_WRITE;
          if (prot & VM_PROT_EXECUTE)
                  nflags |= PVF_EXEC;
          if (wired)
                  nflags |= PVF_WIRED;
          PDEBUG(1, printf("pmap_enter: pmap = %08x, va = %08x, m = %08x, prot = %x, "
              "wired = %x\n", (uint32_t) pmap, va, (uint32_t) m, prot, wired));
              
          if (pmap == pmap_kernel()) {
                  l2b = pmap_get_l2_bucket(pmap, va);
                  if (l2b == NULL)
                          l2b = pmap_grow_l2_bucket(pmap, va);
          } else
                  l2b = pmap_alloc_l2_bucket(pmap, va);
                  KASSERT(l2b != NULL,
                      ("pmap_enter: failed to allocate l2 bucket"));
          ptep = &l2b->l2b_kva[l2pte_index(va)];
                      
          opte = *ptep;
          npte = pa;
          oflags = 0;
          if (opte) {
                  /*
                   * There is already a mapping at this address.
                   * If the physical address is different, lookup the
                   * vm_page.
                   */
                  if (l2pte_pa(opte) != pa)
                          opg = PHYS_TO_VM_PAGE(l2pte_pa(opte));
                  else
                          opg = m;
          } else
                  opg = NULL;
  
          if ((prot & (VM_PROT_ALL)) ||
              (!m || m->md.pvh_attrs & PVF_REF)) {
                  /*
                   * - The access type indicates that we don't need
                   *   to do referenced emulation.
                   * OR
                   * - The physical page has already been referenced
                   *   so no need to re-do referenced emulation here.
                   */
                  npte |= L2_S_PROTO;
                  
                  nflags |= PVF_REF;
                  
                  if (m && ((prot & VM_PROT_WRITE) != 0 ||
                      (m->md.pvh_attrs & PVF_MOD))) {
                          /*
                           * This is a writable mapping, and the
                           * page's mod state indicates it has
                           * already been modified. Make it
                           * writable from the outset.
                           */
                          nflags |= PVF_MOD;
                          if (!(m->md.pvh_attrs & PVF_MOD) &&
                              pmap_track_modified(va))
                                  vm_page_dirty(m);
                  }
                  if (m && opte)
                          vm_page_flag_set(m, PG_REFERENCED);
          } else {
                  /*
                   * Need to do page referenced emulation.
                   */
                  npte |= L2_TYPE_INV;
          }
          
          if (prot & VM_PROT_WRITE)
                  npte |= L2_S_PROT_W;
          npte |= pte_l2_s_cache_mode;
          if (m && m == opg) {
                  /*
                   * We're changing the attrs of an existing mapping.
                   */
  #if 0
                  simple_lock(&pg->mdpage.pvh_slock);
  #endif
                  oflags = pmap_modify_pv(m, pmap, va,
                      PVF_WRITE | PVF_EXEC | PVF_WIRED |
                      PVF_MOD | PVF_REF, nflags);
  #if 0
                  simple_unlock(&pg->mdpage.pvh_slock);
  #endif
                  
                  /*
                   * We may need to flush the cache if we're
                   * doing rw-ro...
                   */
                  if (pmap_is_current(pmap) &&
                      (oflags & PVF_NC) == 0 &&
                              (opte & L2_S_PROT_W) != 0 &&
                              (prot & VM_PROT_WRITE) == 0)
                          cpu_dcache_wb_range(va, PAGE_SIZE);
          } else {
                  /*
                   * New mapping, or changing the backing page
                   * of an existing mapping.
                   */
                  if (opg) {
                          /*
                           * Replacing an existing mapping with a new one.
                           * It is part of our managed memory so we
                           * must remove it from the PV list
                           */
  #if 0
                          simple_lock(&opg->mdpage.pvh_slock);
  #endif
                          pve = pmap_remove_pv(opg, pmap, va);
                          if (m && (m->flags & (PG_UNMANAGED | PG_FICTITIOUS)) && 
                              pve)
                                  pmap_free_pv_entry(pve);
                          else if (!pve &&
                              !(m->flags & (PG_UNMANAGED | PG_FICTITIOUS)))
                                  pve = pmap_get_pv_entry();
                          KASSERT(pve != NULL, ("No pv"));
  #if 0
                          simple_unlock(&opg->mdpage.pvh_slock);
  #endif
                          oflags = pve->pv_flags;
                          
                          /*
                           * If the old mapping was valid (ref/mod
                           * emulation creates 'invalid' mappings
                           * initially) then make sure to frob
                           * the cache.
                           */
                          if ((oflags & PVF_NC) == 0 &&
                              l2pte_valid(opte)) {
                                  if (PV_BEEN_EXECD(oflags)) {
                                          pmap_idcache_wbinv_range(pmap, va,
                                              PAGE_SIZE);
                                  } else
                                          if (PV_BEEN_REFD(oflags)) {
                                                  pmap_dcache_wb_range(pmap, va,
                                                      PAGE_SIZE, TRUE,
                                                      (oflags & PVF_WRITE) == 0);
                                          }
                          }
                  } else if (m && !(m->flags & (PG_UNMANAGED | PG_FICTITIOUS)))
                          if ((pve = pmap_get_pv_entry()) == NULL) {
                                  panic("pmap_enter: no pv entries");     
                          }
                  if (m && !(m->flags & (PG_UNMANAGED | PG_FICTITIOUS)))
                          pmap_enter_pv(m, pve, pmap, va, nflags);
          }
          /*
           * Make sure userland mappings get the right permissions
           */
          if (pmap != pmap_kernel() && va != vector_page) {
                  npte |= L2_S_PROT_U;
          }
  
          /*
           * Keep the stats up to date
           */
          if (opte == 0) {
                  l2b->l2b_occupancy++;
                  pmap->pm_stats.resident_count++;
          } 
  
  
          /*
           * If this is just a wiring change, the two PTEs will be
           * identical, so there's no need to update the page table.
           */
          if (npte != opte) {
                  boolean_t is_cached = pmap_is_current(pmap);
  
                  *ptep = npte;
                  if (is_cached) {
                          /*
                           * We only need to frob the cache/tlb if this pmap
                           * is current
                           */
                          PTE_SYNC(ptep);
                          if (L1_IDX(va) != L1_IDX(vector_page) &&
                              l2pte_valid(npte)) {
                                  /*
                                   * This mapping is likely to be accessed as
                                   * soon as we return to userland. Fix up the
                                   * L1 entry to avoid taking another
                                   * page/domain fault.
                                   */
                                  pd_entry_t *pl1pd, l1pd;
  
                                  pl1pd = &pmap->pm_l1->l1_kva[L1_IDX(va)];
                                  l1pd = l2b->l2b_phys | L1_C_DOM(pmap->pm_domain) |
                                      L1_C_PROTO;
                                  if (*pl1pd != l1pd) {
                                          *pl1pd = l1pd;
                                          PTE_SYNC(pl1pd);
                                  }
                          }
                  }
  
                  if (PV_BEEN_EXECD(oflags))
                          pmap_tlb_flushID_SE(pmap, va);
                  else if (PV_BEEN_REFD(oflags))
                          pmap_tlb_flushD_SE(pmap, va);
  
  
                  if (m)
                          pmap_vac_me_harder(m, pmap, va);
          }
          vm_page_unlock_queues();
  }
  
  /*
   * this code makes some *MAJOR* assumptions:
   * 1. Current pmap & pmap exists.
   * 2. Not wired.
   * 3. Read access.
   * 4. No page table pages.
   * but is *MUCH* faster than pmap_enter...
   */
  
  vm_page_t
  pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
      vm_page_t mpte)
  {
  
          vm_page_busy(m);
          vm_page_unlock_queues();
          VM_OBJECT_UNLOCK(m->object);
          mtx_lock(&Giant);
          pmap_enter(pmap, va, m, prot & (VM_PROT_READ | VM_PROT_EXECUTE), FALSE);
          pmap_idcache_wbinv_all(pmap);
          mtx_unlock(&Giant);
          VM_OBJECT_LOCK(m->object);
          vm_page_lock_queues();
          vm_page_wakeup(m);
          return (NULL);
  }
  
  /*
   *      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)
  {
          struct l2_bucket *l2b;
          pt_entry_t *ptep, pte;
          vm_page_t pg;
  
          l2b = pmap_get_l2_bucket(pmap, va);
          KASSERT(l2b, ("No l2b bucket in pmap_change_wiring"));
          ptep = &l2b->l2b_kva[l2pte_index(va)];
          pte = *ptep;
          pg = PHYS_TO_VM_PAGE(l2pte_pa(pte));
          if (pg) 
                  pmap_modify_pv(pg, pmap, va, PVF_WIRED, wired);
  }
  
  
  /*
   *      Copy the range specified by src_addr/len
   *      from the source map to the range dst_addr/len
   *      in the destination map.
   *
   *      This routine is only advisory and need not do anything.
   */
  void
  pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr,
      vm_size_t len, vm_offset_t src_addr)
  {
  }
  
  
  /*
   *      Routine:        pmap_extract
   *      Function:
   *              Extract the physical page address associated
   *              with the given map/virtual_address pair.
   */
  vm_paddr_t
  pmap_extract(pmap_t pm, vm_offset_t va)
  {
          struct l2_dtable *l2;
          pd_entry_t *pl1pd, l1pd;
          pt_entry_t *ptep, pte;
          vm_paddr_t pa;
          u_int l1idx;
          l1idx = L1_IDX(va);
          pl1pd = &pm->pm_l1->l1_kva[l1idx];
          l1pd = *pl1pd;
  
          if (l1pte_section_p(l1pd)) {
                  /*
                   * These should only happen for pmap_kernel()
                   */
                  KASSERT(pm == pmap_kernel(), ("huh"));
                  pa = (l1pd & L1_S_FRAME) | (va & L1_S_OFFSET);
          } else {
                  /*
                   * Note that we can't rely on the validity of the L1
                   * descriptor as an indication that a mapping exists.
                   * We have to look it up in the L2 dtable.
                   */
                  l2 = pm->pm_l2[L2_IDX(l1idx)];
  
                  if (l2 == NULL ||
                      (ptep = l2->l2_bucket[L2_BUCKET(l1idx)].l2b_kva) == NULL) {
                          return (0);
                  }
  
                  ptep = &ptep[l2pte_index(va)];
                  pte = *ptep;
  
                  if (pte == 0)
                          return (0);
  
                  switch (pte & L2_TYPE_MASK) {
                  case L2_TYPE_L:
                          pa = (pte & L2_L_FRAME) | (va & L2_L_OFFSET);
                          break;
  
                  default:
                          pa = (pte & L2_S_FRAME) | (va & L2_S_OFFSET);
                          break;
                  }
          }
  
          return (pa);
  }
  
  /*
   * 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)
  {
          struct l2_dtable *l2;
          pd_entry_t *pl1pd, l1pd;
          pt_entry_t *ptep, pte;
          vm_paddr_t pa;
          vm_page_t m = NULL;
          u_int l1idx;
          l1idx = L1_IDX(va);
          pl1pd = &pmap->pm_l1->l1_kva[l1idx];
          l1pd = *pl1pd;
  
          vm_page_lock_queues();
          if (l1pte_section_p(l1pd)) {
                  /*
                   * These should only happen for pmap_kernel()
                   */
                  KASSERT(pmap == pmap_kernel(), ("huh"));
                  pa = (l1pd & L1_S_FRAME) | (va & L1_S_OFFSET);
                  if (l1pd & L1_S_PROT_W || (prot & VM_PROT_WRITE) == 0) {
                          m = PHYS_TO_VM_PAGE(pa);
                          vm_page_hold(m);
                  }
                          
          } else {
                  /*
                   * Note that we can't rely on the validity of the L1
                   * descriptor as an indication that a mapping exists.
                   * We have to look it up in the L2 dtable.
                   */
                  l2 = pmap->pm_l2[L2_IDX(l1idx)];
  
                  if (l2 == NULL ||
                      (ptep = l2->l2_bucket[L2_BUCKET(l1idx)].l2b_kva) == NULL) {
                          return (NULL);
                  }
  
                  ptep = &ptep[l2pte_index(va)];
                  pte = *ptep;
  
                  if (pte == 0)
                          return (NULL);
  
                  if (pte & L2_S_PROT_W || (prot & VM_PROT_WRITE) == 0) {
                          switch (pte & L2_TYPE_MASK) {
                          case L2_TYPE_L:
                                  pa = (pte & L2_L_FRAME) | (va & L2_L_OFFSET);
                                  break;
                                  
                          default:
                                  pa = (pte & L2_S_FRAME) | (va & L2_S_OFFSET);
                                  break;
                          }
                          m = PHYS_TO_VM_PAGE(pa);
                          vm_page_hold(m);
                  }
          }
  
          vm_page_unlock_queues();
          return (m);
  }
  
  /*
   * Initialize a preallocated and zeroed pmap structure,
   * such as one in a vmspace structure.
   */
  
  void
  pmap_pinit(pmap_t pmap)
  {
          PDEBUG(1, printf("pmap_pinit: pmap = %08x\n", (uint32_t) pmap));
          
          pmap_alloc_l1(pmap);
          bzero(pmap->pm_l2, sizeof(pmap->pm_l2));
  
          LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
          pmap->pm_count = 1;
          pmap->pm_active = 0;
                  
          TAILQ_INIT(&pmap->pm_pvlist);
          bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
          pmap->pm_stats.resident_count = 1;
          if (vector_page < KERNBASE) {
                  pmap_enter(pmap, vector_page, PHYS_TO_VM_PAGE(systempage.pv_pa),
                      VM_PROT_READ, 1);
          } 
  }
  
  
  /***************************************************
   * page management routines.
   ***************************************************/
  
  
  static void
  pmap_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
  pmap_get_pv_entry(void)
  {
          pv_entry_t ret_value;
          
          pv_entry_count++;
          if (pv_entry_high_water &&
              (pv_entry_count > pv_entry_high_water) &&
              (pmap_pagedaemon_waken == 0)) {
                  pmap_pagedaemon_waken = 1;
                  wakeup (&vm_pages_needed);
          }
          ret_value = uma_zalloc(pvzone, M_NOWAIT);
          return ret_value;
  }
  
  
  /*
   *      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.
   */
  #define  PMAP_REMOVE_CLEAN_LIST_SIZE     3
  void
  pmap_remove(pmap_t pm, vm_offset_t sva, vm_offset_t eva)
  {
          struct l2_bucket *l2b;
          vm_offset_t next_bucket;
          pt_entry_t *ptep;
          u_int cleanlist_idx, total, cnt;
          struct {
                  vm_offset_t va;
                  pt_entry_t *pte;
          } cleanlist[PMAP_REMOVE_CLEAN_LIST_SIZE];
          u_int mappings, is_exec, is_refd;
          int flushall = 0;
  
  
          /*
           * we lock in the pmap => pv_head direction
           */
  #if 0
          PMAP_MAP_TO_HEAD_LOCK();
          pmap_acquire_pmap_lock(pm);
  #endif
  
          vm_page_lock_queues();
          if (!pmap_is_current(pm)) {
                  cleanlist_idx = PMAP_REMOVE_CLEAN_LIST_SIZE + 1;
          } else
                  cleanlist_idx = 0;
  
          total = 0;
          while (sva < eva) {
                  /*
                   * Do one L2 bucket's worth at a time.
                   */
                  next_bucket = L2_NEXT_BUCKET(sva);
                  if (next_bucket > eva)
                          next_bucket = eva;
  
                  l2b = pmap_get_l2_bucket(pm, sva);
                  if (l2b == NULL) {
                          sva = next_bucket;
                          continue;
                  }
  
                  ptep = &l2b->l2b_kva[l2pte_index(sva)];
                  mappings = 0;
  
                  while (sva < next_bucket) {
                          struct vm_page *pg;
                          pt_entry_t pte;
                          vm_paddr_t pa;
  
                          pte = *ptep;
  
                          if (pte == 0) {
                                  /*
                                   * Nothing here, move along
                                   */
                                  sva += PAGE_SIZE;
                                  ptep++;
                                  continue;
                          }
  
                          pm->pm_stats.resident_count--;
                          pa = l2pte_pa(pte);
                          is_exec = 0;
                          is_refd = 1;
  
                          /*
                           * Update flags. In a number of circumstances,
                           * we could cluster a lot of these and do a
                           * number of sequential pages in one go.
                           */
                          if ((pg = PHYS_TO_VM_PAGE(pa)) != NULL) {
                                  struct pv_entry *pve;
  #if 0
                                  simple_lock(&pg->mdpage.pvh_slock);
  #endif
                                  pve = pmap_remove_pv(pg, pm, sva);
                                  if (pve) {
  #if 0
                                  simple_unlock(&pg->mdpage.pvh_slock);
  #endif
                                                  is_exec =
                                                     PV_BEEN_EXECD(pve->pv_flags);
                                                  is_refd =
                                                     PV_BEEN_REFD(pve->pv_flags);
                                          pmap_free_pv_entry(pve);
                                  }
                          }
  
                          if (!l2pte_valid(pte)) {
                                  *ptep = 0;
                                  PTE_SYNC_CURRENT(pm, ptep);
                                  sva += PAGE_SIZE;
                                  ptep++;
                                  mappings++;
                                  continue;
                          }
  
                          if (cleanlist_idx < PMAP_REMOVE_CLEAN_LIST_SIZE) {
                                  /* Add to the clean list. */
                                  cleanlist[cleanlist_idx].pte = ptep;
                                  cleanlist[cleanlist_idx].va =
                                      sva | (is_exec & 1);
                                  cleanlist_idx++;
                          } else
                          if (cleanlist_idx == PMAP_REMOVE_CLEAN_LIST_SIZE) {
                                  /* Nuke everything if needed. */
                                  pmap_idcache_wbinv_all(pm);
                                  pmap_tlb_flushID(pm);
  
                                  /*
                                   * Roll back the previous PTE list,
                                   * and zero out the current PTE.
                                   */
                                  for (cnt = 0;
                                       cnt < PMAP_REMOVE_CLEAN_LIST_SIZE; cnt++) {
                                          *cleanlist[cnt].pte = 0;
                                  }
                                  *ptep = 0;
                                  PTE_SYNC(ptep);
                                  cleanlist_idx++;
                                  flushall = 1;
                          } else {
                                  *ptep = 0;
                                  PTE_SYNC(ptep);
                                          if (is_exec)
                                                  pmap_tlb_flushID_SE(pm, sva);
                                          else
                                          if (is_refd)
                                                  pmap_tlb_flushD_SE(pm, sva);
                          }
  
                          sva += PAGE_SIZE;
                          ptep++;
                          mappings++;
                  }
  
                  /*
                   * Deal with any left overs
                   */
                  if (cleanlist_idx <= PMAP_REMOVE_CLEAN_LIST_SIZE) {
                          total += cleanlist_idx;
                          for (cnt = 0; cnt < cleanlist_idx; cnt++) {
                                  vm_offset_t clva =
                                      cleanlist[cnt].va & ~1;
                                  if (cleanlist[cnt].va & 1) {
                                          pmap_idcache_wbinv_range(pm,
                                              clva, PAGE_SIZE);
                                          pmap_tlb_flushID_SE(pm, clva);
                                  } else {
                                          pmap_dcache_wb_range(pm,
                                              clva, PAGE_SIZE, TRUE,
                                              FALSE);
                                          pmap_tlb_flushD_SE(pm, clva);
                                  }
                                  *cleanlist[cnt].pte = 0;
                                  PTE_SYNC_CURRENT(pm, cleanlist[cnt].pte);
                          }
  
                          if (total <= PMAP_REMOVE_CLEAN_LIST_SIZE)
                                  cleanlist_idx = 0;
                          else {
                                  /*
                                   * We are removing so much entries it's just
                                   * easier to flush the whole cache.
                                   */
                                  cleanlist_idx = PMAP_REMOVE_CLEAN_LIST_SIZE + 1;
                                  pmap_idcache_wbinv_all(pm);
                                  flushall = 1;
                          }
                  }
  
                  pmap_free_l2_bucket(pm, l2b, mappings);
          }
  
          vm_page_unlock_queues();
          if (flushall)
                  cpu_tlb_flushID();
  #if 0
          pmap_release_pmap_lock(pm);
          PMAP_MAP_TO_HEAD_UNLOCK();
  #endif
  }
  
  
  
  
  /*
   * pmap_zero_page()
   * 
   * Zero a given physical page by mapping it at a page hook point.
   * In doing the zero page op, the page we zero is mapped cachable, as with
   * StrongARM accesses to non-cached pages are non-burst making writing
   * _any_ bulk data very slow.
   */
  #if (ARM_MMU_GENERIC + ARM_MMU_SA1) != 0
  void
  pmap_zero_page_generic(vm_paddr_t phys, int off, int size)
  {
  #ifdef DEBUG
          struct vm_page *pg = PHYS_TO_VM_PAGE(phys);
  
          if (pg->md.pvh_list != NULL)
                  panic("pmap_zero_page: page has mappings");
  #endif
  
  
          mtx_lock(&cmtx);
          /*
           * Hook in the page, zero it, and purge the cache for that
           * zeroed page. Invalidate the TLB as needed.
           */
          *cdst_pte = L2_S_PROTO | phys |
              L2_S_PROT(PTE_KERNEL, VM_PROT_WRITE) | pte_l2_s_cache_mode;
          PTE_SYNC(cdst_pte);
          cpu_tlb_flushD_SE(cdstp);
          cpu_cpwait();
          if (off || size != PAGE_SIZE)
                  bzero((void *)(cdstp + off), size);
          else
                  bzero_page(cdstp);
          mtx_unlock(&cmtx);
          cpu_dcache_wbinv_range(cdstp, PAGE_SIZE);
  }
  #endif /* (ARM_MMU_GENERIC + ARM_MMU_SA1) != 0 */
  
  #if ARM_MMU_XSCALE == 1
  void
  pmap_zero_page_xscale(vm_paddr_t phys, int off, int size)
  {
  
          mtx_lock(&cmtx);
          /*
           * Hook in the page, zero it, and purge the cache for that
           * zeroed page. Invalidate the TLB as needed.
           */
          *cdst_pte = L2_S_PROTO | phys |
              L2_S_PROT(PTE_KERNEL, VM_PROT_WRITE) |
              L2_C | L2_XSCALE_T_TEX(TEX_XSCALE_X);       /* mini-data */
          PTE_SYNC(cdst_pte);
          cpu_tlb_flushD_SE(cdstp);
          cpu_cpwait();
          if (off || size != PAGE_SIZE)
                  bzero((void *)(cdstp + off), size);
          else
                  bzero_page(cdstp);
          mtx_unlock(&cmtx);
          xscale_cache_clean_minidata();
  }
  
  /*
   * Change the PTEs for the specified kernel mappings such that they
   * will use the mini data cache instead of the main data cache.
   */
  void
  pmap_use_minicache(vm_offset_t va, vm_size_t size)
  {
          struct l2_bucket *l2b;
          pt_entry_t *ptep, *sptep, pte;
          vm_offset_t next_bucket, eva;
  
  #if (ARM_NMMUS > 1)
          if (xscale_use_minidata == 0)
                  return;
  #endif
  
          eva = va + size;
  
          while (va < eva) {
                  next_bucket = L2_NEXT_BUCKET(va);
                  if (next_bucket > eva)
                          next_bucket = eva;
  
                  l2b = pmap_get_l2_bucket(pmap_kernel(), va);
  
                  sptep = ptep = &l2b->l2b_kva[l2pte_index(va)];
  
                  while (va < next_bucket) {
                          pte = *ptep;
                          if (!l2pte_minidata(pte)) {
                                  cpu_dcache_wbinv_range(va, PAGE_SIZE);
                                  cpu_tlb_flushD_SE(va);
                                  *ptep = pte & ~L2_B;
                          }
                          ptep++;
                          va += PAGE_SIZE;
                  }
                  PTE_SYNC_RANGE(sptep, (u_int)(ptep - sptep));
          }
          cpu_cpwait();
  }
  #endif /* ARM_MMU_XSCALE == 1 */
  
  /*
   *      pmap_zero_page zeros the specified hardware page by mapping 
   *      the page into KVM and using bzero to clear its contents.
   */
  void
  pmap_zero_page(vm_page_t m)
  {
          pmap_zero_page_func(VM_PAGE_TO_PHYS(m), 0, PAGE_SIZE);
  }
  
  
  /*
   *      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)
  {
  
          pmap_zero_page_func(VM_PAGE_TO_PHYS(m), off, size);
  }
  
  
  /*
   *      pmap_zero_page_idle zeros the specified hardware page by mapping 
   *      the page into KVM and using bzero to clear its contents.  This
   *      is intended to be called from the vm_pagezero process only and
   *      outside of Giant.
   */
  void
  pmap_zero_page_idle(vm_page_t m)
  {
  
          pmap_zero_page(m);
  }
  
  /*
   * pmap_clean_page()
   *
   * This is a local function used to work out the best strategy to clean
   * a single page referenced by its entry in the PV table. It's used by
   * pmap_copy_page, pmap_zero page and maybe some others later on.
   *
   * Its policy is effectively:
   *  o If there are no mappings, we don't bother doing anything with the cache.
   *  o If there is one mapping, we clean just that page.
   *  o If there are multiple mappings, we clean the entire cache.
   *
   * So that some functions can be further optimised, it returns 0 if it didn't
   * clean the entire cache, or 1 if it did.
   *
   * XXX One bug in this routine is that if the pv_entry has a single page
   * mapped at 0x00000000 a whole cache clean will be performed rather than
   * just the 1 page. Since this should not occur in everyday use and if it does
   * it will just result in not the most efficient clean for the page.
   */
  static int
  pmap_clean_page(struct pv_entry *pv, boolean_t is_src)
  {
          pmap_t pm, pm_to_clean = NULL;
          struct pv_entry *npv;
          u_int cache_needs_cleaning = 0;
          u_int flags = 0;
          vm_offset_t page_to_clean = 0;
  
          if (pv == NULL) {
                  /* nothing mapped in so nothing to flush */
                  return (0);
          }
  
          /*
           * Since we flush the cache each time we change to a different
           * user vmspace, we only need to flush the page if it is in the
           * current pmap.
           */
          if (curthread)
                  pm = vmspace_pmap(curproc->p_vmspace);
          else
                  pm = pmap_kernel();
  
          for (npv = pv; npv; npv = TAILQ_NEXT(npv, pv_list)) {
                  if (npv->pv_pmap == pmap_kernel() || npv->pv_pmap == pm) {
                          flags |= npv->pv_flags;
                          /*
                           * The page is mapped non-cacheable in 
                           * this map.  No need to flush the cache.
                           */
                          if (npv->pv_flags & PVF_NC) {
  #ifdef DIAGNOSTIC
                                  if (cache_needs_cleaning)
                                          panic("pmap_clean_page: "
                                              "cache inconsistency");
  #endif
                                  break;
                          } else if (is_src && (npv->pv_flags & PVF_WRITE) == 0)
                                  continue;
                          if (cache_needs_cleaning) {
                                  page_to_clean = 0;
                                  break;
                          } else {
                                  page_to_clean = npv->pv_va;
                                  pm_to_clean = npv->pv_pmap;
                          }
                          cache_needs_cleaning = 1;
                  }
          }
          if (page_to_clean) {
                  if (PV_BEEN_EXECD(flags))
                          pmap_idcache_wbinv_range(pm_to_clean, page_to_clean,
                              PAGE_SIZE);
                  else
                          pmap_dcache_wb_range(pm_to_clean, page_to_clean,
                              PAGE_SIZE, !is_src, (flags & PVF_WRITE) == 0);
          } else if (cache_needs_cleaning) {
                  if (PV_BEEN_EXECD(flags))
                          pmap_idcache_wbinv_all(pm);
                  else
                          pmap_dcache_wbinv_all(pm);
                  return (1);
          }
          return (0);
  }
  
  /*
   *      pmap_copy_page copies the specified (machine independent)
   *      page by mapping the page into virtual memory and using
   *      bcopy to copy the page, one machine dependent page at a
   *      time.
   */
  
  /*
   * pmap_copy_page()
   *
   * Copy one physical page into another, by mapping the pages into
   * hook points. The same comment regarding cachability as in
   * pmap_zero_page also applies here.
   */
  #if  (ARM_MMU_GENERIC + ARM_MMU_SA1) != 0 
  void
  pmap_copy_page_generic(vm_paddr_t src, vm_paddr_t dst)
  {
          struct vm_page *src_pg = PHYS_TO_VM_PAGE(src);
  #ifdef DEBUG
          struct vm_page *dst_pg = PHYS_TO_VM_PAGE(dst);
  
          if (dst_pg->md.pvh_list != NULL)
                  panic("pmap_copy_page: dst page has mappings");
  #endif
  
  
          /*
           * Clean the source page.  Hold the source page's lock for
           * the duration of the copy so that no other mappings can
           * be created while we have a potentially aliased mapping.
           */
  #if 0
          mtx_lock(&src_pg->md.pvh_mtx);
  #endif
          (void) pmap_clean_page(TAILQ_FIRST(&src_pg->md.pv_list), TRUE);
  
          /*
           * Map the pages into the page hook points, copy them, and purge
           * the cache for the appropriate page. Invalidate the TLB
           * as required.
           */
          mtx_lock(&cmtx);
          *csrc_pte = L2_S_PROTO | src |
              L2_S_PROT(PTE_KERNEL, VM_PROT_READ) | pte_l2_s_cache_mode;
          PTE_SYNC(csrc_pte);
          *cdst_pte = L2_S_PROTO | dst |
              L2_S_PROT(PTE_KERNEL, VM_PROT_WRITE) | pte_l2_s_cache_mode;
          PTE_SYNC(cdst_pte);
          cpu_tlb_flushD_SE(csrcp);
          cpu_tlb_flushD_SE(cdstp);
          cpu_cpwait();
          bcopy_page(csrcp, cdstp);
          mtx_unlock(&cmtx);
          cpu_dcache_inv_range(csrcp, PAGE_SIZE);
  #if 0
          mtx_lock(&src_pg->md.pvh_mtx);
  #endif
          cpu_dcache_wbinv_range(cdstp, PAGE_SIZE);
  }
  #endif /* (ARM_MMU_GENERIC + ARM_MMU_SA1) != 0 */
  
  #if ARM_MMU_XSCALE == 1
  void
  pmap_copy_page_xscale(vm_paddr_t src, vm_paddr_t dst)
  {
          struct vm_page *src_pg = PHYS_TO_VM_PAGE(src);
  #ifdef DEBUG
          struct vm_page *dst_pg = PHYS_TO_VM_PAGE(dst);
  
          if (dst_pg->md.pvh_list != NULL)
                  panic("pmap_copy_page: dst page has mappings");
  #endif
  
  
          /*
           * Clean the source page.  Hold the source page's lock for
           * the duration of the copy so that no other mappings can
           * be created while we have a potentially aliased mapping.
           */
          (void) pmap_clean_page(TAILQ_FIRST(&src_pg->md.pv_list), TRUE);
  
          /*
           * Map the pages into the page hook points, copy them, and purge
           * the cache for the appropriate page. Invalidate the TLB
           * as required.
           */
          mtx_lock(&cmtx);
          *csrc_pte = L2_S_PROTO | src |
              L2_S_PROT(PTE_KERNEL, VM_PROT_READ) |
              L2_C | L2_XSCALE_T_TEX(TEX_XSCALE_X);       /* mini-data */
          PTE_SYNC(csrc_pte);
          *cdst_pte = L2_S_PROTO | dst |
              L2_S_PROT(PTE_KERNEL, VM_PROT_WRITE) |
              L2_C | L2_XSCALE_T_TEX(TEX_XSCALE_X);       /* mini-data */
          PTE_SYNC(cdst_pte);
          cpu_tlb_flushD_SE(csrcp);
          cpu_tlb_flushD_SE(cdstp);
          cpu_cpwait();
          bcopy_page(csrcp, cdstp);
          mtx_unlock(&cmtx);
          xscale_cache_clean_minidata();
  }
  #endif /* ARM_MMU_XSCALE == 1 */
  
  void
  pmap_copy_page(vm_page_t src, vm_page_t dst)
  {
          cpu_dcache_wbinv_all();
          pmap_copy_page_func(VM_PAGE_TO_PHYS(src), VM_PAGE_TO_PHYS(dst));
  }
  
  
  
  
  /*
   * this routine returns true if a physical page resides
   * in the given pmap.
   */
  boolean_t
  pmap_page_exists_quick(pmap_t pmap, vm_page_t m)
  {
          pv_entry_t pv;
          int loops = 0;
          int s;
          
          if (m->flags & PG_FICTITIOUS)
                  return (FALSE);
                  
          s = splvm();
          
          /*
           * Not found, check current mappings returning immediately
           */
          for (pv = TAILQ_FIRST(&m->md.pv_list);
              pv;
              pv = TAILQ_NEXT(pv, pv_list)) {
                  if (pv->pv_pmap == pmap) {
                          splx(s);
                          return (TRUE);
                  }
                  loops++;
                  if (loops >= 16)
                          break;
          }
          splx(s);
          return (FALSE);
  }
  
  
  /*
   *      pmap_ts_referenced:
   *
   *      Return the count of reference bits for a page, clearing all of them.
   */
  int
  pmap_ts_referenced(vm_page_t m)
  {
          return (pmap_clearbit(m, PVF_REF));
  }
  
  
  boolean_t
  pmap_is_modified(vm_page_t m)
  {
  
          if (m->md.pvh_attrs & PVF_MOD)
                  return (TRUE);
          
          return(FALSE);
  }
  
  
  /*
   *      Clear the modify bits on the specified physical page.
   */
  void
  pmap_clear_modify(vm_page_t m)
  {
  
          if (m->md.pvh_attrs & PVF_MOD)
                  pmap_clearbit(m, PVF_MOD);
  }
  
  
  /*
   *      pmap_clear_reference:
   *
   *      Clear the reference bit on the specified physical page.
   */
  void
  pmap_clear_reference(vm_page_t m)
  {
  
          if (m->md.pvh_attrs & PVF_REF) 
                  pmap_clearbit(m, PVF_REF);
  }
  
  
  /*
   * perform the pmap work for mincore
   */
  int
  pmap_mincore(pmap_t pmap, vm_offset_t addr)
  {
          printf("pmap_mincore()\n");
          
          return (0);
  }
  
  
  vm_offset_t
  pmap_addr_hint(vm_object_t obj, vm_offset_t addr, vm_size_t size)
  {
  
          return(addr);
  }
  
  
  /*
   * Map a set of physical memory pages into the kernel virtual
   * address space. Return a pointer to where it is mapped. This
   * routine is intended to be used for mapping device memory,
   * NOT real memory.
   */
  void *
  pmap_mapdev(vm_offset_t pa, vm_size_t size)
  {
          vm_offset_t va, tmpva, offset;
          
          offset = pa & PAGE_MASK;
          size = roundup(size, PAGE_SIZE);
          
          GIANT_REQUIRED;
          
          va = kmem_alloc_nofault(kernel_map, size);
          if (!va)
                  panic("pmap_mapdev: Couldn't alloc kernel virtual memory");
          for (tmpva = va; size > 0;) {
                  pmap_kenter_internal(tmpva, pa, 0);
                  size -= PAGE_SIZE;
                  tmpva += PAGE_SIZE;
                  pa += PAGE_SIZE;
          }
          
          return ((void *)(va + offset));
  }
  
  #define BOOTSTRAP_DEBUG
  
  /*
   * pmap_map_section:
   *
   *      Create a single section mapping.
   */
  void
  pmap_map_section(vm_offset_t l1pt, vm_offset_t va, vm_offset_t pa,
      int prot, int cache)
  {
          pd_entry_t *pde = (pd_entry_t *) l1pt;
          pd_entry_t fl;
  
          KASSERT(((va | pa) & L1_S_OFFSET) == 0, ("ouin2"));
  
          switch (cache) {
          case PTE_NOCACHE:
          default:
                  fl = 0;
                  break;
  
          case PTE_CACHE:
                  fl = pte_l1_s_cache_mode;
                  break;
  
          case PTE_PAGETABLE:
                  fl = pte_l1_s_cache_mode_pt;
                  break;
          }
  
          pde[va >> L1_S_SHIFT] = L1_S_PROTO | pa |
              L1_S_PROT(PTE_KERNEL, prot) | fl | L1_S_DOM(PMAP_DOMAIN_KERNEL);
          PTE_SYNC(&pde[va >> L1_S_SHIFT]);
  
  }
  
  /*
   * pmap_link_l2pt:
   *
   *      Link the L2 page table specified by "pa" into the L1
   *      page table at the slot for "va".
   */
  void
  pmap_link_l2pt(vm_offset_t l1pt, vm_offset_t va, struct pv_addr *l2pv)
  {
          pd_entry_t *pde = (pd_entry_t *) l1pt, proto;
          u_int slot = va >> L1_S_SHIFT;
  
  #ifndef ARM32_NEW_VM_LAYOUT
          KASSERT((va & ((L1_S_SIZE * 4) - 1)) == 0, ("blah"));
          KASSERT((l2pv->pv_pa & PAGE_MASK) == 0, ("ouin"));
  #endif
  
          proto = L1_S_DOM(PMAP_DOMAIN_KERNEL) | L1_C_PROTO;
  
          pde[slot + 0] = proto | (l2pv->pv_pa + 0x000);
  #ifdef ARM32_NEW_VM_LAYOUT
          PTE_SYNC(&pde[slot]);
  #else
          pde[slot + 1] = proto | (l2pv->pv_pa + 0x400);
          pde[slot + 2] = proto | (l2pv->pv_pa + 0x800);
          pde[slot + 3] = proto | (l2pv->pv_pa + 0xc00);
          PTE_SYNC_RANGE(&pde[slot + 0], 4);
  #endif
  
          SLIST_INSERT_HEAD(&kernel_pt_list, l2pv, pv_list);
  
          
  }
  
  /*
   * pmap_map_entry
   *
   *      Create a single page mapping.
   */
  void
  pmap_map_entry(vm_offset_t l1pt, vm_offset_t va, vm_offset_t pa, int prot,
      int cache)
  {
          pd_entry_t *pde = (pd_entry_t *) l1pt;
          pt_entry_t fl;
          pt_entry_t *pte;
  
          KASSERT(((va | pa) & PAGE_MASK) == 0, ("ouin"));
  
          switch (cache) {
          case PTE_NOCACHE:
          default:
                  fl = 0;
                  break;
  
          case PTE_CACHE:
                  fl = pte_l2_s_cache_mode;
                  break;
  
          case PTE_PAGETABLE:
                  fl = pte_l2_s_cache_mode_pt;
                  break;
          }
  
          if ((pde[va >> L1_S_SHIFT] & L1_TYPE_MASK) != L1_TYPE_C)
                  panic("pmap_map_entry: no L2 table for VA 0x%08x", va);
  
  #ifndef ARM32_NEW_VM_LAYOUT
          pte = (pt_entry_t *)
              kernel_pt_lookup(pde[va >> L1_S_SHIFT] & L2_S_FRAME);
  #else
          pte = (pt_entry_t *) kernel_pt_lookup(pde[L1_IDX(va)] & L1_C_ADDR_MASK);
  #endif
  
          if (pte == NULL)
                  panic("pmap_map_entry: can't find L2 table for VA 0x%08x", va);
  
  #ifndef ARM32_NEW_VM_LAYOUT
          pte[(va >> PAGE_SHIFT) & 0x3ff] =
              L2_S_PROTO | pa | L2_S_PROT(PTE_KERNEL, prot) | fl;
          PTE_SYNC(&pte[(va >> PAGE_SHIFT) & 0x3ff]);
  #else
          pte[l2pte_index(va)] =
              L2_S_PROTO | pa | L2_S_PROT(PTE_KERNEL, prot) | fl;
          PTE_SYNC(&pte[l2pte_index(va)]);
  #endif
  }
  
  /*
   * pmap_map_chunk:
   *
   *      Map a chunk of memory using the most efficient mappings
   *      possible (section. large page, small page) into the
   *      provided L1 and L2 tables at the specified virtual address.
   */
  vm_size_t
  pmap_map_chunk(vm_offset_t l1pt, vm_offset_t va, vm_offset_t pa,
      vm_size_t size, int prot, int cache)
  {
          pd_entry_t *pde = (pd_entry_t *) l1pt;
          pt_entry_t *pte, f1, f2s, f2l;
          vm_size_t resid;  
          int i;
  
          resid = (size + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
  
          if (l1pt == 0)
                  panic("pmap_map_chunk: no L1 table provided");
  
  #ifdef VERBOSE_INIT_ARM     
          printf("pmap_map_chunk: pa=0x%lx va=0x%lx size=0x%lx resid=0x%lx "
              "prot=0x%x cache=%d\n", pa, va, size, resid, prot, cache);
  #endif
  
          switch (cache) {
          case PTE_NOCACHE:
          default:
                  f1 = 0;
                  f2l = 0;
                  f2s = 0;
                  break;
  
          case PTE_CACHE:
                  f1 = pte_l1_s_cache_mode;
                  f2l = pte_l2_l_cache_mode;
                  f2s = pte_l2_s_cache_mode;
                  break;
  
          case PTE_PAGETABLE:
                  f1 = pte_l1_s_cache_mode_pt;
                  f2l = pte_l2_l_cache_mode_pt;
                  f2s = pte_l2_s_cache_mode_pt;
                  break;
          }
  
          size = resid;
  
          while (resid > 0) {
                  /* See if we can use a section mapping. */
                  if (L1_S_MAPPABLE_P(va, pa, resid)) {
  #ifdef VERBOSE_INIT_ARM
                          printf("S");
  #endif
                          pde[va >> L1_S_SHIFT] = L1_S_PROTO | pa |
                              L1_S_PROT(PTE_KERNEL, prot) | f1 |
                              L1_S_DOM(PMAP_DOMAIN_KERNEL);
                          PTE_SYNC(&pde[va >> L1_S_SHIFT]);
                          va += L1_S_SIZE;
                          pa += L1_S_SIZE;
                          resid -= L1_S_SIZE;
                          continue;
                  }
  
                  /*
                   * Ok, we're going to use an L2 table.  Make sure
                   * one is actually in the corresponding L1 slot
                   * for the current VA.
                   */
                  if ((pde[va >> L1_S_SHIFT] & L1_TYPE_MASK) != L1_TYPE_C)
                          panic("pmap_map_chunk: no L2 table for VA 0x%08x", va);
  
  #ifndef ARM32_NEW_VM_LAYOUT
                  pte = (pt_entry_t *)
                      kernel_pt_lookup(pde[va >> L1_S_SHIFT] & L2_S_FRAME);
  #else
                  pte = (pt_entry_t *) kernel_pt_lookup(
                      pde[L1_IDX(va)] & L1_C_ADDR_MASK);
  #endif
                  if (pte == NULL)
                          panic("pmap_map_chunk: can't find L2 table for VA"
                              "0x%08x", va);
                  /* See if we can use a L2 large page mapping. */
                  if (L2_L_MAPPABLE_P(va, pa, resid)) {
  #ifdef VERBOSE_INIT_ARM
                          printf("L");
  #endif
                          for (i = 0; i < 16; i++) {
  #ifndef ARM32_NEW_VM_LAYOUT
                                  pte[((va >> PAGE_SHIFT) & 0x3f0) + i] =
                                      L2_L_PROTO | pa |
                                      L2_L_PROT(PTE_KERNEL, prot) | f2l;
                                  PTE_SYNC(&pte[((va >> PAGE_SHIFT) & 0x3f0) + i]);
  #else
                                  pte[l2pte_index(va) + i] =
                                      L2_L_PROTO | pa |
                                      L2_L_PROT(PTE_KERNEL, prot) | f2l;
                                  PTE_SYNC(&pte[l2pte_index(va) + i]);
  #endif
                          }
                          va += L2_L_SIZE;
                          pa += L2_L_SIZE;
                          resid -= L2_L_SIZE;
                          continue;
                  }
  
                  /* Use a small page mapping. */
  #ifdef VERBOSE_INIT_ARM
                  printf("P");
  #endif
  #ifndef ARM32_NEW_VM_LAYOUT
                  pte[(va >> PAGE_SHIFT) & 0x3ff] =
                      L2_S_PROTO | pa | L2_S_PROT(PTE_KERNEL, prot) | f2s;
                  PTE_SYNC(&pte[(va >> PAGE_SHIFT) & 0x3ff]);
  #else
                  pte[l2pte_index(va)] =
                      L2_S_PROTO | pa | L2_S_PROT(PTE_KERNEL, prot) | f2s;
                  PTE_SYNC(&pte[l2pte_index(va)]);
  #endif
                  va += PAGE_SIZE;
                  pa += PAGE_SIZE;
                  resid -= PAGE_SIZE;
          }
  #ifdef VERBOSE_INIT_ARM
          printf("\n");
  #endif
          return (size);
  
  }
  
  /********************** Static device map routines ***************************/
  
  static const struct pmap_devmap *pmap_devmap_table;
  
  /*
   * Register the devmap table.  This is provided in case early console
   * initialization needs to register mappings created by bootstrap code
   * before pmap_devmap_bootstrap() is called.
   */
  void
  pmap_devmap_register(const struct pmap_devmap *table)
  {
  
          pmap_devmap_table = table;
  }
  
  /*
   * Map all of the static regions in the devmap table, and remember
   * the devmap table so other parts of the kernel can look up entries
   * later.
   */
  void
  pmap_devmap_bootstrap(vm_offset_t l1pt, const struct pmap_devmap *table)
  {
          int i;
  
          pmap_devmap_table = table;
  
          for (i = 0; pmap_devmap_table[i].pd_size != 0; i++) {
  #ifdef VERBOSE_INIT_ARM
                  printf("devmap: %08lx -> %08lx @ %08lx\n",
                      pmap_devmap_table[i].pd_pa,
                      pmap_devmap_table[i].pd_pa +
                          pmap_devmap_table[i].pd_size - 1,
                      pmap_devmap_table[i].pd_va);
  #endif
                  pmap_map_chunk(l1pt, pmap_devmap_table[i].pd_va,
                      pmap_devmap_table[i].pd_pa,
                      pmap_devmap_table[i].pd_size,
                      pmap_devmap_table[i].pd_prot,
                      pmap_devmap_table[i].pd_cache);
          }
  }
  
  const struct pmap_devmap *
  pmap_devmap_find_pa(vm_paddr_t pa, vm_size_t size)
  {
          int i;
  
          if (pmap_devmap_table == NULL)
                  return (NULL);
  
          for (i = 0; pmap_devmap_table[i].pd_size != 0; i++) {
                  if (pa >= pmap_devmap_table[i].pd_pa &&
                      pa + size <= pmap_devmap_table[i].pd_pa +
                                   pmap_devmap_table[i].pd_size)
                          return (&pmap_devmap_table[i]);
          }
  
          return (NULL);
  }
  
  const struct pmap_devmap *
  pmap_devmap_find_va(vm_offset_t va, vm_size_t size)
  {
          int i;
  
          if (pmap_devmap_table == NULL)
                  return (NULL);
  
          for (i = 0; pmap_devmap_table[i].pd_size != 0; i++) {
                  if (va >= pmap_devmap_table[i].pd_va &&
                      va + size <= pmap_devmap_table[i].pd_va +
                                   pmap_devmap_table[i].pd_size)
                          return (&pmap_devmap_table[i]);
          }
  
          return (NULL);
  }