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[FreeBSD/FreeBSD.git] / sys / riscv / riscv / pmap.c

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1991 Regents of the University of California.
 * All rights reserved.
 * Copyright (c) 1994 John S. Dyson
 * All rights reserved.
 * Copyright (c) 1994 David Greenman
 * All rights reserved.
 * Copyright (c) 2003 Peter Wemm
 * All rights reserved.
 * Copyright (c) 2005-2010 Alan L. Cox <alc@cs.rice.edu>
 * All rights reserved.
 * Copyright (c) 2014 Andrew Turner
 * All rights reserved.
 * Copyright (c) 2014 The FreeBSD Foundation
 * All rights reserved.
 * Copyright (c) 2015-2017 Ruslan Bukin <br@bsdpad.com>
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department and William Jolitz of UUNET Technologies Inc.
 *
 * Portions of this software were developed by Andrew Turner under
 * sponsorship from The FreeBSD Foundation.
 *
 * Portions of this software were developed by SRI International and the
 * University of Cambridge Computer Laboratory under DARPA/AFRL contract
 * FA8750-10-C-0237 ("CTSRD"), as part of the DARPA CRASH research programme.
 *
 * Portions of this software were developed by the University of Cambridge
 * Computer Laboratory as part of the CTSRD Project, with support from the
 * UK Higher Education Innovation Fund (HEIF).
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from:   @(#)pmap.c      7.7 (Berkeley)  5/12/91
 */
/*-
 * Copyright (c) 2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Jake Burkholder,
 * Safeport Network Services, and Network Associates Laboratories, the
 * Security Research Division of Network Associates, Inc. under
 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA
 * CHATS research program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 *      Manages physical address maps.
 *
 *      Since the information managed by this module is
 *      also stored by the logical address mapping module,
 *      this module may throw away valid virtual-to-physical
 *      mappings at almost any time.  However, invalidations
 *      of virtual-to-physical mappings must be done as
 *      requested.
 *
 *      In order to cope with hardware architectures which
 *      make virtual-to-physical map invalidates expensive,
 *      this module may delay invalidate or reduced protection
 *      operations until such time as they are actually
 *      necessary.  This module is given full information as
 *      to which processors are currently using which maps,
 *      and to when physical maps must be made correct.
 */

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/msgbuf.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sx.h>
#include <sys/vmem.h>
#include <sys/vmmeter.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/smp.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/vm_radix.h>
#include <vm/vm_reserv.h>
#include <vm/uma.h>

#include <machine/machdep.h>
#include <machine/md_var.h>
#include <machine/pcb.h>

#define NPDEPG          (PAGE_SIZE/(sizeof (pd_entry_t)))
#define NUPDE                   (NPDEPG * NPDEPG)
#define NUSERPGTBLS             (NUPDE + NPDEPG)

#if !defined(DIAGNOSTIC)
#ifdef __GNUC_GNU_INLINE__
#define PMAP_INLINE     __attribute__((__gnu_inline__)) inline
#else
#define PMAP_INLINE     extern inline
#endif
#else
#define PMAP_INLINE
#endif

#ifdef PV_STATS
#define PV_STAT(x)      do { x ; } while (0)
#else
#define PV_STAT(x)      do { } while (0)
#endif

#define pmap_l2_pindex(v)       ((v) >> L2_SHIFT)

#define NPV_LIST_LOCKS  MAXCPU

#define PHYS_TO_PV_LIST_LOCK(pa)        \
                        (&pv_list_locks[pa_index(pa) % NPV_LIST_LOCKS])

#define CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa)  do {    \
        struct rwlock **_lockp = (lockp);               \
        struct rwlock *_new_lock;                       \
                                                        \
        _new_lock = PHYS_TO_PV_LIST_LOCK(pa);           \
        if (_new_lock != *_lockp) {                     \
                if (*_lockp != NULL)                    \
                        rw_wunlock(*_lockp);            \
                *_lockp = _new_lock;                    \
                rw_wlock(*_lockp);                      \
        }                                               \
} while (0)

#define CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m)        \
                        CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, VM_PAGE_TO_PHYS(m))

#define RELEASE_PV_LIST_LOCK(lockp)             do {    \
        struct rwlock **_lockp = (lockp);               \
                                                        \
        if (*_lockp != NULL) {                          \
                rw_wunlock(*_lockp);                    \
                *_lockp = NULL;                         \
        }                                               \
} while (0)

#define VM_PAGE_TO_PV_LIST_LOCK(m)      \
                        PHYS_TO_PV_LIST_LOCK(VM_PAGE_TO_PHYS(m))

/* The list of all the user pmaps */
LIST_HEAD(pmaplist, pmap);
static struct pmaplist allpmaps;

static MALLOC_DEFINE(M_VMPMAP, "pmap", "PMAP L1");

struct pmap kernel_pmap_store;

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 kernel_vm_end = 0;

vm_paddr_t dmap_phys_base;      /* The start of the dmap region */
vm_paddr_t dmap_phys_max;       /* The limit of the dmap region */
vm_offset_t dmap_max_addr;      /* The virtual address limit of the dmap */

/* This code assumes all L1 DMAP entries will be used */
CTASSERT((DMAP_MIN_ADDRESS  & ~L1_OFFSET) == DMAP_MIN_ADDRESS);
CTASSERT((DMAP_MAX_ADDRESS  & ~L1_OFFSET) == DMAP_MAX_ADDRESS);

static struct rwlock_padalign pvh_global_lock;

/*
 * Data for the pv entry allocation mechanism
 */
static TAILQ_HEAD(pch, pv_chunk) pv_chunks = TAILQ_HEAD_INITIALIZER(pv_chunks);
static struct mtx pv_chunks_mutex;
static struct rwlock pv_list_locks[NPV_LIST_LOCKS];

static void     free_pv_chunk(struct pv_chunk *pc);
static void     free_pv_entry(pmap_t pmap, pv_entry_t pv);
static pv_entry_t get_pv_entry(pmap_t pmap, struct rwlock **lockp);
static vm_page_t reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp);
static void     pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va);
static pv_entry_t pmap_pvh_remove(struct md_page *pvh, pmap_t pmap,
                    vm_offset_t va);
static vm_page_t pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va,
    vm_page_t m, vm_prot_t prot, vm_page_t mpte, struct rwlock **lockp);
static int pmap_remove_l3(pmap_t pmap, pt_entry_t *l3, vm_offset_t sva,
    pd_entry_t ptepde, struct spglist *free, struct rwlock **lockp);
static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va,
    vm_page_t m, struct rwlock **lockp);

static vm_page_t _pmap_alloc_l3(pmap_t pmap, vm_pindex_t ptepindex,
                struct rwlock **lockp);

static void _pmap_unwire_l3(pmap_t pmap, vm_offset_t va, vm_page_t m,
    struct spglist *free);
static int pmap_unuse_l3(pmap_t, vm_offset_t, pd_entry_t, struct spglist *);

/*
 * These load the old table data and store the new value.
 * They need to be atomic as the System MMU may write to the table at
 * the same time as the CPU.
 */
#define pmap_load_store(table, entry) atomic_swap_64(table, entry)
#define pmap_set(table, mask) atomic_set_64(table, mask)
#define pmap_load_clear(table) atomic_swap_64(table, 0)
#define pmap_load(table) (*table)

/********************/
/* Inline functions */
/********************/

static __inline void
pagecopy(void *s, void *d)
{

        memcpy(d, s, PAGE_SIZE);
}

static __inline void
pagezero(void *p)
{

        bzero(p, PAGE_SIZE);
}

#define pmap_l1_index(va)       (((va) >> L1_SHIFT) & Ln_ADDR_MASK)
#define pmap_l2_index(va)       (((va) >> L2_SHIFT) & Ln_ADDR_MASK)
#define pmap_l3_index(va)       (((va) >> L3_SHIFT) & Ln_ADDR_MASK)

#define PTE_TO_PHYS(pte)        ((pte >> PTE_PPN0_S) * PAGE_SIZE)

static __inline pd_entry_t *
pmap_l1(pmap_t pmap, vm_offset_t va)
{

        return (&pmap->pm_l1[pmap_l1_index(va)]);
}

static __inline pd_entry_t *
pmap_l1_to_l2(pd_entry_t *l1, vm_offset_t va)
{
        vm_paddr_t phys;
        pd_entry_t *l2;

        phys = PTE_TO_PHYS(pmap_load(l1));
        l2 = (pd_entry_t *)PHYS_TO_DMAP(phys);

        return (&l2[pmap_l2_index(va)]);
}

static __inline pd_entry_t *
pmap_l2(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t *l1;

        l1 = pmap_l1(pmap, va);
        if (l1 == NULL)
                return (NULL);
        if ((pmap_load(l1) & PTE_V) == 0)
                return (NULL);
        if ((pmap_load(l1) & PTE_RX) != 0)
                return (NULL);

        return (pmap_l1_to_l2(l1, va));
}

static __inline pt_entry_t *
pmap_l2_to_l3(pd_entry_t *l2, vm_offset_t va)
{
        vm_paddr_t phys;
        pt_entry_t *l3;

        phys = PTE_TO_PHYS(pmap_load(l2));
        l3 = (pd_entry_t *)PHYS_TO_DMAP(phys);

        return (&l3[pmap_l3_index(va)]);
}

static __inline pt_entry_t *
pmap_l3(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t *l2;

        l2 = pmap_l2(pmap, va);
        if (l2 == NULL)
                return (NULL);
        if ((pmap_load(l2) & PTE_V) == 0)
                return (NULL);
        if ((pmap_load(l2) & PTE_RX) != 0)
                return (NULL);

        return (pmap_l2_to_l3(l2, va));
}


static __inline int
pmap_is_write(pt_entry_t entry)
{

        return (entry & PTE_W);
}

static __inline int
pmap_is_current(pmap_t pmap)
{

        return ((pmap == pmap_kernel()) ||
            (pmap == curthread->td_proc->p_vmspace->vm_map.pmap));
}

static __inline int
pmap_l3_valid(pt_entry_t l3)
{

        return (l3 & PTE_V);
}

static __inline int
pmap_l3_valid_cacheable(pt_entry_t l3)
{

        /* TODO */

        return (0);
}

#define PTE_SYNC(pte)   cpu_dcache_wb_range((vm_offset_t)pte, sizeof(*pte))

/* Checks if the page is dirty. */
static inline int
pmap_page_dirty(pt_entry_t pte)
{

        return (pte & PTE_D);
}

static __inline void
pmap_resident_count_inc(pmap_t pmap, int count)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        pmap->pm_stats.resident_count += count;
}

static __inline void
pmap_resident_count_dec(pmap_t pmap, int count)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT(pmap->pm_stats.resident_count >= count,
            ("pmap %p resident count underflow %ld %d", pmap,
            pmap->pm_stats.resident_count, count));
        pmap->pm_stats.resident_count -= count;
}

static void
pmap_distribute_l1(struct pmap *pmap, vm_pindex_t l1index,
    pt_entry_t entry)
{
        struct pmap *user_pmap;
        pd_entry_t *l1;

        /* Distribute new kernel L1 entry to all the user pmaps */
        if (pmap != kernel_pmap)
                return;

        LIST_FOREACH(user_pmap, &allpmaps, pm_list) {
                l1 = &user_pmap->pm_l1[l1index];
                if (entry)
                        pmap_load_store(l1, entry);
                else
                        pmap_load_clear(l1);
        }
}

static pt_entry_t *
pmap_early_page_idx(vm_offset_t l1pt, vm_offset_t va, u_int *l1_slot,
    u_int *l2_slot)
{
        pt_entry_t *l2;
        pd_entry_t *l1;

        l1 = (pd_entry_t *)l1pt;
        *l1_slot = (va >> L1_SHIFT) & Ln_ADDR_MASK;

        /* Check locore has used a table L1 map */
        KASSERT((l1[*l1_slot] & PTE_RX) == 0,
                ("Invalid bootstrap L1 table"));

        /* Find the address of the L2 table */
        l2 = (pt_entry_t *)init_pt_va;
        *l2_slot = pmap_l2_index(va);

        return (l2);
}

static vm_paddr_t
pmap_early_vtophys(vm_offset_t l1pt, vm_offset_t va)
{
        u_int l1_slot, l2_slot;
        pt_entry_t *l2;
        u_int ret;

        l2 = pmap_early_page_idx(l1pt, va, &l1_slot, &l2_slot);

        /* Check locore has used L2 superpages */
        KASSERT((l2[l2_slot] & PTE_RX) != 0,
                ("Invalid bootstrap L2 table"));

        /* L2 is superpages */
        ret = (l2[l2_slot] >> PTE_PPN1_S) << L2_SHIFT;
        ret += (va & L2_OFFSET);

        return (ret);
}

static void
pmap_bootstrap_dmap(vm_offset_t kern_l1, vm_paddr_t min_pa, vm_paddr_t max_pa)
{
        vm_offset_t va;
        vm_paddr_t pa;
        pd_entry_t *l1;
        u_int l1_slot;
        pt_entry_t entry;
        pn_t pn;

        pa = dmap_phys_base = min_pa & ~L1_OFFSET;
        va = DMAP_MIN_ADDRESS;
        l1 = (pd_entry_t *)kern_l1;
        l1_slot = pmap_l1_index(DMAP_MIN_ADDRESS);

        for (; va < DMAP_MAX_ADDRESS && pa < max_pa;
            pa += L1_SIZE, va += L1_SIZE, l1_slot++) {
                KASSERT(l1_slot < Ln_ENTRIES, ("Invalid L1 index"));

                /* superpages */
                pn = (pa / PAGE_SIZE);
                entry = (PTE_V | PTE_RWX);
                entry |= (pn << PTE_PPN0_S);
                pmap_load_store(&l1[l1_slot], entry);
        }

        /* Set the upper limit of the DMAP region */
        dmap_phys_max = pa;
        dmap_max_addr = va;

        cpu_dcache_wb_range((vm_offset_t)l1, PAGE_SIZE);
        cpu_tlb_flushID();
}

static vm_offset_t
pmap_bootstrap_l3(vm_offset_t l1pt, vm_offset_t va, vm_offset_t l3_start)
{
        vm_offset_t l2pt, l3pt;
        pt_entry_t entry;
        pd_entry_t *l2;
        vm_paddr_t pa;
        u_int l2_slot;
        pn_t pn;

        KASSERT((va & L2_OFFSET) == 0, ("Invalid virtual address"));

        l2 = pmap_l2(kernel_pmap, va);
        l2 = (pd_entry_t *)((uintptr_t)l2 & ~(PAGE_SIZE - 1));
        l2pt = (vm_offset_t)l2;
        l2_slot = pmap_l2_index(va);
        l3pt = l3_start;

        for (; va < VM_MAX_KERNEL_ADDRESS; l2_slot++, va += L2_SIZE) {
                KASSERT(l2_slot < Ln_ENTRIES, ("Invalid L2 index"));

                pa = pmap_early_vtophys(l1pt, l3pt);
                pn = (pa / PAGE_SIZE);
                entry = (PTE_V);
                entry |= (pn << PTE_PPN0_S);
                pmap_load_store(&l2[l2_slot], entry);
                l3pt += PAGE_SIZE;
        }


        /* Clean the L2 page table */
        memset((void *)l3_start, 0, l3pt - l3_start);
        cpu_dcache_wb_range(l3_start, l3pt - l3_start);

        cpu_dcache_wb_range((vm_offset_t)l2, PAGE_SIZE);

        return (l3pt);
}

/*
 *      Bootstrap the system enough to run with virtual memory.
 */
void
pmap_bootstrap(vm_offset_t l1pt, vm_paddr_t kernstart, vm_size_t kernlen)
{
        u_int l1_slot, l2_slot, avail_slot, map_slot, used_map_slot;
        uint64_t kern_delta;
        pt_entry_t *l2;
        vm_offset_t va, freemempos;
        vm_offset_t dpcpu, msgbufpv;
        vm_paddr_t pa, min_pa, max_pa;
        int i;

        kern_delta = KERNBASE - kernstart;
        physmem = 0;

        printf("pmap_bootstrap %lx %lx %lx\n", l1pt, kernstart, kernlen);
        printf("%lx\n", l1pt);
        printf("%lx\n", (KERNBASE >> L1_SHIFT) & Ln_ADDR_MASK);

        /* Set this early so we can use the pagetable walking functions */
        kernel_pmap_store.pm_l1 = (pd_entry_t *)l1pt;
        PMAP_LOCK_INIT(kernel_pmap);

        /*
         * Initialize the global pv list lock.
         */
        rw_init(&pvh_global_lock, "pmap pv global");

        LIST_INIT(&allpmaps);

        /* Assume the address we were loaded to is a valid physical address */
        min_pa = max_pa = KERNBASE - kern_delta;

        /*
         * Find the minimum physical address. physmap is sorted,
         * but may contain empty ranges.
         */
        for (i = 0; i < (physmap_idx * 2); i += 2) {
                if (physmap[i] == physmap[i + 1])
                        continue;
                if (physmap[i] <= min_pa)
                        min_pa = physmap[i];
                if (physmap[i + 1] > max_pa)
                        max_pa = physmap[i + 1];
        }
        printf("physmap_idx %lx\n", physmap_idx);
        printf("min_pa %lx\n", min_pa);
        printf("max_pa %lx\n", max_pa);

        /* Create a direct map region early so we can use it for pa -> va */
        pmap_bootstrap_dmap(l1pt, min_pa, max_pa);

        va = KERNBASE;
        pa = KERNBASE - kern_delta;

        /*
         * Start to initialize phys_avail by copying from physmap
         * up to the physical address KERNBASE points at.
         */
        map_slot = avail_slot = 0;
        for (; map_slot < (physmap_idx * 2); map_slot += 2) {
                if (physmap[map_slot] == physmap[map_slot + 1])
                        continue;

                if (physmap[map_slot] <= pa &&
                    physmap[map_slot + 1] > pa)
                        break;

                phys_avail[avail_slot] = physmap[map_slot];
                phys_avail[avail_slot + 1] = physmap[map_slot + 1];
                physmem += (phys_avail[avail_slot + 1] -
                    phys_avail[avail_slot]) >> PAGE_SHIFT;
                avail_slot += 2;
        }

        /* Add the memory before the kernel */
        if (physmap[avail_slot] < pa) {
                phys_avail[avail_slot] = physmap[map_slot];
                phys_avail[avail_slot + 1] = pa;
                physmem += (phys_avail[avail_slot + 1] -
                    phys_avail[avail_slot]) >> PAGE_SHIFT;
                avail_slot += 2;
        }
        used_map_slot = map_slot;

        /*
         * Read the page table to find out what is already mapped.
         * This assumes we have mapped a block of memory from KERNBASE
         * using a single L1 entry.
         */
        l2 = pmap_early_page_idx(l1pt, KERNBASE, &l1_slot, &l2_slot);

        /* Sanity check the index, KERNBASE should be the first VA */
        KASSERT(l2_slot == 0, ("The L2 index is non-zero"));

        /* Find how many pages we have mapped */
        for (; l2_slot < Ln_ENTRIES; l2_slot++) {
                if ((l2[l2_slot] & PTE_V) == 0)
                        break;

                /* Check locore used L2 superpages */
                KASSERT((l2[l2_slot] & PTE_RX) != 0,
                    ("Invalid bootstrap L2 table"));

                va += L2_SIZE;
                pa += L2_SIZE;
        }

        va = roundup2(va, L2_SIZE);

        freemempos = KERNBASE + kernlen;
        freemempos = roundup2(freemempos, PAGE_SIZE);

        /* Create the l3 tables for the early devmap */
        freemempos = pmap_bootstrap_l3(l1pt,
            VM_MAX_KERNEL_ADDRESS - L2_SIZE, freemempos);

        cpu_tlb_flushID();

#define alloc_pages(var, np)                                            \
        (var) = freemempos;                                             \
        freemempos += (np * PAGE_SIZE);                                 \
        memset((char *)(var), 0, ((np) * PAGE_SIZE));

        /* Allocate dynamic per-cpu area. */
        alloc_pages(dpcpu, DPCPU_SIZE / PAGE_SIZE);
        dpcpu_init((void *)dpcpu, 0);

        /* Allocate memory for the msgbuf, e.g. for /sbin/dmesg */
        alloc_pages(msgbufpv, round_page(msgbufsize) / PAGE_SIZE);
        msgbufp = (void *)msgbufpv;

        virtual_avail = roundup2(freemempos, L2_SIZE);
        virtual_end = VM_MAX_KERNEL_ADDRESS - L2_SIZE;
        kernel_vm_end = virtual_avail;
        
        pa = pmap_early_vtophys(l1pt, freemempos);

        /* Finish initialising physmap */
        map_slot = used_map_slot;
        for (; avail_slot < (PHYS_AVAIL_SIZE - 2) &&
            map_slot < (physmap_idx * 2); map_slot += 2) {
                if (physmap[map_slot] == physmap[map_slot + 1]) {
                        continue;
                }

                /* Have we used the current range? */
                if (physmap[map_slot + 1] <= pa) {
                        continue;
                }

                /* Do we need to split the entry? */
                if (physmap[map_slot] < pa) {
                        phys_avail[avail_slot] = pa;
                        phys_avail[avail_slot + 1] = physmap[map_slot + 1];
                } else {
                        phys_avail[avail_slot] = physmap[map_slot];
                        phys_avail[avail_slot + 1] = physmap[map_slot + 1];
                }
                physmem += (phys_avail[avail_slot + 1] -
                    phys_avail[avail_slot]) >> PAGE_SHIFT;

                avail_slot += 2;
        }
        phys_avail[avail_slot] = 0;
        phys_avail[avail_slot + 1] = 0;

        /*
         * Maxmem isn't the "maximum memory", it's one larger than the
         * highest page of the physical address space.  It should be
         * called something like "Maxphyspage".
         */
        Maxmem = atop(phys_avail[avail_slot - 1]);

        cpu_tlb_flushID();
}

/*
 *      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_memattr = VM_MEMATTR_WRITE_BACK;
}

/*
 *      Initialize the pmap module.
 *      Called by vm_init, to initialize any structures that the pmap
 *      system needs to map virtual memory.
 */
void
pmap_init(void)
{
        int i;

        /*
         * Initialize the pv chunk list mutex.
         */
        mtx_init(&pv_chunks_mutex, "pmap pv chunk list", NULL, MTX_DEF);

        /*
         * Initialize the pool of pv list locks.
         */
        for (i = 0; i < NPV_LIST_LOCKS; i++)
                rw_init(&pv_list_locks[i], "pmap pv list");
}

/*
 * Normal, non-SMP, invalidation functions.
 * We inline these within pmap.c for speed.
 */
PMAP_INLINE void
pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
{

        /* TODO */

        sched_pin();
        __asm __volatile("sfence.vma %0" :: "r" (va) : "memory");
        sched_unpin();
}

PMAP_INLINE void
pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{

        /* TODO */

        sched_pin();
        __asm __volatile("sfence.vma");
        sched_unpin();
}

PMAP_INLINE void
pmap_invalidate_all(pmap_t pmap)
{

        /* TODO */

        sched_pin();
        __asm __volatile("sfence.vma");
        sched_unpin();
}

/*
 *      Routine:        pmap_extract
 *      Function:
 *              Extract the physical page address associated
 *              with the given map/virtual_address pair.
 */
vm_paddr_t 
pmap_extract(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t *l2p, l2;
        pt_entry_t *l3p, l3;
        vm_paddr_t pa;

        pa = 0;
        PMAP_LOCK(pmap);
        /*
         * Start with the l2 tabel. We are unable to allocate
         * pages in the l1 table.
         */
        l2p = pmap_l2(pmap, va);
        if (l2p != NULL) {
                l2 = pmap_load(l2p);
                if ((l2 & PTE_RX) == 0) {
                        l3p = pmap_l2_to_l3(l2p, va);
                        if (l3p != NULL) {
                                l3 = pmap_load(l3p);
                                pa = PTE_TO_PHYS(l3);
                                pa |= (va & L3_OFFSET);
                        }
                } else {
                        /* L2 is superpages */
                        pa = (l2 >> PTE_PPN1_S) << L2_SHIFT;
                        pa |= (va & L2_OFFSET);
                }
        }
        PMAP_UNLOCK(pmap);
        return (pa);
}

/*
 *      Routine:        pmap_extract_and_hold
 *      Function:
 *              Atomically extract and hold the physical page
 *              with the given pmap and virtual address pair
 *              if that mapping permits the given protection.
 */
vm_page_t
pmap_extract_and_hold(pmap_t pmap, vm_offset_t va, vm_prot_t prot)
{
        pt_entry_t *l3p, l3;
        vm_paddr_t phys;
        vm_paddr_t pa;
        vm_page_t m;

        pa = 0;
        m = NULL;
        PMAP_LOCK(pmap);
retry:
        l3p = pmap_l3(pmap, va);
        if (l3p != NULL && (l3 = pmap_load(l3p)) != 0) {
                if ((pmap_is_write(l3)) || ((prot & VM_PROT_WRITE) == 0)) {
                        phys = PTE_TO_PHYS(l3);
                        if (vm_page_pa_tryrelock(pmap, phys, &pa))
                                goto retry;
                        m = PHYS_TO_VM_PAGE(phys);
                        vm_page_hold(m);
                }
        }
        PA_UNLOCK_COND(pa);
        PMAP_UNLOCK(pmap);
        return (m);
}

vm_paddr_t
pmap_kextract(vm_offset_t va)
{
        pd_entry_t *l2;
        pt_entry_t *l3;
        vm_paddr_t pa;

        if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS) {
                pa = DMAP_TO_PHYS(va);
        } else {
                l2 = pmap_l2(kernel_pmap, va);
                if (l2 == NULL)
                        panic("pmap_kextract: No l2");
                if ((pmap_load(l2) & PTE_RX) != 0) {
                        /* superpages */
                        pa = (pmap_load(l2) >> PTE_PPN1_S) << L2_SHIFT;
                        pa |= (va & L2_OFFSET);
                        return (pa);
                }

                l3 = pmap_l2_to_l3(l2, va);
                if (l3 == NULL)
                        panic("pmap_kextract: No l3...");
                pa = PTE_TO_PHYS(pmap_load(l3));
                pa |= (va & PAGE_MASK);
        }
        return (pa);
}

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

void
pmap_kenter_device(vm_offset_t sva, vm_size_t size, vm_paddr_t pa)
{
        pt_entry_t entry;
        pt_entry_t *l3;
        vm_offset_t va;
        pn_t pn;

        KASSERT((pa & L3_OFFSET) == 0,
           ("pmap_kenter_device: Invalid physical address"));
        KASSERT((sva & L3_OFFSET) == 0,
           ("pmap_kenter_device: Invalid virtual address"));
        KASSERT((size & PAGE_MASK) == 0,
            ("pmap_kenter_device: Mapping is not page-sized"));

        va = sva;
        while (size != 0) {
                l3 = pmap_l3(kernel_pmap, va);
                KASSERT(l3 != NULL, ("Invalid page table, va: 0x%lx", va));

                pn = (pa / PAGE_SIZE);
                entry = (PTE_V | PTE_RWX);
                entry |= (pn << PTE_PPN0_S);
                pmap_load_store(l3, entry);

                PTE_SYNC(l3);

                va += PAGE_SIZE;
                pa += PAGE_SIZE;
                size -= PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/*
 * Remove a page from the kernel pagetables.
 * Note: not SMP coherent.
 */
PMAP_INLINE void
pmap_kremove(vm_offset_t va)
{
        pt_entry_t *l3;

        l3 = pmap_l3(kernel_pmap, va);
        KASSERT(l3 != NULL, ("pmap_kremove: Invalid address"));

        if (pmap_l3_valid_cacheable(pmap_load(l3)))
                cpu_dcache_wb_range(va, L3_SIZE);
        pmap_load_clear(l3);
        PTE_SYNC(l3);
        pmap_invalidate_page(kernel_pmap, va);
}

void
pmap_kremove_device(vm_offset_t sva, vm_size_t size)
{
        pt_entry_t *l3;
        vm_offset_t va;

        KASSERT((sva & L3_OFFSET) == 0,
           ("pmap_kremove_device: Invalid virtual address"));
        KASSERT((size & PAGE_MASK) == 0,
            ("pmap_kremove_device: Mapping is not page-sized"));

        va = sva;
        while (size != 0) {
                l3 = pmap_l3(kernel_pmap, va);
                KASSERT(l3 != NULL, ("Invalid page table, va: 0x%lx", va));
                pmap_load_clear(l3);
                PTE_SYNC(l3);

                va += PAGE_SIZE;
                size -= PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/*
 *      Used to map a range of physical addresses into kernel
 *      virtual address space.
 *
 *      The value passed in '*virt' is a suggested virtual address for
 *      the mapping. Architectures which can support a direct-mapped
 *      physical to virtual region can return the appropriate address
 *      within that region, leaving '*virt' unchanged. Other
 *      architectures should map the pages starting at '*virt' and
 *      update '*virt' with the first usable address after the mapped
 *      region.
 */
vm_offset_t
pmap_map(vm_offset_t *virt, vm_paddr_t start, vm_paddr_t end, int prot)
{

        return PHYS_TO_DMAP(start);
}


/*
 * Add a list of wired pages to the kva
 * this routine is only used for temporary
 * kernel mappings that do not need to have
 * page modification or references recorded.
 * Note that old mappings are simply written
 * over.  The page *must* be wired.
 * Note: SMP coherent.  Uses a ranged shootdown IPI.
 */
void
pmap_qenter(vm_offset_t sva, vm_page_t *ma, int count)
{
        pt_entry_t *l3, pa;
        vm_offset_t va;
        vm_page_t m;
        pt_entry_t entry;
        pn_t pn;
        int i;

        va = sva;
        for (i = 0; i < count; i++) {
                m = ma[i];
                pa = VM_PAGE_TO_PHYS(m);
                pn = (pa / PAGE_SIZE);
                l3 = pmap_l3(kernel_pmap, va);

                entry = (PTE_V | PTE_RWX);
                entry |= (pn << PTE_PPN0_S);
                pmap_load_store(l3, entry);

                PTE_SYNC(l3);
                va += L3_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/*
 * This routine tears out page mappings from the
 * kernel -- it is meant only for temporary mappings.
 * Note: SMP coherent.  Uses a ranged shootdown IPI.
 */
void
pmap_qremove(vm_offset_t sva, int count)
{
        pt_entry_t *l3;
        vm_offset_t va;

        KASSERT(sva >= VM_MIN_KERNEL_ADDRESS, ("usermode va %lx", sva));

        va = sva;
        while (count-- > 0) {
                l3 = pmap_l3(kernel_pmap, va);
                KASSERT(l3 != NULL, ("pmap_kremove: Invalid address"));

                if (pmap_l3_valid_cacheable(pmap_load(l3)))
                        cpu_dcache_wb_range(va, L3_SIZE);
                pmap_load_clear(l3);
                PTE_SYNC(l3);

                va += PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/***************************************************
 * Page table page management routines.....
 ***************************************************/
static __inline void
pmap_free_zero_pages(struct spglist *free)
{
        vm_page_t m;

        while ((m = SLIST_FIRST(free)) != NULL) {
                SLIST_REMOVE_HEAD(free, plinks.s.ss);
                /* Preserve the page's PG_ZERO setting. */
                vm_page_free_toq(m);
        }
}

/*
 * Schedule the specified unused page table page to be freed.  Specifically,
 * add the page to the specified list of pages that will be released to the
 * physical memory manager after the TLB has been updated.
 */
static __inline void
pmap_add_delayed_free_list(vm_page_t m, struct spglist *free,
    boolean_t set_PG_ZERO)
{

        if (set_PG_ZERO)
                m->flags |= PG_ZERO;
        else
                m->flags &= ~PG_ZERO;
        SLIST_INSERT_HEAD(free, m, plinks.s.ss);
}
        
/*
 * Decrements a page table page's wire count, which is used to record the
 * number of valid page table entries within the page.  If the wire count
 * drops to zero, then the page table page is unmapped.  Returns TRUE if the
 * page table page was unmapped and FALSE otherwise.
 */
static inline boolean_t
pmap_unwire_l3(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
{

        --m->wire_count;
        if (m->wire_count == 0) {
                _pmap_unwire_l3(pmap, va, m, free);
                return (TRUE);
        } else {
                return (FALSE);
        }
}

static void
_pmap_unwire_l3(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
{
        vm_paddr_t phys;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        /*
         * unmap the page table page
         */
        if (m->pindex >= NUPDE) {
                /* PD page */
                pd_entry_t *l1;
                l1 = pmap_l1(pmap, va);
                pmap_load_clear(l1);
                pmap_distribute_l1(pmap, pmap_l1_index(va), 0);
                PTE_SYNC(l1);
        } else {
                /* PTE page */
                pd_entry_t *l2;
                l2 = pmap_l2(pmap, va);
                pmap_load_clear(l2);
                PTE_SYNC(l2);
        }
        pmap_resident_count_dec(pmap, 1);
        if (m->pindex < NUPDE) {
                pd_entry_t *l1;
                /* We just released a PT, unhold the matching PD */
                vm_page_t pdpg;

                l1 = pmap_l1(pmap, va);
                phys = PTE_TO_PHYS(pmap_load(l1));
                pdpg = PHYS_TO_VM_PAGE(phys);
                pmap_unwire_l3(pmap, va, pdpg, free);
        }
        pmap_invalidate_page(pmap, va);

        /*
         * This is a release store so that the ordinary store unmapping
         * the page table page is globally performed before TLB shoot-
         * down is begun.
         */
        atomic_subtract_rel_int(&vm_cnt.v_wire_count, 1);

        /* 
         * Put page on a list so that it is released after
         * *ALL* TLB shootdown is done
         */
        pmap_add_delayed_free_list(m, free, TRUE);
}

/*
 * After removing an l3 entry, this routine is used to
 * conditionally free the page, and manage the hold/wire counts.
 */
static int
pmap_unuse_l3(pmap_t pmap, vm_offset_t va, pd_entry_t ptepde,
    struct spglist *free)
{
        vm_paddr_t phys;
        vm_page_t mpte;

        if (va >= VM_MAXUSER_ADDRESS)
                return (0);
        KASSERT(ptepde != 0, ("pmap_unuse_pt: ptepde != 0"));

        phys = PTE_TO_PHYS(ptepde);

        mpte = PHYS_TO_VM_PAGE(phys);
        return (pmap_unwire_l3(pmap, va, mpte, free));
}

void
pmap_pinit0(pmap_t pmap)
{

        PMAP_LOCK_INIT(pmap);
        bzero(&pmap->pm_stats, sizeof(pmap->pm_stats));
        pmap->pm_l1 = kernel_pmap->pm_l1;
}

int
pmap_pinit(pmap_t pmap)
{
        vm_paddr_t l1phys;
        vm_page_t l1pt;

        /*
         * allocate the l1 page
         */
        while ((l1pt = vm_page_alloc(NULL, 0xdeadbeef, VM_ALLOC_NORMAL |
            VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL)
                VM_WAIT;

        l1phys = VM_PAGE_TO_PHYS(l1pt);
        pmap->pm_l1 = (pd_entry_t *)PHYS_TO_DMAP(l1phys);

        if ((l1pt->flags & PG_ZERO) == 0)
                pagezero(pmap->pm_l1);

        bzero(&pmap->pm_stats, sizeof(pmap->pm_stats));

        /* Install kernel pagetables */
        memcpy(pmap->pm_l1, kernel_pmap->pm_l1, PAGE_SIZE);

        /* Add to the list of all user pmaps */
        LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);

        return (1);
}

/*
 * This routine is called if the desired page table page does not exist.
 *
 * If page table page allocation fails, this routine may sleep before
 * returning NULL.  It sleeps only if a lock pointer was given.
 *
 * Note: If a page allocation fails at page table level two or three,
 * one or two pages may be held during the wait, only to be released
 * afterwards.  This conservative approach is easily argued to avoid
 * race conditions.
 */
static vm_page_t
_pmap_alloc_l3(pmap_t pmap, vm_pindex_t ptepindex, struct rwlock **lockp)
{
        vm_page_t m, /*pdppg, */pdpg;
        pt_entry_t entry;
        vm_paddr_t phys;
        pn_t pn;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        /*
         * Allocate a page table page.
         */
        if ((m = vm_page_alloc(NULL, ptepindex, VM_ALLOC_NOOBJ |
            VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
                if (lockp != NULL) {
                        RELEASE_PV_LIST_LOCK(lockp);
                        PMAP_UNLOCK(pmap);
                        rw_runlock(&pvh_global_lock);
                        VM_WAIT;
                        rw_rlock(&pvh_global_lock);
                        PMAP_LOCK(pmap);
                }

                /*
                 * Indicate the need to retry.  While waiting, the page table
                 * page may have been allocated.
                 */
                return (NULL);
        }

        if ((m->flags & PG_ZERO) == 0)
                pmap_zero_page(m);

        /*
         * Map the pagetable page into the process address space, if
         * it isn't already there.
         */

        if (ptepindex >= NUPDE) {
                pd_entry_t *l1;
                vm_pindex_t l1index;

                l1index = ptepindex - NUPDE;
                l1 = &pmap->pm_l1[l1index];

                pn = (VM_PAGE_TO_PHYS(m) / PAGE_SIZE);
                entry = (PTE_V);
                entry |= (pn << PTE_PPN0_S);
                pmap_load_store(l1, entry);
                pmap_distribute_l1(pmap, l1index, entry);

                PTE_SYNC(l1);

        } else {
                vm_pindex_t l1index;
                pd_entry_t *l1, *l2;

                l1index = ptepindex >> (L1_SHIFT - L2_SHIFT);
                l1 = &pmap->pm_l1[l1index];
                if (pmap_load(l1) == 0) {
                        /* recurse for allocating page dir */
                        if (_pmap_alloc_l3(pmap, NUPDE + l1index,
                            lockp) == NULL) {
                                --m->wire_count;
                                atomic_subtract_int(&vm_cnt.v_wire_count, 1);
                                vm_page_free_zero(m);
                                return (NULL);
                        }
                } else {
                        phys = PTE_TO_PHYS(pmap_load(l1));
                        pdpg = PHYS_TO_VM_PAGE(phys);
                        pdpg->wire_count++;
                }

                phys = PTE_TO_PHYS(pmap_load(l1));
                l2 = (pd_entry_t *)PHYS_TO_DMAP(phys);
                l2 = &l2[ptepindex & Ln_ADDR_MASK];

                pn = (VM_PAGE_TO_PHYS(m) / PAGE_SIZE);
                entry = (PTE_V);
                entry |= (pn << PTE_PPN0_S);
                pmap_load_store(l2, entry);

                PTE_SYNC(l2);
        }

        pmap_resident_count_inc(pmap, 1);

        return (m);
}

static vm_page_t
pmap_alloc_l3(pmap_t pmap, vm_offset_t va, struct rwlock **lockp)
{
        vm_pindex_t ptepindex;
        pd_entry_t *l2;
        vm_paddr_t phys;
        vm_page_t m;

        /*
         * Calculate pagetable page index
         */
        ptepindex = pmap_l2_pindex(va);
retry:
        /*
         * Get the page directory entry
         */
        l2 = pmap_l2(pmap, va);

        /*
         * If the page table page is mapped, we just increment the
         * hold count, and activate it.
         */
        if (l2 != NULL && pmap_load(l2) != 0) {
                phys = PTE_TO_PHYS(pmap_load(l2));
                m = PHYS_TO_VM_PAGE(phys);
                m->wire_count++;
        } else {
                /*
                 * Here if the pte page isn't mapped, or if it has been
                 * deallocated.
                 */
                m = _pmap_alloc_l3(pmap, ptepindex, lockp);
                if (m == NULL && lockp != NULL)
                        goto retry;
        }
        return (m);
}


/***************************************************
 * Pmap allocation/deallocation routines.
 ***************************************************/

/*
 * Release any resources held by the given physical map.
 * Called when a pmap initialized by pmap_pinit is being released.
 * Should only be called if the map contains no valid mappings.
 */
void
pmap_release(pmap_t pmap)
{
        vm_page_t m;

        KASSERT(pmap->pm_stats.resident_count == 0,
            ("pmap_release: pmap resident count %ld != 0",
            pmap->pm_stats.resident_count));

        m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pmap->pm_l1));
        m->wire_count--;
        atomic_subtract_int(&vm_cnt.v_wire_count, 1);
        vm_page_free_zero(m);

        /* Remove pmap from the allpmaps list */
        LIST_REMOVE(pmap, pm_list);

        /* Remove kernel pagetables */
        bzero(pmap->pm_l1, PAGE_SIZE);
}

#if 0
static int
kvm_size(SYSCTL_HANDLER_ARGS)
{
        unsigned long ksize = VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS;

        return sysctl_handle_long(oidp, &ksize, 0, req);
}
SYSCTL_PROC(_vm, OID_AUTO, kvm_size, CTLTYPE_LONG|CTLFLAG_RD, 
    0, 0, kvm_size, "LU", "Size of KVM");

static int
kvm_free(SYSCTL_HANDLER_ARGS)
{
        unsigned long kfree = VM_MAX_KERNEL_ADDRESS - kernel_vm_end;

        return sysctl_handle_long(oidp, &kfree, 0, req);
}
SYSCTL_PROC(_vm, OID_AUTO, kvm_free, CTLTYPE_LONG|CTLFLAG_RD, 
    0, 0, kvm_free, "LU", "Amount of KVM free");
#endif /* 0 */

/*
 * grow the number of kernel page table entries, if needed
 */
void
pmap_growkernel(vm_offset_t addr)
{
        vm_paddr_t paddr;
        vm_page_t nkpg;
        pd_entry_t *l1, *l2;
        pt_entry_t entry;
        pn_t pn;

        mtx_assert(&kernel_map->system_mtx, MA_OWNED);

        addr = roundup2(addr, L2_SIZE);
        if (addr - 1 >= kernel_map->max_offset)
                addr = kernel_map->max_offset;
        while (kernel_vm_end < addr) {
                l1 = pmap_l1(kernel_pmap, kernel_vm_end);
                if (pmap_load(l1) == 0) {
                        /* We need a new PDP entry */
                        nkpg = vm_page_alloc(NULL, kernel_vm_end >> L1_SHIFT,
                            VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ |
                            VM_ALLOC_WIRED | VM_ALLOC_ZERO);
                        if (nkpg == NULL)
                                panic("pmap_growkernel: no memory to grow kernel");
                        if ((nkpg->flags & PG_ZERO) == 0)
                                pmap_zero_page(nkpg);
                        paddr = VM_PAGE_TO_PHYS(nkpg);

                        pn = (paddr / PAGE_SIZE);
                        entry = (PTE_V);
                        entry |= (pn << PTE_PPN0_S);
                        pmap_load_store(l1, entry);
                        pmap_distribute_l1(kernel_pmap,
                            pmap_l1_index(kernel_vm_end), entry);

                        PTE_SYNC(l1);
                        continue; /* try again */
                }
                l2 = pmap_l1_to_l2(l1, kernel_vm_end);
                if ((pmap_load(l2) & PTE_A) != 0) {
                        kernel_vm_end = (kernel_vm_end + L2_SIZE) & ~L2_OFFSET;
                        if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                                kernel_vm_end = kernel_map->max_offset;
                                break;
                        }
                        continue;
                }

                nkpg = vm_page_alloc(NULL, kernel_vm_end >> L2_SHIFT,
                    VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED |
                    VM_ALLOC_ZERO);
                if (nkpg == NULL)
                        panic("pmap_growkernel: no memory to grow kernel");
                if ((nkpg->flags & PG_ZERO) == 0) {
                        pmap_zero_page(nkpg);
                }
                paddr = VM_PAGE_TO_PHYS(nkpg);

                pn = (paddr / PAGE_SIZE);
                entry = (PTE_V);
                entry |= (pn << PTE_PPN0_S);
                pmap_load_store(l2, entry);

                PTE_SYNC(l2);
                pmap_invalidate_page(kernel_pmap, kernel_vm_end);

                kernel_vm_end = (kernel_vm_end + L2_SIZE) & ~L2_OFFSET;
                if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                        kernel_vm_end = kernel_map->max_offset;
                        break;                       
                }
        }
}


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

CTASSERT(sizeof(struct pv_chunk) == PAGE_SIZE);
CTASSERT(_NPCM == 3);
CTASSERT(_NPCPV == 168);

static __inline struct pv_chunk *
pv_to_chunk(pv_entry_t pv)
{

        return ((struct pv_chunk *)((uintptr_t)pv & ~(uintptr_t)PAGE_MASK));
}

#define PV_PMAP(pv) (pv_to_chunk(pv)->pc_pmap)

#define PC_FREE0        0xfffffffffffffffful
#define PC_FREE1        0xfffffffffffffffful
#define PC_FREE2        0x000000fffffffffful

static const uint64_t pc_freemask[_NPCM] = { PC_FREE0, PC_FREE1, PC_FREE2 };

#if 0
#ifdef PV_STATS
static int pc_chunk_count, pc_chunk_allocs, pc_chunk_frees, pc_chunk_tryfail;

SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_count, CTLFLAG_RD, &pc_chunk_count, 0,
        "Current number of pv entry chunks");
SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_allocs, CTLFLAG_RD, &pc_chunk_allocs, 0,
        "Current number of pv entry chunks allocated");
SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_frees, CTLFLAG_RD, &pc_chunk_frees, 0,
        "Current number of pv entry chunks frees");
SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_tryfail, CTLFLAG_RD, &pc_chunk_tryfail, 0,
        "Number of times tried to get a chunk page but failed.");

static long pv_entry_frees, pv_entry_allocs, pv_entry_count;
static int pv_entry_spare;

SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_frees, CTLFLAG_RD, &pv_entry_frees, 0,
        "Current number of pv entry frees");
SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_allocs, CTLFLAG_RD, &pv_entry_allocs, 0,
        "Current number of pv entry allocs");
SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_count, CTLFLAG_RD, &pv_entry_count, 0,
        "Current number of pv entries");
SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_spare, CTLFLAG_RD, &pv_entry_spare, 0,
        "Current number of spare pv entries");
#endif
#endif /* 0 */

/*
 * We are in a serious low memory condition.  Resort to
 * drastic measures to free some pages so we can allocate
 * another pv entry chunk.
 *
 * Returns NULL if PV entries were reclaimed from the specified pmap.
 *
 * We do not, however, unmap 2mpages because subsequent accesses will
 * allocate per-page pv entries until repromotion occurs, thereby
 * exacerbating the shortage of free pv entries.
 */
static vm_page_t
reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp)
{

        panic("RISCVTODO: reclaim_pv_chunk");
}

/*
 * free the pv_entry back to the free list
 */
static void
free_pv_entry(pmap_t pmap, pv_entry_t pv)
{
        struct pv_chunk *pc;
        int idx, field, bit;

        rw_assert(&pvh_global_lock, RA_LOCKED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PV_STAT(atomic_add_long(&pv_entry_frees, 1));
        PV_STAT(atomic_add_int(&pv_entry_spare, 1));
        PV_STAT(atomic_subtract_long(&pv_entry_count, 1));
        pc = pv_to_chunk(pv);
        idx = pv - &pc->pc_pventry[0];
        field = idx / 64;
        bit = idx % 64;
        pc->pc_map[field] |= 1ul << bit;
        if (pc->pc_map[0] != PC_FREE0 || pc->pc_map[1] != PC_FREE1 ||
            pc->pc_map[2] != PC_FREE2) {
                /* 98% of the time, pc is already at the head of the list. */
                if (__predict_false(pc != TAILQ_FIRST(&pmap->pm_pvchunk))) {
                        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                        TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                }
                return;
        }
        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
        free_pv_chunk(pc);
}

static void
free_pv_chunk(struct pv_chunk *pc)
{
        vm_page_t m;

        mtx_lock(&pv_chunks_mutex);
        TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
        mtx_unlock(&pv_chunks_mutex);
        PV_STAT(atomic_subtract_int(&pv_entry_spare, _NPCPV));
        PV_STAT(atomic_subtract_int(&pc_chunk_count, 1));
        PV_STAT(atomic_add_int(&pc_chunk_frees, 1));
        /* entire chunk is free, return it */
        m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pc));
#if 0 /* TODO: For minidump */
        dump_drop_page(m->phys_addr);
#endif
        vm_page_unwire(m, PQ_NONE);
        vm_page_free(m);
}

/*
 * Returns a new PV entry, allocating a new PV chunk from the system when
 * needed.  If this PV chunk allocation fails and a PV list lock pointer was
 * given, a PV chunk is reclaimed from an arbitrary pmap.  Otherwise, NULL is
 * returned.
 *
 * The given PV list lock may be released.
 */
static pv_entry_t
get_pv_entry(pmap_t pmap, struct rwlock **lockp)
{
        int bit, field;
        pv_entry_t pv;
        struct pv_chunk *pc;
        vm_page_t m;

        rw_assert(&pvh_global_lock, RA_LOCKED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PV_STAT(atomic_add_long(&pv_entry_allocs, 1));
retry:
        pc = TAILQ_FIRST(&pmap->pm_pvchunk);
        if (pc != NULL) {
                for (field = 0; field < _NPCM; field++) {
                        if (pc->pc_map[field]) {
                                bit = ffsl(pc->pc_map[field]) - 1;
                                break;
                        }
                }
                if (field < _NPCM) {
                        pv = &pc->pc_pventry[field * 64 + bit];
                        pc->pc_map[field] &= ~(1ul << bit);
                        /* If this was the last item, move it to tail */
                        if (pc->pc_map[0] == 0 && pc->pc_map[1] == 0 &&
                            pc->pc_map[2] == 0) {
                                TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                                TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc,
                                    pc_list);
                        }
                        PV_STAT(atomic_add_long(&pv_entry_count, 1));
                        PV_STAT(atomic_subtract_int(&pv_entry_spare, 1));
                        return (pv);
                }
        }
        /* No free items, allocate another chunk */
        m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
            VM_ALLOC_WIRED);
        if (m == NULL) {
                if (lockp == NULL) {
                        PV_STAT(pc_chunk_tryfail++);
                        return (NULL);
                }
                m = reclaim_pv_chunk(pmap, lockp);
                if (m == NULL)
                        goto retry;
        }
        PV_STAT(atomic_add_int(&pc_chunk_count, 1));
        PV_STAT(atomic_add_int(&pc_chunk_allocs, 1));
#if 0 /* TODO: This is for minidump */
        dump_add_page(m->phys_addr);
#endif
        pc = (void *)PHYS_TO_DMAP(m->phys_addr);
        pc->pc_pmap = pmap;
        pc->pc_map[0] = PC_FREE0 & ~1ul;        /* preallocated bit 0 */
        pc->pc_map[1] = PC_FREE1;
        pc->pc_map[2] = PC_FREE2;
        mtx_lock(&pv_chunks_mutex);
        TAILQ_INSERT_TAIL(&pv_chunks, pc, pc_lru);
        mtx_unlock(&pv_chunks_mutex);
        pv = &pc->pc_pventry[0];
        TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
        PV_STAT(atomic_add_long(&pv_entry_count, 1));
        PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV - 1));
        return (pv);
}

/*
 * First find and then remove the pv entry for the specified pmap and virtual
 * address from the specified pv list.  Returns the pv entry if found and NULL
 * otherwise.  This operation can be performed on pv lists for either 4KB or
 * 2MB page mappings.
 */
static __inline pv_entry_t
pmap_pvh_remove(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
{
        pv_entry_t pv;

        rw_assert(&pvh_global_lock, RA_LOCKED);
        TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                if (pmap == PV_PMAP(pv) && va == pv->pv_va) {
                        TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                        pvh->pv_gen++;
                        break;
                }
        }
        return (pv);
}

/*
 * First find and then destroy the pv entry for the specified pmap and virtual
 * address.  This operation can be performed on pv lists for either 4KB or 2MB
 * page mappings.
 */
static void
pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
{
        pv_entry_t pv;

        pv = pmap_pvh_remove(pvh, pmap, va);

        KASSERT(pv != NULL, ("pmap_pvh_free: pv not found"));
        free_pv_entry(pmap, pv);
}

/*
 * Conditionally create the PV entry for a 4KB page mapping if the required
 * memory can be allocated without resorting to reclamation.
 */
static boolean_t
pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va, vm_page_t m,
    struct rwlock **lockp)
{
        pv_entry_t pv;

        rw_assert(&pvh_global_lock, RA_LOCKED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        /* Pass NULL instead of the lock pointer to disable reclamation. */
        if ((pv = get_pv_entry(pmap, NULL)) != NULL) {
                pv->pv_va = va;
                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                m->md.pv_gen++;
                return (TRUE);
        } else
                return (FALSE);
}

/*
 * pmap_remove_l3: do the things to unmap a page in a process
 */
static int
pmap_remove_l3(pmap_t pmap, pt_entry_t *l3, vm_offset_t va, 
    pd_entry_t l2e, struct spglist *free, struct rwlock **lockp)
{
        pt_entry_t old_l3;
        vm_paddr_t phys;
        vm_page_t m;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        if (pmap_is_current(pmap) && pmap_l3_valid_cacheable(pmap_load(l3)))
                cpu_dcache_wb_range(va, L3_SIZE);
        old_l3 = pmap_load_clear(l3);
        PTE_SYNC(l3);
        pmap_invalidate_page(pmap, va);
        if (old_l3 & PTE_SW_WIRED)
                pmap->pm_stats.wired_count -= 1;
        pmap_resident_count_dec(pmap, 1);
        if (old_l3 & PTE_SW_MANAGED) {
                phys = PTE_TO_PHYS(old_l3);
                m = PHYS_TO_VM_PAGE(phys);
                if (pmap_page_dirty(old_l3))
                        vm_page_dirty(m);
                if (old_l3 & PTE_A)
                        vm_page_aflag_set(m, PGA_REFERENCED);
                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                pmap_pvh_free(&m->md, pmap, va);
        }

        return (pmap_unuse_l3(pmap, va, l2e, free));
}

/*
 *      Remove the given range of addresses from the specified map.
 *
 *      It is assumed that the start and end are properly
 *      rounded to the page size.
 */
void
pmap_remove(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        struct rwlock *lock;
        vm_offset_t va, va_next;
        pd_entry_t *l1, *l2;
        pt_entry_t l3_pte, *l3;
        struct spglist free;

        /*
         * Perform an unsynchronized read.  This is, however, safe.
         */
        if (pmap->pm_stats.resident_count == 0)
                return;

        SLIST_INIT(&free);

        rw_rlock(&pvh_global_lock);
        PMAP_LOCK(pmap);

        lock = NULL;
        for (; sva < eva; sva = va_next) {
                if (pmap->pm_stats.resident_count == 0)
                        break;

                l1 = pmap_l1(pmap, sva);
                if (pmap_load(l1) == 0) {
                        va_next = (sva + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                /*
                 * Calculate index for next page table.
                 */
                va_next = (sva + L2_SIZE) & ~L2_OFFSET;
                if (va_next < sva)
                        va_next = eva;

                l2 = pmap_l1_to_l2(l1, sva);
                if (l2 == NULL)
                        continue;

                l3_pte = pmap_load(l2);

                /*
                 * Weed out invalid mappings.
                 */
                if (l3_pte == 0)
                        continue;
                if ((pmap_load(l2) & PTE_RX) != 0)
                        continue;

                /*
                 * Limit our scan to either the end of the va represented
                 * by the current page table page, or to the end of the
                 * range being removed.
                 */
                if (va_next > eva)
                        va_next = eva;

                va = va_next;
                for (l3 = pmap_l2_to_l3(l2, sva); sva != va_next; l3++,
                    sva += L3_SIZE) {
                        if (l3 == NULL)
                                panic("l3 == NULL");
                        if (pmap_load(l3) == 0) {
                                if (va != va_next) {
                                        pmap_invalidate_range(pmap, va, sva);
                                        va = va_next;
                                }
                                continue;
                        }
                        if (va == va_next)
                                va = sva;
                        if (pmap_remove_l3(pmap, l3, sva, l3_pte, &free,
                            &lock)) {
                                sva += L3_SIZE;
                                break;
                        }
                }
                if (va != va_next)
                        pmap_invalidate_range(pmap, va, sva);
        }
        if (lock != NULL)
                rw_wunlock(lock);
        rw_runlock(&pvh_global_lock);   
        PMAP_UNLOCK(pmap);
        pmap_free_zero_pages(&free);
}

/*
 *      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;
        pmap_t pmap;
        pt_entry_t *l3, tl3;
        pd_entry_t *l2, tl2;
        struct spglist free;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_remove_all: page %p is not managed", m));
        SLIST_INIT(&free);
        rw_wlock(&pvh_global_lock);
        while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pmap_resident_count_dec(pmap, 1);
                l2 = pmap_l2(pmap, pv->pv_va);
                KASSERT(l2 != NULL, ("pmap_remove_all: no l2 table found"));
                tl2 = pmap_load(l2);

                KASSERT((tl2 & PTE_RX) == 0,
                    ("pmap_remove_all: found a table when expecting "
                    "a block in %p's pv list", m));

                l3 = pmap_l2_to_l3(l2, pv->pv_va);
                if (pmap_is_current(pmap) &&
                    pmap_l3_valid_cacheable(pmap_load(l3)))
                        cpu_dcache_wb_range(pv->pv_va, L3_SIZE);
                tl3 = pmap_load_clear(l3);
                PTE_SYNC(l3);
                pmap_invalidate_page(pmap, pv->pv_va);
                if (tl3 & PTE_SW_WIRED)
                        pmap->pm_stats.wired_count--;
                if ((tl3 & PTE_A) != 0)
                        vm_page_aflag_set(m, PGA_REFERENCED);

                /*
                 * Update the vm_page_t clean and reference bits.
                 */
                if (pmap_page_dirty(tl3))
                        vm_page_dirty(m);
                pmap_unuse_l3(pmap, pv->pv_va, pmap_load(l2), &free);
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                m->md.pv_gen++;
                free_pv_entry(pmap, pv);
                PMAP_UNLOCK(pmap);
        }
        vm_page_aflag_clear(m, PGA_WRITEABLE);
        rw_wunlock(&pvh_global_lock);
        pmap_free_zero_pages(&free);
}

/*
 *      Set the physical protection on the
 *      specified range of this map as requested.
 */
void
pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
{
        vm_offset_t va, va_next;
        pd_entry_t *l1, *l2;
        pt_entry_t *l3p, l3;
        pt_entry_t entry;

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

        if ((prot & VM_PROT_WRITE) == VM_PROT_WRITE)
                return;

        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {

                l1 = pmap_l1(pmap, sva);
                if (pmap_load(l1) == 0) {
                        va_next = (sva + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                va_next = (sva + L2_SIZE) & ~L2_OFFSET;
                if (va_next < sva)
                        va_next = eva;

                l2 = pmap_l1_to_l2(l1, sva);
                if (l2 == NULL)
                        continue;
                if (pmap_load(l2) == 0)
                        continue;
                if ((pmap_load(l2) & PTE_RX) != 0)
                        continue;

                if (va_next > eva)
                        va_next = eva;

                va = va_next;
                for (l3p = pmap_l2_to_l3(l2, sva); sva != va_next; l3p++,
                    sva += L3_SIZE) {
                        l3 = pmap_load(l3p);
                        if (pmap_l3_valid(l3)) {
                                entry = pmap_load(l3p);
                                entry &= ~(PTE_W);
                                pmap_load_store(l3p, entry);
                                PTE_SYNC(l3p);
                                /* XXX: Use pmap_invalidate_range */
                                pmap_invalidate_page(pmap, sva);
                        }
                }
        }
        PMAP_UNLOCK(pmap);
}

/*
 *      Insert the given physical page (p) at
 *      the specified virtual address (v) in the
 *      target physical map with the protection requested.
 *
 *      If specified, the page will be wired down, meaning
 *      that the related pte can not be reclaimed.
 *
 *      NB:  This is the only routine which MAY NOT lazy-evaluate
 *      or lose information.  That is, this routine must actually
 *      insert this page into the given map NOW.
 */
int
pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
    u_int flags, int8_t psind __unused)
{
        struct rwlock *lock;
        pd_entry_t *l1, *l2;
        pt_entry_t new_l3, orig_l3;
        pt_entry_t *l3;
        pv_entry_t pv;
        vm_paddr_t opa, pa, l2_pa, l3_pa;
        vm_page_t mpte, om, l2_m, l3_m;
        boolean_t nosleep;
        pt_entry_t entry;
        pn_t l2_pn;
        pn_t l3_pn;
        pn_t pn;

        va = trunc_page(va);
        if ((m->oflags & VPO_UNMANAGED) == 0 && !vm_page_xbusied(m))
                VM_OBJECT_ASSERT_LOCKED(m->object);
        pa = VM_PAGE_TO_PHYS(m);
        pn = (pa / PAGE_SIZE);

        new_l3 = PTE_V | PTE_R | PTE_X;
        if (prot & VM_PROT_WRITE)
                new_l3 |= PTE_W;
        if ((va >> 63) == 0)
                new_l3 |= PTE_U;

        new_l3 |= (pn << PTE_PPN0_S);
        if ((flags & PMAP_ENTER_WIRED) != 0)
                new_l3 |= PTE_SW_WIRED;

        CTR2(KTR_PMAP, "pmap_enter: %.16lx -> %.16lx", va, pa);

        mpte = NULL;

        lock = NULL;
        rw_rlock(&pvh_global_lock);
        PMAP_LOCK(pmap);

        if (va < VM_MAXUSER_ADDRESS) {
                nosleep = (flags & PMAP_ENTER_NOSLEEP) != 0;
                mpte = pmap_alloc_l3(pmap, va, nosleep ? NULL : &lock);
                if (mpte == NULL && nosleep) {
                        CTR0(KTR_PMAP, "pmap_enter: mpte == NULL");
                        if (lock != NULL)
                                rw_wunlock(lock);
                        rw_runlock(&pvh_global_lock);
                        PMAP_UNLOCK(pmap);
                        return (KERN_RESOURCE_SHORTAGE);
                }
                l3 = pmap_l3(pmap, va);
        } else {
                l3 = pmap_l3(pmap, va);
                /* TODO: This is not optimal, but should mostly work */
                if (l3 == NULL) {
                        l2 = pmap_l2(pmap, va);
                        if (l2 == NULL) {
                                l2_m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
                                    VM_ALLOC_NOOBJ | VM_ALLOC_WIRED |
                                    VM_ALLOC_ZERO);
                                if (l2_m == NULL)
                                        panic("pmap_enter: l2 pte_m == NULL");
                                if ((l2_m->flags & PG_ZERO) == 0)
                                        pmap_zero_page(l2_m);

                                l2_pa = VM_PAGE_TO_PHYS(l2_m);
                                l2_pn = (l2_pa / PAGE_SIZE);

                                l1 = pmap_l1(pmap, va);
                                entry = (PTE_V);
                                entry |= (l2_pn << PTE_PPN0_S);
                                pmap_load_store(l1, entry);
                                pmap_distribute_l1(pmap, pmap_l1_index(va), entry);
                                PTE_SYNC(l1);

                                l2 = pmap_l1_to_l2(l1, va);
                        }

                        KASSERT(l2 != NULL,
                            ("No l2 table after allocating one"));

                        l3_m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
                            VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
                        if (l3_m == NULL)
                                panic("pmap_enter: l3 pte_m == NULL");
                        if ((l3_m->flags & PG_ZERO) == 0)
                                pmap_zero_page(l3_m);

                        l3_pa = VM_PAGE_TO_PHYS(l3_m);
                        l3_pn = (l3_pa / PAGE_SIZE);
                        entry = (PTE_V);
                        entry |= (l3_pn << PTE_PPN0_S);
                        pmap_load_store(l2, entry);
                        PTE_SYNC(l2);
                        l3 = pmap_l2_to_l3(l2, va);
                }
                pmap_invalidate_page(pmap, va);
        }

        om = NULL;
        orig_l3 = pmap_load(l3);
        opa = PTE_TO_PHYS(orig_l3);

        /*
         * Is the specified virtual address already mapped?
         */
        if (pmap_l3_valid(orig_l3)) {
                /*
                 * Wiring change, just update stats. We don't worry about
                 * wiring PT pages as they remain resident as long as there
                 * are valid mappings in them. Hence, if a user page is wired,
                 * the PT page will be also.
                 */
                if ((flags & PMAP_ENTER_WIRED) != 0 &&
                    (orig_l3 & PTE_SW_WIRED) == 0)
                        pmap->pm_stats.wired_count++;
                else if ((flags & PMAP_ENTER_WIRED) == 0 &&
                    (orig_l3 & PTE_SW_WIRED) != 0)
                        pmap->pm_stats.wired_count--;

                /*
                 * Remove the extra PT page reference.
                 */
                if (mpte != NULL) {
                        mpte->wire_count--;
                        KASSERT(mpte->wire_count > 0,
                            ("pmap_enter: missing reference to page table page,"
                             " va: 0x%lx", va));
                }

                /*
                 * Has the physical page changed?
                 */
                if (opa == pa) {
                        /*
                         * No, might be a protection or wiring change.
                         */
                        if ((orig_l3 & PTE_SW_MANAGED) != 0) {
                                new_l3 |= PTE_SW_MANAGED;
                                if (pmap_is_write(new_l3))
                                        vm_page_aflag_set(m, PGA_WRITEABLE);
                        }
                        goto validate;
                }

                /* Flush the cache, there might be uncommitted data in it */
                if (pmap_is_current(pmap) && pmap_l3_valid_cacheable(orig_l3))
                        cpu_dcache_wb_range(va, L3_SIZE);
        } else {
                /*
                 * Increment the counters.
                 */
                if ((new_l3 & PTE_SW_WIRED) != 0)
                        pmap->pm_stats.wired_count++;
                pmap_resident_count_inc(pmap, 1);
        }
        /*
         * Enter on the PV list if part of our managed memory.
         */
        if ((m->oflags & VPO_UNMANAGED) == 0) {
                new_l3 |= PTE_SW_MANAGED;
                pv = get_pv_entry(pmap, &lock);
                pv->pv_va = va;
                CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, pa);
                TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                m->md.pv_gen++;
                if (pmap_is_write(new_l3))
                        vm_page_aflag_set(m, PGA_WRITEABLE);
        }

        /*
         * Update the L3 entry.
         */
        if (orig_l3 != 0) {
validate:
                orig_l3 = pmap_load_store(l3, new_l3);
                PTE_SYNC(l3);
                opa = PTE_TO_PHYS(orig_l3);

                if (opa != pa) {
                        if ((orig_l3 & PTE_SW_MANAGED) != 0) {
                                om = PHYS_TO_VM_PAGE(opa);
                                if (pmap_page_dirty(orig_l3))
                                        vm_page_dirty(om);
                                if ((orig_l3 & PTE_A) != 0)
                                        vm_page_aflag_set(om, PGA_REFERENCED);
                                CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, opa);
                                pmap_pvh_free(&om->md, pmap, va);
                        }
                } else if (pmap_page_dirty(orig_l3)) {
                        if ((orig_l3 & PTE_SW_MANAGED) != 0)
                                vm_page_dirty(m);
                }
        } else {
                pmap_load_store(l3, new_l3);
                PTE_SYNC(l3);
        }
        pmap_invalidate_page(pmap, va);
        if ((pmap != pmap_kernel()) && (pmap == &curproc->p_vmspace->vm_pmap))
            cpu_icache_sync_range(va, PAGE_SIZE);

        if (lock != NULL)
                rw_wunlock(lock);
        rw_runlock(&pvh_global_lock);
        PMAP_UNLOCK(pmap);
        return (KERN_SUCCESS);
}

/*
 * Maps a sequence of resident pages belonging to the same object.
 * The sequence begins with the given page m_start.  This page is
 * mapped at the given virtual address start.  Each subsequent page is
 * mapped at a virtual address that is offset from start by the same
 * amount as the page is offset from m_start within the object.  The
 * last page in the sequence is the page with the largest offset from
 * m_start that can be mapped at a virtual address less than the given
 * virtual address end.  Not every virtual page between start and end
 * is mapped; only those for which a resident page exists with the
 * corresponding offset from m_start are mapped.
 */
void
pmap_enter_object(pmap_t pmap, vm_offset_t start, vm_offset_t end,
    vm_page_t m_start, vm_prot_t prot)
{
        struct rwlock *lock;
        vm_offset_t va;
        vm_page_t m, mpte;
        vm_pindex_t diff, psize;

        VM_OBJECT_ASSERT_LOCKED(m_start->object);

        psize = atop(end - start);
        mpte = NULL;
        m = m_start;
        lock = NULL;
        rw_rlock(&pvh_global_lock);
        PMAP_LOCK(pmap);
        while (m != NULL && (diff = m->pindex - m_start->pindex) < psize) {
                va = start + ptoa(diff);
                mpte = pmap_enter_quick_locked(pmap, va, m, prot, mpte, &lock);
                m = TAILQ_NEXT(m, listq);
        }
        if (lock != NULL)
                rw_wunlock(lock);
        rw_runlock(&pvh_global_lock);
        PMAP_UNLOCK(pmap);
}

/*
 * this code makes some *MAJOR* assumptions:
 * 1. Current pmap & pmap exists.
 * 2. Not wired.
 * 3. Read access.
 * 4. No page table pages.
 * but is *MUCH* faster than pmap_enter...
 */

void
pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
{
        struct rwlock *lock;

        lock = NULL;
        rw_rlock(&pvh_global_lock);
        PMAP_LOCK(pmap);
        (void)pmap_enter_quick_locked(pmap, va, m, prot, NULL, &lock);
        if (lock != NULL)
                rw_wunlock(lock);
        rw_runlock(&pvh_global_lock);
        PMAP_UNLOCK(pmap);
}

static vm_page_t
pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, vm_page_t m,
    vm_prot_t prot, vm_page_t mpte, struct rwlock **lockp)
{
        struct spglist free;
        vm_paddr_t phys;
        pd_entry_t *l2;
        pt_entry_t *l3;
        vm_paddr_t pa;
        pt_entry_t entry;
        pn_t pn;

        KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
            (m->oflags & VPO_UNMANAGED) != 0,
            ("pmap_enter_quick_locked: managed mapping within the clean submap"));
        rw_assert(&pvh_global_lock, RA_LOCKED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        CTR2(KTR_PMAP, "pmap_enter_quick_locked: %p %lx", pmap, va);
        /*
         * In the case that a page table page is not
         * resident, we are creating it here.
         */
        if (va < VM_MAXUSER_ADDRESS) {
                vm_pindex_t l2pindex;

                /*
                 * Calculate pagetable page index
                 */
                l2pindex = pmap_l2_pindex(va);
                if (mpte && (mpte->pindex == l2pindex)) {
                        mpte->wire_count++;
                } else {
                        /*
                         * Get the l2 entry
                         */
                        l2 = pmap_l2(pmap, va);

                        /*
                         * If the page table page is mapped, we just increment
                         * the hold count, and activate it.  Otherwise, we
                         * attempt to allocate a page table page.  If this
                         * attempt fails, we don't retry.  Instead, we give up.
                         */
                        if (l2 != NULL && pmap_load(l2) != 0) {
                                phys = PTE_TO_PHYS(pmap_load(l2));
                                mpte = PHYS_TO_VM_PAGE(phys);
                                mpte->wire_count++;
                        } else {
                                /*
                                 * Pass NULL instead of the PV list lock
                                 * pointer, because we don't intend to sleep.
                                 */
                                mpte = _pmap_alloc_l3(pmap, l2pindex, NULL);
                                if (mpte == NULL)
                                        return (mpte);
                        }
                }
                l3 = (pt_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mpte));
                l3 = &l3[pmap_l3_index(va)];
        } else {
                mpte = NULL;
                l3 = pmap_l3(kernel_pmap, va);
        }
        if (l3 == NULL)
                panic("pmap_enter_quick_locked: No l3");
        if (pmap_load(l3) != 0) {
                if (mpte != NULL) {
                        mpte->wire_count--;
                        mpte = NULL;
                }
                return (mpte);
        }

        /*
         * Enter on the PV list if part of our managed memory.
         */
        if ((m->oflags & VPO_UNMANAGED) == 0 &&
            !pmap_try_insert_pv_entry(pmap, va, m, lockp)) {
                if (mpte != NULL) {
                        SLIST_INIT(&free);
                        if (pmap_unwire_l3(pmap, va, mpte, &free)) {
                                pmap_invalidate_page(pmap, va);
                                pmap_free_zero_pages(&free);
                        }
                        mpte = NULL;
                }
                return (mpte);
        }

        /*
         * Increment counters
         */
        pmap_resident_count_inc(pmap, 1);

        pa = VM_PAGE_TO_PHYS(m);
        pn = (pa / PAGE_SIZE);

        /* RISCVTODO: check permissions */
        entry = (PTE_V | PTE_RWX);
        entry |= (pn << PTE_PPN0_S);

        /*
         * Now validate mapping with RO protection
         */
        if ((m->oflags & VPO_UNMANAGED) == 0)
                entry |= PTE_SW_MANAGED;
        pmap_load_store(l3, entry);

        PTE_SYNC(l3);
        pmap_invalidate_page(pmap, va);
        return (mpte);
}

/*
 * This code maps large physical mmap regions into the
 * processor address space.  Note that some shortcuts
 * are taken, but the code works.
 */
void
pmap_object_init_pt(pmap_t pmap, vm_offset_t addr, vm_object_t object,
    vm_pindex_t pindex, vm_size_t size)
{

        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT(object->type == OBJT_DEVICE || object->type == OBJT_SG,
            ("pmap_object_init_pt: non-device object"));
}

/*
 *      Clear the wired attribute from the mappings for the specified range of
 *      addresses in the given pmap.  Every valid mapping within that range
 *      must have the wired attribute set.  In contrast, invalid mappings
 *      cannot have the wired attribute set, so they are ignored.
 *
 *      The wired attribute of the page table entry is not a hardware feature,
 *      so there is no need to invalidate any TLB entries.
 */
void
pmap_unwire(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        vm_offset_t va_next;
        pd_entry_t *l1, *l2;
        pt_entry_t *l3;
        boolean_t pv_lists_locked;

        pv_lists_locked = FALSE;
        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {
                l1 = pmap_l1(pmap, sva);
                if (pmap_load(l1) == 0) {
                        va_next = (sva + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                va_next = (sva + L2_SIZE) & ~L2_OFFSET;
                if (va_next < sva)
                        va_next = eva;

                l2 = pmap_l1_to_l2(l1, sva);
                if (pmap_load(l2) == 0)
                        continue;

                if (va_next > eva)
                        va_next = eva;
                for (l3 = pmap_l2_to_l3(l2, sva); sva != va_next; l3++,
                    sva += L3_SIZE) {
                        if (pmap_load(l3) == 0)
                                continue;
                        if ((pmap_load(l3) & PTE_SW_WIRED) == 0)
                                panic("pmap_unwire: l3 %#jx is missing "
                                    "PTE_SW_WIRED", (uintmax_t)*l3);

                        /*
                         * PG_W must be cleared atomically.  Although the pmap
                         * lock synchronizes access to PG_W, another processor
                         * could be setting PG_M and/or PG_A concurrently.
                         */
                        atomic_clear_long(l3, PTE_SW_WIRED);
                        pmap->pm_stats.wired_count--;
                }
        }
        if (pv_lists_locked)
                rw_runlock(&pvh_global_lock);
        PMAP_UNLOCK(pmap);
}

/*
 *      Copy the range specified by src_addr/len
 *      from the source map to the range dst_addr/len
 *      in the destination map.
 *
 *      This routine is only advisory and need not do anything.
 */

void
pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len,
    vm_offset_t src_addr)
{

}

/*
 *      pmap_zero_page zeros the specified hardware page by mapping
 *      the page into KVM and using bzero to clear its contents.
 */
void
pmap_zero_page(vm_page_t m)
{
        vm_offset_t va = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));

        pagezero((void *)va);
}

/*
 *      pmap_zero_page_area zeros the specified hardware page by mapping 
 *      the page into KVM and using bzero to clear its contents.
 *
 *      off and size may not cover an area beyond a single hardware page.
 */
void
pmap_zero_page_area(vm_page_t m, int off, int size)
{
        vm_offset_t va = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));

        if (off == 0 && size == PAGE_SIZE)
                pagezero((void *)va);
        else
                bzero((char *)va + off, size);
}

/*
 *      pmap_copy_page copies the specified (machine independent)
 *      page by mapping the page into virtual memory and using
 *      bcopy to copy the page, one machine dependent page at a
 *      time.
 */
void
pmap_copy_page(vm_page_t msrc, vm_page_t mdst)
{
        vm_offset_t src = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(msrc));
        vm_offset_t dst = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mdst));

        pagecopy((void *)src, (void *)dst);
}

int unmapped_buf_allowed = 1;

void
pmap_copy_pages(vm_page_t ma[], vm_offset_t a_offset, vm_page_t mb[],
    vm_offset_t b_offset, int xfersize)
{
        void *a_cp, *b_cp;
        vm_page_t m_a, m_b;
        vm_paddr_t p_a, p_b;
        vm_offset_t a_pg_offset, b_pg_offset;
        int cnt;

        while (xfersize > 0) {
                a_pg_offset = a_offset & PAGE_MASK;
                m_a = ma[a_offset >> PAGE_SHIFT];
                p_a = m_a->phys_addr;
                b_pg_offset = b_offset & PAGE_MASK;
                m_b = mb[b_offset >> PAGE_SHIFT];
                p_b = m_b->phys_addr;
                cnt = min(xfersize, PAGE_SIZE - a_pg_offset);
                cnt = min(cnt, PAGE_SIZE - b_pg_offset);
                if (__predict_false(!PHYS_IN_DMAP(p_a))) {
                        panic("!DMAP a %lx", p_a);
                } else {
                        a_cp = (char *)PHYS_TO_DMAP(p_a) + a_pg_offset;
                }
                if (__predict_false(!PHYS_IN_DMAP(p_b))) {
                        panic("!DMAP b %lx", p_b);
                } else {
                        b_cp = (char *)PHYS_TO_DMAP(p_b) + b_pg_offset;
                }
                bcopy(a_cp, b_cp, cnt);
                a_offset += cnt;
                b_offset += cnt;
                xfersize -= cnt;
        }
}

vm_offset_t
pmap_quick_enter_page(vm_page_t m)
{

        return (PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)));
}

void
pmap_quick_remove_page(vm_offset_t addr)
{
}

/*
 * Returns true if the pmap's pv is one of the first
 * 16 pvs linked to from this page.  This count may
 * be changed upwards or downwards in the future; it
 * is only necessary that true be returned for a small
 * subset of pmaps for proper page aging.
 */
boolean_t
pmap_page_exists_quick(pmap_t pmap, vm_page_t m)
{
        struct rwlock *lock;
        pv_entry_t pv;
        int loops = 0;
        boolean_t rv;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_page_exists_quick: page %p is not managed", m));
        rv = FALSE;
        rw_rlock(&pvh_global_lock);
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_rlock(lock);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                if (PV_PMAP(pv) == pmap) {
                        rv = TRUE;
                        break;
                }
                loops++;
                if (loops >= 16)
                        break;
        }
        rw_runlock(lock);
        rw_runlock(&pvh_global_lock);
        return (rv);
}

/*
 *      pmap_page_wired_mappings:
 *
 *      Return the number of managed mappings to the given physical page
 *      that are wired.
 */
int
pmap_page_wired_mappings(vm_page_t m)
{
        struct rwlock *lock;
        pmap_t pmap;
        pt_entry_t *l3;
        pv_entry_t pv;
        int count, md_gen;

        if ((m->oflags & VPO_UNMANAGED) != 0)
                return (0);
        rw_rlock(&pvh_global_lock);
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_rlock(lock);
restart:
        count = 0;
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        md_gen = m->md.pv_gen;
                        rw_runlock(lock);
                        PMAP_LOCK(pmap);
                        rw_rlock(lock);
                        if (md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto restart;
                        }
                }
                l3 = pmap_l3(pmap, pv->pv_va);
                if (l3 != NULL && (pmap_load(l3) & PTE_SW_WIRED) != 0)
                        count++;
                PMAP_UNLOCK(pmap);
        }
        rw_runlock(lock);
        rw_runlock(&pvh_global_lock);
        return (count);
}

/*
 * Destroy all managed, non-wired mappings in the given user-space
 * pmap.  This pmap cannot be active on any processor besides the
 * caller.
 *
 * This function cannot be applied to the kernel pmap.  Moreover, it
 * is not intended for general use.  It is only to be used during
 * process termination.  Consequently, it can be implemented in ways
 * that make it faster than pmap_remove().  First, it can more quickly
 * destroy mappings by iterating over the pmap's collection of PV
 * entries, rather than searching the page table.  Second, it doesn't
 * have to test and clear the page table entries atomically, because
 * no processor is currently accessing the user address space.  In
 * particular, a page table entry's dirty bit won't change state once
 * this function starts.
 */
void
pmap_remove_pages(pmap_t pmap)
{
        pd_entry_t ptepde, *l2;
        pt_entry_t *l3, tl3;
        struct spglist free;
        vm_page_t m;
        pv_entry_t pv;
        struct pv_chunk *pc, *npc;
        struct rwlock *lock;
        int64_t bit;
        uint64_t inuse, bitmask;
        int allfree, field, freed, idx;
        vm_paddr_t pa;

        lock = NULL;

        SLIST_INIT(&free);
        rw_rlock(&pvh_global_lock);
        PMAP_LOCK(pmap);
        TAILQ_FOREACH_SAFE(pc, &pmap->pm_pvchunk, pc_list, npc) {
                allfree = 1;
                freed = 0;
                for (field = 0; field < _NPCM; field++) {
                        inuse = ~pc->pc_map[field] & pc_freemask[field];
                        while (inuse != 0) {
                                bit = ffsl(inuse) - 1;
                                bitmask = 1UL << bit;
                                idx = field * 64 + bit;
                                pv = &pc->pc_pventry[idx];
                                inuse &= ~bitmask;

                                l2 = pmap_l2(pmap, pv->pv_va);
                                ptepde = pmap_load(l2);
                                l3 = pmap_l2_to_l3(l2, pv->pv_va);
                                tl3 = pmap_load(l3);

/*
 * We cannot remove wired pages from a process' mapping at this time
 */
                                if (tl3 & PTE_SW_WIRED) {
                                        allfree = 0;
                                        continue;
                                }

                                pa = PTE_TO_PHYS(tl3);
                                m = PHYS_TO_VM_PAGE(pa);
                                KASSERT(m->phys_addr == pa,
                                    ("vm_page_t %p phys_addr mismatch %016jx %016jx",
                                    m, (uintmax_t)m->phys_addr,
                                    (uintmax_t)tl3));

                                KASSERT((m->flags & PG_FICTITIOUS) != 0 ||
                                    m < &vm_page_array[vm_page_array_size],
                                    ("pmap_remove_pages: bad l3 %#jx",
                                    (uintmax_t)tl3));

                                if (pmap_is_current(pmap) &&
                                    pmap_l3_valid_cacheable(pmap_load(l3)))
                                        cpu_dcache_wb_range(pv->pv_va, L3_SIZE);
                                pmap_load_clear(l3);
                                PTE_SYNC(l3);
                                pmap_invalidate_page(pmap, pv->pv_va);

                                /*
                                 * Update the vm_page_t clean/reference bits.
                                 */
                                if (pmap_page_dirty(tl3))
                                        vm_page_dirty(m);

                                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(&lock, m);

                                /* Mark free */
                                pc->pc_map[field] |= bitmask;

                                pmap_resident_count_dec(pmap, 1);
                                TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                                m->md.pv_gen++;

                                pmap_unuse_l3(pmap, pv->pv_va, ptepde, &free);
                                freed++;
                        }
                }
                PV_STAT(atomic_add_long(&pv_entry_frees, freed));
                PV_STAT(atomic_add_int(&pv_entry_spare, freed));
                PV_STAT(atomic_subtract_long(&pv_entry_count, freed));
                if (allfree) {
                        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                        free_pv_chunk(pc);
                }
        }
        pmap_invalidate_all(pmap);
        if (lock != NULL)
                rw_wunlock(lock);
        rw_runlock(&pvh_global_lock);
        PMAP_UNLOCK(pmap);
        pmap_free_zero_pages(&free);
}

/*
 * This is used to check if a page has been accessed or modified. As we
 * don't have a bit to see if it has been modified we have to assume it
 * has been if the page is read/write.
 */
static boolean_t
pmap_page_test_mappings(vm_page_t m, boolean_t accessed, boolean_t modified)
{
        struct rwlock *lock;
        pv_entry_t pv;
        pt_entry_t *l3, mask, value;
        pmap_t pmap;
        int md_gen;
        boolean_t rv;

        rv = FALSE;
        rw_rlock(&pvh_global_lock);
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_rlock(lock);
restart:
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        md_gen = m->md.pv_gen;
                        rw_runlock(lock);
                        PMAP_LOCK(pmap);
                        rw_rlock(lock);
                        if (md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto restart;
                        }
                }
                l3 = pmap_l3(pmap, pv->pv_va);
                mask = 0;
                value = 0;
                if (modified) {
                        mask |= PTE_D;
                        value |= PTE_D;
                }
                if (accessed) {
                        mask |= PTE_A;
                        value |= PTE_A;
                }

#if 0
                if (modified) {
                        mask |= ATTR_AP_RW_BIT;
                        value |= ATTR_AP(ATTR_AP_RW);
                }
                if (accessed) {
                        mask |= ATTR_AF | ATTR_DESCR_MASK;
                        value |= ATTR_AF | L3_PAGE;
                }
#endif

                rv = (pmap_load(l3) & mask) == value;
                PMAP_UNLOCK(pmap);
                if (rv)
                        goto out;
        }
out:
        rw_runlock(lock);
        rw_runlock(&pvh_global_lock);
        return (rv);
}

/*
 *      pmap_is_modified:
 *
 *      Return whether or not the specified physical page was modified
 *      in any physical maps.
 */
boolean_t
pmap_is_modified(vm_page_t m)
{

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_is_modified: page %p is not managed", m));

        /*
         * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
         * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
         * is clear, no PTEs can have PG_M set.
         */
        VM_OBJECT_ASSERT_WLOCKED(m->object);
        if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
                return (FALSE);
        return (pmap_page_test_mappings(m, FALSE, TRUE));
}

/*
 *      pmap_is_prefaultable:
 *
 *      Return whether or not the specified virtual address is eligible
 *      for prefault.
 */
boolean_t
pmap_is_prefaultable(pmap_t pmap, vm_offset_t addr)
{
        pt_entry_t *l3;
        boolean_t rv;

        rv = FALSE;
        PMAP_LOCK(pmap);
        l3 = pmap_l3(pmap, addr);
        if (l3 != NULL && pmap_load(l3) != 0) {
                rv = TRUE;
        }
        PMAP_UNLOCK(pmap);
        return (rv);
}

/*
 *      pmap_is_referenced:
 *
 *      Return whether or not the specified physical page was referenced
 *      in any physical maps.
 */
boolean_t
pmap_is_referenced(vm_page_t m)
{

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_is_referenced: page %p is not managed", m));
        return (pmap_page_test_mappings(m, TRUE, FALSE));
}

/*
 * Clear the write and modified bits in each of the given page's mappings.
 */
void
pmap_remove_write(vm_page_t m)
{
        pmap_t pmap;
        struct rwlock *lock;
        pv_entry_t pv;
        pt_entry_t *l3, oldl3;
        pt_entry_t newl3;
        int md_gen;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_remove_write: page %p is not managed", m));

        /*
         * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
         * set by another thread while the object is locked.  Thus,
         * if PGA_WRITEABLE is clear, no page table entries need updating.
         */
        VM_OBJECT_ASSERT_WLOCKED(m->object);
        if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
                return;
        rw_rlock(&pvh_global_lock);
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
retry_pv_loop:
        rw_wlock(lock);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        md_gen = m->md.pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                rw_wunlock(lock);
                                goto retry_pv_loop;
                        }
                }
                l3 = pmap_l3(pmap, pv->pv_va);
retry:
                oldl3 = pmap_load(l3);

                if (pmap_is_write(oldl3)) {
                        newl3 = oldl3 & ~(PTE_W);
                        if (!atomic_cmpset_long(l3, oldl3, newl3))
                                goto retry;
                        /* TODO: use pmap_page_dirty(oldl3) ? */
                        if ((oldl3 & PTE_A) != 0)
                                vm_page_dirty(m);
                        pmap_invalidate_page(pmap, pv->pv_va);
                }
                PMAP_UNLOCK(pmap);
        }
        rw_wunlock(lock);
        vm_page_aflag_clear(m, PGA_WRITEABLE);
        rw_runlock(&pvh_global_lock);
}

static __inline boolean_t
safe_to_clear_referenced(pmap_t pmap, pt_entry_t pte)
{

        return (FALSE);
}

/*
 *      pmap_ts_referenced:
 *
 *      Return a count of reference bits for a page, clearing those bits.
 *      It is not necessary for every reference bit to be cleared, but it
 *      is necessary that 0 only be returned when there are truly no
 *      reference bits set.
 *
 *      As an optimization, update the page's dirty field if a modified bit is
 *      found while counting reference bits.  This opportunistic update can be
 *      performed at low cost and can eliminate the need for some future calls
 *      to pmap_is_modified().  However, since this function stops after
 *      finding PMAP_TS_REFERENCED_MAX reference bits, it may not detect some
 *      dirty pages.  Those dirty pages will only be detected by a future call
 *      to pmap_is_modified().
 */
int
pmap_ts_referenced(vm_page_t m)
{
        pv_entry_t pv, pvf;
        pmap_t pmap;
        struct rwlock *lock;
        pd_entry_t *l2;
        pt_entry_t *l3, old_l3;
        vm_paddr_t pa;
        int cleared, md_gen, not_cleared;
        struct spglist free;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_ts_referenced: page %p is not managed", m));
        SLIST_INIT(&free);
        cleared = 0;
        pa = VM_PAGE_TO_PHYS(m);
        lock = PHYS_TO_PV_LIST_LOCK(pa);
        rw_rlock(&pvh_global_lock);
        rw_wlock(lock);
retry:
        not_cleared = 0;
        if ((pvf = TAILQ_FIRST(&m->md.pv_list)) == NULL)
                goto out;
        pv = pvf;
        do {
                if (pvf == NULL)
                        pvf = pv;
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        md_gen = m->md.pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto retry;
                        }
                }
                l2 = pmap_l2(pmap, pv->pv_va);

                KASSERT((pmap_load(l2) & PTE_RX) == 0,
                    ("pmap_ts_referenced: found an invalid l2 table"));

                l3 = pmap_l2_to_l3(l2, pv->pv_va);
                old_l3 = pmap_load(l3);
                if (pmap_page_dirty(old_l3))
                        vm_page_dirty(m);
                if ((old_l3 & PTE_A) != 0) {
                        if (safe_to_clear_referenced(pmap, old_l3)) {
                                /*
                                 * TODO: We don't handle the access flag
                                 * at all. We need to be able to set it in
                                 * the exception handler.
                                 */
                                panic("RISCVTODO: safe_to_clear_referenced\n");
                        } else if ((old_l3 & PTE_SW_WIRED) == 0) {
                                /*
                                 * Wired pages cannot be paged out so
                                 * doing accessed bit emulation for
                                 * them is wasted effort. We do the
                                 * hard work for unwired pages only.
                                 */
                                pmap_remove_l3(pmap, l3, pv->pv_va,
                                    pmap_load(l2), &free, &lock);
                                pmap_invalidate_page(pmap, pv->pv_va);
                                cleared++;
                                if (pvf == pv)
                                        pvf = NULL;
                                pv = NULL;
                                KASSERT(lock == VM_PAGE_TO_PV_LIST_LOCK(m),
                                    ("inconsistent pv lock %p %p for page %p",
                                    lock, VM_PAGE_TO_PV_LIST_LOCK(m), m));
                        } else
                                not_cleared++;
                }
                PMAP_UNLOCK(pmap);
                /* Rotate the PV list if it has more than one entry. */
                if (pv != NULL && TAILQ_NEXT(pv, pv_next) != NULL) {
                        TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                        m->md.pv_gen++;
                }
        } while ((pv = TAILQ_FIRST(&m->md.pv_list)) != pvf && cleared +
            not_cleared < PMAP_TS_REFERENCED_MAX);
out:
        rw_wunlock(lock);
        rw_runlock(&pvh_global_lock);
        pmap_free_zero_pages(&free);
        return (cleared + not_cleared);
}

/*
 *      Apply the given advice to the specified range of addresses within the
 *      given pmap.  Depending on the advice, clear the referenced and/or
 *      modified flags in each mapping and set the mapped page's dirty field.
 */
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
}

/*
 *      Clear the modify bits on the specified physical page.
 */
void
pmap_clear_modify(vm_page_t m)
{

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_clear_modify: page %p is not managed", m));
        VM_OBJECT_ASSERT_WLOCKED(m->object);
        KASSERT(!vm_page_xbusied(m),
            ("pmap_clear_modify: page %p is exclusive busied", m));

        /*
         * If the page is not PGA_WRITEABLE, then no PTEs can have PG_M set.
         * If the object containing the page is locked and the page is not
         * exclusive busied, then PGA_WRITEABLE cannot be concurrently set.
         */
        if ((m->aflags & PGA_WRITEABLE) == 0)
                return;

        /* RISCVTODO: We lack support for tracking if a page is modified */
}

void *
pmap_mapbios(vm_paddr_t pa, vm_size_t size)
{

        return ((void *)PHYS_TO_DMAP(pa));
}

void
pmap_unmapbios(vm_paddr_t pa, vm_size_t size)
{
}

/*
 * Sets the memory attribute for the specified page.
 */
void
pmap_page_set_memattr(vm_page_t m, vm_memattr_t ma)
{

        m->md.pv_memattr = ma;

        /*
         * RISCVTODO: Implement the below (from the amd64 pmap)
         * If "m" is a normal page, update its direct mapping.  This update
         * can be relied upon to perform any cache operations that are
         * required for data coherence.
         */
        if ((m->flags & PG_FICTITIOUS) == 0 &&
            PHYS_IN_DMAP(VM_PAGE_TO_PHYS(m)))
                panic("RISCVTODO: pmap_page_set_memattr");
}

/*
 * perform the pmap work for mincore
 */
int
pmap_mincore(pmap_t pmap, vm_offset_t addr, vm_paddr_t *locked_pa)
{

        panic("RISCVTODO: pmap_mincore");
}

void
pmap_activate(struct thread *td)
{
        pmap_t pmap;
        uint64_t reg;

        critical_enter();
        pmap = vmspace_pmap(td->td_proc->p_vmspace);
        td->td_pcb->pcb_l1addr = vtophys(pmap->pm_l1);

        reg = SATP_MODE_SV39;
        reg |= (td->td_pcb->pcb_l1addr >> PAGE_SHIFT);
        __asm __volatile("csrw sptbr, %0" :: "r"(reg));

        pmap_invalidate_all(pmap);
        critical_exit();
}

void
pmap_sync_icache(pmap_t pm, vm_offset_t va, vm_size_t sz)
{

        panic("RISCVTODO: pmap_sync_icache");
}

/*
 *      Increase the starting virtual address of the given mapping if a
 *      different alignment might result in more superpage mappings.
 */
void
pmap_align_superpage(vm_object_t object, vm_ooffset_t offset,
    vm_offset_t *addr, vm_size_t size)
{
}

/**
 * Get the kernel virtual address of a set of physical pages. If there are
 * physical addresses not covered by the DMAP perform a transient mapping
 * that will be removed when calling pmap_unmap_io_transient.
 *
 * \param page        The pages the caller wishes to obtain the virtual
 *                    address on the kernel memory map.
 * \param vaddr       On return contains the kernel virtual memory address
 *                    of the pages passed in the page parameter.
 * \param count       Number of pages passed in.
 * \param can_fault   TRUE if the thread using the mapped pages can take
 *                    page faults, FALSE otherwise.
 *
 * \returns TRUE if the caller must call pmap_unmap_io_transient when
 *          finished or FALSE otherwise.
 *
 */
boolean_t
pmap_map_io_transient(vm_page_t page[], vm_offset_t vaddr[], int count,
    boolean_t can_fault)
{
        vm_paddr_t paddr;
        boolean_t needs_mapping;
        int error, i;

        /*
         * Allocate any KVA space that we need, this is done in a separate
         * loop to prevent calling vmem_alloc while pinned.
         */
        needs_mapping = FALSE;
        for (i = 0; i < count; i++) {
                paddr = VM_PAGE_TO_PHYS(page[i]);
                if (__predict_false(paddr >= DMAP_MAX_PHYSADDR)) {
                        error = vmem_alloc(kernel_arena, PAGE_SIZE,
                            M_BESTFIT | M_WAITOK, &vaddr[i]);
                        KASSERT(error == 0, ("vmem_alloc failed: %d", error));
                        needs_mapping = TRUE;
                } else {
                        vaddr[i] = PHYS_TO_DMAP(paddr);
                }
        }

        /* Exit early if everything is covered by the DMAP */
        if (!needs_mapping)
                return (FALSE);

        if (!can_fault)
                sched_pin();
        for (i = 0; i < count; i++) {
                paddr = VM_PAGE_TO_PHYS(page[i]);
                if (paddr >= DMAP_MAX_PHYSADDR) {
                        panic(
                           "pmap_map_io_transient: TODO: Map out of DMAP data");
                }
        }

        return (needs_mapping);
}

void
pmap_unmap_io_transient(vm_page_t page[], vm_offset_t vaddr[], int count,
    boolean_t can_fault)
{
        vm_paddr_t paddr;
        int i;

        if (!can_fault)
                sched_unpin();
        for (i = 0; i < count; i++) {
                paddr = VM_PAGE_TO_PHYS(page[i]);
                if (paddr >= DMAP_MAX_PHYSADDR) {
                        panic("RISCVTODO: pmap_unmap_io_transient: Unmap data");
                }
        }
}