phys_pager.c

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/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2000 Peter Wemm
 *
 * 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 AUTHORS 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 AUTHORS 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("$FreeBSD$");
 
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/proc.h>
#include <sys/mutex.h>
#include <sys/mman.h>
#include <sys/rwlock.h>
#include <sys/sysctl.h>
#include <sys/user.h>
 
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
 
/* list of phys pager objects */
static struct pagerlst phys_pager_object_list;
/* protect access to phys_pager_object_list */
static struct mtx phys_pager_mtx;
 
static int default_phys_pager_getpages(vm_object_t object, vm_page_t *m,
    int count, int *rbehind, int *rahead);
static int default_phys_pager_populate(vm_object_t object, vm_pindex_t pidx,
    int fault_type, vm_prot_t max_prot, vm_pindex_t *first, vm_pindex_t *last);
static boolean_t default_phys_pager_haspage(vm_object_t object,
    vm_pindex_t pindex, int *before, int *after);
const struct phys_pager_ops default_phys_pg_ops = {
        .phys_pg_getpages = default_phys_pager_getpages,
        .phys_pg_populate = default_phys_pager_populate,
        .phys_pg_haspage = default_phys_pager_haspage,
        .phys_pg_ctor = NULL,
        .phys_pg_dtor = NULL,
};
 
static void
phys_pager_init(void)
{
 
        TAILQ_INIT(&phys_pager_object_list);
        mtx_init(&phys_pager_mtx, "phys_pager list", NULL, MTX_DEF);
}
 
vm_object_t
phys_pager_allocate(void *handle, const struct phys_pager_ops *ops, void *data,
    vm_ooffset_t size, vm_prot_t prot, vm_ooffset_t foff, struct ucred *cred)
{
        vm_object_t object, object1;
        vm_pindex_t pindex;
        bool init;
 
        /*
         * Offset should be page aligned.
         */
        if (foff & PAGE_MASK)
                return (NULL);
 
        pindex = OFF_TO_IDX(foff + PAGE_MASK + size);
        init = true;
 
        if (handle != NULL) {
                mtx_lock(&phys_pager_mtx);
                /*
                 * Look up pager, creating as necessary.
                 */
                object1 = NULL;
                object = vm_pager_object_lookup(&phys_pager_object_list, handle);
                if (object == NULL) {
                        /*
                         * Allocate object and associate it with the pager.
                         */
                        mtx_unlock(&phys_pager_mtx);
                        object1 = vm_object_allocate(OBJT_PHYS, pindex);
                        mtx_lock(&phys_pager_mtx);
                        object = vm_pager_object_lookup(&phys_pager_object_list,
                            handle);
                        if (object != NULL) {
                                /*
                                 * We raced with other thread while
                                 * allocating object.
                                 */
                                if (pindex > object->size)
                                        object->size = pindex;
                                init = false;
                        } else {
                                object = object1;
                                object1 = NULL;
                                object->handle = handle;
                                object->un_pager.phys.ops = ops;
                                object->un_pager.phys.data_ptr = data;
                                if (ops->phys_pg_populate != NULL)
                                        vm_object_set_flag(object, OBJ_POPULATE);
                                TAILQ_INSERT_TAIL(&phys_pager_object_list,
                                    object, pager_object_list);
                        }
                } else {
                        if (pindex > object->size)
                                object->size = pindex;
                }
                mtx_unlock(&phys_pager_mtx);
                vm_object_deallocate(object1);
        } else {
                object = vm_object_allocate(OBJT_PHYS, pindex);
                object->un_pager.phys.ops = ops;
                object->un_pager.phys.data_ptr = data;
                if (ops->phys_pg_populate != NULL)
                        vm_object_set_flag(object, OBJ_POPULATE);
        }
        if (init && ops->phys_pg_ctor != NULL)
                ops->phys_pg_ctor(object, prot, foff, cred);
 
        return (object);
}
 
static vm_object_t
phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
    vm_ooffset_t foff, struct ucred *ucred)
{
        return (phys_pager_allocate(handle, &default_phys_pg_ops, NULL,
            size, prot, foff, ucred));
}
 
static void
phys_pager_dealloc(vm_object_t object)
{
 
        if (object->handle != NULL) {
                VM_OBJECT_WUNLOCK(object);
                mtx_lock(&phys_pager_mtx);
                TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
                mtx_unlock(&phys_pager_mtx);
                VM_OBJECT_WLOCK(object);
        }
        object->type = OBJT_DEAD;
        if (object->un_pager.phys.ops->phys_pg_dtor != NULL)
                object->un_pager.phys.ops->phys_pg_dtor(object);
        object->handle = NULL;
}
 
/*
 * Fill as many pages as vm_fault has allocated for us.
 */
static int
default_phys_pager_getpages(vm_object_t object, vm_page_t *m, int count,
    int *rbehind, int *rahead)
{
        int i;
 
        for (i = 0; i < count; i++) {
                if (vm_page_none_valid(m[i])) {
                        if ((m[i]->flags & PG_ZERO) == 0)
                                pmap_zero_page(m[i]);
                        vm_page_valid(m[i]);
                }
                KASSERT(vm_page_all_valid(m[i]),
                    ("phys_pager_getpages: partially valid page %p", m[i]));
                KASSERT(m[i]->dirty == 0,
                    ("phys_pager_getpages: dirty page %p", m[i]));
        }
        if (rbehind)
                *rbehind = 0;
        if (rahead)
                *rahead = 0;
        return (VM_PAGER_OK);
}
 
static int
phys_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
    int *rahead)
{
        return (object->un_pager.phys.ops->phys_pg_getpages(object, m,
            count, rbehind, rahead));
}
 
/*
 * Implement a pretty aggressive clustered getpages strategy.  Hint that
 * everything in an entire 4MB window should be prefaulted at once.
 *
 * 4MB (1024 slots per page table page) is convenient for x86,
 * but may not be for other arches.
 */
#ifndef PHYSCLUSTER
#define PHYSCLUSTER 1024
#endif
static int phys_pager_cluster = PHYSCLUSTER;
SYSCTL_INT(_vm, OID_AUTO, phys_pager_cluster, CTLFLAG_RWTUN,
    &phys_pager_cluster, 0,
    "prefault window size for phys pager");
 
/*
 * Max hint to vm_page_alloc() about the further allocation needs
 * inside the phys_pager_populate() loop.  The number of bits used to
 * implement VM_ALLOC_COUNT() determines the hard limit on this value.
 * That limit is currently 65535.
 */
#define PHYSALLOC       16
 
static int
default_phys_pager_populate(vm_object_t object, vm_pindex_t pidx,
    int fault_type __unused, vm_prot_t max_prot __unused, vm_pindex_t *first,
    vm_pindex_t *last)
{
        vm_page_t m;
        vm_pindex_t base, end, i;
        int ahead;
 
        base = rounddown(pidx, phys_pager_cluster);
        end = base + phys_pager_cluster - 1;
        if (end >= object->size)
                end = object->size - 1;
        if (*first > base)
                base = *first;
        if (end > *last)
                end = *last;
        *first = base;
        *last = end;
 
        for (i = base; i <= end; i++) {
                ahead = MIN(end - i, PHYSALLOC);
                m = vm_page_grab(object, i,
                    VM_ALLOC_NORMAL | VM_ALLOC_COUNT(ahead));
                if (!vm_page_all_valid(m))
                        vm_page_zero_invalid(m, TRUE);
                KASSERT(m->dirty == 0,
                    ("phys_pager_populate: dirty page %p", m));
        }
        return (VM_PAGER_OK);
}
 
static int
phys_pager_populate(vm_object_t object, vm_pindex_t pidx, int fault_type,
    vm_prot_t max_prot, vm_pindex_t *first, vm_pindex_t *last)
{
        return (object->un_pager.phys.ops->phys_pg_populate(object, pidx,
            fault_type, max_prot, first, last));
}
 
static void
phys_pager_putpages(vm_object_t object, vm_page_t *m, int count, boolean_t sync,
    int *rtvals)
{
 
        panic("phys_pager_putpage called");
}
 
static boolean_t
default_phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
    int *after)
{
        vm_pindex_t base, end;
 
        base = rounddown(pindex, phys_pager_cluster);
        end = base + phys_pager_cluster - 1;
        if (before != NULL)
                *before = pindex - base;
        if (after != NULL)
                *after = end - pindex;
        return (TRUE);
}
 
static boolean_t
phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
    int *after)
{
        return (object->un_pager.phys.ops->phys_pg_haspage(object, pindex,
            before, after));
}
 
const struct pagerops physpagerops = {
        .pgo_kvme_type = KVME_TYPE_PHYS,
        .pgo_init =     phys_pager_init,
        .pgo_alloc =    phys_pager_alloc,
        .pgo_dealloc =  phys_pager_dealloc,
        .pgo_getpages = phys_pager_getpages,
        .pgo_putpages = phys_pager_putpages,
        .pgo_haspage =  phys_pager_haspage,
        .pgo_populate = phys_pager_populate,
};