sys/vm/sg_pager.c

   1 /*-
   2  * Copyright (c) 2009 Hudson River Trading LLC
   3  * Written by: John H. Baldwin <jhb@FreeBSD.org>
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  */
  27
  28 #include <sys/cdefs.h>
  29 __FBSDID("$FreeBSD$");
  30
  31 /*
  32  * This pager manages OBJT_SG objects.  These objects are backed by
  33  * a scatter/gather list of physical address ranges.
  34  */
  35
  36 #include <sys/param.h>
  37 #include <sys/lock.h>
  38 #include <sys/mutex.h>
  39 #include <sys/rwlock.h>
  40 #include <sys/sglist.h>
  41 #include <vm/vm.h>
  42 #include <vm/vm_param.h>
  43 #include <vm/vm_object.h>
  44 #include <vm/vm_page.h>
  45 #include <vm/vm_pager.h>
  46 #include <vm/vm_phys.h>
  47 #include <vm/uma.h>
  48
  49 static vm_object_t sg_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
  50     vm_ooffset_t, struct ucred *);
  51 static void sg_pager_dealloc(vm_object_t);
  52 static int sg_pager_getpages(vm_object_t, vm_page_t *, int, int *, int *);
  53 static void sg_pager_putpages(vm_object_t, vm_page_t *, int,
  54                 boolean_t, int *);
  55 static boolean_t sg_pager_haspage(vm_object_t, vm_pindex_t, int *,
  56                 int *);
  57
  58 struct pagerops sgpagerops = {
  59         .pgo_alloc =    sg_pager_alloc,
  60         .pgo_dealloc =  sg_pager_dealloc,
  61         .pgo_getpages = sg_pager_getpages,
  62         .pgo_putpages = sg_pager_putpages,
  63         .pgo_haspage =  sg_pager_haspage,
  64 };
  65
  66 static vm_object_t
  67 sg_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
  68     vm_ooffset_t foff, struct ucred *cred)
  69 {
  70         struct sglist *sg;
  71         vm_object_t object;
  72         vm_pindex_t npages, pindex;
  73         int i;
  74
  75         /*
  76          * Offset should be page aligned.
  77          */
  78         if (foff & PAGE_MASK)
  79                 return (NULL);
  80
  81         /*
  82          * The scatter/gather list must only include page-aligned
  83          * ranges.
  84          */
  85         npages = 0;
  86         sg = handle;
  87         for (i = 0; i < sg->sg_nseg; i++) {
  88                 if ((sg->sg_segs[i].ss_paddr % PAGE_SIZE) != 0 ||
  89                     (sg->sg_segs[i].ss_len % PAGE_SIZE) != 0)
  90                         return (NULL);
  91                 npages += sg->sg_segs[i].ss_len / PAGE_SIZE;
  92         }
  93
  94         /*
  95          * The scatter/gather list has a fixed size.  Refuse requests
  96          * to map beyond that.
  97          */
  98         size = round_page(size);
  99         pindex = OFF_TO_IDX(foff + size);
 100         if (pindex > npages)
 101                 return (NULL);
 102
 103         /*
 104          * Allocate a new object and associate it with the
 105          * scatter/gather list.  It is ok for our purposes to have
 106          * multiple VM objects associated with the same scatter/gather
 107          * list because scatter/gather lists are static.  This is also
 108          * simpler than ensuring a unique object per scatter/gather
 109          * list.
 110          */
 111         object = vm_object_allocate(OBJT_SG, npages);
 112         object->handle = sglist_hold(sg);
 113         TAILQ_INIT(&object->un_pager.sgp.sgp_pglist);
 114         return (object);
 115 }
 116
 117 static void
 118 sg_pager_dealloc(vm_object_t object)
 119 {
 120         struct sglist *sg;
 121         vm_page_t m;
 122
 123         /*
 124          * Free up our fake pages.
 125          */
 126         while ((m = TAILQ_FIRST(&object->un_pager.sgp.sgp_pglist)) != 0) {
 127                 TAILQ_REMOVE(&object->un_pager.sgp.sgp_pglist, m, plinks.q);
 128                 vm_page_putfake(m);
 129         }
 130
 131         sg = object->handle;
 132         sglist_free(sg);
 133         object->handle = NULL;
 134         object->type = OBJT_DEAD;
 135 }
 136
 137 static int
 138 sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
 139     int *rahead)
 140 {
 141         struct sglist *sg;
 142         vm_page_t m_paddr, page;
 143         vm_pindex_t offset;
 144         vm_paddr_t paddr;
 145         vm_memattr_t memattr;
 146         size_t space;
 147         int i;
 148
 149         /* Since our haspage reports zero after/before, the count is 1. */
 150         KASSERT(count == 1, ("%s: count %d", __func__, count));
 151         VM_OBJECT_ASSERT_WLOCKED(object);
 152         sg = object->handle;
 153         memattr = object->memattr;
 154         VM_OBJECT_WUNLOCK(object);
 155         offset = m[0]->pindex;
 156
 157         /*
 158          * Lookup the physical address of the requested page.  An initial
 159          * value of '1' instead of '0' is used so we can assert that the
 160          * page is found since '0' can be a valid page-aligned physical
 161          * address.
 162          */
 163         space = 0;
 164         paddr = 1;
 165         for (i = 0; i < sg->sg_nseg; i++) {
 166                 if (space + sg->sg_segs[i].ss_len <= (offset * PAGE_SIZE)) {
 167                         space += sg->sg_segs[i].ss_len;
 168                         continue;
 169                 }
 170                 paddr = sg->sg_segs[i].ss_paddr + offset * PAGE_SIZE - space;
 171                 break;
 172         }
 173         KASSERT(paddr != 1, ("invalid SG page index"));
 174
 175         /* If "paddr" is a real page, perform a sanity check on "memattr". */
 176         if ((m_paddr = vm_phys_paddr_to_vm_page(paddr)) != NULL &&
 177             pmap_page_get_memattr(m_paddr) != memattr) {
 178                 memattr = pmap_page_get_memattr(m_paddr);
 179                 printf(
 180             "WARNING: A device driver has set \"memattr\" inconsistently.\n");
 181         }
 182
 183         /* Return a fake page for the requested page. */
 184         KASSERT(!(m[0]->flags & PG_FICTITIOUS),
 185             ("backing page for SG is fake"));
 186
 187         /* Construct a new fake page. */
 188         page = vm_page_getfake(paddr, memattr);
 189         VM_OBJECT_WLOCK(object);
 190         TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, plinks.q);
 191         vm_page_replace_checked(page, object, offset, m[0]);
 192         vm_page_lock(m[0]);
 193         vm_page_free(m[0]);
 194         vm_page_unlock(m[0]);
 195         m[0] = page;
 196         page->valid = VM_PAGE_BITS_ALL;
 197
 198         if (rbehind)
 199                 *rbehind = 0;
 200         if (rahead)
 201                 *rahead = 0;
 202
 203         return (VM_PAGER_OK);
 204 }
 205
 206 static void
 207 sg_pager_putpages(vm_object_t object, vm_page_t *m, int count,
 208     boolean_t sync, int *rtvals)
 209 {
 210
 211         panic("sg_pager_putpage called");
 212 }
 213
 214 static boolean_t
 215 sg_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
 216     int *after)
 217 {
 218
 219         if (before != NULL)
 220                 *before = 0;
 221         if (after != NULL)
 222                 *after = 0;
 223         return (TRUE);
 224 }