FreeBSD/Linux Kernel Cross Reference
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: releng/11.0/sys/vm/sg_pager.c 295330 2016-02-05 19:35:53Z markj $");
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 '' is used so we can assert that the
160 * page is found since '' 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 }
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