xref: /freebsd/sys/vm/sg_pager.c (revision cd0c3137f8a21968ce147251633b8dbdde8829e7)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2009 Hudson River Trading LLC
5  * Written by: John H. Baldwin <jhb@FreeBSD.org>
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
32 
33 /*
34  * This pager manages OBJT_SG objects.  These objects are backed by
35  * a scatter/gather list of physical address ranges.
36  */
37 
38 #include <sys/param.h>
39 #include <sys/lock.h>
40 #include <sys/mutex.h>
41 #include <sys/rwlock.h>
42 #include <sys/sglist.h>
43 #include <sys/vmmeter.h>
44 
45 #include <vm/vm.h>
46 #include <vm/vm_param.h>
47 #include <vm/vm_object.h>
48 #include <vm/vm_page.h>
49 #include <vm/vm_pager.h>
50 #include <vm/vm_phys.h>
51 #include <vm/uma.h>
52 
53 static vm_object_t sg_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
54     vm_ooffset_t, struct ucred *);
55 static void sg_pager_dealloc(vm_object_t);
56 static int sg_pager_getpages(vm_object_t, vm_page_t *, int, int *, int *);
57 static void sg_pager_putpages(vm_object_t, vm_page_t *, int,
58 		boolean_t, int *);
59 static boolean_t sg_pager_haspage(vm_object_t, vm_pindex_t, int *,
60 		int *);
61 
62 struct pagerops sgpagerops = {
63 	.pgo_alloc =	sg_pager_alloc,
64 	.pgo_dealloc =	sg_pager_dealloc,
65 	.pgo_getpages =	sg_pager_getpages,
66 	.pgo_putpages =	sg_pager_putpages,
67 	.pgo_haspage =	sg_pager_haspage,
68 };
69 
70 static vm_object_t
71 sg_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
72     vm_ooffset_t foff, struct ucred *cred)
73 {
74 	struct sglist *sg;
75 	vm_object_t object;
76 	vm_pindex_t npages, pindex;
77 	int i;
78 
79 	/*
80 	 * Offset should be page aligned.
81 	 */
82 	if (foff & PAGE_MASK)
83 		return (NULL);
84 
85 	/*
86 	 * The scatter/gather list must only include page-aligned
87 	 * ranges.
88 	 */
89 	npages = 0;
90 	sg = handle;
91 	for (i = 0; i < sg->sg_nseg; i++) {
92 		if ((sg->sg_segs[i].ss_paddr % PAGE_SIZE) != 0 ||
93 		    (sg->sg_segs[i].ss_len % PAGE_SIZE) != 0)
94 			return (NULL);
95 		npages += sg->sg_segs[i].ss_len / PAGE_SIZE;
96 	}
97 
98 	/*
99 	 * The scatter/gather list has a fixed size.  Refuse requests
100 	 * to map beyond that.
101 	 */
102 	size = round_page(size);
103 	pindex = OFF_TO_IDX(foff) + OFF_TO_IDX(size);
104 	if (pindex > npages || pindex < OFF_TO_IDX(foff) ||
105 	    pindex < OFF_TO_IDX(size))
106 		return (NULL);
107 
108 	/*
109 	 * Allocate a new object and associate it with the
110 	 * scatter/gather list.  It is ok for our purposes to have
111 	 * multiple VM objects associated with the same scatter/gather
112 	 * list because scatter/gather lists are static.  This is also
113 	 * simpler than ensuring a unique object per scatter/gather
114 	 * list.
115 	 */
116 	object = vm_object_allocate(OBJT_SG, npages);
117 	object->handle = sglist_hold(sg);
118 	TAILQ_INIT(&object->un_pager.sgp.sgp_pglist);
119 	return (object);
120 }
121 
122 static void
123 sg_pager_dealloc(vm_object_t object)
124 {
125 	struct sglist *sg;
126 	vm_page_t m;
127 
128 	/*
129 	 * Free up our fake pages.
130 	 */
131 	while ((m = TAILQ_FIRST(&object->un_pager.sgp.sgp_pglist)) != 0) {
132 		if (vm_page_busy_acquire(m, VM_ALLOC_WAITFAIL) == 0)
133 			continue;
134 		TAILQ_REMOVE(&object->un_pager.sgp.sgp_pglist, m, plinks.q);
135 		vm_page_putfake(m);
136 	}
137 
138 	sg = object->handle;
139 	sglist_free(sg);
140 	object->handle = NULL;
141 	object->type = OBJT_DEAD;
142 }
143 
144 static int
145 sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
146     int *rahead)
147 {
148 	struct sglist *sg;
149 	vm_page_t m_paddr, page;
150 	vm_pindex_t offset;
151 	vm_paddr_t paddr;
152 	vm_memattr_t memattr;
153 	size_t space;
154 	int i;
155 
156 	/* Since our haspage reports zero after/before, the count is 1. */
157 	KASSERT(count == 1, ("%s: count %d", __func__, count));
158 	VM_OBJECT_ASSERT_WLOCKED(object);
159 	sg = object->handle;
160 	memattr = object->memattr;
161 	VM_OBJECT_WUNLOCK(object);
162 	offset = m[0]->pindex;
163 
164 	/*
165 	 * Lookup the physical address of the requested page.  An initial
166 	 * value of '1' instead of '0' is used so we can assert that the
167 	 * page is found since '0' can be a valid page-aligned physical
168 	 * address.
169 	 */
170 	space = 0;
171 	paddr = 1;
172 	for (i = 0; i < sg->sg_nseg; i++) {
173 		if (space + sg->sg_segs[i].ss_len <= (offset * PAGE_SIZE)) {
174 			space += sg->sg_segs[i].ss_len;
175 			continue;
176 		}
177 		paddr = sg->sg_segs[i].ss_paddr + offset * PAGE_SIZE - space;
178 		break;
179 	}
180 	KASSERT(paddr != 1, ("invalid SG page index"));
181 
182 	/* If "paddr" is a real page, perform a sanity check on "memattr". */
183 	if ((m_paddr = vm_phys_paddr_to_vm_page(paddr)) != NULL &&
184 	    pmap_page_get_memattr(m_paddr) != memattr) {
185 		memattr = pmap_page_get_memattr(m_paddr);
186 		printf(
187 	    "WARNING: A device driver has set \"memattr\" inconsistently.\n");
188 	}
189 
190 	/* Return a fake page for the requested page. */
191 	KASSERT(!(m[0]->flags & PG_FICTITIOUS),
192 	    ("backing page for SG is fake"));
193 
194 	/* Construct a new fake page. */
195 	page = vm_page_getfake(paddr, memattr);
196 	VM_OBJECT_WLOCK(object);
197 	TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, plinks.q);
198 	vm_page_replace(page, object, offset, m[0]);
199 	m[0] = page;
200 	vm_page_valid(page);
201 
202 	if (rbehind)
203 		*rbehind = 0;
204 	if (rahead)
205 		*rahead = 0;
206 
207 	return (VM_PAGER_OK);
208 }
209 
210 static void
211 sg_pager_putpages(vm_object_t object, vm_page_t *m, int count,
212     boolean_t sync, int *rtvals)
213 {
214 
215 	panic("sg_pager_putpage called");
216 }
217 
218 static boolean_t
219 sg_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
220     int *after)
221 {
222 
223 	if (before != NULL)
224 		*before = 0;
225 	if (after != NULL)
226 		*after = 0;
227 	return (TRUE);
228 }
229