1 /******************************************************************************
2 * include/asm-x86/mem_sharing.h
3 *
4 * Memory sharing support.
5 *
6 * Copyright (c) 2009 Citrix Systems, Inc. (Grzegorz Milos)
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; If not, see <http://www.gnu.org/licenses/>.
20 */
21 #ifndef __MEM_SHARING_H__
22 #define __MEM_SHARING_H__
23
24 #include <public/domctl.h>
25 #include <public/memory.h>
26
27 #ifdef CONFIG_MEM_SHARING
28
29 #define mem_sharing_enabled(d) ((d)->arch.hvm.mem_sharing.enabled)
30
31 /* Auditing of memory sharing code? */
32 #ifndef NDEBUG
33 #define MEM_SHARING_AUDIT 1
34 #else
35 #define MEM_SHARING_AUDIT 0
36 #endif
37
38 typedef uint64_t shr_handle_t;
39
40 typedef struct rmap_hashtab {
41 struct list_head *bucket;
42 /*
43 * Overlaps with prev pointer of list_head in union below.
44 * Unlike the prev pointer, this can be NULL.
45 */
46 void *flag;
47 } rmap_hashtab_t;
48
49 struct page_sharing_info
50 {
51 struct page_info *pg; /* Back pointer to the page. */
52 shr_handle_t handle; /* Globally unique version / handle. */
53 #if MEM_SHARING_AUDIT
54 struct list_head entry; /* List of all shared pages (entry). */
55 struct rcu_head rcu_head; /* List of all shared pages (entry). */
56 #endif
57 /* Reverse map of <domain,gfn> tuples for this shared frame. */
58 union {
59 struct list_head gfns;
60 rmap_hashtab_t hash_table;
61 };
62 };
63
64 unsigned int mem_sharing_get_nr_saved_mfns(void);
65 unsigned int mem_sharing_get_nr_shared_mfns(void);
66
67 /* Only fails with -ENOMEM. Enforce it with a BUG_ON wrapper. */
68 int __mem_sharing_unshare_page(struct domain *d,
69 unsigned long gfn,
70 bool destroy);
71
mem_sharing_unshare_page(struct domain * d,unsigned long gfn)72 static inline int mem_sharing_unshare_page(struct domain *d,
73 unsigned long gfn)
74 {
75 int rc = __mem_sharing_unshare_page(d, gfn, false);
76 BUG_ON(rc && (rc != -ENOMEM));
77 return rc;
78 }
79
mem_sharing_is_fork(const struct domain * d)80 static inline bool mem_sharing_is_fork(const struct domain *d)
81 {
82 return d->parent;
83 }
84
85 int mem_sharing_fork_page(struct domain *d, gfn_t gfn,
86 bool unsharing);
87
88 /*
89 * If called by a foreign domain, possible errors are
90 * -EBUSY -> ring full
91 * -ENOSYS -> no ring to begin with
92 * and the foreign mapper is responsible for retrying.
93 *
94 * If called by the guest vcpu itself and allow_sleep is set, may
95 * sleep on a wait queue, so the caller is responsible for not
96 * holding locks on entry. It may only fail with ENOSYS
97 *
98 * If called by the guest vcpu itself and allow_sleep is not set,
99 * then it's the same as a foreign domain.
100 */
101 int mem_sharing_notify_enomem(struct domain *d, unsigned long gfn,
102 bool allow_sleep);
103 int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg);
104 int mem_sharing_domctl(struct domain *d,
105 struct xen_domctl_mem_sharing_op *mec);
106
107 /*
108 * Scans the p2m and relinquishes any shared pages, destroying
109 * those for which this domain holds the final reference.
110 * Preemptible.
111 */
112 int relinquish_shared_pages(struct domain *d);
113
114 #else
115
116 #define mem_sharing_enabled(d) false
117
mem_sharing_get_nr_saved_mfns(void)118 static inline unsigned int mem_sharing_get_nr_saved_mfns(void)
119 {
120 return 0;
121 }
122
mem_sharing_get_nr_shared_mfns(void)123 static inline unsigned int mem_sharing_get_nr_shared_mfns(void)
124 {
125 return 0;
126 }
127
mem_sharing_unshare_page(struct domain * d,unsigned long gfn)128 static inline int mem_sharing_unshare_page(struct domain *d, unsigned long gfn)
129 {
130 ASSERT_UNREACHABLE();
131 return -EOPNOTSUPP;
132 }
133
mem_sharing_notify_enomem(struct domain * d,unsigned long gfn,bool allow_sleep)134 static inline int mem_sharing_notify_enomem(struct domain *d, unsigned long gfn,
135 bool allow_sleep)
136 {
137 ASSERT_UNREACHABLE();
138 return -EOPNOTSUPP;
139 }
140
mem_sharing_is_fork(const struct domain * d)141 static inline bool mem_sharing_is_fork(const struct domain *d)
142 {
143 return false;
144 }
145
mem_sharing_fork_page(struct domain * d,gfn_t gfn,bool lock)146 static inline int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool lock)
147 {
148 return -EOPNOTSUPP;
149 }
150
151 #endif
152
153 #endif /* __MEM_SHARING_H__ */
154