1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /******************************************************************************
3 * include/asm-x86/mem_sharing.h
4 *
5 * Memory sharing support.
6 *
7 * Copyright (c) 2009 Citrix Systems, Inc. (Grzegorz Milos)
8 */
9 #ifndef __MEM_SHARING_H__
10 #define __MEM_SHARING_H__
11
12 #include <public/domctl.h>
13 #include <public/memory.h>
14
15 #ifdef CONFIG_MEM_SHARING
16
17 #define mem_sharing_enabled(d) ((d)->arch.hvm.mem_sharing.enabled)
18
19 /* Auditing of memory sharing code? */
20 #ifndef NDEBUG
21 #define MEM_SHARING_AUDIT 1
22 #else
23 #define MEM_SHARING_AUDIT 0
24 #endif
25
26 typedef uint64_t shr_handle_t;
27
28 typedef struct rmap_hashtab {
29 struct list_head *bucket;
30 /*
31 * Overlaps with prev pointer of list_head in union below.
32 * Unlike the prev pointer, this can be NULL.
33 */
34 void *flag;
35 } rmap_hashtab_t;
36
37 struct page_sharing_info
38 {
39 struct page_info *pg; /* Back pointer to the page. */
40 shr_handle_t handle; /* Globally unique version / handle. */
41 #if MEM_SHARING_AUDIT
42 struct list_head entry; /* List of all shared pages (entry). */
43 struct rcu_head rcu_head; /* List of all shared pages (entry). */
44 #endif
45 /* Reverse map of <domain,gfn> tuples for this shared frame. */
46 union {
47 struct list_head gfns;
48 rmap_hashtab_t hash_table;
49 };
50 };
51
52 unsigned int mem_sharing_get_nr_saved_mfns(void);
53 unsigned int mem_sharing_get_nr_shared_mfns(void);
54
55 /* Only fails with -ENOMEM. Enforce it with a BUG_ON wrapper. */
56 int __mem_sharing_unshare_page(struct domain *d,
57 unsigned long gfn,
58 bool destroy);
59
mem_sharing_unshare_page(struct domain * d,unsigned long gfn)60 static inline int mem_sharing_unshare_page(struct domain *d,
61 unsigned long gfn)
62 {
63 int rc = __mem_sharing_unshare_page(d, gfn, false);
64 BUG_ON(rc && (rc != -ENOMEM));
65 return rc;
66 }
67
mem_sharing_is_fork(const struct domain * d)68 static inline bool mem_sharing_is_fork(const struct domain *d)
69 {
70 return d->parent;
71 }
72
73 int mem_sharing_fork_page(struct domain *d, gfn_t gfn,
74 bool unsharing);
75
76 int mem_sharing_fork_reset(struct domain *d, bool reset_state,
77 bool reset_memory);
78
79 /*
80 * If called by a foreign domain, possible errors are
81 * -EBUSY -> ring full
82 * -ENOSYS -> no ring to begin with
83 * and the foreign mapper is responsible for retrying.
84 *
85 * If called by the guest vcpu itself and allow_sleep is set, may
86 * sleep on a wait queue, so the caller is responsible for not
87 * holding locks on entry. It may only fail with ENOSYS
88 *
89 * If called by the guest vcpu itself and allow_sleep is not set,
90 * then it's the same as a foreign domain.
91 */
92 int mem_sharing_notify_enomem(struct domain *d, unsigned long gfn,
93 bool allow_sleep);
94 int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg);
95 int mem_sharing_domctl(struct domain *d,
96 struct xen_domctl_mem_sharing_op *mec);
97
98 /*
99 * Scans the p2m and relinquishes any shared pages, destroying
100 * those for which this domain holds the final reference.
101 * Preemptible.
102 */
103 int relinquish_shared_pages(struct domain *d);
104
105 #else
106
107 #define mem_sharing_enabled(d) false
108
mem_sharing_get_nr_saved_mfns(void)109 static inline unsigned int mem_sharing_get_nr_saved_mfns(void)
110 {
111 return 0;
112 }
113
mem_sharing_get_nr_shared_mfns(void)114 static inline unsigned int mem_sharing_get_nr_shared_mfns(void)
115 {
116 return 0;
117 }
118
mem_sharing_unshare_page(struct domain * d,unsigned long gfn)119 static inline int mem_sharing_unshare_page(struct domain *d, unsigned long gfn)
120 {
121 ASSERT_UNREACHABLE();
122 return -EOPNOTSUPP;
123 }
124
mem_sharing_notify_enomem(struct domain * d,unsigned long gfn,bool allow_sleep)125 static inline int mem_sharing_notify_enomem(struct domain *d, unsigned long gfn,
126 bool allow_sleep)
127 {
128 ASSERT_UNREACHABLE();
129 return -EOPNOTSUPP;
130 }
131
mem_sharing_is_fork(const struct domain * d)132 static inline bool mem_sharing_is_fork(const struct domain *d)
133 {
134 return false;
135 }
136
mem_sharing_fork_page(struct domain * d,gfn_t gfn,bool lock)137 static inline int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool lock)
138 {
139 return -EOPNOTSUPP;
140 }
141
mem_sharing_fork_reset(struct domain * d,bool reset_state,bool reset_memory)142 static inline int mem_sharing_fork_reset(struct domain *d, bool reset_state,
143 bool reset_memory)
144 {
145 return -EOPNOTSUPP;
146 }
147
148 #endif
149
150 #endif /* __MEM_SHARING_H__ */
151