xref: /openbmc/qemu/migration/postcopy-ram.h (revision 4146b77e)
1 /*
2  * Postcopy migration for RAM
3  *
4  * Copyright 2013 Red Hat, Inc. and/or its affiliates
5  *
6  * Authors:
7  *  Dave Gilbert  <dgilbert@redhat.com>
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
10  * See the COPYING file in the top-level directory.
11  *
12  */
13 #ifndef QEMU_POSTCOPY_RAM_H
14 #define QEMU_POSTCOPY_RAM_H
15 
16 #include "qapi/qapi-types-migration.h"
17 
18 /* Return true if the host supports everything we need to do postcopy-ram */
19 bool postcopy_ram_supported_by_host(MigrationIncomingState *mis,
20                                     Error **errp);
21 
22 /*
23  * Make all of RAM sensitive to accesses to areas that haven't yet been written
24  * and wire up anything necessary to deal with it.
25  */
26 int postcopy_ram_incoming_setup(MigrationIncomingState *mis);
27 
28 /*
29  * Initialise postcopy-ram, setting the RAM to a state where we can go into
30  * postcopy later; must be called prior to any precopy.
31  * called from ram.c's similarly named ram_postcopy_incoming_init
32  */
33 int postcopy_ram_incoming_init(MigrationIncomingState *mis);
34 
35 /*
36  * At the end of a migration where postcopy_ram_incoming_init was called.
37  */
38 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
39 
40 /*
41  * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
42  * however leaving it until after precopy means that most of the precopy
43  * data is still THPd
44  */
45 int postcopy_ram_prepare_discard(MigrationIncomingState *mis);
46 
47 /*
48  * Called at the start of each RAMBlock by the bitmap code.
49  */
50 void postcopy_discard_send_init(MigrationState *ms, const char *name);
51 
52 /*
53  * Called by the bitmap code for each chunk to discard.
54  * May send a discard message, may just leave it queued to
55  * be sent later.
56  * @start,@length: a range of pages in the migration bitmap in the
57  *  RAM block passed to postcopy_discard_send_init() (length=1 is one page)
58  */
59 void postcopy_discard_send_range(MigrationState *ms, unsigned long start,
60                                  unsigned long length);
61 
62 /*
63  * Called at the end of each RAMBlock by the bitmap code.
64  * Sends any outstanding discard messages.
65  */
66 void postcopy_discard_send_finish(MigrationState *ms);
67 
68 /*
69  * Place a page (from) at (host) efficiently
70  *    There are restrictions on how 'from' must be mapped, in general best
71  *    to use other postcopy_ routines to allocate.
72  * returns 0 on success
73  */
74 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
75                         RAMBlock *rb);
76 
77 /*
78  * Place a zero page at (host) atomically
79  * returns 0 on success
80  */
81 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
82                              RAMBlock *rb);
83 
84 /* The current postcopy state is read/set by postcopy_state_get/set
85  * which update it atomically.
86  * The state is updated as postcopy messages are received, and
87  * in general only one thread should be writing to the state at any one
88  * time, initially the main thread and then the listen thread;
89  * Corner cases are where either thread finishes early and/or errors.
90  * The state is checked as messages are received to ensure that
91  * the source is sending us messages in the correct order.
92  * The state is also used by the RAM reception code to know if it
93  * has to place pages atomically, and the cleanup code at the end of
94  * the main thread to know if it has to delay cleanup until the end
95  * of postcopy.
96  */
97 typedef enum {
98     POSTCOPY_INCOMING_NONE = 0,  /* Initial state - no postcopy */
99     POSTCOPY_INCOMING_ADVISE,
100     POSTCOPY_INCOMING_DISCARD,
101     POSTCOPY_INCOMING_LISTENING,
102     POSTCOPY_INCOMING_RUNNING,
103     POSTCOPY_INCOMING_END
104 } PostcopyState;
105 
106 PostcopyState postcopy_state_get(void);
107 /* Set the state and return the old state */
108 PostcopyState postcopy_state_set(PostcopyState new_state);
109 
110 void postcopy_fault_thread_notify(MigrationIncomingState *mis);
111 
112 /*
113  * To be called once at the start before any device initialisation
114  */
115 void postcopy_infrastructure_init(void);
116 
117 /* Add a notifier to a list to be called when checking whether the devices
118  * can support postcopy.
119  * It's data is a *PostcopyNotifyData
120  * It should return 0 if OK, or a negative value on failure.
121  * On failure it must set the data->errp to an error.
122  *
123  */
124 enum PostcopyNotifyReason {
125     POSTCOPY_NOTIFY_PROBE = 0,
126     POSTCOPY_NOTIFY_INBOUND_ADVISE,
127     POSTCOPY_NOTIFY_INBOUND_LISTEN,
128     POSTCOPY_NOTIFY_INBOUND_END,
129 };
130 
131 struct PostcopyNotifyData {
132     enum PostcopyNotifyReason reason;
133 };
134 
135 void postcopy_add_notifier(NotifierWithReturn *nn);
136 void postcopy_remove_notifier(NotifierWithReturn *n);
137 /* Call the notifier list set by postcopy_add_start_notifier */
138 int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp);
139 
140 void postcopy_thread_create(MigrationIncomingState *mis,
141                             QemuThread *thread, const char *name,
142                             void *(*fn)(void *), int joinable);
143 
144 struct PostCopyFD;
145 
146 /* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */
147 typedef int (*pcfdhandler)(struct PostCopyFD *pcfd, void *ufd);
148 /* Notification to wake, either on place or on reception of
149  * a fault on something that's already arrived (race)
150  */
151 typedef int (*pcfdwake)(struct PostCopyFD *pcfd, RAMBlock *rb, uint64_t offset);
152 
153 struct PostCopyFD {
154     int fd;
155     /* Data to pass to handler */
156     void *data;
157     /* Handler to be called whenever we get a poll event */
158     pcfdhandler handler;
159     /* Notification to wake shared client */
160     pcfdwake waker;
161     /* A string to use in error messages */
162     const char *idstr;
163 };
164 
165 /* Register a userfaultfd owned by an external process for
166  * shared memory.
167  */
168 void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
169 void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
170 /* Call each of the shared 'waker's registered telling them of
171  * availability of a block.
172  */
173 int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset);
174 /* postcopy_wake_shared: Notify a client ufd that a page is available
175  *
176  * Returns 0 on success
177  *
178  * @pcfd: Structure with fd, handler and name as above
179  * @client_addr: Address in the client program, not QEMU
180  * @rb: The RAMBlock the page is in
181  */
182 int postcopy_wake_shared(struct PostCopyFD *pcfd, uint64_t client_addr,
183                          RAMBlock *rb);
184 /* Callback from shared fault handlers to ask for a page */
185 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
186                                  uint64_t client_addr, uint64_t offset);
187 
188 /* Hard-code channels for now for postcopy preemption */
189 enum PostcopyChannels {
190     RAM_CHANNEL_PRECOPY = 0,
191     RAM_CHANNEL_POSTCOPY = 1,
192     RAM_CHANNEL_MAX,
193 };
194 
195 void postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file);
196 void postcopy_preempt_setup(MigrationState *s);
197 int postcopy_preempt_establish_channel(MigrationState *s);
198 bool postcopy_is_paused(MigrationStatus status);
199 
200 #endif
201