migration/postcopy-ram.h

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