migration.c

   1 /*
   2  * QEMU live migration
   3  *
   4  * Copyright IBM, Corp. 2008
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <[email protected]>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  * Contributions after 2012-01-13 are licensed under the terms of the
  13  * GNU GPL, version 2 or (at your option) any later version.
  14  */
  15
  16 #include "qemu-common.h"
  17 #include "migration/migration.h"
  18 #include "monitor/monitor.h"
  19 #include "migration/qemu-file.h"
  20 #include "sysemu/sysemu.h"
  21 #include "block/block.h"
  22 #include "qemu/sockets.h"
  23 #include "migration/block.h"
  24 #include "qemu/thread.h"
  25 #include "qmp-commands.h"
  26
  27 //#define DEBUG_MIGRATION
  28
  29 #ifdef DEBUG_MIGRATION
  30 #define DPRINTF(fmt, ...) \
  31     do { printf("migration: " fmt, ## __VA_ARGS__); } while (0)
  32 #else
  33 #define DPRINTF(fmt, ...) \
  34     do { } while (0)
  35 #endif
  36
  37 enum {
  38     MIG_STATE_ERROR,
  39     MIG_STATE_SETUP,
  40     MIG_STATE_CANCELLED,
  41     MIG_STATE_ACTIVE,
  42     MIG_STATE_COMPLETED,
  43 };
  44
  45 #define MAX_THROTTLE  (32 << 20)      /* Migration speed throttling */
  46
  47 /* Amount of time to allocate to each "chunk" of bandwidth-throttled
  48  * data. */
  49 #define BUFFER_DELAY     100
  50 #define XFER_LIMIT_RATIO (1000 / BUFFER_DELAY)
  51
  52 /* Migration XBZRLE default cache size */
  53 #define DEFAULT_MIGRATE_CACHE_SIZE (64 * 1024 * 1024)
  54
  55 static NotifierList migration_state_notifiers =
  56     NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);
  57
  58 /* When we add fault tolerance, we could have several
  59    migrations at once.  For now we don't need to add
  60    dynamic creation of migration */
  61
  62 MigrationState *migrate_get_current(void)
  63 {
  64     static MigrationState current_migration = {
  65         .state = MIG_STATE_SETUP,
  66         .bandwidth_limit = MAX_THROTTLE,
  67         .xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE,
  68     };
  69
  70     return &current_migration;
  71 }
  72
  73 void qemu_start_incoming_migration(const char *uri, Error **errp)
  74 {
  75     const char *p;
  76
  77     if (strstart(uri, "tcp:", &p))
  78         tcp_start_incoming_migration(p, errp);
  79 #if !defined(WIN32)
  80     else if (strstart(uri, "exec:", &p))
  81         exec_start_incoming_migration(p, errp);
  82     else if (strstart(uri, "unix:", &p))
  83         unix_start_incoming_migration(p, errp);
  84     else if (strstart(uri, "fd:", &p))
  85         fd_start_incoming_migration(p, errp);
  86 #endif
  87     else {
  88         error_setg(errp, "unknown migration protocol: %s\n", uri);
  89     }
  90 }
  91
  92 static void process_incoming_migration_co(void *opaque)
  93 {
  94     QEMUFile *f = opaque;
  95     int ret;
  96
  97     ret = qemu_loadvm_state(f);
  98     qemu_set_fd_handler(qemu_get_fd(f), NULL, NULL, NULL);
  99     qemu_fclose(f);
 100     if (ret < 0) {
 101         fprintf(stderr, "load of migration failed\n");
 102         exit(0);
 103     }
 104     qemu_announce_self();
 105     DPRINTF("successfully loaded vm state\n");
 106
 107     bdrv_clear_incoming_migration_all();
 108     /* Make sure all file formats flush their mutable metadata */
 109     bdrv_invalidate_cache_all();
 110
 111     if (autostart) {
 112         vm_start();
 113     } else {
 114         runstate_set(RUN_STATE_PAUSED);
 115     }
 116 }
 117
 118 static void enter_migration_coroutine(void *opaque)
 119 {
 120     Coroutine *co = opaque;
 121     qemu_coroutine_enter(co, NULL);
 122 }
 123
 124 void process_incoming_migration(QEMUFile *f)
 125 {
 126     Coroutine *co = qemu_coroutine_create(process_incoming_migration_co);
 127     int fd = qemu_get_fd(f);
 128
 129     assert(fd != -1);
 130     socket_set_nonblock(fd);
 131     qemu_set_fd_handler(fd, enter_migration_coroutine, NULL, co);
 132     qemu_coroutine_enter(co, f);
 133 }
 134
 135 /* amount of nanoseconds we are willing to wait for migration to be down.
 136  * the choice of nanoseconds is because it is the maximum resolution that
 137  * get_clock() can achieve. It is an internal measure. All user-visible
 138  * units must be in seconds */
 139 static uint64_t max_downtime = 30000000;
 140
 141 uint64_t migrate_max_downtime(void)
 142 {
 143     return max_downtime;
 144 }
 145
 146 MigrationCapabilityStatusList *qmp_query_migrate_capabilities(Error **errp)
 147 {
 148     MigrationCapabilityStatusList *head = NULL;
 149     MigrationCapabilityStatusList *caps;
 150     MigrationState *s = migrate_get_current();
 151     int i;
 152
 153     for (i = 0; i < MIGRATION_CAPABILITY_MAX; i++) {
 154         if (head == NULL) {
 155             head = g_malloc0(sizeof(*caps));
 156             caps = head;
 157         } else {
 158             caps->next = g_malloc0(sizeof(*caps));
 159             caps = caps->next;
 160         }
 161         caps->value =
 162             g_malloc(sizeof(*caps->value));
 163         caps->value->capability = i;
 164         caps->value->state = s->enabled_capabilities[i];
 165     }
 166
 167     return head;
 168 }
 169
 170 static void get_xbzrle_cache_stats(MigrationInfo *info)
 171 {
 172     if (migrate_use_xbzrle()) {
 173         info->has_xbzrle_cache = true;
 174         info->xbzrle_cache = g_malloc0(sizeof(*info->xbzrle_cache));
 175         info->xbzrle_cache->cache_size = migrate_xbzrle_cache_size();
 176         info->xbzrle_cache->bytes = xbzrle_mig_bytes_transferred();
 177         info->xbzrle_cache->pages = xbzrle_mig_pages_transferred();
 178         info->xbzrle_cache->cache_miss = xbzrle_mig_pages_cache_miss();
 179         info->xbzrle_cache->overflow = xbzrle_mig_pages_overflow();
 180     }
 181 }
 182
 183 MigrationInfo *qmp_query_migrate(Error **errp)
 184 {
 185     MigrationInfo *info = g_malloc0(sizeof(*info));
 186     MigrationState *s = migrate_get_current();
 187
 188     switch (s->state) {
 189     case MIG_STATE_SETUP:
 190         /* no migration has happened ever */
 191         break;
 192     case MIG_STATE_ACTIVE:
 193         info->has_status = true;
 194         info->status = g_strdup("active");
 195         info->has_total_time = true;
 196         info->total_time = qemu_get_clock_ms(rt_clock)
 197             - s->total_time;
 198         info->has_expected_downtime = true;
 199         info->expected_downtime = s->expected_downtime;
 200
 201         info->has_ram = true;
 202         info->ram = g_malloc0(sizeof(*info->ram));
 203         info->ram->transferred = ram_bytes_transferred();
 204         info->ram->remaining = ram_bytes_remaining();
 205         info->ram->total = ram_bytes_total();
 206         info->ram->duplicate = dup_mig_pages_transferred();
 207         info->ram->normal = norm_mig_pages_transferred();
 208         info->ram->normal_bytes = norm_mig_bytes_transferred();
 209         info->ram->dirty_pages_rate = s->dirty_pages_rate;
 210
 211
 212         if (blk_mig_active()) {
 213             info->has_disk = true;
 214             info->disk = g_malloc0(sizeof(*info->disk));
 215             info->disk->transferred = blk_mig_bytes_transferred();
 216             info->disk->remaining = blk_mig_bytes_remaining();
 217             info->disk->total = blk_mig_bytes_total();
 218         }
 219
 220         get_xbzrle_cache_stats(info);
 221         break;
 222     case MIG_STATE_COMPLETED:
 223         get_xbzrle_cache_stats(info);
 224
 225         info->has_status = true;
 226         info->status = g_strdup("completed");
 227         info->total_time = s->total_time;
 228         info->has_downtime = true;
 229         info->downtime = s->downtime;
 230
 231         info->has_ram = true;
 232         info->ram = g_malloc0(sizeof(*info->ram));
 233         info->ram->transferred = ram_bytes_transferred();
 234         info->ram->remaining = 0;
 235         info->ram->total = ram_bytes_total();
 236         info->ram->duplicate = dup_mig_pages_transferred();
 237         info->ram->normal = norm_mig_pages_transferred();
 238         info->ram->normal_bytes = norm_mig_bytes_transferred();
 239         break;
 240     case MIG_STATE_ERROR:
 241         info->has_status = true;
 242         info->status = g_strdup("failed");
 243         break;
 244     case MIG_STATE_CANCELLED:
 245         info->has_status = true;
 246         info->status = g_strdup("cancelled");
 247         break;
 248     }
 249
 250     return info;
 251 }
 252
 253 void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
 254                                   Error **errp)
 255 {
 256     MigrationState *s = migrate_get_current();
 257     MigrationCapabilityStatusList *cap;
 258
 259     if (s->state == MIG_STATE_ACTIVE) {
 260         error_set(errp, QERR_MIGRATION_ACTIVE);
 261         return;
 262     }
 263
 264     for (cap = params; cap; cap = cap->next) {
 265         s->enabled_capabilities[cap->value->capability] = cap->value->state;
 266     }
 267 }
 268
 269 /* shared migration helpers */
 270
 271 static int migrate_fd_cleanup(MigrationState *s)
 272 {
 273     int ret = 0;
 274
 275     if (s->file) {
 276         DPRINTF("closing file\n");
 277         ret = qemu_fclose(s->file);
 278         s->file = NULL;
 279     }
 280
 281     assert(s->fd == -1);
 282     return ret;
 283 }
 284
 285 void migrate_fd_error(MigrationState *s)
 286 {
 287     DPRINTF("setting error state\n");
 288     s->state = MIG_STATE_ERROR;
 289     notifier_list_notify(&migration_state_notifiers, s);
 290     migrate_fd_cleanup(s);
 291 }
 292
 293 static void migrate_fd_completed(MigrationState *s)
 294 {
 295     DPRINTF("setting completed state\n");
 296     if (migrate_fd_cleanup(s) < 0) {
 297         s->state = MIG_STATE_ERROR;
 298     } else {
 299         s->state = MIG_STATE_COMPLETED;
 300         runstate_set(RUN_STATE_POSTMIGRATE);
 301     }
 302     notifier_list_notify(&migration_state_notifiers, s);
 303 }
 304
 305 static ssize_t migrate_fd_put_buffer(MigrationState *s, const void *data,
 306                                      size_t size)
 307 {
 308     ssize_t ret;
 309
 310     if (s->state != MIG_STATE_ACTIVE) {
 311         return -EIO;
 312     }
 313
 314     do {
 315         ret = s->write(s, data, size);
 316     } while (ret == -1 && ((s->get_error(s)) == EINTR));
 317
 318     if (ret == -1)
 319         ret = -(s->get_error(s));
 320
 321     return ret;
 322 }
 323
 324 static void migrate_fd_cancel(MigrationState *s)
 325 {
 326     if (s->state != MIG_STATE_ACTIVE)
 327         return;
 328
 329     DPRINTF("cancelling migration\n");
 330
 331     s->state = MIG_STATE_CANCELLED;
 332     notifier_list_notify(&migration_state_notifiers, s);
 333     qemu_savevm_state_cancel();
 334
 335     migrate_fd_cleanup(s);
 336 }
 337
 338 int migrate_fd_close(MigrationState *s)
 339 {
 340     int rc = 0;
 341     if (s->fd != -1) {
 342         rc = s->close(s);
 343         s->fd = -1;
 344     }
 345     return rc;
 346 }
 347
 348 void add_migration_state_change_notifier(Notifier *notify)
 349 {
 350     notifier_list_add(&migration_state_notifiers, notify);
 351 }
 352
 353 void remove_migration_state_change_notifier(Notifier *notify)
 354 {
 355     notifier_remove(notify);
 356 }
 357
 358 bool migration_is_active(MigrationState *s)
 359 {
 360     return s->state == MIG_STATE_ACTIVE;
 361 }
 362
 363 bool migration_has_finished(MigrationState *s)
 364 {
 365     return s->state == MIG_STATE_COMPLETED;
 366 }
 367
 368 bool migration_has_failed(MigrationState *s)
 369 {
 370     return (s->state == MIG_STATE_CANCELLED ||
 371             s->state == MIG_STATE_ERROR);
 372 }
 373
 374 static MigrationState *migrate_init(const MigrationParams *params)
 375 {
 376     MigrationState *s = migrate_get_current();
 377     int64_t bandwidth_limit = s->bandwidth_limit;
 378     bool enabled_capabilities[MIGRATION_CAPABILITY_MAX];
 379     int64_t xbzrle_cache_size = s->xbzrle_cache_size;
 380
 381     memcpy(enabled_capabilities, s->enabled_capabilities,
 382            sizeof(enabled_capabilities));
 383
 384     memset(s, 0, sizeof(*s));
 385     s->bandwidth_limit = bandwidth_limit;
 386     s->params = *params;
 387     memcpy(s->enabled_capabilities, enabled_capabilities,
 388            sizeof(enabled_capabilities));
 389     s->xbzrle_cache_size = xbzrle_cache_size;
 390
 391     s->bandwidth_limit = bandwidth_limit;
 392     s->state = MIG_STATE_SETUP;
 393     s->total_time = qemu_get_clock_ms(rt_clock);
 394
 395     return s;
 396 }
 397
 398 static GSList *migration_blockers;
 399
 400 void migrate_add_blocker(Error *reason)
 401 {
 402     migration_blockers = g_slist_prepend(migration_blockers, reason);
 403 }
 404
 405 void migrate_del_blocker(Error *reason)
 406 {
 407     migration_blockers = g_slist_remove(migration_blockers, reason);
 408 }
 409
 410 void qmp_migrate(const char *uri, bool has_blk, bool blk,
 411                  bool has_inc, bool inc, bool has_detach, bool detach,
 412                  Error **errp)
 413 {
 414     Error *local_err = NULL;
 415     MigrationState *s = migrate_get_current();
 416     MigrationParams params;
 417     const char *p;
 418
 419     params.blk = blk;
 420     params.shared = inc;
 421
 422     if (s->state == MIG_STATE_ACTIVE) {
 423         error_set(errp, QERR_MIGRATION_ACTIVE);
 424         return;
 425     }
 426
 427     if (qemu_savevm_state_blocked(errp)) {
 428         return;
 429     }
 430
 431     if (migration_blockers) {
 432         *errp = error_copy(migration_blockers->data);
 433         return;
 434     }
 435
 436     s = migrate_init(&params);
 437
 438     if (strstart(uri, "tcp:", &p)) {
 439         tcp_start_outgoing_migration(s, p, &local_err);
 440 #if !defined(WIN32)
 441     } else if (strstart(uri, "exec:", &p)) {
 442         exec_start_outgoing_migration(s, p, &local_err);
 443     } else if (strstart(uri, "unix:", &p)) {
 444         unix_start_outgoing_migration(s, p, &local_err);
 445     } else if (strstart(uri, "fd:", &p)) {
 446         fd_start_outgoing_migration(s, p, &local_err);
 447 #endif
 448     } else {
 449         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "uri", "a valid migration protocol");
 450         return;
 451     }
 452
 453     if (local_err) {
 454         migrate_fd_error(s);
 455         error_propagate(errp, local_err);
 456         return;
 457     }
 458 }
 459
 460 void qmp_migrate_cancel(Error **errp)
 461 {
 462     migrate_fd_cancel(migrate_get_current());
 463 }
 464
 465 void qmp_migrate_set_cache_size(int64_t value, Error **errp)
 466 {
 467     MigrationState *s = migrate_get_current();
 468
 469     /* Check for truncation */
 470     if (value != (size_t)value) {
 471         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
 472                   "exceeding address space");
 473         return;
 474     }
 475
 476     s->xbzrle_cache_size = xbzrle_cache_resize(value);
 477 }
 478
 479 int64_t qmp_query_migrate_cache_size(Error **errp)
 480 {
 481     return migrate_xbzrle_cache_size();
 482 }
 483
 484 void qmp_migrate_set_speed(int64_t value, Error **errp)
 485 {
 486     MigrationState *s;
 487
 488     if (value < 0) {
 489         value = 0;
 490     }
 491
 492     s = migrate_get_current();
 493     s->bandwidth_limit = value;
 494     qemu_file_set_rate_limit(s->file, s->bandwidth_limit);
 495 }
 496
 497 void qmp_migrate_set_downtime(double value, Error **errp)
 498 {
 499     value *= 1e9;
 500     value = MAX(0, MIN(UINT64_MAX, value));
 501     max_downtime = (uint64_t)value;
 502 }
 503
 504 int migrate_use_xbzrle(void)
 505 {
 506     MigrationState *s;
 507
 508     s = migrate_get_current();
 509
 510     return s->enabled_capabilities[MIGRATION_CAPABILITY_XBZRLE];
 511 }
 512
 513 int64_t migrate_xbzrle_cache_size(void)
 514 {
 515     MigrationState *s;
 516
 517     s = migrate_get_current();
 518
 519     return s->xbzrle_cache_size;
 520 }
 521
 522 /* migration thread support */
 523
 524
 525 static ssize_t buffered_flush(MigrationState *s)
 526 {
 527     size_t offset = 0;
 528     ssize_t ret = 0;
 529
 530     DPRINTF("flushing %zu byte(s) of data\n", s->buffer_size);
 531
 532     while (s->bytes_xfer < s->xfer_limit && offset < s->buffer_size) {
 533         size_t to_send = MIN(s->buffer_size - offset, s->xfer_limit - s->bytes_xfer);
 534         ret = migrate_fd_put_buffer(s, s->buffer + offset, to_send);
 535         if (ret <= 0) {
 536             DPRINTF("error flushing data, %zd\n", ret);
 537             break;
 538         } else {
 539             DPRINTF("flushed %zd byte(s)\n", ret);
 540             offset += ret;
 541             s->bytes_xfer += ret;
 542         }
 543     }
 544
 545     DPRINTF("flushed %zu of %zu byte(s)\n", offset, s->buffer_size);
 546     memmove(s->buffer, s->buffer + offset, s->buffer_size - offset);
 547     s->buffer_size -= offset;
 548
 549     if (ret < 0) {
 550         return ret;
 551     }
 552     return offset;
 553 }
 554
 555 static int buffered_put_buffer(void *opaque, const uint8_t *buf,
 556                                int64_t pos, int size)
 557 {
 558     MigrationState *s = opaque;
 559     ssize_t error;
 560
 561     DPRINTF("putting %d bytes at %" PRId64 "\n", size, pos);
 562
 563     error = qemu_file_get_error(s->file);
 564     if (error) {
 565         DPRINTF("flush when error, bailing: %s\n", strerror(-error));
 566         return error;
 567     }
 568
 569     if (size <= 0) {
 570         return size;
 571     }
 572
 573     if (size > (s->buffer_capacity - s->buffer_size)) {
 574         DPRINTF("increasing buffer capacity from %zu by %zu\n",
 575                 s->buffer_capacity, size + 1024);
 576
 577         s->buffer_capacity += size + 1024;
 578
 579         s->buffer = g_realloc(s->buffer, s->buffer_capacity);
 580     }
 581
 582     memcpy(s->buffer + s->buffer_size, buf, size);
 583     s->buffer_size += size;
 584
 585     return size;
 586 }
 587
 588 static int buffered_close(void *opaque)
 589 {
 590     MigrationState *s = opaque;
 591     ssize_t ret = 0;
 592     int ret2;
 593
 594     DPRINTF("closing\n");
 595
 596     s->xfer_limit = INT_MAX;
 597     while (!qemu_file_get_error(s->file) && s->buffer_size) {
 598         ret = buffered_flush(s);
 599         if (ret < 0) {
 600             break;
 601         }
 602     }
 603
 604     ret2 = migrate_fd_close(s);
 605     if (ret >= 0) {
 606         ret = ret2;
 607     }
 608     s->complete = true;
 609     return ret;
 610 }
 611
 612 static int buffered_get_fd(void *opaque)
 613 {
 614     MigrationState *s = opaque;
 615
 616     return s->fd;
 617 }
 618
 619 /*
 620  * The meaning of the return values is:
 621  *   0: We can continue sending
 622  *   1: Time to stop
 623  *   negative: There has been an error
 624  */
 625 static int buffered_rate_limit(void *opaque)
 626 {
 627     MigrationState *s = opaque;
 628     int ret;
 629
 630     ret = qemu_file_get_error(s->file);
 631     if (ret) {
 632         return ret;
 633     }
 634
 635     if (s->bytes_xfer >= s->xfer_limit) {
 636         return 1;
 637     }
 638
 639     return 0;
 640 }
 641
 642 static int64_t buffered_set_rate_limit(void *opaque, int64_t new_rate)
 643 {
 644     MigrationState *s = opaque;
 645     if (qemu_file_get_error(s->file)) {
 646         goto out;
 647     }
 648     if (new_rate > SIZE_MAX) {
 649         new_rate = SIZE_MAX;
 650     }
 651
 652     s->xfer_limit = new_rate / XFER_LIMIT_RATIO;
 653
 654 out:
 655     return s->xfer_limit;
 656 }
 657
 658 static int64_t buffered_get_rate_limit(void *opaque)
 659 {
 660     MigrationState *s = opaque;
 661
 662     return s->xfer_limit;
 663 }
 664
 665 static void *buffered_file_thread(void *opaque)
 666 {
 667     MigrationState *s = opaque;
 668     int64_t initial_time = qemu_get_clock_ms(rt_clock);
 669     int64_t max_size = 0;
 670     bool last_round = false;
 671     int ret;
 672
 673     qemu_mutex_lock_iothread();
 674     DPRINTF("beginning savevm\n");
 675     ret = qemu_savevm_state_begin(s->file, &s->params);
 676     if (ret < 0) {
 677         DPRINTF("failed, %d\n", ret);
 678         qemu_mutex_unlock_iothread();
 679         goto out;
 680     }
 681     qemu_mutex_unlock_iothread();
 682
 683     while (true) {
 684         int64_t current_time = qemu_get_clock_ms(rt_clock);
 685         uint64_t pending_size;
 686
 687         qemu_mutex_lock_iothread();
 688         if (s->state != MIG_STATE_ACTIVE) {
 689             DPRINTF("put_ready returning because of non-active state\n");
 690             qemu_mutex_unlock_iothread();
 691             break;
 692         }
 693         if (s->complete) {
 694             qemu_mutex_unlock_iothread();
 695             break;
 696         }
 697         if (s->bytes_xfer < s->xfer_limit) {
 698             DPRINTF("iterate\n");
 699             pending_size = qemu_savevm_state_pending(s->file, max_size);
 700             DPRINTF("pending size %lu max %lu\n", pending_size, max_size);
 701             if (pending_size && pending_size >= max_size) {
 702                 ret = qemu_savevm_state_iterate(s->file);
 703                 if (ret < 0) {
 704                     qemu_mutex_unlock_iothread();
 705                     break;
 706                 }
 707             } else {
 708                 int old_vm_running = runstate_is_running();
 709                 int64_t start_time, end_time;
 710
 711                 DPRINTF("done iterating\n");
 712                 start_time = qemu_get_clock_ms(rt_clock);
 713                 qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
 714                 if (old_vm_running) {
 715                     vm_stop(RUN_STATE_FINISH_MIGRATE);
 716                 } else {
 717                     vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
 718                 }
 719                 ret = qemu_savevm_state_complete(s->file);
 720                 if (ret < 0) {
 721                     qemu_mutex_unlock_iothread();
 722                     break;
 723                 } else {
 724                     migrate_fd_completed(s);
 725                 }
 726                 end_time = qemu_get_clock_ms(rt_clock);
 727                 s->total_time = end_time - s->total_time;
 728                 s->downtime = end_time - start_time;
 729                 if (s->state != MIG_STATE_COMPLETED) {
 730                     if (old_vm_running) {
 731                         vm_start();
 732                     }
 733                 }
 734                 last_round = true;
 735             }
 736         }
 737         qemu_mutex_unlock_iothread();
 738         if (current_time >= initial_time + BUFFER_DELAY) {
 739             uint64_t transferred_bytes = s->bytes_xfer;
 740             uint64_t time_spent = current_time - initial_time;
 741             double bandwidth = transferred_bytes / time_spent;
 742             max_size = bandwidth * migrate_max_downtime() / 1000000;
 743
 744             DPRINTF("transferred %" PRIu64 " time_spent %" PRIu64
 745                     " bandwidth %g max_size %" PRId64 "\n",
 746                     transferred_bytes, time_spent, bandwidth, max_size);
 747
 748             s->bytes_xfer = 0;
 749             initial_time = current_time;
 750         }
 751         if (!last_round && (s->bytes_xfer >= s->xfer_limit)) {
 752             /* usleep expects microseconds */
 753             g_usleep((initial_time + BUFFER_DELAY - current_time)*1000);
 754         }
 755         ret = buffered_flush(s);
 756         if (ret < 0) {
 757             break;
 758         }
 759     }
 760
 761 out:
 762     if (ret < 0) {
 763         migrate_fd_error(s);
 764     }
 765     g_free(s->buffer);
 766     return NULL;
 767 }
 768
 769 static const QEMUFileOps buffered_file_ops = {
 770     .get_fd =         buffered_get_fd,
 771     .put_buffer =     buffered_put_buffer,
 772     .close =          buffered_close,
 773     .rate_limit =     buffered_rate_limit,
 774     .get_rate_limit = buffered_get_rate_limit,
 775     .set_rate_limit = buffered_set_rate_limit,
 776 };
 777
 778 void migrate_fd_connect(MigrationState *s)
 779 {
 780     s->state = MIG_STATE_ACTIVE;
 781     s->bytes_xfer = 0;
 782     s->buffer = NULL;
 783     s->buffer_size = 0;
 784     s->buffer_capacity = 0;
 785
 786     s->xfer_limit = s->bandwidth_limit / XFER_LIMIT_RATIO;
 787     s->complete = false;
 788
 789     s->file = qemu_fopen_ops(s, &buffered_file_ops);
 790
 791     qemu_thread_create(&s->thread, buffered_file_thread, s,
 792                        QEMU_THREAD_DETACHED);
 793     notifier_list_notify(&migration_state_notifiers, s);
 794 }