migration/block-dirty-bitmap.c

   1 /*
   2  * Block dirty bitmap postcopy migration
   3  *
   4  * Copyright IBM, Corp. 2009
   5  * Copyright (c) 2016-2017 Virtuozzo International GmbH. All rights reserved.
   6  *
   7  * Authors:
   8  *  Liran Schour   <lirans@il.ibm.com>
   9  *  Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
  10  *
  11  * This work is licensed under the terms of the GNU GPL, version 2.  See
  12  * the COPYING file in the top-level directory.
  13  * This file is derived from migration/block.c, so it's author and IBM copyright
  14  * are here, although content is quite different.
  15  *
  16  * Contributions after 2012-01-13 are licensed under the terms of the
  17  * GNU GPL, version 2 or (at your option) any later version.
  18  *
  19  *                                ***
  20  *
  21  * Here postcopy migration of dirty bitmaps is realized. Only QMP-addressable
  22  * bitmaps are migrated.
  23  *
  24  * Bitmap migration implies creating bitmap with the same name and granularity
  25  * in destination QEMU. If the bitmap with the same name (for the same node)
  26  * already exists on destination an error will be generated.
  27  *
  28  * format of migration:
  29  *
  30  * # Header (shared for different chunk types)
  31  * 1, 2 or 4 bytes: flags (see qemu_{put,put}_flags)
  32  * [ 1 byte: node name size ] \  flags & DEVICE_NAME
  33  * [ n bytes: node name     ] /
  34  * [ 1 byte: bitmap name size ] \  flags & BITMAP_NAME
  35  * [ n bytes: bitmap name     ] /
  36  *
  37  * # Start of bitmap migration (flags & START)
  38  * header
  39  * be64: granularity
  40  * 1 byte: bitmap flags (corresponds to BdrvDirtyBitmap)
  41  *   bit 0    -  bitmap is enabled
  42  *   bit 1    -  bitmap is persistent
  43  *   bit 2    -  bitmap is autoloading
  44  *   bits 3-7 - reserved, must be zero
  45  *
  46  * # Complete of bitmap migration (flags & COMPLETE)
  47  * header
  48  *
  49  * # Data chunk of bitmap migration
  50  * header
  51  * be64: start sector
  52  * be32: number of sectors
  53  * [ be64: buffer size  ] \ ! (flags & ZEROES)
  54  * [ n bytes: buffer    ] /
  55  *
  56  * The last chunk in stream should contain flags & EOS. The chunk may skip
  57  * device and/or bitmap names, assuming them to be the same with the previous
  58  * chunk.
  59  */
  60
  61 #include "qemu/osdep.h"
  62 #include "block/block.h"
  63 #include "block/block_int.h"
  64 #include "sysemu/block-backend.h"
  65 #include "sysemu/runstate.h"
  66 #include "qemu/main-loop.h"
  67 #include "qemu/error-report.h"
  68 #include "migration/misc.h"
  69 #include "migration/migration.h"
  70 #include "qemu-file.h"
  71 #include "migration/vmstate.h"
  72 #include "migration/register.h"
  73 #include "qemu/hbitmap.h"
  74 #include "qemu/cutils.h"
  75 #include "qapi/error.h"
  76 #include "trace.h"
  77
  78 #define CHUNK_SIZE     (1 << 10)
  79
  80 /* Flags occupy one, two or four bytes (Big Endian). The size is determined as
  81  * follows:
  82  * in first (most significant) byte bit 8 is clear  -->  one byte
  83  * in first byte bit 8 is set    -->  two or four bytes, depending on second
  84  *                                    byte:
  85  *    | in second byte bit 8 is clear  -->  two bytes
  86  *    | in second byte bit 8 is set    -->  four bytes
  87  */
  88 #define DIRTY_BITMAP_MIG_FLAG_EOS           0x01
  89 #define DIRTY_BITMAP_MIG_FLAG_ZEROES        0x02
  90 #define DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME   0x04
  91 #define DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME   0x08
  92 #define DIRTY_BITMAP_MIG_FLAG_START         0x10
  93 #define DIRTY_BITMAP_MIG_FLAG_COMPLETE      0x20
  94 #define DIRTY_BITMAP_MIG_FLAG_BITS          0x40
  95
  96 #define DIRTY_BITMAP_MIG_EXTRA_FLAGS        0x80
  97
  98 #define DIRTY_BITMAP_MIG_START_FLAG_ENABLED          0x01
  99 #define DIRTY_BITMAP_MIG_START_FLAG_PERSISTENT       0x02
 100 /* 0x04 was "AUTOLOAD" flags on elder versions, no it is ignored */
 101 #define DIRTY_BITMAP_MIG_START_FLAG_RESERVED_MASK    0xf8
 102
 103 typedef struct DirtyBitmapMigBitmapState {
 104     /* Written during setup phase. */
 105     BlockDriverState *bs;
 106     const char *node_name;
 107     BdrvDirtyBitmap *bitmap;
 108     uint64_t total_sectors;
 109     uint64_t sectors_per_chunk;
 110     QSIMPLEQ_ENTRY(DirtyBitmapMigBitmapState) entry;
 111     uint8_t flags;
 112
 113     /* For bulk phase. */
 114     bool bulk_completed;
 115     uint64_t cur_sector;
 116 } DirtyBitmapMigBitmapState;
 117
 118 typedef struct DirtyBitmapMigState {
 119     QSIMPLEQ_HEAD(, DirtyBitmapMigBitmapState) dbms_list;
 120
 121     bool bulk_completed;
 122     bool no_bitmaps;
 123
 124     /* for send_bitmap_bits() */
 125     BlockDriverState *prev_bs;
 126     BdrvDirtyBitmap *prev_bitmap;
 127 } DirtyBitmapMigState;
 128
 129 typedef struct DirtyBitmapLoadState {
 130     uint32_t flags;
 131     char node_name[256];
 132     char bitmap_name[256];
 133     BlockDriverState *bs;
 134     BdrvDirtyBitmap *bitmap;
 135 } DirtyBitmapLoadState;
 136
 137 static DirtyBitmapMigState dirty_bitmap_mig_state;
 138
 139 typedef struct DirtyBitmapLoadBitmapState {
 140     BlockDriverState *bs;
 141     BdrvDirtyBitmap *bitmap;
 142     bool migrated;
 143 } DirtyBitmapLoadBitmapState;
 144 static GSList *enabled_bitmaps;
 145 QemuMutex finish_lock;
 146
 147 void init_dirty_bitmap_incoming_migration(void)
 148 {
 149     qemu_mutex_init(&finish_lock);
 150 }
 151
 152 static uint32_t qemu_get_bitmap_flags(QEMUFile *f)
 153 {
 154     uint8_t flags = qemu_get_byte(f);
 155     if (flags & DIRTY_BITMAP_MIG_EXTRA_FLAGS) {
 156         flags = flags << 8 | qemu_get_byte(f);
 157         if (flags & DIRTY_BITMAP_MIG_EXTRA_FLAGS) {
 158             flags = flags << 16 | qemu_get_be16(f);
 159         }
 160     }
 161
 162     return flags;
 163 }
 164
 165 static void qemu_put_bitmap_flags(QEMUFile *f, uint32_t flags)
 166 {
 167     /* The code currently do not send flags more than one byte */
 168     assert(!(flags & (0xffffff00 | DIRTY_BITMAP_MIG_EXTRA_FLAGS)));
 169
 170     qemu_put_byte(f, flags);
 171 }
 172
 173 static void send_bitmap_header(QEMUFile *f, DirtyBitmapMigBitmapState *dbms,
 174                                uint32_t additional_flags)
 175 {
 176     BlockDriverState *bs = dbms->bs;
 177     BdrvDirtyBitmap *bitmap = dbms->bitmap;
 178     uint32_t flags = additional_flags;
 179     trace_send_bitmap_header_enter();
 180
 181     if (bs != dirty_bitmap_mig_state.prev_bs) {
 182         dirty_bitmap_mig_state.prev_bs = bs;
 183         flags |= DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME;
 184     }
 185
 186     if (bitmap != dirty_bitmap_mig_state.prev_bitmap) {
 187         dirty_bitmap_mig_state.prev_bitmap = bitmap;
 188         flags |= DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME;
 189     }
 190
 191     qemu_put_bitmap_flags(f, flags);
 192
 193     if (flags & DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME) {
 194         qemu_put_counted_string(f, dbms->node_name);
 195     }
 196
 197     if (flags & DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME) {
 198         qemu_put_counted_string(f, bdrv_dirty_bitmap_name(bitmap));
 199     }
 200 }
 201
 202 static void send_bitmap_start(QEMUFile *f, DirtyBitmapMigBitmapState *dbms)
 203 {
 204     send_bitmap_header(f, dbms, DIRTY_BITMAP_MIG_FLAG_START);
 205     qemu_put_be32(f, bdrv_dirty_bitmap_granularity(dbms->bitmap));
 206     qemu_put_byte(f, dbms->flags);
 207 }
 208
 209 static void send_bitmap_complete(QEMUFile *f, DirtyBitmapMigBitmapState *dbms)
 210 {
 211     send_bitmap_header(f, dbms, DIRTY_BITMAP_MIG_FLAG_COMPLETE);
 212 }
 213
 214 static void send_bitmap_bits(QEMUFile *f, DirtyBitmapMigBitmapState *dbms,
 215                              uint64_t start_sector, uint32_t nr_sectors)
 216 {
 217     /* align for buffer_is_zero() */
 218     uint64_t align = 4 * sizeof(long);
 219     uint64_t unaligned_size =
 220         bdrv_dirty_bitmap_serialization_size(
 221             dbms->bitmap, start_sector << BDRV_SECTOR_BITS,
 222             (uint64_t)nr_sectors << BDRV_SECTOR_BITS);
 223     uint64_t buf_size = QEMU_ALIGN_UP(unaligned_size, align);
 224     uint8_t *buf = g_malloc0(buf_size);
 225     uint32_t flags = DIRTY_BITMAP_MIG_FLAG_BITS;
 226
 227     bdrv_dirty_bitmap_serialize_part(
 228         dbms->bitmap, buf, start_sector << BDRV_SECTOR_BITS,
 229         (uint64_t)nr_sectors << BDRV_SECTOR_BITS);
 230
 231     if (buffer_is_zero(buf, buf_size)) {
 232         g_free(buf);
 233         buf = NULL;
 234         flags |= DIRTY_BITMAP_MIG_FLAG_ZEROES;
 235     }
 236
 237     trace_send_bitmap_bits(flags, start_sector, nr_sectors, buf_size);
 238
 239     send_bitmap_header(f, dbms, flags);
 240
 241     qemu_put_be64(f, start_sector);
 242     qemu_put_be32(f, nr_sectors);
 243
 244     /* if a block is zero we need to flush here since the network
 245      * bandwidth is now a lot higher than the storage device bandwidth.
 246      * thus if we queue zero blocks we slow down the migration. */
 247     if (flags & DIRTY_BITMAP_MIG_FLAG_ZEROES) {
 248         qemu_fflush(f);
 249     } else {
 250         qemu_put_be64(f, buf_size);
 251         qemu_put_buffer(f, buf, buf_size);
 252     }
 253
 254     g_free(buf);
 255 }
 256
 257 /* Called with iothread lock taken.  */
 258 static void dirty_bitmap_mig_cleanup(void)
 259 {
 260     DirtyBitmapMigBitmapState *dbms;
 261
 262     while ((dbms = QSIMPLEQ_FIRST(&dirty_bitmap_mig_state.dbms_list)) != NULL) {
 263         QSIMPLEQ_REMOVE_HEAD(&dirty_bitmap_mig_state.dbms_list, entry);
 264         bdrv_dirty_bitmap_set_busy(dbms->bitmap, false);
 265         bdrv_unref(dbms->bs);
 266         g_free(dbms);
 267     }
 268 }
 269
 270 /* Called with iothread lock taken. */
 271 static int add_bitmaps_to_list(BlockDriverState *bs, const char *bs_name)
 272 {
 273     BdrvDirtyBitmap *bitmap;
 274     DirtyBitmapMigBitmapState *dbms;
 275     Error *local_err = NULL;
 276
 277     bitmap = bdrv_dirty_bitmap_first(bs);
 278     if (!bitmap) {
 279         return 0;
 280     }
 281
 282     if (!bs_name || strcmp(bs_name, "") == 0) {
 283         error_report("Bitmap '%s' in unnamed node can't be migrated",
 284                      bdrv_dirty_bitmap_name(bitmap));
 285         return -1;
 286     }
 287
 288     if (bs_name[0] == '#') {
 289         error_report("Bitmap '%s' in a node with auto-generated "
 290                      "name '%s' can't be migrated",
 291                      bdrv_dirty_bitmap_name(bitmap), bs_name);
 292         return -1;
 293     }
 294
 295     FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
 296         if (!bdrv_dirty_bitmap_name(bitmap)) {
 297             continue;
 298         }
 299
 300         if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_DEFAULT, &local_err)) {
 301             error_report_err(local_err);
 302             return -1;
 303         }
 304
 305         bdrv_ref(bs);
 306         bdrv_dirty_bitmap_set_busy(bitmap, true);
 307
 308         dbms = g_new0(DirtyBitmapMigBitmapState, 1);
 309         dbms->bs = bs;
 310         dbms->node_name = bs_name;
 311         dbms->bitmap = bitmap;
 312         dbms->total_sectors = bdrv_nb_sectors(bs);
 313         dbms->sectors_per_chunk = CHUNK_SIZE * 8 *
 314             bdrv_dirty_bitmap_granularity(bitmap) >> BDRV_SECTOR_BITS;
 315         if (bdrv_dirty_bitmap_enabled(bitmap)) {
 316             dbms->flags |= DIRTY_BITMAP_MIG_START_FLAG_ENABLED;
 317         }
 318         if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
 319             dbms->flags |= DIRTY_BITMAP_MIG_START_FLAG_PERSISTENT;
 320         }
 321
 322         QSIMPLEQ_INSERT_TAIL(&dirty_bitmap_mig_state.dbms_list,
 323                              dbms, entry);
 324     }
 325
 326     return 0;
 327 }
 328
 329 /* Called with iothread lock taken. */
 330 static int init_dirty_bitmap_migration(void)
 331 {
 332     BlockDriverState *bs;
 333     DirtyBitmapMigBitmapState *dbms;
 334     GHashTable *handled_by_blk = g_hash_table_new(NULL, NULL);
 335     BlockBackend *blk;
 336
 337     dirty_bitmap_mig_state.bulk_completed = false;
 338     dirty_bitmap_mig_state.prev_bs = NULL;
 339     dirty_bitmap_mig_state.prev_bitmap = NULL;
 340     dirty_bitmap_mig_state.no_bitmaps = false;
 341
 342     /*
 343      * Use blockdevice name for direct (or filtered) children of named block
 344      * backends.
 345      */
 346     for (blk = blk_next(NULL); blk; blk = blk_next(blk)) {
 347         const char *name = blk_name(blk);
 348
 349         if (!name || strcmp(name, "") == 0) {
 350             continue;
 351         }
 352
 353         bs = blk_bs(blk);
 354
 355         /* Skip filters without bitmaps */
 356         while (bs && bs->drv && bs->drv->is_filter &&
 357                !bdrv_has_named_bitmaps(bs))
 358         {
 359             if (bs->backing) {
 360                 bs = bs->backing->bs;
 361             } else if (bs->file) {
 362                 bs = bs->file->bs;
 363             } else {
 364                 bs = NULL;
 365             }
 366         }
 367
 368         if (bs && bs->drv && !bs->drv->is_filter) {
 369             if (add_bitmaps_to_list(bs, name)) {
 370                 goto fail;
 371             }
 372             g_hash_table_add(handled_by_blk, bs);
 373         }
 374     }
 375
 376     for (bs = bdrv_next_all_states(NULL); bs; bs = bdrv_next_all_states(bs)) {
 377         if (g_hash_table_contains(handled_by_blk, bs)) {
 378             continue;
 379         }
 380
 381         if (add_bitmaps_to_list(bs, bdrv_get_node_name(bs))) {
 382             goto fail;
 383         }
 384     }
 385
 386     /* unset migration flags here, to not roll back it */
 387     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 388         bdrv_dirty_bitmap_skip_store(dbms->bitmap, true);
 389     }
 390
 391     if (QSIMPLEQ_EMPTY(&dirty_bitmap_mig_state.dbms_list)) {
 392         dirty_bitmap_mig_state.no_bitmaps = true;
 393     }
 394
 395     g_hash_table_destroy(handled_by_blk);
 396
 397     return 0;
 398
 399 fail:
 400     g_hash_table_destroy(handled_by_blk);
 401     dirty_bitmap_mig_cleanup();
 402
 403     return -1;
 404 }
 405
 406 /* Called with no lock taken.  */
 407 static void bulk_phase_send_chunk(QEMUFile *f, DirtyBitmapMigBitmapState *dbms)
 408 {
 409     uint32_t nr_sectors = MIN(dbms->total_sectors - dbms->cur_sector,
 410                              dbms->sectors_per_chunk);
 411
 412     send_bitmap_bits(f, dbms, dbms->cur_sector, nr_sectors);
 413
 414     dbms->cur_sector += nr_sectors;
 415     if (dbms->cur_sector >= dbms->total_sectors) {
 416         dbms->bulk_completed = true;
 417     }
 418 }
 419
 420 /* Called with no lock taken.  */
 421 static void bulk_phase(QEMUFile *f, bool limit)
 422 {
 423     DirtyBitmapMigBitmapState *dbms;
 424
 425     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 426         while (!dbms->bulk_completed) {
 427             bulk_phase_send_chunk(f, dbms);
 428             if (limit && qemu_file_rate_limit(f)) {
 429                 return;
 430             }
 431         }
 432     }
 433
 434     dirty_bitmap_mig_state.bulk_completed = true;
 435 }
 436
 437 /* for SaveVMHandlers */
 438 static void dirty_bitmap_save_cleanup(void *opaque)
 439 {
 440     dirty_bitmap_mig_cleanup();
 441 }
 442
 443 static int dirty_bitmap_save_iterate(QEMUFile *f, void *opaque)
 444 {
 445     trace_dirty_bitmap_save_iterate(migration_in_postcopy());
 446
 447     if (migration_in_postcopy() && !dirty_bitmap_mig_state.bulk_completed) {
 448         bulk_phase(f, true);
 449     }
 450
 451     qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
 452
 453     return dirty_bitmap_mig_state.bulk_completed;
 454 }
 455
 456 /* Called with iothread lock taken.  */
 457
 458 static int dirty_bitmap_save_complete(QEMUFile *f, void *opaque)
 459 {
 460     DirtyBitmapMigBitmapState *dbms;
 461     trace_dirty_bitmap_save_complete_enter();
 462
 463     if (!dirty_bitmap_mig_state.bulk_completed) {
 464         bulk_phase(f, false);
 465     }
 466
 467     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 468         send_bitmap_complete(f, dbms);
 469     }
 470
 471     qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
 472
 473     trace_dirty_bitmap_save_complete_finish();
 474
 475     dirty_bitmap_mig_cleanup();
 476     return 0;
 477 }
 478
 479 static void dirty_bitmap_save_pending(QEMUFile *f, void *opaque,
 480                                       uint64_t max_size,
 481                                       uint64_t *res_precopy_only,
 482                                       uint64_t *res_compatible,
 483                                       uint64_t *res_postcopy_only)
 484 {
 485     DirtyBitmapMigBitmapState *dbms;
 486     uint64_t pending = 0;
 487
 488     qemu_mutex_lock_iothread();
 489
 490     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 491         uint64_t gran = bdrv_dirty_bitmap_granularity(dbms->bitmap);
 492         uint64_t sectors = dbms->bulk_completed ? 0 :
 493                            dbms->total_sectors - dbms->cur_sector;
 494
 495         pending += DIV_ROUND_UP(sectors * BDRV_SECTOR_SIZE, gran);
 496     }
 497
 498     qemu_mutex_unlock_iothread();
 499
 500     trace_dirty_bitmap_save_pending(pending, max_size);
 501
 502     *res_postcopy_only += pending;
 503 }
 504
 505 /* First occurrence of this bitmap. It should be created if doesn't exist */
 506 static int dirty_bitmap_load_start(QEMUFile *f, DirtyBitmapLoadState *s)
 507 {
 508     Error *local_err = NULL;
 509     uint32_t granularity = qemu_get_be32(f);
 510     uint8_t flags = qemu_get_byte(f);
 511
 512     if (s->bitmap) {
 513         error_report("Bitmap with the same name ('%s') already exists on "
 514                      "destination", bdrv_dirty_bitmap_name(s->bitmap));
 515         return -EINVAL;
 516     } else {
 517         s->bitmap = bdrv_create_dirty_bitmap(s->bs, granularity,
 518                                              s->bitmap_name, &local_err);
 519         if (!s->bitmap) {
 520             error_report_err(local_err);
 521             return -EINVAL;
 522         }
 523     }
 524
 525     if (flags & DIRTY_BITMAP_MIG_START_FLAG_RESERVED_MASK) {
 526         error_report("Unknown flags in migrated dirty bitmap header: %x",
 527                      flags);
 528         return -EINVAL;
 529     }
 530
 531     if (flags & DIRTY_BITMAP_MIG_START_FLAG_PERSISTENT) {
 532         bdrv_dirty_bitmap_set_persistence(s->bitmap, true);
 533     }
 534
 535     bdrv_disable_dirty_bitmap(s->bitmap);
 536     if (flags & DIRTY_BITMAP_MIG_START_FLAG_ENABLED) {
 537         DirtyBitmapLoadBitmapState *b;
 538
 539         bdrv_dirty_bitmap_create_successor(s->bitmap, &local_err);
 540         if (local_err) {
 541             error_report_err(local_err);
 542             return -EINVAL;
 543         }
 544
 545         b = g_new(DirtyBitmapLoadBitmapState, 1);
 546         b->bs = s->bs;
 547         b->bitmap = s->bitmap;
 548         b->migrated = false;
 549         enabled_bitmaps = g_slist_prepend(enabled_bitmaps, b);
 550     }
 551
 552     return 0;
 553 }
 554
 555 void dirty_bitmap_mig_before_vm_start(void)
 556 {
 557     GSList *item;
 558
 559     qemu_mutex_lock(&finish_lock);
 560
 561     for (item = enabled_bitmaps; item; item = g_slist_next(item)) {
 562         DirtyBitmapLoadBitmapState *b = item->data;
 563
 564         if (b->migrated) {
 565             bdrv_enable_dirty_bitmap_locked(b->bitmap);
 566         } else {
 567             bdrv_dirty_bitmap_enable_successor(b->bitmap);
 568         }
 569
 570         g_free(b);
 571     }
 572
 573     g_slist_free(enabled_bitmaps);
 574     enabled_bitmaps = NULL;
 575
 576     qemu_mutex_unlock(&finish_lock);
 577 }
 578
 579 static void dirty_bitmap_load_complete(QEMUFile *f, DirtyBitmapLoadState *s)
 580 {
 581     GSList *item;
 582     trace_dirty_bitmap_load_complete();
 583     bdrv_dirty_bitmap_deserialize_finish(s->bitmap);
 584
 585     qemu_mutex_lock(&finish_lock);
 586
 587     for (item = enabled_bitmaps; item; item = g_slist_next(item)) {
 588         DirtyBitmapLoadBitmapState *b = item->data;
 589
 590         if (b->bitmap == s->bitmap) {
 591             b->migrated = true;
 592             break;
 593         }
 594     }
 595
 596     if (bdrv_dirty_bitmap_has_successor(s->bitmap)) {
 597         bdrv_dirty_bitmap_lock(s->bitmap);
 598         if (enabled_bitmaps == NULL) {
 599             /* in postcopy */
 600             bdrv_reclaim_dirty_bitmap_locked(s->bitmap, &error_abort);
 601             bdrv_enable_dirty_bitmap_locked(s->bitmap);
 602         } else {
 603             /* target not started, successor must be empty */
 604             int64_t count = bdrv_get_dirty_count(s->bitmap);
 605             BdrvDirtyBitmap *ret = bdrv_reclaim_dirty_bitmap_locked(s->bitmap,
 606                                                                     NULL);
 607             /* bdrv_reclaim_dirty_bitmap can fail only on no successor (it
 608              * must be) or on merge fail, but merge can't fail when second
 609              * bitmap is empty
 610              */
 611             assert(ret == s->bitmap &&
 612                    count == bdrv_get_dirty_count(s->bitmap));
 613         }
 614         bdrv_dirty_bitmap_unlock(s->bitmap);
 615     }
 616
 617     qemu_mutex_unlock(&finish_lock);
 618 }
 619
 620 static int dirty_bitmap_load_bits(QEMUFile *f, DirtyBitmapLoadState *s)
 621 {
 622     uint64_t first_byte = qemu_get_be64(f) << BDRV_SECTOR_BITS;
 623     uint64_t nr_bytes = (uint64_t)qemu_get_be32(f) << BDRV_SECTOR_BITS;
 624     trace_dirty_bitmap_load_bits_enter(first_byte >> BDRV_SECTOR_BITS,
 625                                        nr_bytes >> BDRV_SECTOR_BITS);
 626
 627     if (s->flags & DIRTY_BITMAP_MIG_FLAG_ZEROES) {
 628         trace_dirty_bitmap_load_bits_zeroes();
 629         bdrv_dirty_bitmap_deserialize_zeroes(s->bitmap, first_byte, nr_bytes,
 630                                              false);
 631     } else {
 632         size_t ret;
 633         uint8_t *buf;
 634         uint64_t buf_size = qemu_get_be64(f);
 635         uint64_t needed_size =
 636             bdrv_dirty_bitmap_serialization_size(s->bitmap,
 637                                                  first_byte, nr_bytes);
 638
 639         if (needed_size > buf_size ||
 640             buf_size > QEMU_ALIGN_UP(needed_size, 4 * sizeof(long))
 641              /* Here used same alignment as in send_bitmap_bits */
 642         ) {
 643             error_report("Migrated bitmap granularity doesn't "
 644                          "match the destination bitmap '%s' granularity",
 645                          bdrv_dirty_bitmap_name(s->bitmap));
 646             return -EINVAL;
 647         }
 648
 649         buf = g_malloc(buf_size);
 650         ret = qemu_get_buffer(f, buf, buf_size);
 651         if (ret != buf_size) {
 652             error_report("Failed to read bitmap bits");
 653             g_free(buf);
 654             return -EIO;
 655         }
 656
 657         bdrv_dirty_bitmap_deserialize_part(s->bitmap, buf, first_byte, nr_bytes,
 658                                            false);
 659         g_free(buf);
 660     }
 661
 662     return 0;
 663 }
 664
 665 static int dirty_bitmap_load_header(QEMUFile *f, DirtyBitmapLoadState *s)
 666 {
 667     Error *local_err = NULL;
 668     bool nothing;
 669     s->flags = qemu_get_bitmap_flags(f);
 670     trace_dirty_bitmap_load_header(s->flags);
 671
 672     nothing = s->flags == (s->flags & DIRTY_BITMAP_MIG_FLAG_EOS);
 673
 674     if (s->flags & DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME) {
 675         if (!qemu_get_counted_string(f, s->node_name)) {
 676             error_report("Unable to read node name string");
 677             return -EINVAL;
 678         }
 679         s->bs = bdrv_lookup_bs(s->node_name, s->node_name, &local_err);
 680         if (!s->bs) {
 681             error_report_err(local_err);
 682             return -EINVAL;
 683         }
 684     } else if (!s->bs && !nothing) {
 685         error_report("Error: block device name is not set");
 686         return -EINVAL;
 687     }
 688
 689     if (s->flags & DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME) {
 690         if (!qemu_get_counted_string(f, s->bitmap_name)) {
 691             error_report("Unable to read bitmap name string");
 692             return -EINVAL;
 693         }
 694         s->bitmap = bdrv_find_dirty_bitmap(s->bs, s->bitmap_name);
 695
 696         /* bitmap may be NULL here, it wouldn't be an error if it is the
 697          * first occurrence of the bitmap */
 698         if (!s->bitmap && !(s->flags & DIRTY_BITMAP_MIG_FLAG_START)) {
 699             error_report("Error: unknown dirty bitmap "
 700                          "'%s' for block device '%s'",
 701                          s->bitmap_name, s->node_name);
 702             return -EINVAL;
 703         }
 704     } else if (!s->bitmap && !nothing) {
 705         error_report("Error: block device name is not set");
 706         return -EINVAL;
 707     }
 708
 709     return 0;
 710 }
 711
 712 static int dirty_bitmap_load(QEMUFile *f, void *opaque, int version_id)
 713 {
 714     static DirtyBitmapLoadState s;
 715     int ret = 0;
 716
 717     trace_dirty_bitmap_load_enter();
 718
 719     if (version_id != 1) {
 720         return -EINVAL;
 721     }
 722
 723     do {
 724         ret = dirty_bitmap_load_header(f, &s);
 725         if (ret < 0) {
 726             return ret;
 727         }
 728
 729         if (s.flags & DIRTY_BITMAP_MIG_FLAG_START) {
 730             ret = dirty_bitmap_load_start(f, &s);
 731         } else if (s.flags & DIRTY_BITMAP_MIG_FLAG_COMPLETE) {
 732             dirty_bitmap_load_complete(f, &s);
 733         } else if (s.flags & DIRTY_BITMAP_MIG_FLAG_BITS) {
 734             ret = dirty_bitmap_load_bits(f, &s);
 735         }
 736
 737         if (!ret) {
 738             ret = qemu_file_get_error(f);
 739         }
 740
 741         if (ret) {
 742             return ret;
 743         }
 744     } while (!(s.flags & DIRTY_BITMAP_MIG_FLAG_EOS));
 745
 746     trace_dirty_bitmap_load_success();
 747     return 0;
 748 }
 749
 750 static int dirty_bitmap_save_setup(QEMUFile *f, void *opaque)
 751 {
 752     DirtyBitmapMigBitmapState *dbms = NULL;
 753     if (init_dirty_bitmap_migration() < 0) {
 754         return -1;
 755     }
 756
 757     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 758         send_bitmap_start(f, dbms);
 759     }
 760     qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
 761
 762     return 0;
 763 }
 764
 765 static bool dirty_bitmap_is_active(void *opaque)
 766 {
 767     return migrate_dirty_bitmaps() && !dirty_bitmap_mig_state.no_bitmaps;
 768 }
 769
 770 static bool dirty_bitmap_is_active_iterate(void *opaque)
 771 {
 772     return dirty_bitmap_is_active(opaque) && !runstate_is_running();
 773 }
 774
 775 static bool dirty_bitmap_has_postcopy(void *opaque)
 776 {
 777     return true;
 778 }
 779
 780 static SaveVMHandlers savevm_dirty_bitmap_handlers = {
 781     .save_setup = dirty_bitmap_save_setup,
 782     .save_live_complete_postcopy = dirty_bitmap_save_complete,
 783     .save_live_complete_precopy = dirty_bitmap_save_complete,
 784     .has_postcopy = dirty_bitmap_has_postcopy,
 785     .save_live_pending = dirty_bitmap_save_pending,
 786     .save_live_iterate = dirty_bitmap_save_iterate,
 787     .is_active_iterate = dirty_bitmap_is_active_iterate,
 788     .load_state = dirty_bitmap_load,
 789     .save_cleanup = dirty_bitmap_save_cleanup,
 790     .is_active = dirty_bitmap_is_active,
 791 };
 792
 793 void dirty_bitmap_mig_init(void)
 794 {
 795     QSIMPLEQ_INIT(&dirty_bitmap_mig_state.dbms_list);
 796
 797     register_savevm_live("dirty-bitmap", 0, 1,
 798                          &savevm_dirty_bitmap_handlers,
 799                          &dirty_bitmap_mig_state);
 800 }