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 "qemu/main-loop.h"
  66 #include "qemu/error-report.h"
  67 #include "migration/misc.h"
  68 #include "migration/migration.h"
  69 #include "qemu-file.h"
  70 #include "migration/vmstate.h"
  71 #include "migration/register.h"
  72 #include "qemu/hbitmap.h"
  73 #include "sysemu/sysemu.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(dbms_list, 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_qmp_locked(dbms->bitmap, false);
 265         bdrv_unref(dbms->bs);
 266         g_free(dbms);
 267     }
 268 }
 269
 270 /* Called with iothread lock taken. */
 271 static int init_dirty_bitmap_migration(void)
 272 {
 273     BlockDriverState *bs;
 274     BdrvDirtyBitmap *bitmap;
 275     DirtyBitmapMigBitmapState *dbms;
 276     BdrvNextIterator it;
 277
 278     dirty_bitmap_mig_state.bulk_completed = false;
 279     dirty_bitmap_mig_state.prev_bs = NULL;
 280     dirty_bitmap_mig_state.prev_bitmap = NULL;
 281     dirty_bitmap_mig_state.no_bitmaps = false;
 282
 283     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 284         const char *drive_name = bdrv_get_device_or_node_name(bs);
 285
 286         /* skip automatically inserted nodes */
 287         while (bs && bs->drv && bs->implicit) {
 288             bs = backing_bs(bs);
 289         }
 290
 291         for (bitmap = bdrv_dirty_bitmap_next(bs, NULL); bitmap;
 292              bitmap = bdrv_dirty_bitmap_next(bs, bitmap))
 293         {
 294             if (!bdrv_dirty_bitmap_name(bitmap)) {
 295                 continue;
 296             }
 297
 298             if (drive_name == NULL) {
 299                 error_report("Found bitmap '%s' in unnamed node %p. It can't "
 300                              "be migrated", bdrv_dirty_bitmap_name(bitmap), bs);
 301                 goto fail;
 302             }
 303
 304             if (bdrv_dirty_bitmap_frozen(bitmap)) {
 305                 error_report("Can't migrate frozen dirty bitmap: '%s",
 306                              bdrv_dirty_bitmap_name(bitmap));
 307                 goto fail;
 308             }
 309
 310             if (bdrv_dirty_bitmap_qmp_locked(bitmap)) {
 311                 error_report("Can't migrate locked dirty bitmap: '%s",
 312                              bdrv_dirty_bitmap_name(bitmap));
 313                 goto fail;
 314             }
 315
 316             bdrv_ref(bs);
 317             bdrv_dirty_bitmap_set_qmp_locked(bitmap, true);
 318
 319             dbms = g_new0(DirtyBitmapMigBitmapState, 1);
 320             dbms->bs = bs;
 321             dbms->node_name = drive_name;
 322             dbms->bitmap = bitmap;
 323             dbms->total_sectors = bdrv_nb_sectors(bs);
 324             dbms->sectors_per_chunk = CHUNK_SIZE * 8 *
 325                 bdrv_dirty_bitmap_granularity(bitmap) >> BDRV_SECTOR_BITS;
 326             if (bdrv_dirty_bitmap_enabled(bitmap)) {
 327                 dbms->flags |= DIRTY_BITMAP_MIG_START_FLAG_ENABLED;
 328             }
 329             if (bdrv_dirty_bitmap_get_persistance(bitmap)) {
 330                 dbms->flags |= DIRTY_BITMAP_MIG_START_FLAG_PERSISTENT;
 331             }
 332
 333             QSIMPLEQ_INSERT_TAIL(&dirty_bitmap_mig_state.dbms_list,
 334                                  dbms, entry);
 335         }
 336     }
 337
 338     /* unset persistance here, to not roll back it */
 339     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 340         bdrv_dirty_bitmap_set_persistance(dbms->bitmap, false);
 341     }
 342
 343     if (QSIMPLEQ_EMPTY(&dirty_bitmap_mig_state.dbms_list)) {
 344         dirty_bitmap_mig_state.no_bitmaps = true;
 345     }
 346
 347     return 0;
 348
 349 fail:
 350     dirty_bitmap_mig_cleanup();
 351
 352     return -1;
 353 }
 354
 355 /* Called with no lock taken.  */
 356 static void bulk_phase_send_chunk(QEMUFile *f, DirtyBitmapMigBitmapState *dbms)
 357 {
 358     uint32_t nr_sectors = MIN(dbms->total_sectors - dbms->cur_sector,
 359                              dbms->sectors_per_chunk);
 360
 361     send_bitmap_bits(f, dbms, dbms->cur_sector, nr_sectors);
 362
 363     dbms->cur_sector += nr_sectors;
 364     if (dbms->cur_sector >= dbms->total_sectors) {
 365         dbms->bulk_completed = true;
 366     }
 367 }
 368
 369 /* Called with no lock taken.  */
 370 static void bulk_phase(QEMUFile *f, bool limit)
 371 {
 372     DirtyBitmapMigBitmapState *dbms;
 373
 374     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 375         while (!dbms->bulk_completed) {
 376             bulk_phase_send_chunk(f, dbms);
 377             if (limit && qemu_file_rate_limit(f)) {
 378                 return;
 379             }
 380         }
 381     }
 382
 383     dirty_bitmap_mig_state.bulk_completed = true;
 384 }
 385
 386 /* for SaveVMHandlers */
 387 static void dirty_bitmap_save_cleanup(void *opaque)
 388 {
 389     dirty_bitmap_mig_cleanup();
 390 }
 391
 392 static int dirty_bitmap_save_iterate(QEMUFile *f, void *opaque)
 393 {
 394     trace_dirty_bitmap_save_iterate(migration_in_postcopy());
 395
 396     if (migration_in_postcopy() && !dirty_bitmap_mig_state.bulk_completed) {
 397         bulk_phase(f, true);
 398     }
 399
 400     qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
 401
 402     return dirty_bitmap_mig_state.bulk_completed;
 403 }
 404
 405 /* Called with iothread lock taken.  */
 406
 407 static int dirty_bitmap_save_complete(QEMUFile *f, void *opaque)
 408 {
 409     DirtyBitmapMigBitmapState *dbms;
 410     trace_dirty_bitmap_save_complete_enter();
 411
 412     if (!dirty_bitmap_mig_state.bulk_completed) {
 413         bulk_phase(f, false);
 414     }
 415
 416     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 417         send_bitmap_complete(f, dbms);
 418     }
 419
 420     qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
 421
 422     trace_dirty_bitmap_save_complete_finish();
 423
 424     dirty_bitmap_mig_cleanup();
 425     return 0;
 426 }
 427
 428 static void dirty_bitmap_save_pending(QEMUFile *f, void *opaque,
 429                                       uint64_t max_size,
 430                                       uint64_t *res_precopy_only,
 431                                       uint64_t *res_compatible,
 432                                       uint64_t *res_postcopy_only)
 433 {
 434     DirtyBitmapMigBitmapState *dbms;
 435     uint64_t pending = 0;
 436
 437     qemu_mutex_lock_iothread();
 438
 439     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 440         uint64_t gran = bdrv_dirty_bitmap_granularity(dbms->bitmap);
 441         uint64_t sectors = dbms->bulk_completed ? 0 :
 442                            dbms->total_sectors - dbms->cur_sector;
 443
 444         pending += DIV_ROUND_UP(sectors * BDRV_SECTOR_SIZE, gran);
 445     }
 446
 447     qemu_mutex_unlock_iothread();
 448
 449     trace_dirty_bitmap_save_pending(pending, max_size);
 450
 451     *res_postcopy_only += pending;
 452 }
 453
 454 /* First occurrence of this bitmap. It should be created if doesn't exist */
 455 static int dirty_bitmap_load_start(QEMUFile *f, DirtyBitmapLoadState *s)
 456 {
 457     Error *local_err = NULL;
 458     uint32_t granularity = qemu_get_be32(f);
 459     uint8_t flags = qemu_get_byte(f);
 460
 461     if (s->bitmap) {
 462         error_report("Bitmap with the same name ('%s') already exists on "
 463                      "destination", bdrv_dirty_bitmap_name(s->bitmap));
 464         return -EINVAL;
 465     } else {
 466         s->bitmap = bdrv_create_dirty_bitmap(s->bs, granularity,
 467                                              s->bitmap_name, &local_err);
 468         if (!s->bitmap) {
 469             error_report_err(local_err);
 470             return -EINVAL;
 471         }
 472     }
 473
 474     if (flags & DIRTY_BITMAP_MIG_START_FLAG_RESERVED_MASK) {
 475         error_report("Unknown flags in migrated dirty bitmap header: %x",
 476                      flags);
 477         return -EINVAL;
 478     }
 479
 480     if (flags & DIRTY_BITMAP_MIG_START_FLAG_PERSISTENT) {
 481         bdrv_dirty_bitmap_set_persistance(s->bitmap, true);
 482     }
 483
 484     bdrv_disable_dirty_bitmap(s->bitmap);
 485     if (flags & DIRTY_BITMAP_MIG_START_FLAG_ENABLED) {
 486         DirtyBitmapLoadBitmapState *b;
 487
 488         bdrv_dirty_bitmap_create_successor(s->bs, s->bitmap, &local_err);
 489         if (local_err) {
 490             error_report_err(local_err);
 491             return -EINVAL;
 492         }
 493
 494         b = g_new(DirtyBitmapLoadBitmapState, 1);
 495         b->bs = s->bs;
 496         b->bitmap = s->bitmap;
 497         b->migrated = false;
 498         enabled_bitmaps = g_slist_prepend(enabled_bitmaps, b);
 499     }
 500
 501     return 0;
 502 }
 503
 504 void dirty_bitmap_mig_before_vm_start(void)
 505 {
 506     GSList *item;
 507
 508     qemu_mutex_lock(&finish_lock);
 509
 510     for (item = enabled_bitmaps; item; item = g_slist_next(item)) {
 511         DirtyBitmapLoadBitmapState *b = item->data;
 512
 513         if (b->migrated) {
 514             bdrv_enable_dirty_bitmap(b->bitmap);
 515         } else {
 516             bdrv_dirty_bitmap_enable_successor(b->bitmap);
 517         }
 518
 519         g_free(b);
 520     }
 521
 522     g_slist_free(enabled_bitmaps);
 523     enabled_bitmaps = NULL;
 524
 525     qemu_mutex_unlock(&finish_lock);
 526 }
 527
 528 static void dirty_bitmap_load_complete(QEMUFile *f, DirtyBitmapLoadState *s)
 529 {
 530     GSList *item;
 531     trace_dirty_bitmap_load_complete();
 532     bdrv_dirty_bitmap_deserialize_finish(s->bitmap);
 533
 534     qemu_mutex_lock(&finish_lock);
 535
 536     for (item = enabled_bitmaps; item; item = g_slist_next(item)) {
 537         DirtyBitmapLoadBitmapState *b = item->data;
 538
 539         if (b->bitmap == s->bitmap) {
 540             b->migrated = true;
 541             break;
 542         }
 543     }
 544
 545     if (bdrv_dirty_bitmap_frozen(s->bitmap)) {
 546         bdrv_dirty_bitmap_lock(s->bitmap);
 547         if (enabled_bitmaps == NULL) {
 548             /* in postcopy */
 549             bdrv_reclaim_dirty_bitmap_locked(s->bs, s->bitmap, &error_abort);
 550             bdrv_enable_dirty_bitmap(s->bitmap);
 551         } else {
 552             /* target not started, successor must be empty */
 553             int64_t count = bdrv_get_dirty_count(s->bitmap);
 554             BdrvDirtyBitmap *ret = bdrv_reclaim_dirty_bitmap_locked(s->bs,
 555                                                                     s->bitmap,
 556                                                                     NULL);
 557             /* bdrv_reclaim_dirty_bitmap can fail only on no successor (it
 558              * must be) or on merge fail, but merge can't fail when second
 559              * bitmap is empty
 560              */
 561             assert(ret == s->bitmap &&
 562                    count == bdrv_get_dirty_count(s->bitmap));
 563         }
 564         bdrv_dirty_bitmap_unlock(s->bitmap);
 565     }
 566
 567     qemu_mutex_unlock(&finish_lock);
 568 }
 569
 570 static int dirty_bitmap_load_bits(QEMUFile *f, DirtyBitmapLoadState *s)
 571 {
 572     uint64_t first_byte = qemu_get_be64(f) << BDRV_SECTOR_BITS;
 573     uint64_t nr_bytes = (uint64_t)qemu_get_be32(f) << BDRV_SECTOR_BITS;
 574     trace_dirty_bitmap_load_bits_enter(first_byte >> BDRV_SECTOR_BITS,
 575                                        nr_bytes >> BDRV_SECTOR_BITS);
 576
 577     if (s->flags & DIRTY_BITMAP_MIG_FLAG_ZEROES) {
 578         trace_dirty_bitmap_load_bits_zeroes();
 579         bdrv_dirty_bitmap_deserialize_zeroes(s->bitmap, first_byte, nr_bytes,
 580                                              false);
 581     } else {
 582         size_t ret;
 583         uint8_t *buf;
 584         uint64_t buf_size = qemu_get_be64(f);
 585         uint64_t needed_size =
 586             bdrv_dirty_bitmap_serialization_size(s->bitmap,
 587                                                  first_byte, nr_bytes);
 588
 589         if (needed_size > buf_size ||
 590             buf_size > QEMU_ALIGN_UP(needed_size, 4 * sizeof(long))
 591              /* Here used same alignment as in send_bitmap_bits */
 592         ) {
 593             error_report("Migrated bitmap granularity doesn't "
 594                          "match the destination bitmap '%s' granularity",
 595                          bdrv_dirty_bitmap_name(s->bitmap));
 596             return -EINVAL;
 597         }
 598
 599         buf = g_malloc(buf_size);
 600         ret = qemu_get_buffer(f, buf, buf_size);
 601         if (ret != buf_size) {
 602             error_report("Failed to read bitmap bits");
 603             g_free(buf);
 604             return -EIO;
 605         }
 606
 607         bdrv_dirty_bitmap_deserialize_part(s->bitmap, buf, first_byte, nr_bytes,
 608                                            false);
 609         g_free(buf);
 610     }
 611
 612     return 0;
 613 }
 614
 615 static int dirty_bitmap_load_header(QEMUFile *f, DirtyBitmapLoadState *s)
 616 {
 617     Error *local_err = NULL;
 618     bool nothing;
 619     s->flags = qemu_get_bitmap_flags(f);
 620     trace_dirty_bitmap_load_header(s->flags);
 621
 622     nothing = s->flags == (s->flags & DIRTY_BITMAP_MIG_FLAG_EOS);
 623
 624     if (s->flags & DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME) {
 625         if (!qemu_get_counted_string(f, s->node_name)) {
 626             error_report("Unable to read node name string");
 627             return -EINVAL;
 628         }
 629         s->bs = bdrv_lookup_bs(s->node_name, s->node_name, &local_err);
 630         if (!s->bs) {
 631             error_report_err(local_err);
 632             return -EINVAL;
 633         }
 634     } else if (!s->bs && !nothing) {
 635         error_report("Error: block device name is not set");
 636         return -EINVAL;
 637     }
 638
 639     if (s->flags & DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME) {
 640         if (!qemu_get_counted_string(f, s->bitmap_name)) {
 641             error_report("Unable to read bitmap name string");
 642             return -EINVAL;
 643         }
 644         s->bitmap = bdrv_find_dirty_bitmap(s->bs, s->bitmap_name);
 645
 646         /* bitmap may be NULL here, it wouldn't be an error if it is the
 647          * first occurrence of the bitmap */
 648         if (!s->bitmap && !(s->flags & DIRTY_BITMAP_MIG_FLAG_START)) {
 649             error_report("Error: unknown dirty bitmap "
 650                          "'%s' for block device '%s'",
 651                          s->bitmap_name, s->node_name);
 652             return -EINVAL;
 653         }
 654     } else if (!s->bitmap && !nothing) {
 655         error_report("Error: block device name is not set");
 656         return -EINVAL;
 657     }
 658
 659     return 0;
 660 }
 661
 662 static int dirty_bitmap_load(QEMUFile *f, void *opaque, int version_id)
 663 {
 664     static DirtyBitmapLoadState s;
 665     int ret = 0;
 666
 667     trace_dirty_bitmap_load_enter();
 668
 669     if (version_id != 1) {
 670         return -EINVAL;
 671     }
 672
 673     do {
 674         ret = dirty_bitmap_load_header(f, &s);
 675         if (ret < 0) {
 676             return ret;
 677         }
 678
 679         if (s.flags & DIRTY_BITMAP_MIG_FLAG_START) {
 680             ret = dirty_bitmap_load_start(f, &s);
 681         } else if (s.flags & DIRTY_BITMAP_MIG_FLAG_COMPLETE) {
 682             dirty_bitmap_load_complete(f, &s);
 683         } else if (s.flags & DIRTY_BITMAP_MIG_FLAG_BITS) {
 684             ret = dirty_bitmap_load_bits(f, &s);
 685         }
 686
 687         if (!ret) {
 688             ret = qemu_file_get_error(f);
 689         }
 690
 691         if (ret) {
 692             return ret;
 693         }
 694     } while (!(s.flags & DIRTY_BITMAP_MIG_FLAG_EOS));
 695
 696     trace_dirty_bitmap_load_success();
 697     return 0;
 698 }
 699
 700 static int dirty_bitmap_save_setup(QEMUFile *f, void *opaque)
 701 {
 702     DirtyBitmapMigBitmapState *dbms = NULL;
 703     if (init_dirty_bitmap_migration() < 0) {
 704         return -1;
 705     }
 706
 707     QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) {
 708         send_bitmap_start(f, dbms);
 709     }
 710     qemu_put_bitmap_flags(f, DIRTY_BITMAP_MIG_FLAG_EOS);
 711
 712     return 0;
 713 }
 714
 715 static bool dirty_bitmap_is_active(void *opaque)
 716 {
 717     return migrate_dirty_bitmaps() && !dirty_bitmap_mig_state.no_bitmaps;
 718 }
 719
 720 static bool dirty_bitmap_is_active_iterate(void *opaque)
 721 {
 722     return dirty_bitmap_is_active(opaque) && !runstate_is_running();
 723 }
 724
 725 static bool dirty_bitmap_has_postcopy(void *opaque)
 726 {
 727     return true;
 728 }
 729
 730 static SaveVMHandlers savevm_dirty_bitmap_handlers = {
 731     .save_setup = dirty_bitmap_save_setup,
 732     .save_live_complete_postcopy = dirty_bitmap_save_complete,
 733     .save_live_complete_precopy = dirty_bitmap_save_complete,
 734     .has_postcopy = dirty_bitmap_has_postcopy,
 735     .save_live_pending = dirty_bitmap_save_pending,
 736     .save_live_iterate = dirty_bitmap_save_iterate,
 737     .is_active_iterate = dirty_bitmap_is_active_iterate,
 738     .load_state = dirty_bitmap_load,
 739     .save_cleanup = dirty_bitmap_save_cleanup,
 740     .is_active = dirty_bitmap_is_active,
 741 };
 742
 743 void dirty_bitmap_mig_init(void)
 744 {
 745     QSIMPLEQ_INIT(&dirty_bitmap_mig_state.dbms_list);
 746
 747     register_savevm_live(NULL, "dirty-bitmap", 0, 1,
 748                          &savevm_dirty_bitmap_handlers,
 749                          &dirty_bitmap_mig_state);
 750 }