summaryrefslogtreecommitdiff
path: root/block/vdi.c
blob: 0c34f6bae4662eacab5c04613430e0d9cdb35dd9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
/*
 * Block driver for the Virtual Disk Image (VDI) format
 *
 * Copyright (c) 2009, 2012 Stefan Weil
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) version 3 or any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Reference:
 * http://forums.virtualbox.org/viewtopic.php?t=8046
 *
 * This driver supports create / read / write operations on VDI images.
 *
 * Todo (see also TODO in code):
 *
 * Some features like snapshots are still missing.
 *
 * Deallocation of zero-filled blocks and shrinking images are missing, too
 * (might be added to common block layer).
 *
 * Allocation of blocks could be optimized (less writes to block map and
 * header).
 *
 * Read and write of adjacent blocks could be done in one operation
 * (current code uses one operation per block (1 MiB).
 *
 * The code is not thread safe (missing locks for changes in header and
 * block table, no problem with current QEMU).
 *
 * Hints:
 *
 * Blocks (VDI documentation) correspond to clusters (QEMU).
 * QEMU's backing files could be implemented using VDI snapshot files (TODO).
 * VDI snapshot files may also contain the complete machine state.
 * Maybe this machine state can be converted to QEMU PC machine snapshot data.
 *
 * The driver keeps a block cache (little endian entries) in memory.
 * For the standard block size (1 MiB), a 1 TiB disk will use 4 MiB RAM,
 * so this seems to be reasonable.
 */

#include "qemu/osdep.h"
#include "qemu/units.h"
#include "qapi/error.h"
#include "qapi/qobject-input-visitor.h"
#include "qapi/qapi-visit-block-core.h"
#include "block/block_int.h"
#include "block/qdict.h"
#include "sysemu/block-backend.h"
#include "qemu/module.h"
#include "qemu/option.h"
#include "qemu/bswap.h"
#include "migration/blocker.h"
#include "qemu/coroutine.h"
#include "qemu/cutils.h"
#include "qemu/uuid.h"

/* Code configuration options. */

/* Enable debug messages. */
//~ #define CONFIG_VDI_DEBUG

/* Support write operations on VDI images. */
#define CONFIG_VDI_WRITE

/* Support non-standard block (cluster) size. This is untested.
 * Maybe it will be needed for very large images.
 */
//~ #define CONFIG_VDI_BLOCK_SIZE

/* Support static (fixed, pre-allocated) images. */
#define CONFIG_VDI_STATIC_IMAGE

/* Command line option for static images. */
#define BLOCK_OPT_STATIC "static"

#define SECTOR_SIZE 512
#define DEFAULT_CLUSTER_SIZE S_1MiB

#if defined(CONFIG_VDI_DEBUG)
#define VDI_DEBUG 1
#else
#define VDI_DEBUG 0
#endif

#define logout(fmt, ...) \
    do {                                                                \
        if (VDI_DEBUG) {                                                \
            fprintf(stderr, "vdi\t%-24s" fmt, __func__, ##__VA_ARGS__); \
        }                                                               \
    } while (0)

/* Image signature. */
#define VDI_SIGNATURE 0xbeda107f

/* Image version. */
#define VDI_VERSION_1_1 0x00010001

/* Image type. */
#define VDI_TYPE_DYNAMIC 1
#define VDI_TYPE_STATIC  2

/* Innotek / SUN images use these strings in header.text:
 * "<<< innotek VirtualBox Disk Image >>>\n"
 * "<<< Sun xVM VirtualBox Disk Image >>>\n"
 * "<<< Sun VirtualBox Disk Image >>>\n"
 * The value does not matter, so QEMU created images use a different text.
 */
#define VDI_TEXT "<<< QEMU VM Virtual Disk Image >>>\n"

/* A never-allocated block; semantically arbitrary content. */
#define VDI_UNALLOCATED 0xffffffffU

/* A discarded (no longer allocated) block; semantically zero-filled. */
#define VDI_DISCARDED   0xfffffffeU

#define VDI_IS_ALLOCATED(X) ((X) < VDI_DISCARDED)

/* The bmap will take up VDI_BLOCKS_IN_IMAGE_MAX * sizeof(uint32_t) bytes; since
 * the bmap is read and written in a single operation, its size needs to be
 * limited to INT_MAX; furthermore, when opening an image, the bmap size is
 * rounded up to be aligned on BDRV_SECTOR_SIZE.
 * Therefore this should satisfy the following:
 * VDI_BLOCKS_IN_IMAGE_MAX * sizeof(uint32_t) + BDRV_SECTOR_SIZE == INT_MAX + 1
 * (INT_MAX + 1 is the first value not representable as an int)
 * This guarantees that any value below or equal to the constant will, when
 * multiplied by sizeof(uint32_t) and rounded up to a BDRV_SECTOR_SIZE boundary,
 * still be below or equal to INT_MAX. */
#define VDI_BLOCKS_IN_IMAGE_MAX \
    ((unsigned)((INT_MAX + 1u - BDRV_SECTOR_SIZE) / sizeof(uint32_t)))
#define VDI_DISK_SIZE_MAX        ((uint64_t)VDI_BLOCKS_IN_IMAGE_MAX * \
                                  (uint64_t)DEFAULT_CLUSTER_SIZE)

static QemuOptsList vdi_create_opts;

typedef struct {
    char text[0x40];
    uint32_t signature;
    uint32_t version;
    uint32_t header_size;
    uint32_t image_type;
    uint32_t image_flags;
    char description[256];
    uint32_t offset_bmap;
    uint32_t offset_data;
    uint32_t cylinders;         /* disk geometry, unused here */
    uint32_t heads;             /* disk geometry, unused here */
    uint32_t sectors;           /* disk geometry, unused here */
    uint32_t sector_size;
    uint32_t unused1;
    uint64_t disk_size;
    uint32_t block_size;
    uint32_t block_extra;       /* unused here */
    uint32_t blocks_in_image;
    uint32_t blocks_allocated;
    QemuUUID uuid_image;
    QemuUUID uuid_last_snap;
    QemuUUID uuid_link;
    QemuUUID uuid_parent;
    uint64_t unused2[7];
} QEMU_PACKED VdiHeader;

typedef struct {
    /* The block map entries are little endian (even in memory). */
    uint32_t *bmap;
    /* Size of block (bytes). */
    uint32_t block_size;
    /* First sector of block map. */
    uint32_t bmap_sector;
    /* VDI header (converted to host endianness). */
    VdiHeader header;

    CoRwlock bmap_lock;

    Error *migration_blocker;
} BDRVVdiState;

static void vdi_header_to_cpu(VdiHeader *header)
{
    header->signature = le32_to_cpu(header->signature);
    header->version = le32_to_cpu(header->version);
    header->header_size = le32_to_cpu(header->header_size);
    header->image_type = le32_to_cpu(header->image_type);
    header->image_flags = le32_to_cpu(header->image_flags);
    header->offset_bmap = le32_to_cpu(header->offset_bmap);
    header->offset_data = le32_to_cpu(header->offset_data);
    header->cylinders = le32_to_cpu(header->cylinders);
    header->heads = le32_to_cpu(header->heads);
    header->sectors = le32_to_cpu(header->sectors);
    header->sector_size = le32_to_cpu(header->sector_size);
    header->disk_size = le64_to_cpu(header->disk_size);
    header->block_size = le32_to_cpu(header->block_size);
    header->block_extra = le32_to_cpu(header->block_extra);
    header->blocks_in_image = le32_to_cpu(header->blocks_in_image);
    header->blocks_allocated = le32_to_cpu(header->blocks_allocated);
    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
}

static void vdi_header_to_le(VdiHeader *header)
{
    header->signature = cpu_to_le32(header->signature);
    header->version = cpu_to_le32(header->version);
    header->header_size = cpu_to_le32(header->header_size);
    header->image_type = cpu_to_le32(header->image_type);
    header->image_flags = cpu_to_le32(header->image_flags);
    header->offset_bmap = cpu_to_le32(header->offset_bmap);
    header->offset_data = cpu_to_le32(header->offset_data);
    header->cylinders = cpu_to_le32(header->cylinders);
    header->heads = cpu_to_le32(header->heads);
    header->sectors = cpu_to_le32(header->sectors);
    header->sector_size = cpu_to_le32(header->sector_size);
    header->disk_size = cpu_to_le64(header->disk_size);
    header->block_size = cpu_to_le32(header->block_size);
    header->block_extra = cpu_to_le32(header->block_extra);
    header->blocks_in_image = cpu_to_le32(header->blocks_in_image);
    header->blocks_allocated = cpu_to_le32(header->blocks_allocated);
    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
}

static void vdi_header_print(VdiHeader *header)
{
    char uuidstr[37];
    QemuUUID uuid;
    logout("text        %s", header->text);
    logout("signature   0x%08x\n", header->signature);
    logout("header size 0x%04x\n", header->header_size);
    logout("image type  0x%04x\n", header->image_type);
    logout("image flags 0x%04x\n", header->image_flags);
    logout("description %s\n", header->description);
    logout("offset bmap 0x%04x\n", header->offset_bmap);
    logout("offset data 0x%04x\n", header->offset_data);
    logout("cylinders   0x%04x\n", header->cylinders);
    logout("heads       0x%04x\n", header->heads);
    logout("sectors     0x%04x\n", header->sectors);
    logout("sector size 0x%04x\n", header->sector_size);
    logout("image size  0x%" PRIx64 " B (%" PRIu64 " MiB)\n",
           header->disk_size, header->disk_size / MiB);
    logout("block size  0x%04x\n", header->block_size);
    logout("block extra 0x%04x\n", header->block_extra);
    logout("blocks tot. 0x%04x\n", header->blocks_in_image);
    logout("blocks all. 0x%04x\n", header->blocks_allocated);
    uuid = header->uuid_image;
    qemu_uuid_unparse(&uuid, uuidstr);
    logout("uuid image  %s\n", uuidstr);
    uuid = header->uuid_last_snap;
    qemu_uuid_unparse(&uuid, uuidstr);
    logout("uuid snap   %s\n", uuidstr);
    uuid = header->uuid_link;
    qemu_uuid_unparse(&uuid, uuidstr);
    logout("uuid link   %s\n", uuidstr);
    uuid = header->uuid_parent;
    qemu_uuid_unparse(&uuid, uuidstr);
    logout("uuid parent %s\n", uuidstr);
}

static int coroutine_fn vdi_co_check(BlockDriverState *bs, BdrvCheckResult *res,
                                     BdrvCheckMode fix)
{
    /* TODO: additional checks possible. */
    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
    uint32_t blocks_allocated = 0;
    uint32_t block;
    uint32_t *bmap;
    logout("\n");

    if (fix) {
        return -ENOTSUP;
    }

    bmap = g_try_new(uint32_t, s->header.blocks_in_image);
    if (s->header.blocks_in_image && bmap == NULL) {
        res->check_errors++;
        return -ENOMEM;
    }

    memset(bmap, 0xff, s->header.blocks_in_image * sizeof(uint32_t));

    /* Check block map and value of blocks_allocated. */
    for (block = 0; block < s->header.blocks_in_image; block++) {
        uint32_t bmap_entry = le32_to_cpu(s->bmap[block]);
        if (VDI_IS_ALLOCATED(bmap_entry)) {
            if (bmap_entry < s->header.blocks_in_image) {
                blocks_allocated++;
                if (!VDI_IS_ALLOCATED(bmap[bmap_entry])) {
                    bmap[bmap_entry] = bmap_entry;
                } else {
                    fprintf(stderr, "ERROR: block index %" PRIu32
                            " also used by %" PRIu32 "\n", bmap[bmap_entry], bmap_entry);
                    res->corruptions++;
                }
            } else {
                fprintf(stderr, "ERROR: block index %" PRIu32
                        " too large, is %" PRIu32 "\n", block, bmap_entry);
                res->corruptions++;
            }
        }
    }
    if (blocks_allocated != s->header.blocks_allocated) {
        fprintf(stderr, "ERROR: allocated blocks mismatch, is %" PRIu32
               ", should be %" PRIu32 "\n",
               blocks_allocated, s->header.blocks_allocated);
        res->corruptions++;
    }

    g_free(bmap);

    return 0;
}

static int vdi_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
    /* TODO: vdi_get_info would be needed for machine snapshots.
       vm_state_offset is still missing. */
    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
    logout("\n");
    bdi->cluster_size = s->block_size;
    bdi->vm_state_offset = 0;
    bdi->unallocated_blocks_are_zero = true;
    return 0;
}

static int vdi_make_empty(BlockDriverState *bs)
{
    /* TODO: missing code. */
    logout("\n");
    /* The return value for missing code must be 0, see block.c. */
    return 0;
}

static int vdi_probe(const uint8_t *buf, int buf_size, const char *filename)
{
    const VdiHeader *header = (const VdiHeader *)buf;
    int ret = 0;

    logout("\n");

    if (buf_size < sizeof(*header)) {
        /* Header too small, no VDI. */
    } else if (le32_to_cpu(header->signature) == VDI_SIGNATURE) {
        ret = 100;
    }

    if (ret == 0) {
        logout("no vdi image\n");
    } else {
        logout("%s", header->text);
    }

    return ret;
}

static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
                    Error **errp)
{
    BDRVVdiState *s = bs->opaque;
    VdiHeader header;
    size_t bmap_size;
    int ret;
    Error *local_err = NULL;
    QemuUUID uuid_link, uuid_parent;

    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
                               false, errp);
    if (!bs->file) {
        return -EINVAL;
    }

    logout("\n");

    ret = bdrv_read(bs->file, 0, (uint8_t *)&header, 1);
    if (ret < 0) {
        goto fail;
    }

    vdi_header_to_cpu(&header);
    if (VDI_DEBUG) {
        vdi_header_print(&header);
    }

    if (header.disk_size > VDI_DISK_SIZE_MAX) {
        error_setg(errp, "Unsupported VDI image size (size is 0x%" PRIx64
                          ", max supported is 0x%" PRIx64 ")",
                          header.disk_size, VDI_DISK_SIZE_MAX);
        ret = -ENOTSUP;
        goto fail;
    }

    uuid_link = header.uuid_link;
    uuid_parent = header.uuid_parent;

    if (header.disk_size % SECTOR_SIZE != 0) {
        /* 'VBoxManage convertfromraw' can create images with odd disk sizes.
           We accept them but round the disk size to the next multiple of
           SECTOR_SIZE. */
        logout("odd disk size %" PRIu64 " B, round up\n", header.disk_size);
        header.disk_size = ROUND_UP(header.disk_size, SECTOR_SIZE);
    }

    if (header.signature != VDI_SIGNATURE) {
        error_setg(errp, "Image not in VDI format (bad signature %08" PRIx32
                   ")", header.signature);
        ret = -EINVAL;
        goto fail;
    } else if (header.version != VDI_VERSION_1_1) {
        error_setg(errp, "unsupported VDI image (version %" PRIu32 ".%" PRIu32
                   ")", header.version >> 16, header.version & 0xffff);
        ret = -ENOTSUP;
        goto fail;
    } else if (header.offset_bmap % SECTOR_SIZE != 0) {
        /* We only support block maps which start on a sector boundary. */
        error_setg(errp, "unsupported VDI image (unaligned block map offset "
                   "0x%" PRIx32 ")", header.offset_bmap);
        ret = -ENOTSUP;
        goto fail;
    } else if (header.offset_data % SECTOR_SIZE != 0) {
        /* We only support data blocks which start on a sector boundary. */
        error_setg(errp, "unsupported VDI image (unaligned data offset 0x%"
                   PRIx32 ")", header.offset_data);
        ret = -ENOTSUP;
        goto fail;
    } else if (header.sector_size != SECTOR_SIZE) {
        error_setg(errp, "unsupported VDI image (sector size %" PRIu32
                   " is not %u)", header.sector_size, SECTOR_SIZE);
        ret = -ENOTSUP;
        goto fail;
    } else if (header.block_size != DEFAULT_CLUSTER_SIZE) {
        error_setg(errp, "unsupported VDI image (block size %" PRIu32
                         " is not %" PRIu32 ")",
                   header.block_size, DEFAULT_CLUSTER_SIZE);
        ret = -ENOTSUP;
        goto fail;
    } else if (header.disk_size >
               (uint64_t)header.blocks_in_image * header.block_size) {
        error_setg(errp, "unsupported VDI image (disk size %" PRIu64 ", "
                   "image bitmap has room for %" PRIu64 ")",
                   header.disk_size,
                   (uint64_t)header.blocks_in_image * header.block_size);
        ret = -ENOTSUP;
        goto fail;
    } else if (!qemu_uuid_is_null(&uuid_link)) {
        error_setg(errp, "unsupported VDI image (non-NULL link UUID)");
        ret = -ENOTSUP;
        goto fail;
    } else if (!qemu_uuid_is_null(&uuid_parent)) {
        error_setg(errp, "unsupported VDI image (non-NULL parent UUID)");
        ret = -ENOTSUP;
        goto fail;
    } else if (header.blocks_in_image > VDI_BLOCKS_IN_IMAGE_MAX) {
        error_setg(errp, "unsupported VDI image "
                         "(too many blocks %u, max is %u)",
                          header.blocks_in_image, VDI_BLOCKS_IN_IMAGE_MAX);
        ret = -ENOTSUP;
        goto fail;
    }

    bs->total_sectors = header.disk_size / SECTOR_SIZE;

    s->block_size = header.block_size;
    s->bmap_sector = header.offset_bmap / SECTOR_SIZE;
    s->header = header;

    bmap_size = header.blocks_in_image * sizeof(uint32_t);
    bmap_size = DIV_ROUND_UP(bmap_size, SECTOR_SIZE);
    s->bmap = qemu_try_blockalign(bs->file->bs, bmap_size * SECTOR_SIZE);
    if (s->bmap == NULL) {
        ret = -ENOMEM;
        goto fail;
    }

    ret = bdrv_read(bs->file, s->bmap_sector, (uint8_t *)s->bmap,
                    bmap_size);
    if (ret < 0) {
        goto fail_free_bmap;
    }

    /* Disable migration when vdi images are used */
    error_setg(&s->migration_blocker, "The vdi format used by node '%s' "
               "does not support live migration",
               bdrv_get_device_or_node_name(bs));
    ret = migrate_add_blocker(s->migration_blocker, &local_err);
    if (local_err) {
        error_propagate(errp, local_err);
        error_free(s->migration_blocker);
        goto fail_free_bmap;
    }

    qemu_co_rwlock_init(&s->bmap_lock);

    return 0;

 fail_free_bmap:
    qemu_vfree(s->bmap);

 fail:
    return ret;
}

static int vdi_reopen_prepare(BDRVReopenState *state,
                              BlockReopenQueue *queue, Error **errp)
{
    return 0;
}

static int coroutine_fn vdi_co_block_status(BlockDriverState *bs,
                                            bool want_zero,
                                            int64_t offset, int64_t bytes,
                                            int64_t *pnum, int64_t *map,
                                            BlockDriverState **file)
{
    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
    size_t bmap_index = offset / s->block_size;
    size_t index_in_block = offset % s->block_size;
    uint32_t bmap_entry = le32_to_cpu(s->bmap[bmap_index]);
    int result;

    logout("%p, %" PRId64 ", %" PRId64 ", %p\n", bs, offset, bytes, pnum);
    *pnum = MIN(s->block_size - index_in_block, bytes);
    result = VDI_IS_ALLOCATED(bmap_entry);
    if (!result) {
        return 0;
    }

    *map = s->header.offset_data + (uint64_t)bmap_entry * s->block_size +
        index_in_block;
    *file = bs->file->bs;
    return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID;
}

static int coroutine_fn
vdi_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
              QEMUIOVector *qiov, int flags)
{
    BDRVVdiState *s = bs->opaque;
    QEMUIOVector local_qiov;
    uint32_t bmap_entry;
    uint32_t block_index;
    uint32_t offset_in_block;
    uint32_t n_bytes;
    uint64_t bytes_done = 0;
    int ret = 0;

    logout("\n");

    qemu_iovec_init(&local_qiov, qiov->niov);

    while (ret >= 0 && bytes > 0) {
        block_index = offset / s->block_size;
        offset_in_block = offset % s->block_size;
        n_bytes = MIN(bytes, s->block_size - offset_in_block);

        logout("will read %u bytes starting at offset %" PRIu64 "\n",
               n_bytes, offset);

        /* prepare next AIO request */
        qemu_co_rwlock_rdlock(&s->bmap_lock);
        bmap_entry = le32_to_cpu(s->bmap[block_index]);
        qemu_co_rwlock_unlock(&s->bmap_lock);
        if (!VDI_IS_ALLOCATED(bmap_entry)) {
            /* Block not allocated, return zeros, no need to wait. */
            qemu_iovec_memset(qiov, bytes_done, 0, n_bytes);
            ret = 0;
        } else {
            uint64_t data_offset = s->header.offset_data +
                                   (uint64_t)bmap_entry * s->block_size +
                                   offset_in_block;

            qemu_iovec_reset(&local_qiov);
            qemu_iovec_concat(&local_qiov, qiov, bytes_done, n_bytes);

            ret = bdrv_co_preadv(bs->file, data_offset, n_bytes,
                                 &local_qiov, 0);
        }
        logout("%u bytes read\n", n_bytes);

        bytes -= n_bytes;
        offset += n_bytes;
        bytes_done += n_bytes;
    }

    qemu_iovec_destroy(&local_qiov);

    return ret;
}

static int coroutine_fn
vdi_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
               QEMUIOVector *qiov, int flags)
{
    BDRVVdiState *s = bs->opaque;
    QEMUIOVector local_qiov;
    uint32_t bmap_entry;
    uint32_t block_index;
    uint32_t offset_in_block;
    uint32_t n_bytes;
    uint64_t data_offset;
    uint32_t bmap_first = VDI_UNALLOCATED;
    uint32_t bmap_last = VDI_UNALLOCATED;
    uint8_t *block = NULL;
    uint64_t bytes_done = 0;
    int ret = 0;

    logout("\n");

    qemu_iovec_init(&local_qiov, qiov->niov);

    while (ret >= 0 && bytes > 0) {
        block_index = offset / s->block_size;
        offset_in_block = offset % s->block_size;
        n_bytes = MIN(bytes, s->block_size - offset_in_block);

        logout("will write %u bytes starting at offset %" PRIu64 "\n",
               n_bytes, offset);

        /* prepare next AIO request */
        qemu_co_rwlock_rdlock(&s->bmap_lock);
        bmap_entry = le32_to_cpu(s->bmap[block_index]);
        if (!VDI_IS_ALLOCATED(bmap_entry)) {
            /* Allocate new block and write to it. */
            uint64_t data_offset;
            qemu_co_rwlock_upgrade(&s->bmap_lock);
            bmap_entry = le32_to_cpu(s->bmap[block_index]);
            if (VDI_IS_ALLOCATED(bmap_entry)) {
                /* A concurrent allocation did the work for us.  */
                qemu_co_rwlock_downgrade(&s->bmap_lock);
                goto nonallocating_write;
            }

            bmap_entry = s->header.blocks_allocated;
            s->bmap[block_index] = cpu_to_le32(bmap_entry);
            s->header.blocks_allocated++;
            data_offset = s->header.offset_data +
                          (uint64_t)bmap_entry * s->block_size;
            if (block == NULL) {
                block = g_malloc(s->block_size);
                bmap_first = block_index;
            }
            bmap_last = block_index;
            /* Copy data to be written to new block and zero unused parts. */
            memset(block, 0, offset_in_block);
            qemu_iovec_to_buf(qiov, bytes_done, block + offset_in_block,
                              n_bytes);
            memset(block + offset_in_block + n_bytes, 0,
                   s->block_size - n_bytes - offset_in_block);

            /* Write the new block under CoRwLock write-side protection,
             * so this full-cluster write does not overlap a partial write
             * of the same cluster, issued from the "else" branch.
             */
            ret = bdrv_pwrite(bs->file, data_offset, block, s->block_size);
            qemu_co_rwlock_unlock(&s->bmap_lock);
        } else {
nonallocating_write:
            data_offset = s->header.offset_data +
                           (uint64_t)bmap_entry * s->block_size +
                           offset_in_block;
            qemu_co_rwlock_unlock(&s->bmap_lock);

            qemu_iovec_reset(&local_qiov);
            qemu_iovec_concat(&local_qiov, qiov, bytes_done, n_bytes);

            ret = bdrv_co_pwritev(bs->file, data_offset, n_bytes,
                                  &local_qiov, 0);
        }

        bytes -= n_bytes;
        offset += n_bytes;
        bytes_done += n_bytes;

        logout("%u bytes written\n", n_bytes);
    }

    qemu_iovec_destroy(&local_qiov);

    logout("finished data write\n");
    if (ret < 0) {
        return ret;
    }

    if (block) {
        /* One or more new blocks were allocated. */
        VdiHeader *header = (VdiHeader *) block;
        uint8_t *base;
        uint64_t offset;
        uint32_t n_sectors;

        logout("now writing modified header\n");
        assert(VDI_IS_ALLOCATED(bmap_first));
        *header = s->header;
        vdi_header_to_le(header);
        ret = bdrv_write(bs->file, 0, block, 1);
        g_free(block);
        block = NULL;

        if (ret < 0) {
            return ret;
        }

        logout("now writing modified block map entry %u...%u\n",
               bmap_first, bmap_last);
        /* Write modified sectors from block map. */
        bmap_first /= (SECTOR_SIZE / sizeof(uint32_t));
        bmap_last /= (SECTOR_SIZE / sizeof(uint32_t));
        n_sectors = bmap_last - bmap_first + 1;
        offset = s->bmap_sector + bmap_first;
        base = ((uint8_t *)&s->bmap[0]) + bmap_first * SECTOR_SIZE;
        logout("will write %u block map sectors starting from entry %u\n",
               n_sectors, bmap_first);
        ret = bdrv_write(bs->file, offset, base, n_sectors);
    }

    return ret;
}

static int coroutine_fn vdi_co_do_create(BlockdevCreateOptions *create_options,
                                         size_t block_size, Error **errp)
{
    BlockdevCreateOptionsVdi *vdi_opts;
    int ret = 0;
    uint64_t bytes = 0;
    uint32_t blocks;
    uint32_t image_type;
    VdiHeader header;
    size_t i;
    size_t bmap_size;
    int64_t offset = 0;
    BlockDriverState *bs_file = NULL;
    BlockBackend *blk = NULL;
    uint32_t *bmap = NULL;
    QemuUUID uuid;

    assert(create_options->driver == BLOCKDEV_DRIVER_VDI);
    vdi_opts = &create_options->u.vdi;

    logout("\n");

    /* Validate options and set default values */
    bytes = vdi_opts->size;

    if (!vdi_opts->has_preallocation) {
        vdi_opts->preallocation = PREALLOC_MODE_OFF;
    }
    switch (vdi_opts->preallocation) {
    case PREALLOC_MODE_OFF:
        image_type = VDI_TYPE_DYNAMIC;
        break;
    case PREALLOC_MODE_METADATA:
        image_type = VDI_TYPE_STATIC;
        break;
    default:
        error_setg(errp, "Preallocation mode not supported for vdi");
        return -EINVAL;
    }

#ifndef CONFIG_VDI_STATIC_IMAGE
    if (image_type == VDI_TYPE_STATIC) {
        ret = -ENOTSUP;
        error_setg(errp, "Statically allocated images cannot be created in "
                   "this build");
        goto exit;
    }
#endif
#ifndef CONFIG_VDI_BLOCK_SIZE
    if (block_size != DEFAULT_CLUSTER_SIZE) {
        ret = -ENOTSUP;
        error_setg(errp,
                   "A non-default cluster size is not supported in this build");
        goto exit;
    }
#endif

    if (bytes > VDI_DISK_SIZE_MAX) {
        ret = -ENOTSUP;
        error_setg(errp, "Unsupported VDI image size (size is 0x%" PRIx64
                          ", max supported is 0x%" PRIx64 ")",
                          bytes, VDI_DISK_SIZE_MAX);
        goto exit;
    }

    /* Create BlockBackend to write to the image */
    bs_file = bdrv_open_blockdev_ref(vdi_opts->file, errp);
    if (!bs_file) {
        ret = -EIO;
        goto exit;
    }

    blk = blk_new(BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
    ret = blk_insert_bs(blk, bs_file, errp);
    if (ret < 0) {
        goto exit;
    }

    blk_set_allow_write_beyond_eof(blk, true);

    /* We need enough blocks to store the given disk size,
       so always round up. */
    blocks = DIV_ROUND_UP(bytes, block_size);

    bmap_size = blocks * sizeof(uint32_t);
    bmap_size = ROUND_UP(bmap_size, SECTOR_SIZE);

    memset(&header, 0, sizeof(header));
    pstrcpy(header.text, sizeof(header.text), VDI_TEXT);
    header.signature = VDI_SIGNATURE;
    header.version = VDI_VERSION_1_1;
    header.header_size = 0x180;
    header.image_type = image_type;
    header.offset_bmap = 0x200;
    header.offset_data = 0x200 + bmap_size;
    header.sector_size = SECTOR_SIZE;
    header.disk_size = bytes;
    header.block_size = block_size;
    header.blocks_in_image = blocks;
    if (image_type == VDI_TYPE_STATIC) {
        header.blocks_allocated = blocks;
    }
    qemu_uuid_generate(&uuid);
    header.uuid_image = uuid;
    qemu_uuid_generate(&uuid);
    header.uuid_last_snap = uuid;
    /* There is no need to set header.uuid_link or header.uuid_parent here. */
    if (VDI_DEBUG) {
        vdi_header_print(&header);
    }
    vdi_header_to_le(&header);
    ret = blk_pwrite(blk, offset, &header, sizeof(header), 0);
    if (ret < 0) {
        error_setg(errp, "Error writing header");
        goto exit;
    }
    offset += sizeof(header);

    if (bmap_size > 0) {
        bmap = g_try_malloc0(bmap_size);
        if (bmap == NULL) {
            ret = -ENOMEM;
            error_setg(errp, "Could not allocate bmap");
            goto exit;
        }
        for (i = 0; i < blocks; i++) {
            if (image_type == VDI_TYPE_STATIC) {
                bmap[i] = i;
            } else {
                bmap[i] = VDI_UNALLOCATED;
            }
        }
        ret = blk_pwrite(blk, offset, bmap, bmap_size, 0);
        if (ret < 0) {
            error_setg(errp, "Error writing bmap");
            goto exit;
        }
        offset += bmap_size;
    }

    if (image_type == VDI_TYPE_STATIC) {
        ret = blk_truncate(blk, offset + blocks * block_size,
                           PREALLOC_MODE_OFF, errp);
        if (ret < 0) {
            error_prepend(errp, "Failed to statically allocate file");
            goto exit;
        }
    }

    ret = 0;
exit:
    blk_unref(blk);
    bdrv_unref(bs_file);
    g_free(bmap);
    return ret;
}

static int coroutine_fn vdi_co_create(BlockdevCreateOptions *create_options,
                                      Error **errp)
{
    return vdi_co_do_create(create_options, DEFAULT_CLUSTER_SIZE, errp);
}

static int coroutine_fn vdi_co_create_opts(const char *filename, QemuOpts *opts,
                                           Error **errp)
{
    QDict *qdict = NULL;
    BlockdevCreateOptions *create_options = NULL;
    BlockDriverState *bs_file = NULL;
    uint64_t block_size = DEFAULT_CLUSTER_SIZE;
    bool is_static = false;
    Visitor *v;
    Error *local_err = NULL;
    int ret;

    /* Parse options and convert legacy syntax.
     *
     * Since CONFIG_VDI_BLOCK_SIZE is disabled by default,
     * cluster-size is not part of the QAPI schema; therefore we have
     * to parse it before creating the QAPI object. */
#if defined(CONFIG_VDI_BLOCK_SIZE)
    block_size = qemu_opt_get_size_del(opts,
                                       BLOCK_OPT_CLUSTER_SIZE,
                                       DEFAULT_CLUSTER_SIZE);
    if (block_size < BDRV_SECTOR_SIZE || block_size > UINT32_MAX ||
        !is_power_of_2(block_size))
    {
        error_setg(errp, "Invalid cluster size");
        ret = -EINVAL;
        goto done;
    }
#endif
    if (qemu_opt_get_bool_del(opts, BLOCK_OPT_STATIC, false)) {
        is_static = true;
    }

    qdict = qemu_opts_to_qdict_filtered(opts, NULL, &vdi_create_opts, true);

    /* Create and open the file (protocol layer) */
    ret = bdrv_create_file(filename, opts, errp);
    if (ret < 0) {
        goto done;
    }

    bs_file = bdrv_open(filename, NULL, NULL,
                        BDRV_O_RDWR | BDRV_O_RESIZE | BDRV_O_PROTOCOL, errp);
    if (!bs_file) {
        ret = -EIO;
        goto done;
    }

    qdict_put_str(qdict, "driver", "vdi");
    qdict_put_str(qdict, "file", bs_file->node_name);
    if (is_static) {
        qdict_put_str(qdict, "preallocation", "metadata");
    }

    /* Get the QAPI object */
    v = qobject_input_visitor_new_flat_confused(qdict, errp);
    if (!v) {
        ret = -EINVAL;
        goto done;
    }
    visit_type_BlockdevCreateOptions(v, NULL, &create_options, &local_err);
    visit_free(v);

    if (local_err) {
        error_propagate(errp, local_err);
        ret = -EINVAL;
        goto done;
    }

    /* Silently round up size */
    assert(create_options->driver == BLOCKDEV_DRIVER_VDI);
    create_options->u.vdi.size = ROUND_UP(create_options->u.vdi.size,
                                          BDRV_SECTOR_SIZE);

    /* Create the vdi image (format layer) */
    ret = vdi_co_do_create(create_options, block_size, errp);
done:
    qobject_unref(qdict);
    qapi_free_BlockdevCreateOptions(create_options);
    bdrv_unref(bs_file);
    return ret;
}

static void vdi_close(BlockDriverState *bs)
{
    BDRVVdiState *s = bs->opaque;

    qemu_vfree(s->bmap);

    migrate_del_blocker(s->migration_blocker);
    error_free(s->migration_blocker);
}

static QemuOptsList vdi_create_opts = {
    .name = "vdi-create-opts",
    .head = QTAILQ_HEAD_INITIALIZER(vdi_create_opts.head),
    .desc = {
        {
            .name = BLOCK_OPT_SIZE,
            .type = QEMU_OPT_SIZE,
            .help = "Virtual disk size"
        },
#if defined(CONFIG_VDI_BLOCK_SIZE)
        {
            .name = BLOCK_OPT_CLUSTER_SIZE,
            .type = QEMU_OPT_SIZE,
            .help = "VDI cluster (block) size",
            .def_value_str = stringify(DEFAULT_CLUSTER_SIZE)
        },
#endif
#if defined(CONFIG_VDI_STATIC_IMAGE)
        {
            .name = BLOCK_OPT_STATIC,
            .type = QEMU_OPT_BOOL,
            .help = "VDI static (pre-allocated) image",
            .def_value_str = "off"
        },
#endif
        /* TODO: An additional option to set UUID values might be useful. */
        { /* end of list */ }
    }
};

static BlockDriver bdrv_vdi = {
    .format_name = "vdi",
    .instance_size = sizeof(BDRVVdiState),
    .bdrv_probe = vdi_probe,
    .bdrv_open = vdi_open,
    .bdrv_close = vdi_close,
    .bdrv_reopen_prepare = vdi_reopen_prepare,
    .bdrv_child_perm          = bdrv_format_default_perms,
    .bdrv_co_create      = vdi_co_create,
    .bdrv_co_create_opts = vdi_co_create_opts,
    .bdrv_has_zero_init = bdrv_has_zero_init_1,
    .bdrv_co_block_status = vdi_co_block_status,
    .bdrv_make_empty = vdi_make_empty,

    .bdrv_co_preadv     = vdi_co_preadv,
#if defined(CONFIG_VDI_WRITE)
    .bdrv_co_pwritev    = vdi_co_pwritev,
#endif

    .bdrv_get_info = vdi_get_info,

    .create_opts = &vdi_create_opts,
    .bdrv_co_check = vdi_co_check,
};

static void bdrv_vdi_init(void)
{
    logout("\n");
    bdrv_register(&bdrv_vdi);
}

block_init(bdrv_vdi_init);