summaryrefslogtreecommitdiff
path: root/block/vhdx.c
blob: bb3ed45d5c322e8e33f977e96e8ff309c769bd0b (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
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
/*
 * Block driver for Hyper-V VHDX Images
 *
 * Copyright (c) 2013 Red Hat, Inc.,
 *
 * Authors:
 *  Jeff Cody <jcody@redhat.com>
 *
 *  This is based on the "VHDX Format Specification v1.00", published 8/25/2012
 *  by Microsoft:
 *      https://www.microsoft.com/en-us/download/details.aspx?id=34750
 *
 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
 * See the COPYING.LIB file in the top-level directory.
 *
 */

#include "qemu-common.h"
#include "block/block_int.h"
#include "qemu/module.h"
#include "qemu/crc32c.h"
#include "block/vhdx.h"
#include "migration/migration.h"

#include <uuid/uuid.h>
#include <glib.h>

/* Options for VHDX creation */

#define VHDX_BLOCK_OPT_LOG_SIZE   "log_size"
#define VHDX_BLOCK_OPT_BLOCK_SIZE "block_size"
#define VHDX_BLOCK_OPT_ZERO "block_state_zero"

typedef enum VHDXImageType {
    VHDX_TYPE_DYNAMIC = 0,
    VHDX_TYPE_FIXED,
    VHDX_TYPE_DIFFERENCING,   /* Currently unsupported */
} VHDXImageType;

/* Several metadata and region table data entries are identified by
 * guids in  a MS-specific GUID format. */


/* ------- Known Region Table GUIDs ---------------------- */
static const MSGUID bat_guid =      { .data1 = 0x2dc27766,
                                      .data2 = 0xf623,
                                      .data3 = 0x4200,
                                      .data4 = { 0x9d, 0x64, 0x11, 0x5e,
                                                 0x9b, 0xfd, 0x4a, 0x08} };

static const MSGUID metadata_guid = { .data1 = 0x8b7ca206,
                                      .data2 = 0x4790,
                                      .data3 = 0x4b9a,
                                      .data4 = { 0xb8, 0xfe, 0x57, 0x5f,
                                                 0x05, 0x0f, 0x88, 0x6e} };



/* ------- Known Metadata Entry GUIDs ---------------------- */
static const MSGUID file_param_guid =   { .data1 = 0xcaa16737,
                                          .data2 = 0xfa36,
                                          .data3 = 0x4d43,
                                          .data4 = { 0xb3, 0xb6, 0x33, 0xf0,
                                                     0xaa, 0x44, 0xe7, 0x6b} };

static const MSGUID virtual_size_guid = { .data1 = 0x2FA54224,
                                          .data2 = 0xcd1b,
                                          .data3 = 0x4876,
                                          .data4 = { 0xb2, 0x11, 0x5d, 0xbe,
                                                     0xd8, 0x3b, 0xf4, 0xb8} };

static const MSGUID page83_guid =       { .data1 = 0xbeca12ab,
                                          .data2 = 0xb2e6,
                                          .data3 = 0x4523,
                                          .data4 = { 0x93, 0xef, 0xc3, 0x09,
                                                     0xe0, 0x00, 0xc7, 0x46} };


static const MSGUID phys_sector_guid =  { .data1 = 0xcda348c7,
                                          .data2 = 0x445d,
                                          .data3 = 0x4471,
                                          .data4 = { 0x9c, 0xc9, 0xe9, 0x88,
                                                     0x52, 0x51, 0xc5, 0x56} };

static const MSGUID parent_locator_guid = { .data1 = 0xa8d35f2d,
                                            .data2 = 0xb30b,
                                            .data3 = 0x454d,
                                            .data4 = { 0xab, 0xf7, 0xd3,
                                                       0xd8, 0x48, 0x34,
                                                       0xab, 0x0c} };

static const MSGUID logical_sector_guid = { .data1 = 0x8141bf1d,
                                            .data2 = 0xa96f,
                                            .data3 = 0x4709,
                                            .data4 = { 0xba, 0x47, 0xf2,
                                                       0x33, 0xa8, 0xfa,
                                                       0xab, 0x5f} };

/* Each parent type must have a valid GUID; this is for parent images
 * of type 'VHDX'.  If we were to allow e.g. a QCOW2 parent, we would
 * need to make up our own QCOW2 GUID type */
static const MSGUID parent_vhdx_guid __attribute__((unused))
                                     = { .data1 = 0xb04aefb7,
                                         .data2 = 0xd19e,
                                         .data3 = 0x4a81,
                                         .data4 = { 0xb7, 0x89, 0x25, 0xb8,
                                                    0xe9, 0x44, 0x59, 0x13} };


#define META_FILE_PARAMETER_PRESENT      0x01
#define META_VIRTUAL_DISK_SIZE_PRESENT   0x02
#define META_PAGE_83_PRESENT             0x04
#define META_LOGICAL_SECTOR_SIZE_PRESENT 0x08
#define META_PHYS_SECTOR_SIZE_PRESENT    0x10
#define META_PARENT_LOCATOR_PRESENT      0x20

#define META_ALL_PRESENT    \
    (META_FILE_PARAMETER_PRESENT | META_VIRTUAL_DISK_SIZE_PRESENT | \
     META_PAGE_83_PRESENT | META_LOGICAL_SECTOR_SIZE_PRESENT | \
     META_PHYS_SECTOR_SIZE_PRESENT)


typedef struct VHDXSectorInfo {
    uint32_t bat_idx;       /* BAT entry index */
    uint32_t sectors_avail; /* sectors available in payload block */
    uint32_t bytes_left;    /* bytes left in the block after data to r/w */
    uint32_t bytes_avail;   /* bytes available in payload block */
    uint64_t file_offset;   /* absolute offset in bytes, in file */
    uint64_t block_offset;  /* block offset, in bytes */
} VHDXSectorInfo;

/* Calculates new checksum.
 *
 * Zero is substituted during crc calculation for the original crc field
 * crc_offset: byte offset in buf of the buffer crc
 * buf: buffer pointer
 * size: size of buffer (must be > crc_offset+4)
 *
 * Note: The buffer should have all multi-byte data in little-endian format,
 *       and the resulting checksum is in little endian format.
 */
uint32_t vhdx_update_checksum(uint8_t *buf, size_t size, int crc_offset)
{
    uint32_t crc;

    assert(buf != NULL);
    assert(size > (crc_offset + sizeof(crc)));

    memset(buf + crc_offset, 0, sizeof(crc));
    crc =  crc32c(0xffffffff, buf, size);
    cpu_to_le32s(&crc);
    memcpy(buf + crc_offset, &crc, sizeof(crc));

    return crc;
}

uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size,
                            int crc_offset)
{
    uint32_t crc_new;
    uint32_t crc_orig;
    assert(buf != NULL);

    if (crc_offset > 0) {
        memcpy(&crc_orig, buf + crc_offset, sizeof(crc_orig));
        memset(buf + crc_offset, 0, sizeof(crc_orig));
    }

    crc_new = crc32c(crc, buf, size);
    if (crc_offset > 0) {
        memcpy(buf + crc_offset, &crc_orig, sizeof(crc_orig));
    }

    return crc_new;
}

/* Validates the checksum of the buffer, with an in-place CRC.
 *
 * Zero is substituted during crc calculation for the original crc field,
 * and the crc field is restored afterwards.  But the buffer will be modifed
 * during the calculation, so this may not be not suitable for multi-threaded
 * use.
 *
 * crc_offset: byte offset in buf of the buffer crc
 * buf: buffer pointer
 * size: size of buffer (must be > crc_offset+4)
 *
 * returns true if checksum is valid, false otherwise
 */
bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset)
{
    uint32_t crc_orig;
    uint32_t crc;

    assert(buf != NULL);
    assert(size > (crc_offset + 4));

    memcpy(&crc_orig, buf + crc_offset, sizeof(crc_orig));
    crc_orig = le32_to_cpu(crc_orig);

    crc = vhdx_checksum_calc(0xffffffff, buf, size, crc_offset);

    return crc == crc_orig;
}


/*
 * This generates a UUID that is compliant with the MS GUIDs used
 * in the VHDX spec (and elsewhere).
 */
void vhdx_guid_generate(MSGUID *guid)
{
    uuid_t uuid;
    assert(guid != NULL);

    uuid_generate(uuid);
    memcpy(guid, uuid, sizeof(MSGUID));
}

/* Check for region overlaps inside the VHDX image */
static int vhdx_region_check(BDRVVHDXState *s, uint64_t start, uint64_t length)
{
    int ret = 0;
    uint64_t end;
    VHDXRegionEntry *r;

    end = start + length;
    QLIST_FOREACH(r, &s->regions, entries) {
        if (!((start >= r->end) || (end <= r->start))) {
            ret = -EINVAL;
            goto exit;
        }
    }

exit:
    return ret;
}

/* Register a region for future checks */
static void vhdx_region_register(BDRVVHDXState *s,
                                 uint64_t start, uint64_t length)
{
    VHDXRegionEntry *r;

    r = g_malloc0(sizeof(*r));

    r->start = start;
    r->end = start + length;

    QLIST_INSERT_HEAD(&s->regions, r, entries);
}

/* Free all registered regions */
static void vhdx_region_unregister_all(BDRVVHDXState *s)
{
    VHDXRegionEntry *r, *r_next;

    QLIST_FOREACH_SAFE(r, &s->regions, entries, r_next) {
        QLIST_REMOVE(r, entries);
        g_free(r);
    }
}

static void vhdx_set_shift_bits(BDRVVHDXState *s)
{
    s->logical_sector_size_bits = 31 - clz32(s->logical_sector_size);
    s->sectors_per_block_bits =   31 - clz32(s->sectors_per_block);
    s->chunk_ratio_bits =         63 - clz64(s->chunk_ratio);
    s->block_size_bits =          31 - clz32(s->block_size);
}

/*
 * Per the MS VHDX Specification, for every VHDX file:
 *      - The header section is fixed size - 1 MB
 *      - The header section is always the first "object"
 *      - The first 64KB of the header is the File Identifier
 *      - The first uint64 (8 bytes) is the VHDX Signature ("vhdxfile")
 *      - The following 512 bytes constitute a UTF-16 string identifiying the
 *        software that created the file, and is optional and diagnostic only.
 *
 *  Therefore, we probe by looking for the vhdxfile signature "vhdxfile"
 */
static int vhdx_probe(const uint8_t *buf, int buf_size, const char *filename)
{
    if (buf_size >= 8 && !memcmp(buf, "vhdxfile", 8)) {
        return 100;
    }
    return 0;
}

/*
 * Writes the header to the specified offset.
 *
 * This will optionally read in buffer data from disk (otherwise zero-fill),
 * and then update the header checksum.  Header is converted to proper
 * endianness before being written to the specified file offset
 */
static int vhdx_write_header(BlockDriverState *bs_file, VHDXHeader *hdr,
                             uint64_t offset, bool read)
{
    uint8_t *buffer = NULL;
    int ret;
    VHDXHeader *header_le;

    assert(bs_file != NULL);
    assert(hdr != NULL);

    /* the header checksum is not over just the packed size of VHDXHeader,
     * but rather over the entire 'reserved' range for the header, which is
     * 4KB (VHDX_HEADER_SIZE). */

    buffer = qemu_blockalign(bs_file, VHDX_HEADER_SIZE);
    if (read) {
        /* if true, we can't assume the extra reserved bytes are 0 */
        ret = bdrv_pread(bs_file, offset, buffer, VHDX_HEADER_SIZE);
        if (ret < 0) {
            goto exit;
        }
    } else {
        memset(buffer, 0, VHDX_HEADER_SIZE);
    }

    /* overwrite the actual VHDXHeader portion */
    header_le = (VHDXHeader *)buffer;
    memcpy(header_le, hdr, sizeof(VHDXHeader));
    vhdx_header_le_export(hdr, header_le);
    vhdx_update_checksum(buffer, VHDX_HEADER_SIZE,
                         offsetof(VHDXHeader, checksum));
    ret = bdrv_pwrite_sync(bs_file, offset, header_le, sizeof(VHDXHeader));

exit:
    qemu_vfree(buffer);
    return ret;
}

/* Update the VHDX headers
 *
 * This follows the VHDX spec procedures for header updates.
 *
 *  - non-current header is updated with largest sequence number
 */
static int vhdx_update_header(BlockDriverState *bs, BDRVVHDXState *s,
                              bool generate_data_write_guid, MSGUID *log_guid)
{
    int ret = 0;
    int hdr_idx = 0;
    uint64_t header_offset = VHDX_HEADER1_OFFSET;

    VHDXHeader *active_header;
    VHDXHeader *inactive_header;

    /* operate on the non-current header */
    if (s->curr_header == 0) {
        hdr_idx = 1;
        header_offset = VHDX_HEADER2_OFFSET;
    }

    active_header   = s->headers[s->curr_header];
    inactive_header = s->headers[hdr_idx];

    inactive_header->sequence_number = active_header->sequence_number + 1;

    /* a new file guid must be generated before any file write, including
     * headers */
    inactive_header->file_write_guid = s->session_guid;

    /* a new data guid only needs to be generated before any guest-visible
     * writes (i.e. something observable via virtual disk read) */
    if (generate_data_write_guid) {
        vhdx_guid_generate(&inactive_header->data_write_guid);
    }

    /* update the log guid if present */
    if (log_guid) {
        inactive_header->log_guid = *log_guid;
    }

    ret = vhdx_write_header(bs->file, inactive_header, header_offset, true);
    if (ret < 0) {
        goto exit;
    }
    s->curr_header = hdr_idx;

exit:
    return ret;
}

/*
 * The VHDX spec calls for header updates to be performed twice, so that both
 * the current and non-current header have valid info
 */
int vhdx_update_headers(BlockDriverState *bs, BDRVVHDXState *s,
                        bool generate_data_write_guid, MSGUID *log_guid)
{
    int ret;

    ret = vhdx_update_header(bs, s, generate_data_write_guid, log_guid);
    if (ret < 0) {
        return ret;
    }
    ret = vhdx_update_header(bs, s, generate_data_write_guid, log_guid);
    return ret;
}

/* opens the specified header block from the VHDX file header section */
static void vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s,
                              Error **errp)
{
    int ret;
    VHDXHeader *header1;
    VHDXHeader *header2;
    bool h1_valid = false;
    bool h2_valid = false;
    uint64_t h1_seq = 0;
    uint64_t h2_seq = 0;
    uint8_t *buffer;

    /* header1 & header2 are freed in vhdx_close() */
    header1 = qemu_blockalign(bs, sizeof(VHDXHeader));
    header2 = qemu_blockalign(bs, sizeof(VHDXHeader));

    buffer = qemu_blockalign(bs, VHDX_HEADER_SIZE);

    s->headers[0] = header1;
    s->headers[1] = header2;

    /* We have to read the whole VHDX_HEADER_SIZE instead of
     * sizeof(VHDXHeader), because the checksum is over the whole
     * region */
    ret = bdrv_pread(bs->file, VHDX_HEADER1_OFFSET, buffer, VHDX_HEADER_SIZE);
    if (ret < 0) {
        goto fail;
    }
    /* copy over just the relevant portion that we need */
    memcpy(header1, buffer, sizeof(VHDXHeader));

    if (vhdx_checksum_is_valid(buffer, VHDX_HEADER_SIZE, 4)) {
        vhdx_header_le_import(header1);
        if (header1->signature == VHDX_HEADER_SIGNATURE &&
            header1->version == 1) {
            h1_seq = header1->sequence_number;
            h1_valid = true;
        }
    }

    ret = bdrv_pread(bs->file, VHDX_HEADER2_OFFSET, buffer, VHDX_HEADER_SIZE);
    if (ret < 0) {
        goto fail;
    }
    /* copy over just the relevant portion that we need */
    memcpy(header2, buffer, sizeof(VHDXHeader));

    if (vhdx_checksum_is_valid(buffer, VHDX_HEADER_SIZE, 4)) {
        vhdx_header_le_import(header2);
        if (header2->signature == VHDX_HEADER_SIGNATURE &&
            header2->version == 1) {
            h2_seq = header2->sequence_number;
            h2_valid = true;
        }
    }

    /* If there is only 1 valid header (or no valid headers), we
     * don't care what the sequence numbers are */
    if (h1_valid && !h2_valid) {
        s->curr_header = 0;
    } else if (!h1_valid && h2_valid) {
        s->curr_header = 1;
    } else if (!h1_valid && !h2_valid) {
        goto fail;
    } else {
        /* If both headers are valid, then we choose the active one by the
         * highest sequence number.  If the sequence numbers are equal, that is
         * invalid */
        if (h1_seq > h2_seq) {
            s->curr_header = 0;
        } else if (h2_seq > h1_seq) {
            s->curr_header = 1;
        } else {
            /* The Microsoft Disk2VHD tool will create 2 identical
             * headers, with identical sequence numbers.  If the headers are
             * identical, don't consider the file corrupt */
            if (!memcmp(header1, header2, sizeof(VHDXHeader))) {
                s->curr_header = 0;
            } else {
                goto fail;
            }
        }
    }

    vhdx_region_register(s, s->headers[s->curr_header]->log_offset,
                            s->headers[s->curr_header]->log_length);
    goto exit;

fail:
    error_setg_errno(errp, -ret, "No valid VHDX header found");
    qemu_vfree(header1);
    qemu_vfree(header2);
    s->headers[0] = NULL;
    s->headers[1] = NULL;
exit:
    qemu_vfree(buffer);
}


static int vhdx_open_region_tables(BlockDriverState *bs, BDRVVHDXState *s)
{
    int ret = 0;
    uint8_t *buffer;
    int offset = 0;
    VHDXRegionTableEntry rt_entry;
    uint32_t i;
    bool bat_rt_found = false;
    bool metadata_rt_found = false;

    /* We have to read the whole 64KB block, because the crc32 is over the
     * whole block */
    buffer = qemu_blockalign(bs, VHDX_HEADER_BLOCK_SIZE);

    ret = bdrv_pread(bs->file, VHDX_REGION_TABLE_OFFSET, buffer,
                     VHDX_HEADER_BLOCK_SIZE);
    if (ret < 0) {
        goto fail;
    }
    memcpy(&s->rt, buffer, sizeof(s->rt));
    offset += sizeof(s->rt);

    if (!vhdx_checksum_is_valid(buffer, VHDX_HEADER_BLOCK_SIZE, 4)) {
        ret = -EINVAL;
        goto fail;
    }

    vhdx_region_header_le_import(&s->rt);

    if (s->rt.signature != VHDX_REGION_SIGNATURE) {
        ret = -EINVAL;
        goto fail;
    }


    /* Per spec, maximum region table entry count is 2047 */
    if (s->rt.entry_count > 2047) {
        ret = -EINVAL;
        goto fail;
    }

    for (i = 0; i < s->rt.entry_count; i++) {
        memcpy(&rt_entry, buffer + offset, sizeof(rt_entry));
        offset += sizeof(rt_entry);

        vhdx_region_entry_le_import(&rt_entry);

        /* check for region overlap between these entries, and any
         * other memory regions in the file */
        ret = vhdx_region_check(s, rt_entry.file_offset, rt_entry.length);
        if (ret < 0) {
            goto fail;
        }

        vhdx_region_register(s, rt_entry.file_offset, rt_entry.length);

        /* see if we recognize the entry */
        if (guid_eq(rt_entry.guid, bat_guid)) {
            /* must be unique; if we have already found it this is invalid */
            if (bat_rt_found) {
                ret = -EINVAL;
                goto fail;
            }
            bat_rt_found = true;
            s->bat_rt = rt_entry;
            continue;
        }

        if (guid_eq(rt_entry.guid, metadata_guid)) {
            /* must be unique; if we have already found it this is invalid */
            if (metadata_rt_found) {
                ret = -EINVAL;
                goto fail;
            }
            metadata_rt_found = true;
            s->metadata_rt = rt_entry;
            continue;
        }

        if (rt_entry.data_bits & VHDX_REGION_ENTRY_REQUIRED) {
            /* cannot read vhdx file - required region table entry that
             * we do not understand.  per spec, we must fail to open */
            ret = -ENOTSUP;
            goto fail;
        }
    }

    if (!bat_rt_found || !metadata_rt_found) {
        ret = -EINVAL;
        goto fail;
    }

    ret = 0;

fail:
    qemu_vfree(buffer);
    return ret;
}



/* Metadata initial parser
 *
 * This loads all the metadata entry fields.  This may cause additional
 * fields to be processed (e.g. parent locator, etc..).
 *
 * There are 5 Metadata items that are always required:
 *      - File Parameters (block size, has a parent)
 *      - Virtual Disk Size (size, in bytes, of the virtual drive)
 *      - Page 83 Data (scsi page 83 guid)
 *      - Logical Sector Size (logical sector size in bytes, either 512 or
 *                             4096.  We only support 512 currently)
 *      - Physical Sector Size (512 or 4096)
 *
 * Also, if the File Parameters indicate this is a differencing file,
 * we must also look for the Parent Locator metadata item.
 */
static int vhdx_parse_metadata(BlockDriverState *bs, BDRVVHDXState *s)
{
    int ret = 0;
    uint8_t *buffer;
    int offset = 0;
    uint32_t i = 0;
    VHDXMetadataTableEntry md_entry;

    buffer = qemu_blockalign(bs, VHDX_METADATA_TABLE_MAX_SIZE);

    ret = bdrv_pread(bs->file, s->metadata_rt.file_offset, buffer,
                     VHDX_METADATA_TABLE_MAX_SIZE);
    if (ret < 0) {
        goto exit;
    }
    memcpy(&s->metadata_hdr, buffer, sizeof(s->metadata_hdr));
    offset += sizeof(s->metadata_hdr);

    vhdx_metadata_header_le_import(&s->metadata_hdr);

    if (s->metadata_hdr.signature != VHDX_METADATA_SIGNATURE) {
        ret = -EINVAL;
        goto exit;
    }

    s->metadata_entries.present = 0;

    if ((s->metadata_hdr.entry_count * sizeof(md_entry)) >
        (VHDX_METADATA_TABLE_MAX_SIZE - offset)) {
        ret = -EINVAL;
        goto exit;
    }

    for (i = 0; i < s->metadata_hdr.entry_count; i++) {
        memcpy(&md_entry, buffer + offset, sizeof(md_entry));
        offset += sizeof(md_entry);

        vhdx_metadata_entry_le_import(&md_entry);

        if (guid_eq(md_entry.item_id, file_param_guid)) {
            if (s->metadata_entries.present & META_FILE_PARAMETER_PRESENT) {
                ret = -EINVAL;
                goto exit;
            }
            s->metadata_entries.file_parameters_entry = md_entry;
            s->metadata_entries.present |= META_FILE_PARAMETER_PRESENT;
            continue;
        }

        if (guid_eq(md_entry.item_id, virtual_size_guid)) {
            if (s->metadata_entries.present & META_VIRTUAL_DISK_SIZE_PRESENT) {
                ret = -EINVAL;
                goto exit;
            }
            s->metadata_entries.virtual_disk_size_entry = md_entry;
            s->metadata_entries.present |= META_VIRTUAL_DISK_SIZE_PRESENT;
            continue;
        }

        if (guid_eq(md_entry.item_id, page83_guid)) {
            if (s->metadata_entries.present & META_PAGE_83_PRESENT) {
                ret = -EINVAL;
                goto exit;
            }
            s->metadata_entries.page83_data_entry = md_entry;
            s->metadata_entries.present |= META_PAGE_83_PRESENT;
            continue;
        }

        if (guid_eq(md_entry.item_id, logical_sector_guid)) {
            if (s->metadata_entries.present &
                META_LOGICAL_SECTOR_SIZE_PRESENT) {
                ret = -EINVAL;
                goto exit;
            }
            s->metadata_entries.logical_sector_size_entry = md_entry;
            s->metadata_entries.present |= META_LOGICAL_SECTOR_SIZE_PRESENT;
            continue;
        }

        if (guid_eq(md_entry.item_id, phys_sector_guid)) {
            if (s->metadata_entries.present & META_PHYS_SECTOR_SIZE_PRESENT) {
                ret = -EINVAL;
                goto exit;
            }
            s->metadata_entries.phys_sector_size_entry = md_entry;
            s->metadata_entries.present |= META_PHYS_SECTOR_SIZE_PRESENT;
            continue;
        }

        if (guid_eq(md_entry.item_id, parent_locator_guid)) {
            if (s->metadata_entries.present & META_PARENT_LOCATOR_PRESENT) {
                ret = -EINVAL;
                goto exit;
            }
            s->metadata_entries.parent_locator_entry = md_entry;
            s->metadata_entries.present |= META_PARENT_LOCATOR_PRESENT;
            continue;
        }

        if (md_entry.data_bits & VHDX_META_FLAGS_IS_REQUIRED) {
            /* cannot read vhdx file - required region table entry that
             * we do not understand.  per spec, we must fail to open */
            ret = -ENOTSUP;
            goto exit;
        }
    }

    if (s->metadata_entries.present != META_ALL_PRESENT) {
        ret = -ENOTSUP;
        goto exit;
    }

    ret = bdrv_pread(bs->file,
                     s->metadata_entries.file_parameters_entry.offset
                                         + s->metadata_rt.file_offset,
                     &s->params,
                     sizeof(s->params));

    if (ret < 0) {
        goto exit;
    }

    le32_to_cpus(&s->params.block_size);
    le32_to_cpus(&s->params.data_bits);


    /* We now have the file parameters, so we can tell if this is a
     * differencing file (i.e.. has_parent), is dynamic or fixed
     * sized (leave_blocks_allocated), and the block size */

    /* The parent locator required iff the file parameters has_parent set */
    if (s->params.data_bits & VHDX_PARAMS_HAS_PARENT) {
        if (s->metadata_entries.present & META_PARENT_LOCATOR_PRESENT) {
            /* TODO: parse  parent locator fields */
            ret = -ENOTSUP; /* temp, until differencing files are supported */
            goto exit;
        } else {
            /* if has_parent is set, but there is not parent locator present,
             * then that is an invalid combination */
            ret = -EINVAL;
            goto exit;
        }
    }

    /* determine virtual disk size, logical sector size,
     * and phys sector size */

    ret = bdrv_pread(bs->file,
                     s->metadata_entries.virtual_disk_size_entry.offset
                                           + s->metadata_rt.file_offset,
                     &s->virtual_disk_size,
                     sizeof(uint64_t));
    if (ret < 0) {
        goto exit;
    }
    ret = bdrv_pread(bs->file,
                     s->metadata_entries.logical_sector_size_entry.offset
                                             + s->metadata_rt.file_offset,
                     &s->logical_sector_size,
                     sizeof(uint32_t));
    if (ret < 0) {
        goto exit;
    }
    ret = bdrv_pread(bs->file,
                     s->metadata_entries.phys_sector_size_entry.offset
                                          + s->metadata_rt.file_offset,
                     &s->physical_sector_size,
                     sizeof(uint32_t));
    if (ret < 0) {
        goto exit;
    }

    le64_to_cpus(&s->virtual_disk_size);
    le32_to_cpus(&s->logical_sector_size);
    le32_to_cpus(&s->physical_sector_size);

    if (s->params.block_size < VHDX_BLOCK_SIZE_MIN ||
        s->params.block_size > VHDX_BLOCK_SIZE_MAX) {
        ret = -EINVAL;
        goto exit;
    }

    /* only 2 supported sector sizes */
    if (s->logical_sector_size != 512 && s->logical_sector_size != 4096) {
        ret = -EINVAL;
        goto exit;
    }

    /* Both block_size and sector_size are guaranteed powers of 2, below.
       Due to range checks above, s->sectors_per_block can never be < 256 */
    s->sectors_per_block = s->params.block_size / s->logical_sector_size;
    s->chunk_ratio = (VHDX_MAX_SECTORS_PER_BLOCK) *
                     (uint64_t)s->logical_sector_size /
                     (uint64_t)s->params.block_size;

    /* These values are ones we will want to use for division / multiplication
     * later on, and they are all guaranteed (per the spec) to be powers of 2,
     * so we can take advantage of that for shift operations during
     * reads/writes */
    if (s->logical_sector_size & (s->logical_sector_size - 1)) {
        ret = -EINVAL;
        goto exit;
    }
    if (s->sectors_per_block & (s->sectors_per_block - 1)) {
        ret = -EINVAL;
        goto exit;
    }
    if (s->chunk_ratio & (s->chunk_ratio - 1)) {
        ret = -EINVAL;
        goto exit;
    }
    s->block_size = s->params.block_size;
    if (s->block_size & (s->block_size - 1)) {
        ret = -EINVAL;
        goto exit;
    }

    vhdx_set_shift_bits(s);

    ret = 0;

exit:
    qemu_vfree(buffer);
    return ret;
}

/*
 * Calculate the number of BAT entries, including sector
 * bitmap entries.
 */
static void vhdx_calc_bat_entries(BDRVVHDXState *s)
{
    uint32_t data_blocks_cnt, bitmap_blocks_cnt;

    data_blocks_cnt = s->virtual_disk_size >> s->block_size_bits;
    if (s->virtual_disk_size - (data_blocks_cnt << s->block_size_bits)) {
        data_blocks_cnt++;
    }
    bitmap_blocks_cnt = data_blocks_cnt >> s->chunk_ratio_bits;
    if (data_blocks_cnt - (bitmap_blocks_cnt << s->chunk_ratio_bits)) {
        bitmap_blocks_cnt++;
    }

    if (s->parent_entries) {
        s->bat_entries = bitmap_blocks_cnt * (s->chunk_ratio + 1);
    } else {
        s->bat_entries = data_blocks_cnt +
                         ((data_blocks_cnt - 1) >> s->chunk_ratio_bits);
    }

}

static void vhdx_close(BlockDriverState *bs)
{
    BDRVVHDXState *s = bs->opaque;
    qemu_vfree(s->headers[0]);
    s->headers[0] = NULL;
    qemu_vfree(s->headers[1]);
    s->headers[1] = NULL;
    qemu_vfree(s->bat);
    s->bat = NULL;
    qemu_vfree(s->parent_entries);
    s->parent_entries = NULL;
    migrate_del_blocker(s->migration_blocker);
    error_free(s->migration_blocker);
    qemu_vfree(s->log.hdr);
    s->log.hdr = NULL;
    vhdx_region_unregister_all(s);
}

static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
{
    BDRVVHDXState *s = bs->opaque;
    int ret = 0;
    uint32_t i;
    uint64_t signature;
    Error *local_err = NULL;

    s->bat = NULL;
    s->first_visible_write = true;

    qemu_co_mutex_init(&s->lock);
    QLIST_INIT(&s->regions);

    /* validate the file signature */
    ret = bdrv_pread(bs->file, 0, &signature, sizeof(uint64_t));
    if (ret < 0) {
        goto fail;
    }
    if (memcmp(&signature, "vhdxfile", 8)) {
        ret = -EINVAL;
        goto fail;
    }

    /* This is used for any header updates, for the file_write_guid.
     * The spec dictates that a new value should be used for the first
     * header update */
    vhdx_guid_generate(&s->session_guid);

    vhdx_parse_header(bs, s, &local_err);
    if (local_err != NULL) {
        error_propagate(errp, local_err);
        ret = -EINVAL;
        goto fail;
    }

    ret = vhdx_parse_log(bs, s, &s->log_replayed_on_open, errp);
    if (ret < 0) {
        goto fail;
    }

    ret = vhdx_open_region_tables(bs, s);
    if (ret < 0) {
        goto fail;
    }

    ret = vhdx_parse_metadata(bs, s);
    if (ret < 0) {
        goto fail;
    }

    s->block_size = s->params.block_size;

    /* the VHDX spec dictates that virtual_disk_size is always a multiple of
     * logical_sector_size */
    bs->total_sectors = s->virtual_disk_size >> s->logical_sector_size_bits;

    vhdx_calc_bat_entries(s);

    s->bat_offset = s->bat_rt.file_offset;

    if (s->bat_entries > s->bat_rt.length / sizeof(VHDXBatEntry)) {
        /* BAT allocation is not large enough for all entries */
        ret = -EINVAL;
        goto fail;
    }

    /* s->bat is freed in vhdx_close() */
    s->bat = qemu_try_blockalign(bs->file, s->bat_rt.length);
    if (s->bat == NULL) {
        ret = -ENOMEM;
        goto fail;
    }

    ret = bdrv_pread(bs->file, s->bat_offset, s->bat, s->bat_rt.length);
    if (ret < 0) {
        goto fail;
    }

    uint64_t payblocks = s->chunk_ratio;
    /* endian convert, and verify populated BAT field file offsets against
     * region table and log entries */
    for (i = 0; i < s->bat_entries; i++) {
        le64_to_cpus(&s->bat[i]);
        if (payblocks--) {
            /* payload bat entries */
            if ((s->bat[i] & VHDX_BAT_STATE_BIT_MASK) ==
                    PAYLOAD_BLOCK_FULLY_PRESENT) {
                ret = vhdx_region_check(s, s->bat[i] & VHDX_BAT_FILE_OFF_MASK,
                                        s->block_size);
                if (ret < 0) {
                    goto fail;
                }
            }
        } else {
            payblocks = s->chunk_ratio;
            /* Once differencing files are supported, verify sector bitmap
             * blocks here */
        }
    }

    if (flags & BDRV_O_RDWR) {
        ret = vhdx_update_headers(bs, s, false, NULL);
        if (ret < 0) {
            goto fail;
        }
    }

    /* TODO: differencing files */

    /* Disable migration when VHDX images are used */
    error_set(&s->migration_blocker,
            QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
            "vhdx", bdrv_get_device_name(bs), "live migration");
    migrate_add_blocker(s->migration_blocker);

    return 0;
fail:
    vhdx_close(bs);
    return ret;
}

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


/*
 * Perform sector to block offset translations, to get various
 * sector and file offsets into the image.  See VHDXSectorInfo
 */
static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num,
                                 int nb_sectors, VHDXSectorInfo *sinfo)
{
    uint32_t block_offset;

    sinfo->bat_idx = sector_num >> s->sectors_per_block_bits;
    /* effectively a modulo - this gives us the offset into the block
     * (in sector sizes) for our sector number */
    block_offset = sector_num - (sinfo->bat_idx << s->sectors_per_block_bits);
    /* the chunk ratio gives us the interleaving of the sector
     * bitmaps, so we need to advance our page block index by the
     * sector bitmaps entry number */
    sinfo->bat_idx += sinfo->bat_idx >> s->chunk_ratio_bits;

    /* the number of sectors we can read/write in this cycle */
    sinfo->sectors_avail = s->sectors_per_block - block_offset;

    sinfo->bytes_left = sinfo->sectors_avail << s->logical_sector_size_bits;

    if (sinfo->sectors_avail > nb_sectors) {
        sinfo->sectors_avail = nb_sectors;
    }

    sinfo->bytes_avail = sinfo->sectors_avail << s->logical_sector_size_bits;

    sinfo->file_offset = s->bat[sinfo->bat_idx] & VHDX_BAT_FILE_OFF_MASK;

    sinfo->block_offset = block_offset << s->logical_sector_size_bits;

    /* The file offset must be past the header section, so must be > 0 */
    if (sinfo->file_offset == 0) {
        return;
    }

    /* block offset is the offset in vhdx logical sectors, in
     * the payload data block. Convert that to a byte offset
     * in the block, and add in the payload data block offset
     * in the file, in bytes, to get the final read address */

    sinfo->file_offset += sinfo->block_offset;
}


static int vhdx_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
    BDRVVHDXState *s = bs->opaque;

    bdi->cluster_size = s->block_size;

    bdi->unallocated_blocks_are_zero =
        (s->params.data_bits & VHDX_PARAMS_HAS_PARENT) == 0;

    return 0;
}


static coroutine_fn int vhdx_co_readv(BlockDriverState *bs, int64_t sector_num,
                                      int nb_sectors, QEMUIOVector *qiov)
{
    BDRVVHDXState *s = bs->opaque;
    int ret = 0;
    VHDXSectorInfo sinfo;
    uint64_t bytes_done = 0;
    QEMUIOVector hd_qiov;

    qemu_iovec_init(&hd_qiov, qiov->niov);

    qemu_co_mutex_lock(&s->lock);

    while (nb_sectors > 0) {
        /* We are a differencing file, so we need to inspect the sector bitmap
         * to see if we have the data or not */
        if (s->params.data_bits & VHDX_PARAMS_HAS_PARENT) {
            /* not supported yet */
            ret = -ENOTSUP;
            goto exit;
        } else {
            vhdx_block_translate(s, sector_num, nb_sectors, &sinfo);

            qemu_iovec_reset(&hd_qiov);
            qemu_iovec_concat(&hd_qiov, qiov,  bytes_done, sinfo.bytes_avail);

            /* check the payload block state */
            switch (s->bat[sinfo.bat_idx] & VHDX_BAT_STATE_BIT_MASK) {
            case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
            case PAYLOAD_BLOCK_UNDEFINED:
            case PAYLOAD_BLOCK_UNMAPPED:
            case PAYLOAD_BLOCK_UNMAPPED_v095:
            case PAYLOAD_BLOCK_ZERO:
                /* return zero */
                qemu_iovec_memset(&hd_qiov, 0, 0, sinfo.bytes_avail);
                break;
            case PAYLOAD_BLOCK_FULLY_PRESENT:
                qemu_co_mutex_unlock(&s->lock);
                ret = bdrv_co_readv(bs->file,
                                    sinfo.file_offset >> BDRV_SECTOR_BITS,
                                    sinfo.sectors_avail, &hd_qiov);
                qemu_co_mutex_lock(&s->lock);
                if (ret < 0) {
                    goto exit;
                }
                break;
            case PAYLOAD_BLOCK_PARTIALLY_PRESENT:
                /* we don't yet support difference files, fall through
                 * to error */
            default:
                ret = -EIO;
                goto exit;
                break;
            }
            nb_sectors -= sinfo.sectors_avail;
            sector_num += sinfo.sectors_avail;
            bytes_done += sinfo.bytes_avail;
        }
    }
    ret = 0;
exit:
    qemu_co_mutex_unlock(&s->lock);
    qemu_iovec_destroy(&hd_qiov);
    return ret;
}

/*
 * Allocate a new payload block at the end of the file.
 *
 * Allocation will happen at 1MB alignment inside the file
 *
 * Returns the file offset start of the new payload block
 */
static int vhdx_allocate_block(BlockDriverState *bs, BDRVVHDXState *s,
                                    uint64_t *new_offset)
{
    *new_offset = bdrv_getlength(bs->file);

    /* per the spec, the address for a block is in units of 1MB */
    *new_offset = ROUND_UP(*new_offset, 1024 * 1024);

    return bdrv_truncate(bs->file, *new_offset + s->block_size);
}

/*
 * Update the BAT table entry with the new file offset, and the new entry
 * state */
static void vhdx_update_bat_table_entry(BlockDriverState *bs, BDRVVHDXState *s,
                                       VHDXSectorInfo *sinfo,
                                       uint64_t *bat_entry_le,
                                       uint64_t *bat_offset, int state)
{
    /* The BAT entry is a uint64, with 44 bits for the file offset in units of
     * 1MB, and 3 bits for the block state. */
    if ((state == PAYLOAD_BLOCK_ZERO)        ||
        (state == PAYLOAD_BLOCK_UNDEFINED)   ||
        (state == PAYLOAD_BLOCK_NOT_PRESENT) ||
        (state == PAYLOAD_BLOCK_UNMAPPED)) {
        s->bat[sinfo->bat_idx]  = 0;  /* For PAYLOAD_BLOCK_ZERO, the
                                         FileOffsetMB field is denoted as
                                         'reserved' in the v1.0 spec.  If it is
                                         non-zero, MS Hyper-V will fail to read
                                         the disk image */
    } else {
        s->bat[sinfo->bat_idx]  = sinfo->file_offset;
    }

    s->bat[sinfo->bat_idx] |= state & VHDX_BAT_STATE_BIT_MASK;

    *bat_entry_le = cpu_to_le64(s->bat[sinfo->bat_idx]);
    *bat_offset = s->bat_offset + sinfo->bat_idx * sizeof(VHDXBatEntry);

}

/* Per the spec, on the first write of guest-visible data to the file the
 * data write guid must be updated in the header */
int vhdx_user_visible_write(BlockDriverState *bs, BDRVVHDXState *s)
{
    int ret = 0;
    if (s->first_visible_write) {
        s->first_visible_write = false;
        ret = vhdx_update_headers(bs, s, true, NULL);
    }
    return ret;
}

static coroutine_fn int vhdx_co_writev(BlockDriverState *bs, int64_t sector_num,
                                      int nb_sectors, QEMUIOVector *qiov)
{
    int ret = -ENOTSUP;
    BDRVVHDXState *s = bs->opaque;
    VHDXSectorInfo sinfo;
    uint64_t bytes_done = 0;
    uint64_t bat_entry = 0;
    uint64_t bat_entry_offset = 0;
    QEMUIOVector hd_qiov;
    struct iovec iov1 = { 0 };
    struct iovec iov2 = { 0 };
    int sectors_to_write;
    int bat_state;
    uint64_t bat_prior_offset = 0;
    bool bat_update = false;

    qemu_iovec_init(&hd_qiov, qiov->niov);

    qemu_co_mutex_lock(&s->lock);

    ret = vhdx_user_visible_write(bs, s);
    if (ret < 0) {
        goto exit;
    }

    while (nb_sectors > 0) {
        bool use_zero_buffers = false;
        bat_update = false;
        if (s->params.data_bits & VHDX_PARAMS_HAS_PARENT) {
            /* not supported yet */
            ret = -ENOTSUP;
            goto exit;
        } else {
            vhdx_block_translate(s, sector_num, nb_sectors, &sinfo);
            sectors_to_write = sinfo.sectors_avail;

            qemu_iovec_reset(&hd_qiov);
            /* check the payload block state */
            bat_state = s->bat[sinfo.bat_idx] & VHDX_BAT_STATE_BIT_MASK;
            switch (bat_state) {
            case PAYLOAD_BLOCK_ZERO:
                /* in this case, we need to preserve zero writes for
                 * data that is not part of this write, so we must pad
                 * the rest of the buffer to zeroes */

                /* if we are on a posix system with ftruncate() that extends
                 * a file, then it is zero-filled for us.  On Win32, the raw
                 * layer uses SetFilePointer and SetFileEnd, which does not
                 * zero fill AFAIK */

                /* Queue another write of zero buffers if the underlying file
                 * does not zero-fill on file extension */

                if (bdrv_has_zero_init(bs->file) == 0) {
                    use_zero_buffers = true;

                    /* zero fill the front, if any */
                    if (sinfo.block_offset) {
                        iov1.iov_len = sinfo.block_offset;
                        iov1.iov_base = qemu_blockalign(bs, iov1.iov_len);
                        memset(iov1.iov_base, 0, iov1.iov_len);
                        qemu_iovec_concat_iov(&hd_qiov, &iov1, 1, 0,
                                              sinfo.block_offset);
                        sectors_to_write += iov1.iov_len >> BDRV_SECTOR_BITS;
                    }

                    /* our actual data */
                    qemu_iovec_concat(&hd_qiov, qiov,  bytes_done,
                                      sinfo.bytes_avail);

                    /* zero fill the back, if any */
                    if ((sinfo.bytes_avail - sinfo.block_offset) <
                         s->block_size) {
                        iov2.iov_len = s->block_size -
                                      (sinfo.bytes_avail + sinfo.block_offset);
                        iov2.iov_base = qemu_blockalign(bs, iov2.iov_len);
                        memset(iov2.iov_base, 0, iov2.iov_len);
                        qemu_iovec_concat_iov(&hd_qiov, &iov2, 1, 0,
                                              sinfo.block_offset);
                        sectors_to_write += iov2.iov_len >> BDRV_SECTOR_BITS;
                    }
                }
                /* fall through */
            case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
            case PAYLOAD_BLOCK_UNMAPPED:
            case PAYLOAD_BLOCK_UNMAPPED_v095:
            case PAYLOAD_BLOCK_UNDEFINED:
                bat_prior_offset = sinfo.file_offset;
                ret = vhdx_allocate_block(bs, s, &sinfo.file_offset);
                if (ret < 0) {
                    goto exit;
                }
                /* once we support differencing files, this may also be
                 * partially present */
                /* update block state to the newly specified state */
                vhdx_update_bat_table_entry(bs, s, &sinfo, &bat_entry,
                                            &bat_entry_offset,
                                            PAYLOAD_BLOCK_FULLY_PRESENT);
                bat_update = true;
                /* since we just allocated a block, file_offset is the
                 * beginning of the payload block. It needs to be the
                 * write address, which includes the offset into the block */
                if (!use_zero_buffers) {
                    sinfo.file_offset += sinfo.block_offset;
                }
                /* fall through */
            case PAYLOAD_BLOCK_FULLY_PRESENT:
                /* if the file offset address is in the header zone,
                 * there is a problem */
                if (sinfo.file_offset < (1024 * 1024)) {
                    ret = -EFAULT;
                    goto error_bat_restore;
                }

                if (!use_zero_buffers) {
                    qemu_iovec_concat(&hd_qiov, qiov,  bytes_done,
                                      sinfo.bytes_avail);
                }
                /* block exists, so we can just overwrite it */
                qemu_co_mutex_unlock(&s->lock);
                ret = bdrv_co_writev(bs->file,
                                    sinfo.file_offset >> BDRV_SECTOR_BITS,
                                    sectors_to_write, &hd_qiov);
                qemu_co_mutex_lock(&s->lock);
                if (ret < 0) {
                    goto error_bat_restore;
                }
                break;
            case PAYLOAD_BLOCK_PARTIALLY_PRESENT:
                /* we don't yet support difference files, fall through
                 * to error */
            default:
                ret = -EIO;
                goto exit;
                break;
            }

            if (bat_update) {
                /* this will update the BAT entry into the log journal, and
                 * then flush the log journal out to disk */
                ret =  vhdx_log_write_and_flush(bs, s, &bat_entry,
                                                sizeof(VHDXBatEntry),
                                                bat_entry_offset);
                if (ret < 0) {
                    goto exit;
                }
            }

            nb_sectors -= sinfo.sectors_avail;
            sector_num += sinfo.sectors_avail;
            bytes_done += sinfo.bytes_avail;

        }
    }

    goto exit;

error_bat_restore:
    if (bat_update) {
        /* keep metadata in sync, and restore the bat entry state
         * if error. */
        sinfo.file_offset = bat_prior_offset;
        vhdx_update_bat_table_entry(bs, s, &sinfo, &bat_entry,
                                    &bat_entry_offset, bat_state);
    }
exit:
    qemu_vfree(iov1.iov_base);
    qemu_vfree(iov2.iov_base);
    qemu_co_mutex_unlock(&s->lock);
    qemu_iovec_destroy(&hd_qiov);
    return ret;
}



/*
 * Create VHDX Headers
 *
 * There are 2 headers, and the highest sequence number will represent
 * the active header
 */
static int vhdx_create_new_headers(BlockDriverState *bs, uint64_t image_size,
                                   uint32_t log_size)
{
    int ret = 0;
    VHDXHeader *hdr = NULL;

    hdr = g_new0(VHDXHeader, 1);

    hdr->signature       = VHDX_HEADER_SIGNATURE;
    hdr->sequence_number = g_random_int();
    hdr->log_version     = 0;
    hdr->version         = 1;
    hdr->log_length      = log_size;
    hdr->log_offset      = VHDX_HEADER_SECTION_END;
    vhdx_guid_generate(&hdr->file_write_guid);
    vhdx_guid_generate(&hdr->data_write_guid);

    ret = vhdx_write_header(bs, hdr, VHDX_HEADER1_OFFSET, false);
    if (ret < 0) {
        goto exit;
    }
    hdr->sequence_number++;
    ret = vhdx_write_header(bs, hdr, VHDX_HEADER2_OFFSET, false);
    if (ret < 0) {
        goto exit;
    }

exit:
    g_free(hdr);
    return ret;
}

#define VHDX_METADATA_ENTRY_BUFFER_SIZE \
                                    (sizeof(VHDXFileParameters)               +\
                                     sizeof(VHDXVirtualDiskSize)              +\
                                     sizeof(VHDXPage83Data)                   +\
                                     sizeof(VHDXVirtualDiskLogicalSectorSize) +\
                                     sizeof(VHDXVirtualDiskPhysicalSectorSize))

/*
 * Create the Metadata entries.
 *
 * For more details on the entries, see section 3.5 (pg 29) in the
 * VHDX 1.00 specification.
 *
 * We support 5 metadata entries (all required by spec):
 *          File Parameters,
 *          Virtual Disk Size,
 *          Page 83 Data,
 *          Logical Sector Size,
 *          Physical Sector Size
 *
 * The first 64KB of the Metadata section is reserved for the metadata
 * header and entries; beyond that, the metadata items themselves reside.
 */
static int vhdx_create_new_metadata(BlockDriverState *bs,
                                    uint64_t image_size,
                                    uint32_t block_size,
                                    uint32_t sector_size,
                                    uint64_t metadata_offset,
                                    VHDXImageType type)
{
    int ret = 0;
    uint32_t offset = 0;
    void *buffer = NULL;
    void *entry_buffer;
    VHDXMetadataTableHeader *md_table;;
    VHDXMetadataTableEntry  *md_table_entry;

    /* Metadata entries */
    VHDXFileParameters     *mt_file_params;
    VHDXVirtualDiskSize    *mt_virtual_size;
    VHDXPage83Data         *mt_page83;
    VHDXVirtualDiskLogicalSectorSize  *mt_log_sector_size;
    VHDXVirtualDiskPhysicalSectorSize *mt_phys_sector_size;

    entry_buffer = g_malloc0(VHDX_METADATA_ENTRY_BUFFER_SIZE);

    mt_file_params = entry_buffer;
    offset += sizeof(VHDXFileParameters);
    mt_virtual_size = entry_buffer + offset;
    offset += sizeof(VHDXVirtualDiskSize);
    mt_page83 = entry_buffer + offset;
    offset += sizeof(VHDXPage83Data);
    mt_log_sector_size = entry_buffer + offset;
    offset += sizeof(VHDXVirtualDiskLogicalSectorSize);
    mt_phys_sector_size = entry_buffer + offset;

    mt_file_params->block_size = cpu_to_le32(block_size);
    if (type == VHDX_TYPE_FIXED) {
        mt_file_params->data_bits |= VHDX_PARAMS_LEAVE_BLOCKS_ALLOCED;
        cpu_to_le32s(&mt_file_params->data_bits);
    }

    vhdx_guid_generate(&mt_page83->page_83_data);
    cpu_to_leguids(&mt_page83->page_83_data);
    mt_virtual_size->virtual_disk_size        = cpu_to_le64(image_size);
    mt_log_sector_size->logical_sector_size   = cpu_to_le32(sector_size);
    mt_phys_sector_size->physical_sector_size = cpu_to_le32(sector_size);

    buffer = g_malloc0(VHDX_HEADER_BLOCK_SIZE);
    md_table = buffer;

    md_table->signature   = VHDX_METADATA_SIGNATURE;
    md_table->entry_count = 5;
    vhdx_metadata_header_le_export(md_table);


    /* This will reference beyond the reserved table portion */
    offset = 64 * KiB;

    md_table_entry = buffer + sizeof(VHDXMetadataTableHeader);

    md_table_entry[0].item_id = file_param_guid;
    md_table_entry[0].offset  = offset;
    md_table_entry[0].length  = sizeof(VHDXFileParameters);
    md_table_entry[0].data_bits |= VHDX_META_FLAGS_IS_REQUIRED;
    offset += md_table_entry[0].length;
    vhdx_metadata_entry_le_export(&md_table_entry[0]);

    md_table_entry[1].item_id = virtual_size_guid;
    md_table_entry[1].offset  = offset;
    md_table_entry[1].length  = sizeof(VHDXVirtualDiskSize);
    md_table_entry[1].data_bits |= VHDX_META_FLAGS_IS_REQUIRED |
                                   VHDX_META_FLAGS_IS_VIRTUAL_DISK;
    offset += md_table_entry[1].length;
    vhdx_metadata_entry_le_export(&md_table_entry[1]);

    md_table_entry[2].item_id = page83_guid;
    md_table_entry[2].offset  = offset;
    md_table_entry[2].length  = sizeof(VHDXPage83Data);
    md_table_entry[2].data_bits |= VHDX_META_FLAGS_IS_REQUIRED |
                                   VHDX_META_FLAGS_IS_VIRTUAL_DISK;
    offset += md_table_entry[2].length;
    vhdx_metadata_entry_le_export(&md_table_entry[2]);

    md_table_entry[3].item_id = logical_sector_guid;
    md_table_entry[3].offset  = offset;
    md_table_entry[3].length  = sizeof(VHDXVirtualDiskLogicalSectorSize);
    md_table_entry[3].data_bits |= VHDX_META_FLAGS_IS_REQUIRED |
                                   VHDX_META_FLAGS_IS_VIRTUAL_DISK;
    offset += md_table_entry[3].length;
    vhdx_metadata_entry_le_export(&md_table_entry[3]);

    md_table_entry[4].item_id = phys_sector_guid;
    md_table_entry[4].offset  = offset;
    md_table_entry[4].length  = sizeof(VHDXVirtualDiskPhysicalSectorSize);
    md_table_entry[4].data_bits |= VHDX_META_FLAGS_IS_REQUIRED |
                                   VHDX_META_FLAGS_IS_VIRTUAL_DISK;
    vhdx_metadata_entry_le_export(&md_table_entry[4]);

    ret = bdrv_pwrite(bs, metadata_offset, buffer, VHDX_HEADER_BLOCK_SIZE);
    if (ret < 0) {
        goto exit;
    }

    ret = bdrv_pwrite(bs, metadata_offset + (64 * KiB), entry_buffer,
                      VHDX_METADATA_ENTRY_BUFFER_SIZE);
    if (ret < 0) {
        goto exit;
    }


exit:
    g_free(buffer);
    g_free(entry_buffer);
    return ret;
}

/* This create the actual BAT itself.  We currently only support
 * 'Dynamic' and 'Fixed' image types.
 *
 *  Dynamic images: default state of the BAT is all zeroes.
 *
 *  Fixed images: default state of the BAT is fully populated, with
 *                file offsets and state PAYLOAD_BLOCK_FULLY_PRESENT.
 */
static int vhdx_create_bat(BlockDriverState *bs, BDRVVHDXState *s,
                           uint64_t image_size, VHDXImageType type,
                           bool use_zero_blocks, uint64_t file_offset,
                           uint32_t length)
{
    int ret = 0;
    uint64_t data_file_offset;
    uint64_t total_sectors = 0;
    uint64_t sector_num = 0;
    uint64_t unused;
    int block_state;
    VHDXSectorInfo sinfo;

    assert(s->bat == NULL);

    /* this gives a data start after BAT/bitmap entries, and well
     * past any metadata entries (with a 4 MB buffer for future
     * expansion */
    data_file_offset = file_offset + length + 5 * MiB;
    total_sectors = image_size >> s->logical_sector_size_bits;

    if (type == VHDX_TYPE_DYNAMIC) {
        /* All zeroes, so we can just extend the file - the end of the BAT
         * is the furthest thing we have written yet */
        ret = bdrv_truncate(bs, data_file_offset);
        if (ret < 0) {
            goto exit;
        }
    } else if (type == VHDX_TYPE_FIXED) {
        ret = bdrv_truncate(bs, data_file_offset + image_size);
        if (ret < 0) {
            goto exit;
        }
    } else {
        ret = -ENOTSUP;
        goto exit;
    }

    if (type == VHDX_TYPE_FIXED ||
                use_zero_blocks ||
                bdrv_has_zero_init(bs) == 0) {
        /* for a fixed file, the default BAT entry is not zero */
        s->bat = g_try_malloc0(length);
        if (length && s->bat == NULL) {
            ret = -ENOMEM;
            goto exit;
        }
        block_state = type == VHDX_TYPE_FIXED ? PAYLOAD_BLOCK_FULLY_PRESENT :
                                                PAYLOAD_BLOCK_NOT_PRESENT;
        block_state = use_zero_blocks ? PAYLOAD_BLOCK_ZERO : block_state;
        /* fill the BAT by emulating sector writes of sectors_per_block size */
        while (sector_num < total_sectors) {
            vhdx_block_translate(s, sector_num, s->sectors_per_block, &sinfo);
            sinfo.file_offset = data_file_offset +
                                (sector_num << s->logical_sector_size_bits);
            sinfo.file_offset = ROUND_UP(sinfo.file_offset, MiB);
            vhdx_update_bat_table_entry(bs, s, &sinfo, &unused, &unused,
                                        block_state);
            cpu_to_le64s(&s->bat[sinfo.bat_idx]);
            sector_num += s->sectors_per_block;
        }
        ret = bdrv_pwrite(bs, file_offset, s->bat, length);
        if (ret < 0) {
            goto exit;
        }
    }



exit:
    g_free(s->bat);
    return ret;
}

/* Creates the region table header, and region table entries.
 * There are 2 supported region table entries: BAT, and Metadata/
 *
 * As the calculations for the BAT region table are also needed
 * to create the BAT itself, we will also cause the BAT to be
 * created.
 */
static int vhdx_create_new_region_table(BlockDriverState *bs,
                                        uint64_t image_size,
                                        uint32_t block_size,
                                        uint32_t sector_size,
                                        uint32_t log_size,
                                        bool use_zero_blocks,
                                        VHDXImageType type,
                                        uint64_t *metadata_offset)
{
    int ret = 0;
    uint32_t offset = 0;
    void *buffer = NULL;
    uint64_t bat_file_offset;
    uint32_t bat_length;
    BDRVVHDXState *s = NULL;
    VHDXRegionTableHeader *region_table;
    VHDXRegionTableEntry *rt_bat;
    VHDXRegionTableEntry *rt_metadata;

    assert(metadata_offset != NULL);

    /* Populate enough of the BDRVVHDXState to be able to use the
     * pre-existing BAT calculation, translation, and update functions */
    s = g_new0(BDRVVHDXState, 1);

    s->chunk_ratio = (VHDX_MAX_SECTORS_PER_BLOCK) *
                     (uint64_t) sector_size / (uint64_t) block_size;

    s->sectors_per_block = block_size / sector_size;
    s->virtual_disk_size = image_size;
    s->block_size = block_size;
    s->logical_sector_size = sector_size;

    vhdx_set_shift_bits(s);

    vhdx_calc_bat_entries(s);

    /* At this point the VHDX state is populated enough for creation */

    /* a single buffer is used so we can calculate the checksum over the
     * entire 64KB block */
    buffer = g_malloc0(VHDX_HEADER_BLOCK_SIZE);
    region_table = buffer;
    offset += sizeof(VHDXRegionTableHeader);
    rt_bat = buffer + offset;
    offset += sizeof(VHDXRegionTableEntry);
    rt_metadata  = buffer + offset;

    region_table->signature = VHDX_REGION_SIGNATURE;
    region_table->entry_count = 2;   /* BAT and Metadata */

    rt_bat->guid        = bat_guid;
    rt_bat->length      = ROUND_UP(s->bat_entries * sizeof(VHDXBatEntry), MiB);
    rt_bat->file_offset = ROUND_UP(VHDX_HEADER_SECTION_END + log_size, MiB);
    s->bat_offset = rt_bat->file_offset;

    rt_metadata->guid        = metadata_guid;
    rt_metadata->file_offset = ROUND_UP(rt_bat->file_offset + rt_bat->length,
                                        MiB);
    rt_metadata->length      = 1 * MiB; /* min size, and more than enough */
    *metadata_offset = rt_metadata->file_offset;

    bat_file_offset = rt_bat->file_offset;
    bat_length = rt_bat->length;

    vhdx_region_header_le_export(region_table);
    vhdx_region_entry_le_export(rt_bat);
    vhdx_region_entry_le_export(rt_metadata);

    vhdx_update_checksum(buffer, VHDX_HEADER_BLOCK_SIZE,
                         offsetof(VHDXRegionTableHeader, checksum));


    /* The region table gives us the data we need to create the BAT,
     * so do that now */
    ret = vhdx_create_bat(bs, s, image_size, type, use_zero_blocks,
                          bat_file_offset, bat_length);
    if (ret < 0) {
        goto exit;
    }

    /* Now write out the region headers to disk */
    ret = bdrv_pwrite(bs, VHDX_REGION_TABLE_OFFSET, buffer,
                      VHDX_HEADER_BLOCK_SIZE);
    if (ret < 0) {
        goto exit;
    }

    ret = bdrv_pwrite(bs, VHDX_REGION_TABLE2_OFFSET, buffer,
                      VHDX_HEADER_BLOCK_SIZE);
    if (ret < 0) {
        goto exit;
    }

exit:
    g_free(s);
    g_free(buffer);
    return ret;
}

/* We need to create the following elements:
 *
 *    .-----------------------------------------------------------------.
 *    |   (A)    |   (B)    |    (C)    |     (D)       |     (E)       |
 *    |  File ID |  Header1 |  Header 2 |  Region Tbl 1 |  Region Tbl 2 |
 *    |          |          |           |               |               |
 *    .-----------------------------------------------------------------.
 *    0         64KB      128KB       192KB           256KB           320KB
 *
 *
 *    .---- ~ ----------- ~ ------------ ~ ---------------- ~ -----------.
 *    |     (F)     |     (G)       |    (H)    |                        |
 *    | Journal Log |  BAT / Bitmap |  Metadata |  .... data ......      |
 *    |             |               |           |                        |
 *    .---- ~ ----------- ~ ------------ ~ ---------------- ~ -----------.
 *   1MB
 */
static int vhdx_create(const char *filename, QemuOpts *opts, Error **errp)
{
    int ret = 0;
    uint64_t image_size = (uint64_t) 2 * GiB;
    uint32_t log_size   = 1 * MiB;
    uint32_t block_size = 0;
    uint64_t signature;
    uint64_t metadata_offset;
    bool use_zero_blocks = false;

    gunichar2 *creator = NULL;
    glong creator_items;
    BlockDriverState *bs;
    char *type = NULL;
    VHDXImageType image_type;
    Error *local_err = NULL;

    image_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
                          BDRV_SECTOR_SIZE);
    log_size = qemu_opt_get_size_del(opts, VHDX_BLOCK_OPT_LOG_SIZE, 0);
    block_size = qemu_opt_get_size_del(opts, VHDX_BLOCK_OPT_BLOCK_SIZE, 0);
    type = qemu_opt_get_del(opts, BLOCK_OPT_SUBFMT);
    use_zero_blocks = qemu_opt_get_bool_del(opts, VHDX_BLOCK_OPT_ZERO, true);

    if (image_size > VHDX_MAX_IMAGE_SIZE) {
        error_setg_errno(errp, EINVAL, "Image size too large; max of 64TB");
        ret = -EINVAL;
        goto exit;
    }

    if (type == NULL) {
        type = g_strdup("dynamic");
    }

    if (!strcmp(type, "dynamic")) {
        image_type = VHDX_TYPE_DYNAMIC;
    } else if (!strcmp(type, "fixed")) {
        image_type = VHDX_TYPE_FIXED;
    } else if (!strcmp(type, "differencing")) {
        error_setg_errno(errp, ENOTSUP,
                         "Differencing files not yet supported");
        ret = -ENOTSUP;
        goto exit;
    } else {
        ret = -EINVAL;
        goto exit;
    }

    /* These are pretty arbitrary, and mainly designed to keep the BAT
     * size reasonable to load into RAM */
    if (block_size == 0) {
        if (image_size > 32 * TiB) {
            block_size = 64 * MiB;
        } else if (image_size > (uint64_t) 100 * GiB) {
            block_size = 32 * MiB;
        } else if (image_size > 1 * GiB) {
            block_size = 16 * MiB;
        } else {
            block_size = 8 * MiB;
        }
    }


    /* make the log size close to what was specified, but must be
     * min 1MB, and multiple of 1MB */
    log_size = ROUND_UP(log_size, MiB);

    block_size = ROUND_UP(block_size, MiB);
    block_size = block_size > VHDX_BLOCK_SIZE_MAX ? VHDX_BLOCK_SIZE_MAX :
                                                    block_size;

    ret = bdrv_create_file(filename, opts, &local_err);
    if (ret < 0) {
        error_propagate(errp, local_err);
        goto exit;
    }

    bs = NULL;
    ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
                    NULL, &local_err);
    if (ret < 0) {
        error_propagate(errp, local_err);
        goto exit;
    }

    /* Create (A) */

    /* The creator field is optional, but may be useful for
     * debugging / diagnostics */
    creator = g_utf8_to_utf16("QEMU v" QEMU_VERSION, -1, NULL,
                              &creator_items, NULL);
    signature = cpu_to_le64(VHDX_FILE_SIGNATURE);
    ret = bdrv_pwrite(bs, VHDX_FILE_ID_OFFSET, &signature, sizeof(signature));
    if (ret < 0) {
        goto delete_and_exit;
    }
    if (creator) {
        ret = bdrv_pwrite(bs, VHDX_FILE_ID_OFFSET + sizeof(signature),
                          creator, creator_items * sizeof(gunichar2));
        if (ret < 0) {
            goto delete_and_exit;
        }
    }


    /* Creates (B),(C) */
    ret = vhdx_create_new_headers(bs, image_size, log_size);
    if (ret < 0) {
        goto delete_and_exit;
    }

    /* Creates (D),(E),(G) explicitly. (F) created as by-product */
    ret = vhdx_create_new_region_table(bs, image_size, block_size, 512,
                                       log_size, use_zero_blocks, image_type,
                                       &metadata_offset);
    if (ret < 0) {
        goto delete_and_exit;
    }

    /* Creates (H) */
    ret = vhdx_create_new_metadata(bs, image_size, block_size, 512,
                                   metadata_offset, image_type);
    if (ret < 0) {
        goto delete_and_exit;
    }


delete_and_exit:
    bdrv_unref(bs);
exit:
    g_free(type);
    g_free(creator);
    return ret;
}

/* If opened r/w, the VHDX driver will automatically replay the log,
 * if one is present, inside the vhdx_open() call.
 *
 * If qemu-img check -r all is called, the image is automatically opened
 * r/w and any log has already been replayed, so there is nothing (currently)
 * for us to do here
 */
static int vhdx_check(BlockDriverState *bs, BdrvCheckResult *result,
                       BdrvCheckMode fix)
{
    BDRVVHDXState *s = bs->opaque;

    if (s->log_replayed_on_open) {
        result->corruptions_fixed++;
    }
    return 0;
}

static QemuOptsList vhdx_create_opts = {
    .name = "vhdx-create-opts",
    .head = QTAILQ_HEAD_INITIALIZER(vhdx_create_opts.head),
    .desc = {
        {
           .name = BLOCK_OPT_SIZE,
           .type = QEMU_OPT_SIZE,
           .help = "Virtual disk size; max of 64TB."
       },
       {
           .name = VHDX_BLOCK_OPT_LOG_SIZE,
           .type = QEMU_OPT_SIZE,
           .def_value_str = stringify(DEFAULT_LOG_SIZE),
           .help = "Log size; min 1MB."
       },
       {
           .name = VHDX_BLOCK_OPT_BLOCK_SIZE,
           .type = QEMU_OPT_SIZE,
           .def_value_str = stringify(0),
           .help = "Block Size; min 1MB, max 256MB. " \
                   "0 means auto-calculate based on image size."
       },
       {
           .name = BLOCK_OPT_SUBFMT,
           .type = QEMU_OPT_STRING,
           .help = "VHDX format type, can be either 'dynamic' or 'fixed'. "\
                   "Default is 'dynamic'."
       },
       {
           .name = VHDX_BLOCK_OPT_ZERO,
           .type = QEMU_OPT_BOOL,
           .help = "Force use of payload blocks of type 'ZERO'. "\
                   "Non-standard, but default.  Do not set to 'off' when "\
                   "using 'qemu-img convert' with subformat=dynamic."
       },
       { NULL }
    }
};

static BlockDriver bdrv_vhdx = {
    .format_name            = "vhdx",
    .instance_size          = sizeof(BDRVVHDXState),
    .bdrv_probe             = vhdx_probe,
    .bdrv_open              = vhdx_open,
    .bdrv_close             = vhdx_close,
    .bdrv_reopen_prepare    = vhdx_reopen_prepare,
    .bdrv_co_readv          = vhdx_co_readv,
    .bdrv_co_writev         = vhdx_co_writev,
    .bdrv_create            = vhdx_create,
    .bdrv_get_info          = vhdx_get_info,
    .bdrv_check             = vhdx_check,
    .bdrv_has_zero_init     = bdrv_has_zero_init_1,

    .create_opts            = &vhdx_create_opts,
};

static void bdrv_vhdx_init(void)
{
    bdrv_register(&bdrv_vhdx);
}

block_init(bdrv_vhdx_init);