summaryrefslogtreecommitdiff
path: root/migration/ram.c
blob: 3f057388cb03bc32e74643873d2ebb0a8c338fd4 (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
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
/*
 * QEMU System Emulator
 *
 * Copyright (c) 2003-2008 Fabrice Bellard
 * Copyright (c) 2011-2015 Red Hat Inc
 *
 * Authors:
 *  Juan Quintela <quintela@redhat.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#include "qemu/osdep.h"
#include <zlib.h>
#include "qapi-event.h"
#include "qemu/cutils.h"
#include "qemu/bitops.h"
#include "qemu/bitmap.h"
#include "qemu/timer.h"
#include "qemu/main-loop.h"
#include "migration/migration.h"
#include "migration/postcopy-ram.h"
#include "exec/address-spaces.h"
#include "migration/page_cache.h"
#include "qemu/error-report.h"
#include "trace.h"
#include "exec/ram_addr.h"
#include "qemu/rcu_queue.h"

#ifdef DEBUG_MIGRATION_RAM
#define DPRINTF(fmt, ...) \
    do { fprintf(stdout, "migration_ram: " fmt, ## __VA_ARGS__); } while (0)
#else
#define DPRINTF(fmt, ...) \
    do { } while (0)
#endif

static int dirty_rate_high_cnt;

static uint64_t bitmap_sync_count;

/***********************************************************/
/* ram save/restore */

#define RAM_SAVE_FLAG_FULL     0x01 /* Obsolete, not used anymore */
#define RAM_SAVE_FLAG_COMPRESS 0x02
#define RAM_SAVE_FLAG_MEM_SIZE 0x04
#define RAM_SAVE_FLAG_PAGE     0x08
#define RAM_SAVE_FLAG_EOS      0x10
#define RAM_SAVE_FLAG_CONTINUE 0x20
#define RAM_SAVE_FLAG_XBZRLE   0x40
/* 0x80 is reserved in migration.h start with 0x100 next */
#define RAM_SAVE_FLAG_COMPRESS_PAGE    0x100

static const uint8_t ZERO_TARGET_PAGE[TARGET_PAGE_SIZE];

static inline bool is_zero_range(uint8_t *p, uint64_t size)
{
    return buffer_find_nonzero_offset(p, size) == size;
}

/* struct contains XBZRLE cache and a static page
   used by the compression */
static struct {
    /* buffer used for XBZRLE encoding */
    uint8_t *encoded_buf;
    /* buffer for storing page content */
    uint8_t *current_buf;
    /* Cache for XBZRLE, Protected by lock. */
    PageCache *cache;
    QemuMutex lock;
} XBZRLE;

/* buffer used for XBZRLE decoding */
static uint8_t *xbzrle_decoded_buf;

static void XBZRLE_cache_lock(void)
{
    if (migrate_use_xbzrle())
        qemu_mutex_lock(&XBZRLE.lock);
}

static void XBZRLE_cache_unlock(void)
{
    if (migrate_use_xbzrle())
        qemu_mutex_unlock(&XBZRLE.lock);
}

/*
 * called from qmp_migrate_set_cache_size in main thread, possibly while
 * a migration is in progress.
 * A running migration maybe using the cache and might finish during this
 * call, hence changes to the cache are protected by XBZRLE.lock().
 */
int64_t xbzrle_cache_resize(int64_t new_size)
{
    PageCache *new_cache;
    int64_t ret;

    if (new_size < TARGET_PAGE_SIZE) {
        return -1;
    }

    XBZRLE_cache_lock();

    if (XBZRLE.cache != NULL) {
        if (pow2floor(new_size) == migrate_xbzrle_cache_size()) {
            goto out_new_size;
        }
        new_cache = cache_init(new_size / TARGET_PAGE_SIZE,
                                        TARGET_PAGE_SIZE);
        if (!new_cache) {
            error_report("Error creating cache");
            ret = -1;
            goto out;
        }

        cache_fini(XBZRLE.cache);
        XBZRLE.cache = new_cache;
    }

out_new_size:
    ret = pow2floor(new_size);
out:
    XBZRLE_cache_unlock();
    return ret;
}

/* accounting for migration statistics */
typedef struct AccountingInfo {
    uint64_t dup_pages;
    uint64_t skipped_pages;
    uint64_t norm_pages;
    uint64_t iterations;
    uint64_t xbzrle_bytes;
    uint64_t xbzrle_pages;
    uint64_t xbzrle_cache_miss;
    double xbzrle_cache_miss_rate;
    uint64_t xbzrle_overflows;
} AccountingInfo;

static AccountingInfo acct_info;

static void acct_clear(void)
{
    memset(&acct_info, 0, sizeof(acct_info));
}

uint64_t dup_mig_bytes_transferred(void)
{
    return acct_info.dup_pages * TARGET_PAGE_SIZE;
}

uint64_t dup_mig_pages_transferred(void)
{
    return acct_info.dup_pages;
}

uint64_t skipped_mig_bytes_transferred(void)
{
    return acct_info.skipped_pages * TARGET_PAGE_SIZE;
}

uint64_t skipped_mig_pages_transferred(void)
{
    return acct_info.skipped_pages;
}

uint64_t norm_mig_bytes_transferred(void)
{
    return acct_info.norm_pages * TARGET_PAGE_SIZE;
}

uint64_t norm_mig_pages_transferred(void)
{
    return acct_info.norm_pages;
}

uint64_t xbzrle_mig_bytes_transferred(void)
{
    return acct_info.xbzrle_bytes;
}

uint64_t xbzrle_mig_pages_transferred(void)
{
    return acct_info.xbzrle_pages;
}

uint64_t xbzrle_mig_pages_cache_miss(void)
{
    return acct_info.xbzrle_cache_miss;
}

double xbzrle_mig_cache_miss_rate(void)
{
    return acct_info.xbzrle_cache_miss_rate;
}

uint64_t xbzrle_mig_pages_overflow(void)
{
    return acct_info.xbzrle_overflows;
}

/* This is the last block that we have visited serching for dirty pages
 */
static RAMBlock *last_seen_block;
/* This is the last block from where we have sent data */
static RAMBlock *last_sent_block;
static ram_addr_t last_offset;
static QemuMutex migration_bitmap_mutex;
static uint64_t migration_dirty_pages;
static uint32_t last_version;
static bool ram_bulk_stage;

/* used by the search for pages to send */
struct PageSearchStatus {
    /* Current block being searched */
    RAMBlock    *block;
    /* Current offset to search from */
    ram_addr_t   offset;
    /* Set once we wrap around */
    bool         complete_round;
};
typedef struct PageSearchStatus PageSearchStatus;

static struct BitmapRcu {
    struct rcu_head rcu;
    /* Main migration bitmap */
    unsigned long *bmap;
    /* bitmap of pages that haven't been sent even once
     * only maintained and used in postcopy at the moment
     * where it's used to send the dirtymap at the start
     * of the postcopy phase
     */
    unsigned long *unsentmap;
} *migration_bitmap_rcu;

struct CompressParam {
    bool start;
    bool done;
    QEMUFile *file;
    QemuMutex mutex;
    QemuCond cond;
    RAMBlock *block;
    ram_addr_t offset;
};
typedef struct CompressParam CompressParam;

struct DecompressParam {
    bool start;
    QemuMutex mutex;
    QemuCond cond;
    void *des;
    uint8_t *compbuf;
    int len;
};
typedef struct DecompressParam DecompressParam;

static CompressParam *comp_param;
static QemuThread *compress_threads;
/* comp_done_cond is used to wake up the migration thread when
 * one of the compression threads has finished the compression.
 * comp_done_lock is used to co-work with comp_done_cond.
 */
static QemuMutex *comp_done_lock;
static QemuCond *comp_done_cond;
/* The empty QEMUFileOps will be used by file in CompressParam */
static const QEMUFileOps empty_ops = { };

static bool compression_switch;
static bool quit_comp_thread;
static bool quit_decomp_thread;
static DecompressParam *decomp_param;
static QemuThread *decompress_threads;

static int do_compress_ram_page(CompressParam *param);

static void *do_data_compress(void *opaque)
{
    CompressParam *param = opaque;

    while (!quit_comp_thread) {
        qemu_mutex_lock(&param->mutex);
        /* Re-check the quit_comp_thread in case of
         * terminate_compression_threads is called just before
         * qemu_mutex_lock(&param->mutex) and after
         * while(!quit_comp_thread), re-check it here can make
         * sure the compression thread terminate as expected.
         */
        while (!param->start && !quit_comp_thread) {
            qemu_cond_wait(&param->cond, &param->mutex);
        }
        if (!quit_comp_thread) {
            do_compress_ram_page(param);
        }
        param->start = false;
        qemu_mutex_unlock(&param->mutex);

        qemu_mutex_lock(comp_done_lock);
        param->done = true;
        qemu_cond_signal(comp_done_cond);
        qemu_mutex_unlock(comp_done_lock);
    }

    return NULL;
}

static inline void terminate_compression_threads(void)
{
    int idx, thread_count;

    thread_count = migrate_compress_threads();
    quit_comp_thread = true;
    for (idx = 0; idx < thread_count; idx++) {
        qemu_mutex_lock(&comp_param[idx].mutex);
        qemu_cond_signal(&comp_param[idx].cond);
        qemu_mutex_unlock(&comp_param[idx].mutex);
    }
}

void migrate_compress_threads_join(void)
{
    int i, thread_count;

    if (!migrate_use_compression()) {
        return;
    }
    terminate_compression_threads();
    thread_count = migrate_compress_threads();
    for (i = 0; i < thread_count; i++) {
        qemu_thread_join(compress_threads + i);
        qemu_fclose(comp_param[i].file);
        qemu_mutex_destroy(&comp_param[i].mutex);
        qemu_cond_destroy(&comp_param[i].cond);
    }
    qemu_mutex_destroy(comp_done_lock);
    qemu_cond_destroy(comp_done_cond);
    g_free(compress_threads);
    g_free(comp_param);
    g_free(comp_done_cond);
    g_free(comp_done_lock);
    compress_threads = NULL;
    comp_param = NULL;
    comp_done_cond = NULL;
    comp_done_lock = NULL;
}

void migrate_compress_threads_create(void)
{
    int i, thread_count;

    if (!migrate_use_compression()) {
        return;
    }
    quit_comp_thread = false;
    compression_switch = true;
    thread_count = migrate_compress_threads();
    compress_threads = g_new0(QemuThread, thread_count);
    comp_param = g_new0(CompressParam, thread_count);
    comp_done_cond = g_new0(QemuCond, 1);
    comp_done_lock = g_new0(QemuMutex, 1);
    qemu_cond_init(comp_done_cond);
    qemu_mutex_init(comp_done_lock);
    for (i = 0; i < thread_count; i++) {
        /* com_param[i].file is just used as a dummy buffer to save data, set
         * it's ops to empty.
         */
        comp_param[i].file = qemu_fopen_ops(NULL, &empty_ops);
        comp_param[i].done = true;
        qemu_mutex_init(&comp_param[i].mutex);
        qemu_cond_init(&comp_param[i].cond);
        qemu_thread_create(compress_threads + i, "compress",
                           do_data_compress, comp_param + i,
                           QEMU_THREAD_JOINABLE);
    }
}

/**
 * save_page_header: Write page header to wire
 *
 * If this is the 1st block, it also writes the block identification
 *
 * Returns: Number of bytes written
 *
 * @f: QEMUFile where to send the data
 * @block: block that contains the page we want to send
 * @offset: offset inside the block for the page
 *          in the lower bits, it contains flags
 */
static size_t save_page_header(QEMUFile *f, RAMBlock *block, ram_addr_t offset)
{
    size_t size, len;

    qemu_put_be64(f, offset);
    size = 8;

    if (!(offset & RAM_SAVE_FLAG_CONTINUE)) {
        len = strlen(block->idstr);
        qemu_put_byte(f, len);
        qemu_put_buffer(f, (uint8_t *)block->idstr, len);
        size += 1 + len;
    }
    return size;
}

/* Reduce amount of guest cpu execution to hopefully slow down memory writes.
 * If guest dirty memory rate is reduced below the rate at which we can
 * transfer pages to the destination then we should be able to complete
 * migration. Some workloads dirty memory way too fast and will not effectively
 * converge, even with auto-converge.
 */
static void mig_throttle_guest_down(void)
{
    MigrationState *s = migrate_get_current();
    uint64_t pct_initial =
            s->parameters[MIGRATION_PARAMETER_X_CPU_THROTTLE_INITIAL];
    uint64_t pct_icrement =
            s->parameters[MIGRATION_PARAMETER_X_CPU_THROTTLE_INCREMENT];

    /* We have not started throttling yet. Let's start it. */
    if (!cpu_throttle_active()) {
        cpu_throttle_set(pct_initial);
    } else {
        /* Throttling already on, just increase the rate */
        cpu_throttle_set(cpu_throttle_get_percentage() + pct_icrement);
    }
}

/* Update the xbzrle cache to reflect a page that's been sent as all 0.
 * The important thing is that a stale (not-yet-0'd) page be replaced
 * by the new data.
 * As a bonus, if the page wasn't in the cache it gets added so that
 * when a small write is made into the 0'd page it gets XBZRLE sent
 */
static void xbzrle_cache_zero_page(ram_addr_t current_addr)
{
    if (ram_bulk_stage || !migrate_use_xbzrle()) {
        return;
    }

    /* We don't care if this fails to allocate a new cache page
     * as long as it updated an old one */
    cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE,
                 bitmap_sync_count);
}

#define ENCODING_FLAG_XBZRLE 0x1

/**
 * save_xbzrle_page: compress and send current page
 *
 * Returns: 1 means that we wrote the page
 *          0 means that page is identical to the one already sent
 *          -1 means that xbzrle would be longer than normal
 *
 * @f: QEMUFile where to send the data
 * @current_data:
 * @current_addr:
 * @block: block that contains the page we want to send
 * @offset: offset inside the block for the page
 * @last_stage: if we are at the completion stage
 * @bytes_transferred: increase it with the number of transferred bytes
 */
static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data,
                            ram_addr_t current_addr, RAMBlock *block,
                            ram_addr_t offset, bool last_stage,
                            uint64_t *bytes_transferred)
{
    int encoded_len = 0, bytes_xbzrle;
    uint8_t *prev_cached_page;

    if (!cache_is_cached(XBZRLE.cache, current_addr, bitmap_sync_count)) {
        acct_info.xbzrle_cache_miss++;
        if (!last_stage) {
            if (cache_insert(XBZRLE.cache, current_addr, *current_data,
                             bitmap_sync_count) == -1) {
                return -1;
            } else {
                /* update *current_data when the page has been
                   inserted into cache */
                *current_data = get_cached_data(XBZRLE.cache, current_addr);
            }
        }
        return -1;
    }

    prev_cached_page = get_cached_data(XBZRLE.cache, current_addr);

    /* save current buffer into memory */
    memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE);

    /* XBZRLE encoding (if there is no overflow) */
    encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf,
                                       TARGET_PAGE_SIZE, XBZRLE.encoded_buf,
                                       TARGET_PAGE_SIZE);
    if (encoded_len == 0) {
        DPRINTF("Skipping unmodified page\n");
        return 0;
    } else if (encoded_len == -1) {
        DPRINTF("Overflow\n");
        acct_info.xbzrle_overflows++;
        /* update data in the cache */
        if (!last_stage) {
            memcpy(prev_cached_page, *current_data, TARGET_PAGE_SIZE);
            *current_data = prev_cached_page;
        }
        return -1;
    }

    /* we need to update the data in the cache, in order to get the same data */
    if (!last_stage) {
        memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);
    }

    /* Send XBZRLE based compressed page */
    bytes_xbzrle = save_page_header(f, block, offset | RAM_SAVE_FLAG_XBZRLE);
    qemu_put_byte(f, ENCODING_FLAG_XBZRLE);
    qemu_put_be16(f, encoded_len);
    qemu_put_buffer(f, XBZRLE.encoded_buf, encoded_len);
    bytes_xbzrle += encoded_len + 1 + 2;
    acct_info.xbzrle_pages++;
    acct_info.xbzrle_bytes += bytes_xbzrle;
    *bytes_transferred += bytes_xbzrle;

    return 1;
}

/* Called with rcu_read_lock() to protect migration_bitmap
 * rb: The RAMBlock  to search for dirty pages in
 * start: Start address (typically so we can continue from previous page)
 * ram_addr_abs: Pointer into which to store the address of the dirty page
 *               within the global ram_addr space
 *
 * Returns: byte offset within memory region of the start of a dirty page
 */
static inline
ram_addr_t migration_bitmap_find_dirty(RAMBlock *rb,
                                       ram_addr_t start,
                                       ram_addr_t *ram_addr_abs)
{
    unsigned long base = rb->offset >> TARGET_PAGE_BITS;
    unsigned long nr = base + (start >> TARGET_PAGE_BITS);
    uint64_t rb_size = rb->used_length;
    unsigned long size = base + (rb_size >> TARGET_PAGE_BITS);
    unsigned long *bitmap;

    unsigned long next;

    bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
    if (ram_bulk_stage && nr > base) {
        next = nr + 1;
    } else {
        next = find_next_bit(bitmap, size, nr);
    }

    *ram_addr_abs = next << TARGET_PAGE_BITS;
    return (next - base) << TARGET_PAGE_BITS;
}

static inline bool migration_bitmap_clear_dirty(ram_addr_t addr)
{
    bool ret;
    int nr = addr >> TARGET_PAGE_BITS;
    unsigned long *bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;

    ret = test_and_clear_bit(nr, bitmap);

    if (ret) {
        migration_dirty_pages--;
    }
    return ret;
}

static void migration_bitmap_sync_range(ram_addr_t start, ram_addr_t length)
{
    unsigned long *bitmap;
    bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
    migration_dirty_pages +=
        cpu_physical_memory_sync_dirty_bitmap(bitmap, start, length);
}

/* Fix me: there are too many global variables used in migration process. */
static int64_t start_time;
static int64_t bytes_xfer_prev;
static int64_t num_dirty_pages_period;
static uint64_t xbzrle_cache_miss_prev;
static uint64_t iterations_prev;

static void migration_bitmap_sync_init(void)
{
    start_time = 0;
    bytes_xfer_prev = 0;
    num_dirty_pages_period = 0;
    xbzrle_cache_miss_prev = 0;
    iterations_prev = 0;
}

static void migration_bitmap_sync(void)
{
    RAMBlock *block;
    uint64_t num_dirty_pages_init = migration_dirty_pages;
    MigrationState *s = migrate_get_current();
    int64_t end_time;
    int64_t bytes_xfer_now;

    bitmap_sync_count++;

    if (!bytes_xfer_prev) {
        bytes_xfer_prev = ram_bytes_transferred();
    }

    if (!start_time) {
        start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
    }

    trace_migration_bitmap_sync_start();
    address_space_sync_dirty_bitmap(&address_space_memory);

    qemu_mutex_lock(&migration_bitmap_mutex);
    rcu_read_lock();
    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
        migration_bitmap_sync_range(block->offset, block->used_length);
    }
    rcu_read_unlock();
    qemu_mutex_unlock(&migration_bitmap_mutex);

    trace_migration_bitmap_sync_end(migration_dirty_pages
                                    - num_dirty_pages_init);
    num_dirty_pages_period += migration_dirty_pages - num_dirty_pages_init;
    end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);

    /* more than 1 second = 1000 millisecons */
    if (end_time > start_time + 1000) {
        if (migrate_auto_converge()) {
            /* The following detection logic can be refined later. For now:
               Check to see if the dirtied bytes is 50% more than the approx.
               amount of bytes that just got transferred since the last time we
               were in this routine. If that happens twice, start or increase
               throttling */
            bytes_xfer_now = ram_bytes_transferred();

            if (s->dirty_pages_rate &&
               (num_dirty_pages_period * TARGET_PAGE_SIZE >
                   (bytes_xfer_now - bytes_xfer_prev)/2) &&
               (dirty_rate_high_cnt++ >= 2)) {
                    trace_migration_throttle();
                    dirty_rate_high_cnt = 0;
                    mig_throttle_guest_down();
             }
             bytes_xfer_prev = bytes_xfer_now;
        }

        if (migrate_use_xbzrle()) {
            if (iterations_prev != acct_info.iterations) {
                acct_info.xbzrle_cache_miss_rate =
                   (double)(acct_info.xbzrle_cache_miss -
                            xbzrle_cache_miss_prev) /
                   (acct_info.iterations - iterations_prev);
            }
            iterations_prev = acct_info.iterations;
            xbzrle_cache_miss_prev = acct_info.xbzrle_cache_miss;
        }
        s->dirty_pages_rate = num_dirty_pages_period * 1000
            / (end_time - start_time);
        s->dirty_bytes_rate = s->dirty_pages_rate * TARGET_PAGE_SIZE;
        start_time = end_time;
        num_dirty_pages_period = 0;
    }
    s->dirty_sync_count = bitmap_sync_count;
    if (migrate_use_events()) {
        qapi_event_send_migration_pass(bitmap_sync_count, NULL);
    }
}

/**
 * save_zero_page: Send the zero page to the stream
 *
 * Returns: Number of pages written.
 *
 * @f: QEMUFile where to send the data
 * @block: block that contains the page we want to send
 * @offset: offset inside the block for the page
 * @p: pointer to the page
 * @bytes_transferred: increase it with the number of transferred bytes
 */
static int save_zero_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
                          uint8_t *p, uint64_t *bytes_transferred)
{
    int pages = -1;

    if (is_zero_range(p, TARGET_PAGE_SIZE)) {
        acct_info.dup_pages++;
        *bytes_transferred += save_page_header(f, block,
                                               offset | RAM_SAVE_FLAG_COMPRESS);
        qemu_put_byte(f, 0);
        *bytes_transferred += 1;
        pages = 1;
    }

    return pages;
}

/**
 * ram_save_page: Send the given page to the stream
 *
 * Returns: Number of pages written.
 *          < 0 - error
 *          >=0 - Number of pages written - this might legally be 0
 *                if xbzrle noticed the page was the same.
 *
 * @f: QEMUFile where to send the data
 * @block: block that contains the page we want to send
 * @offset: offset inside the block for the page
 * @last_stage: if we are at the completion stage
 * @bytes_transferred: increase it with the number of transferred bytes
 */
static int ram_save_page(QEMUFile *f, PageSearchStatus *pss,
                         bool last_stage, uint64_t *bytes_transferred)
{
    int pages = -1;
    uint64_t bytes_xmit;
    ram_addr_t current_addr;
    uint8_t *p;
    int ret;
    bool send_async = true;
    RAMBlock *block = pss->block;
    ram_addr_t offset = pss->offset;

    p = block->host + offset;

    /* In doubt sent page as normal */
    bytes_xmit = 0;
    ret = ram_control_save_page(f, block->offset,
                           offset, TARGET_PAGE_SIZE, &bytes_xmit);
    if (bytes_xmit) {
        *bytes_transferred += bytes_xmit;
        pages = 1;
    }

    XBZRLE_cache_lock();

    current_addr = block->offset + offset;

    if (block == last_sent_block) {
        offset |= RAM_SAVE_FLAG_CONTINUE;
    }
    if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
        if (ret != RAM_SAVE_CONTROL_DELAYED) {
            if (bytes_xmit > 0) {
                acct_info.norm_pages++;
            } else if (bytes_xmit == 0) {
                acct_info.dup_pages++;
            }
        }
    } else {
        pages = save_zero_page(f, block, offset, p, bytes_transferred);
        if (pages > 0) {
            /* Must let xbzrle know, otherwise a previous (now 0'd) cached
             * page would be stale
             */
            xbzrle_cache_zero_page(current_addr);
        } else if (!ram_bulk_stage && migrate_use_xbzrle()) {
            pages = save_xbzrle_page(f, &p, current_addr, block,
                                     offset, last_stage, bytes_transferred);
            if (!last_stage) {
                /* Can't send this cached data async, since the cache page
                 * might get updated before it gets to the wire
                 */
                send_async = false;
            }
        }
    }

    /* XBZRLE overflow or normal page */
    if (pages == -1) {
        *bytes_transferred += save_page_header(f, block,
                                               offset | RAM_SAVE_FLAG_PAGE);
        if (send_async) {
            qemu_put_buffer_async(f, p, TARGET_PAGE_SIZE);
        } else {
            qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
        }
        *bytes_transferred += TARGET_PAGE_SIZE;
        pages = 1;
        acct_info.norm_pages++;
    }

    XBZRLE_cache_unlock();

    return pages;
}

static int do_compress_ram_page(CompressParam *param)
{
    int bytes_sent, blen;
    uint8_t *p;
    RAMBlock *block = param->block;
    ram_addr_t offset = param->offset;

    p = block->host + (offset & TARGET_PAGE_MASK);

    bytes_sent = save_page_header(param->file, block, offset |
                                  RAM_SAVE_FLAG_COMPRESS_PAGE);
    blen = qemu_put_compression_data(param->file, p, TARGET_PAGE_SIZE,
                                     migrate_compress_level());
    bytes_sent += blen;

    return bytes_sent;
}

static inline void start_compression(CompressParam *param)
{
    param->done = false;
    qemu_mutex_lock(&param->mutex);
    param->start = true;
    qemu_cond_signal(&param->cond);
    qemu_mutex_unlock(&param->mutex);
}

static inline void start_decompression(DecompressParam *param)
{
    qemu_mutex_lock(&param->mutex);
    param->start = true;
    qemu_cond_signal(&param->cond);
    qemu_mutex_unlock(&param->mutex);
}

static uint64_t bytes_transferred;

static void flush_compressed_data(QEMUFile *f)
{
    int idx, len, thread_count;

    if (!migrate_use_compression()) {
        return;
    }
    thread_count = migrate_compress_threads();
    for (idx = 0; idx < thread_count; idx++) {
        if (!comp_param[idx].done) {
            qemu_mutex_lock(comp_done_lock);
            while (!comp_param[idx].done && !quit_comp_thread) {
                qemu_cond_wait(comp_done_cond, comp_done_lock);
            }
            qemu_mutex_unlock(comp_done_lock);
        }
        if (!quit_comp_thread) {
            len = qemu_put_qemu_file(f, comp_param[idx].file);
            bytes_transferred += len;
        }
    }
}

static inline void set_compress_params(CompressParam *param, RAMBlock *block,
                                       ram_addr_t offset)
{
    param->block = block;
    param->offset = offset;
}

static int compress_page_with_multi_thread(QEMUFile *f, RAMBlock *block,
                                           ram_addr_t offset,
                                           uint64_t *bytes_transferred)
{
    int idx, thread_count, bytes_xmit = -1, pages = -1;

    thread_count = migrate_compress_threads();
    qemu_mutex_lock(comp_done_lock);
    while (true) {
        for (idx = 0; idx < thread_count; idx++) {
            if (comp_param[idx].done) {
                bytes_xmit = qemu_put_qemu_file(f, comp_param[idx].file);
                set_compress_params(&comp_param[idx], block, offset);
                start_compression(&comp_param[idx]);
                pages = 1;
                acct_info.norm_pages++;
                *bytes_transferred += bytes_xmit;
                break;
            }
        }
        if (pages > 0) {
            break;
        } else {
            qemu_cond_wait(comp_done_cond, comp_done_lock);
        }
    }
    qemu_mutex_unlock(comp_done_lock);

    return pages;
}

/**
 * ram_save_compressed_page: compress the given page and send it to the stream
 *
 * Returns: Number of pages written.
 *
 * @f: QEMUFile where to send the data
 * @block: block that contains the page we want to send
 * @offset: offset inside the block for the page
 * @last_stage: if we are at the completion stage
 * @bytes_transferred: increase it with the number of transferred bytes
 */
static int ram_save_compressed_page(QEMUFile *f, PageSearchStatus *pss,
                                    bool last_stage,
                                    uint64_t *bytes_transferred)
{
    int pages = -1;
    uint64_t bytes_xmit;
    uint8_t *p;
    int ret;
    RAMBlock *block = pss->block;
    ram_addr_t offset = pss->offset;

    p = block->host + offset;

    bytes_xmit = 0;
    ret = ram_control_save_page(f, block->offset,
                                offset, TARGET_PAGE_SIZE, &bytes_xmit);
    if (bytes_xmit) {
        *bytes_transferred += bytes_xmit;
        pages = 1;
    }
    if (block == last_sent_block) {
        offset |= RAM_SAVE_FLAG_CONTINUE;
    }
    if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
        if (ret != RAM_SAVE_CONTROL_DELAYED) {
            if (bytes_xmit > 0) {
                acct_info.norm_pages++;
            } else if (bytes_xmit == 0) {
                acct_info.dup_pages++;
            }
        }
    } else {
        /* When starting the process of a new block, the first page of
         * the block should be sent out before other pages in the same
         * block, and all the pages in last block should have been sent
         * out, keeping this order is important, because the 'cont' flag
         * is used to avoid resending the block name.
         */
        if (block != last_sent_block) {
            flush_compressed_data(f);
            pages = save_zero_page(f, block, offset, p, bytes_transferred);
            if (pages == -1) {
                set_compress_params(&comp_param[0], block, offset);
                /* Use the qemu thread to compress the data to make sure the
                 * first page is sent out before other pages
                 */
                bytes_xmit = do_compress_ram_page(&comp_param[0]);
                acct_info.norm_pages++;
                qemu_put_qemu_file(f, comp_param[0].file);
                *bytes_transferred += bytes_xmit;
                pages = 1;
            }
        } else {
            pages = save_zero_page(f, block, offset, p, bytes_transferred);
            if (pages == -1) {
                pages = compress_page_with_multi_thread(f, block, offset,
                                                        bytes_transferred);
            }
        }
    }

    return pages;
}

/*
 * Find the next dirty page and update any state associated with
 * the search process.
 *
 * Returns: True if a page is found
 *
 * @f: Current migration stream.
 * @pss: Data about the state of the current dirty page scan.
 * @*again: Set to false if the search has scanned the whole of RAM
 * *ram_addr_abs: Pointer into which to store the address of the dirty page
 *               within the global ram_addr space
 */
static bool find_dirty_block(QEMUFile *f, PageSearchStatus *pss,
                             bool *again, ram_addr_t *ram_addr_abs)
{
    pss->offset = migration_bitmap_find_dirty(pss->block, pss->offset,
                                              ram_addr_abs);
    if (pss->complete_round && pss->block == last_seen_block &&
        pss->offset >= last_offset) {
        /*
         * We've been once around the RAM and haven't found anything.
         * Give up.
         */
        *again = false;
        return false;
    }
    if (pss->offset >= pss->block->used_length) {
        /* Didn't find anything in this RAM Block */
        pss->offset = 0;
        pss->block = QLIST_NEXT_RCU(pss->block, next);
        if (!pss->block) {
            /* Hit the end of the list */
            pss->block = QLIST_FIRST_RCU(&ram_list.blocks);
            /* Flag that we've looped */
            pss->complete_round = true;
            ram_bulk_stage = false;
            if (migrate_use_xbzrle()) {
                /* If xbzrle is on, stop using the data compression at this
                 * point. In theory, xbzrle can do better than compression.
                 */
                flush_compressed_data(f);
                compression_switch = false;
            }
        }
        /* Didn't find anything this time, but try again on the new block */
        *again = true;
        return false;
    } else {
        /* Can go around again, but... */
        *again = true;
        /* We've found something so probably don't need to */
        return true;
    }
}

/*
 * Helper for 'get_queued_page' - gets a page off the queue
 *      ms:      MigrationState in
 * *offset:      Used to return the offset within the RAMBlock
 * ram_addr_abs: global offset in the dirty/sent bitmaps
 *
 * Returns:      block (or NULL if none available)
 */
static RAMBlock *unqueue_page(MigrationState *ms, ram_addr_t *offset,
                              ram_addr_t *ram_addr_abs)
{
    RAMBlock *block = NULL;

    qemu_mutex_lock(&ms->src_page_req_mutex);
    if (!QSIMPLEQ_EMPTY(&ms->src_page_requests)) {
        struct MigrationSrcPageRequest *entry =
                                QSIMPLEQ_FIRST(&ms->src_page_requests);
        block = entry->rb;
        *offset = entry->offset;
        *ram_addr_abs = (entry->offset + entry->rb->offset) &
                        TARGET_PAGE_MASK;

        if (entry->len > TARGET_PAGE_SIZE) {
            entry->len -= TARGET_PAGE_SIZE;
            entry->offset += TARGET_PAGE_SIZE;
        } else {
            memory_region_unref(block->mr);
            QSIMPLEQ_REMOVE_HEAD(&ms->src_page_requests, next_req);
            g_free(entry);
        }
    }
    qemu_mutex_unlock(&ms->src_page_req_mutex);

    return block;
}

/*
 * Unqueue a page from the queue fed by postcopy page requests; skips pages
 * that are already sent (!dirty)
 *
 *      ms:      MigrationState in
 *     pss:      PageSearchStatus structure updated with found block/offset
 * ram_addr_abs: global offset in the dirty/sent bitmaps
 *
 * Returns:      true if a queued page is found
 */
static bool get_queued_page(MigrationState *ms, PageSearchStatus *pss,
                            ram_addr_t *ram_addr_abs)
{
    RAMBlock  *block;
    ram_addr_t offset;
    bool dirty;

    do {
        block = unqueue_page(ms, &offset, ram_addr_abs);
        /*
         * We're sending this page, and since it's postcopy nothing else
         * will dirty it, and we must make sure it doesn't get sent again
         * even if this queue request was received after the background
         * search already sent it.
         */
        if (block) {
            unsigned long *bitmap;
            bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
            dirty = test_bit(*ram_addr_abs >> TARGET_PAGE_BITS, bitmap);
            if (!dirty) {
                trace_get_queued_page_not_dirty(
                    block->idstr, (uint64_t)offset,
                    (uint64_t)*ram_addr_abs,
                    test_bit(*ram_addr_abs >> TARGET_PAGE_BITS,
                         atomic_rcu_read(&migration_bitmap_rcu)->unsentmap));
            } else {
                trace_get_queued_page(block->idstr,
                                      (uint64_t)offset,
                                      (uint64_t)*ram_addr_abs);
            }
        }

    } while (block && !dirty);

    if (block) {
        /*
         * As soon as we start servicing pages out of order, then we have
         * to kill the bulk stage, since the bulk stage assumes
         * in (migration_bitmap_find_and_reset_dirty) that every page is
         * dirty, that's no longer true.
         */
        ram_bulk_stage = false;

        /*
         * We want the background search to continue from the queued page
         * since the guest is likely to want other pages near to the page
         * it just requested.
         */
        pss->block = block;
        pss->offset = offset;
    }

    return !!block;
}

/**
 * flush_page_queue: Flush any remaining pages in the ram request queue
 *    it should be empty at the end anyway, but in error cases there may be
 *    some left.
 *
 * ms: MigrationState
 */
void flush_page_queue(MigrationState *ms)
{
    struct MigrationSrcPageRequest *mspr, *next_mspr;
    /* This queue generally should be empty - but in the case of a failed
     * migration might have some droppings in.
     */
    rcu_read_lock();
    QSIMPLEQ_FOREACH_SAFE(mspr, &ms->src_page_requests, next_req, next_mspr) {
        memory_region_unref(mspr->rb->mr);
        QSIMPLEQ_REMOVE_HEAD(&ms->src_page_requests, next_req);
        g_free(mspr);
    }
    rcu_read_unlock();
}

/**
 * Queue the pages for transmission, e.g. a request from postcopy destination
 *   ms: MigrationStatus in which the queue is held
 *   rbname: The RAMBlock the request is for - may be NULL (to mean reuse last)
 *   start: Offset from the start of the RAMBlock
 *   len: Length (in bytes) to send
 *   Return: 0 on success
 */
int ram_save_queue_pages(MigrationState *ms, const char *rbname,
                         ram_addr_t start, ram_addr_t len)
{
    RAMBlock *ramblock;

    rcu_read_lock();
    if (!rbname) {
        /* Reuse last RAMBlock */
        ramblock = ms->last_req_rb;

        if (!ramblock) {
            /*
             * Shouldn't happen, we can't reuse the last RAMBlock if
             * it's the 1st request.
             */
            error_report("ram_save_queue_pages no previous block");
            goto err;
        }
    } else {
        ramblock = qemu_ram_block_by_name(rbname);

        if (!ramblock) {
            /* We shouldn't be asked for a non-existent RAMBlock */
            error_report("ram_save_queue_pages no block '%s'", rbname);
            goto err;
        }
        ms->last_req_rb = ramblock;
    }
    trace_ram_save_queue_pages(ramblock->idstr, start, len);
    if (start+len > ramblock->used_length) {
        error_report("%s request overrun start=" RAM_ADDR_FMT " len="
                     RAM_ADDR_FMT " blocklen=" RAM_ADDR_FMT,
                     __func__, start, len, ramblock->used_length);
        goto err;
    }

    struct MigrationSrcPageRequest *new_entry =
        g_malloc0(sizeof(struct MigrationSrcPageRequest));
    new_entry->rb = ramblock;
    new_entry->offset = start;
    new_entry->len = len;

    memory_region_ref(ramblock->mr);
    qemu_mutex_lock(&ms->src_page_req_mutex);
    QSIMPLEQ_INSERT_TAIL(&ms->src_page_requests, new_entry, next_req);
    qemu_mutex_unlock(&ms->src_page_req_mutex);
    rcu_read_unlock();

    return 0;

err:
    rcu_read_unlock();
    return -1;
}

/**
 * ram_save_target_page: Save one target page
 *
 *
 * @f: QEMUFile where to send the data
 * @block: pointer to block that contains the page we want to send
 * @offset: offset inside the block for the page;
 * @last_stage: if we are at the completion stage
 * @bytes_transferred: increase it with the number of transferred bytes
 * @dirty_ram_abs: Address of the start of the dirty page in ram_addr_t space
 *
 * Returns: Number of pages written.
 */
static int ram_save_target_page(MigrationState *ms, QEMUFile *f,
                                PageSearchStatus *pss,
                                bool last_stage,
                                uint64_t *bytes_transferred,
                                ram_addr_t dirty_ram_abs)
{
    int res = 0;

    /* Check the pages is dirty and if it is send it */
    if (migration_bitmap_clear_dirty(dirty_ram_abs)) {
        unsigned long *unsentmap;
        if (compression_switch && migrate_use_compression()) {
            res = ram_save_compressed_page(f, pss,
                                           last_stage,
                                           bytes_transferred);
        } else {
            res = ram_save_page(f, pss, last_stage,
                                bytes_transferred);
        }

        if (res < 0) {
            return res;
        }
        unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap;
        if (unsentmap) {
            clear_bit(dirty_ram_abs >> TARGET_PAGE_BITS, unsentmap);
        }
        /* Only update last_sent_block if a block was actually sent; xbzrle
         * might have decided the page was identical so didn't bother writing
         * to the stream.
         */
        if (res > 0) {
            last_sent_block = pss->block;
        }
    }

    return res;
}

/**
 * ram_save_host_page: Starting at *offset send pages upto the end
 *                     of the current host page.  It's valid for the initial
 *                     offset to point into the middle of a host page
 *                     in which case the remainder of the hostpage is sent.
 *                     Only dirty target pages are sent.
 *
 * Returns: Number of pages written.
 *
 * @f: QEMUFile where to send the data
 * @block: pointer to block that contains the page we want to send
 * @offset: offset inside the block for the page; updated to last target page
 *          sent
 * @last_stage: if we are at the completion stage
 * @bytes_transferred: increase it with the number of transferred bytes
 * @dirty_ram_abs: Address of the start of the dirty page in ram_addr_t space
 */
static int ram_save_host_page(MigrationState *ms, QEMUFile *f,
                              PageSearchStatus *pss,
                              bool last_stage,
                              uint64_t *bytes_transferred,
                              ram_addr_t dirty_ram_abs)
{
    int tmppages, pages = 0;
    do {
        tmppages = ram_save_target_page(ms, f, pss, last_stage,
                                        bytes_transferred, dirty_ram_abs);
        if (tmppages < 0) {
            return tmppages;
        }

        pages += tmppages;
        pss->offset += TARGET_PAGE_SIZE;
        dirty_ram_abs += TARGET_PAGE_SIZE;
    } while (pss->offset & (qemu_host_page_size - 1));

    /* The offset we leave with is the last one we looked at */
    pss->offset -= TARGET_PAGE_SIZE;
    return pages;
}

/**
 * ram_find_and_save_block: Finds a dirty page and sends it to f
 *
 * Called within an RCU critical section.
 *
 * Returns:  The number of pages written
 *           0 means no dirty pages
 *
 * @f: QEMUFile where to send the data
 * @last_stage: if we are at the completion stage
 * @bytes_transferred: increase it with the number of transferred bytes
 *
 * On systems where host-page-size > target-page-size it will send all the
 * pages in a host page that are dirty.
 */

static int ram_find_and_save_block(QEMUFile *f, bool last_stage,
                                   uint64_t *bytes_transferred)
{
    PageSearchStatus pss;
    MigrationState *ms = migrate_get_current();
    int pages = 0;
    bool again, found;
    ram_addr_t dirty_ram_abs; /* Address of the start of the dirty page in
                                 ram_addr_t space */

    pss.block = last_seen_block;
    pss.offset = last_offset;
    pss.complete_round = false;

    if (!pss.block) {
        pss.block = QLIST_FIRST_RCU(&ram_list.blocks);
    }

    do {
        again = true;
        found = get_queued_page(ms, &pss, &dirty_ram_abs);

        if (!found) {
            /* priority queue empty, so just search for something dirty */
            found = find_dirty_block(f, &pss, &again, &dirty_ram_abs);
        }

        if (found) {
            pages = ram_save_host_page(ms, f, &pss,
                                       last_stage, bytes_transferred,
                                       dirty_ram_abs);
        }
    } while (!pages && again);

    last_seen_block = pss.block;
    last_offset = pss.offset;

    return pages;
}

void acct_update_position(QEMUFile *f, size_t size, bool zero)
{
    uint64_t pages = size / TARGET_PAGE_SIZE;
    if (zero) {
        acct_info.dup_pages += pages;
    } else {
        acct_info.norm_pages += pages;
        bytes_transferred += size;
        qemu_update_position(f, size);
    }
}

static ram_addr_t ram_save_remaining(void)
{
    return migration_dirty_pages;
}

uint64_t ram_bytes_remaining(void)
{
    return ram_save_remaining() * TARGET_PAGE_SIZE;
}

uint64_t ram_bytes_transferred(void)
{
    return bytes_transferred;
}

uint64_t ram_bytes_total(void)
{
    RAMBlock *block;
    uint64_t total = 0;

    rcu_read_lock();
    QLIST_FOREACH_RCU(block, &ram_list.blocks, next)
        total += block->used_length;
    rcu_read_unlock();
    return total;
}

void free_xbzrle_decoded_buf(void)
{
    g_free(xbzrle_decoded_buf);
    xbzrle_decoded_buf = NULL;
}

static void migration_bitmap_free(struct BitmapRcu *bmap)
{
    g_free(bmap->bmap);
    g_free(bmap->unsentmap);
    g_free(bmap);
}

static void ram_migration_cleanup(void *opaque)
{
    /* caller have hold iothread lock or is in a bh, so there is
     * no writing race against this migration_bitmap
     */
    struct BitmapRcu *bitmap = migration_bitmap_rcu;
    atomic_rcu_set(&migration_bitmap_rcu, NULL);
    if (bitmap) {
        memory_global_dirty_log_stop();
        call_rcu(bitmap, migration_bitmap_free, rcu);
    }

    XBZRLE_cache_lock();
    if (XBZRLE.cache) {
        cache_fini(XBZRLE.cache);
        g_free(XBZRLE.encoded_buf);
        g_free(XBZRLE.current_buf);
        XBZRLE.cache = NULL;
        XBZRLE.encoded_buf = NULL;
        XBZRLE.current_buf = NULL;
    }
    XBZRLE_cache_unlock();
}

static void reset_ram_globals(void)
{
    last_seen_block = NULL;
    last_sent_block = NULL;
    last_offset = 0;
    last_version = ram_list.version;
    ram_bulk_stage = true;
}

#define MAX_WAIT 50 /* ms, half buffered_file limit */

void migration_bitmap_extend(ram_addr_t old, ram_addr_t new)
{
    /* called in qemu main thread, so there is
     * no writing race against this migration_bitmap
     */
    if (migration_bitmap_rcu) {
        struct BitmapRcu *old_bitmap = migration_bitmap_rcu, *bitmap;
        bitmap = g_new(struct BitmapRcu, 1);
        bitmap->bmap = bitmap_new(new);

        /* prevent migration_bitmap content from being set bit
         * by migration_bitmap_sync_range() at the same time.
         * it is safe to migration if migration_bitmap is cleared bit
         * at the same time.
         */
        qemu_mutex_lock(&migration_bitmap_mutex);
        bitmap_copy(bitmap->bmap, old_bitmap->bmap, old);
        bitmap_set(bitmap->bmap, old, new - old);

        /* We don't have a way to safely extend the sentmap
         * with RCU; so mark it as missing, entry to postcopy
         * will fail.
         */
        bitmap->unsentmap = NULL;

        atomic_rcu_set(&migration_bitmap_rcu, bitmap);
        qemu_mutex_unlock(&migration_bitmap_mutex);
        migration_dirty_pages += new - old;
        call_rcu(old_bitmap, migration_bitmap_free, rcu);
    }
}

/*
 * 'expected' is the value you expect the bitmap mostly to be full
 * of; it won't bother printing lines that are all this value.
 * If 'todump' is null the migration bitmap is dumped.
 */
void ram_debug_dump_bitmap(unsigned long *todump, bool expected)
{
    int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;

    int64_t cur;
    int64_t linelen = 128;
    char linebuf[129];

    if (!todump) {
        todump = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
    }

    for (cur = 0; cur < ram_pages; cur += linelen) {
        int64_t curb;
        bool found = false;
        /*
         * Last line; catch the case where the line length
         * is longer than remaining ram
         */
        if (cur + linelen > ram_pages) {
            linelen = ram_pages - cur;
        }
        for (curb = 0; curb < linelen; curb++) {
            bool thisbit = test_bit(cur + curb, todump);
            linebuf[curb] = thisbit ? '1' : '.';
            found = found || (thisbit != expected);
        }
        if (found) {
            linebuf[curb] = '\0';
            fprintf(stderr,  "0x%08" PRIx64 " : %s\n", cur, linebuf);
        }
    }
}

/* **** functions for postcopy ***** */

/*
 * Callback from postcopy_each_ram_send_discard for each RAMBlock
 * Note: At this point the 'unsentmap' is the processed bitmap combined
 *       with the dirtymap; so a '1' means it's either dirty or unsent.
 * start,length: Indexes into the bitmap for the first bit
 *            representing the named block and length in target-pages
 */
static int postcopy_send_discard_bm_ram(MigrationState *ms,
                                        PostcopyDiscardState *pds,
                                        unsigned long start,
                                        unsigned long length)
{
    unsigned long end = start + length; /* one after the end */
    unsigned long current;
    unsigned long *unsentmap;

    unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap;
    for (current = start; current < end; ) {
        unsigned long one = find_next_bit(unsentmap, end, current);

        if (one <= end) {
            unsigned long zero = find_next_zero_bit(unsentmap, end, one + 1);
            unsigned long discard_length;

            if (zero >= end) {
                discard_length = end - one;
            } else {
                discard_length = zero - one;
            }
            postcopy_discard_send_range(ms, pds, one, discard_length);
            current = one + discard_length;
        } else {
            current = one;
        }
    }

    return 0;
}

/*
 * Utility for the outgoing postcopy code.
 *   Calls postcopy_send_discard_bm_ram for each RAMBlock
 *   passing it bitmap indexes and name.
 * Returns: 0 on success
 * (qemu_ram_foreach_block ends up passing unscaled lengths
 *  which would mean postcopy code would have to deal with target page)
 */
static int postcopy_each_ram_send_discard(MigrationState *ms)
{
    struct RAMBlock *block;
    int ret;

    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
        unsigned long first = block->offset >> TARGET_PAGE_BITS;
        PostcopyDiscardState *pds = postcopy_discard_send_init(ms,
                                                               first,
                                                               block->idstr);

        /*
         * Postcopy sends chunks of bitmap over the wire, but it
         * just needs indexes at this point, avoids it having
         * target page specific code.
         */
        ret = postcopy_send_discard_bm_ram(ms, pds, first,
                                    block->used_length >> TARGET_PAGE_BITS);
        postcopy_discard_send_finish(ms, pds);
        if (ret) {
            return ret;
        }
    }

    return 0;
}

/*
 * Helper for postcopy_chunk_hostpages; it's called twice to cleanup
 *   the two bitmaps, that are similar, but one is inverted.
 *
 * We search for runs of target-pages that don't start or end on a
 * host page boundary;
 * unsent_pass=true: Cleans up partially unsent host pages by searching
 *                 the unsentmap
 * unsent_pass=false: Cleans up partially dirty host pages by searching
 *                 the main migration bitmap
 *
 */
static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
                                          RAMBlock *block,
                                          PostcopyDiscardState *pds)
{
    unsigned long *bitmap;
    unsigned long *unsentmap;
    unsigned int host_ratio = qemu_host_page_size / TARGET_PAGE_SIZE;
    unsigned long first = block->offset >> TARGET_PAGE_BITS;
    unsigned long len = block->used_length >> TARGET_PAGE_BITS;
    unsigned long last = first + (len - 1);
    unsigned long run_start;

    bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
    unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap;

    if (unsent_pass) {
        /* Find a sent page */
        run_start = find_next_zero_bit(unsentmap, last + 1, first);
    } else {
        /* Find a dirty page */
        run_start = find_next_bit(bitmap, last + 1, first);
    }

    while (run_start <= last) {
        bool do_fixup = false;
        unsigned long fixup_start_addr;
        unsigned long host_offset;

        /*
         * If the start of this run of pages is in the middle of a host
         * page, then we need to fixup this host page.
         */
        host_offset = run_start % host_ratio;
        if (host_offset) {
            do_fixup = true;
            run_start -= host_offset;
            fixup_start_addr = run_start;
            /* For the next pass */
            run_start = run_start + host_ratio;
        } else {
            /* Find the end of this run */
            unsigned long run_end;
            if (unsent_pass) {
                run_end = find_next_bit(unsentmap, last + 1, run_start + 1);
            } else {
                run_end = find_next_zero_bit(bitmap, last + 1, run_start + 1);
            }
            /*
             * If the end isn't at the start of a host page, then the
             * run doesn't finish at the end of a host page
             * and we need to discard.
             */
            host_offset = run_end % host_ratio;
            if (host_offset) {
                do_fixup = true;
                fixup_start_addr = run_end - host_offset;
                /*
                 * This host page has gone, the next loop iteration starts
                 * from after the fixup
                 */
                run_start = fixup_start_addr + host_ratio;
            } else {
                /*
                 * No discards on this iteration, next loop starts from
                 * next sent/dirty page
                 */
                run_start = run_end + 1;
            }
        }

        if (do_fixup) {
            unsigned long page;

            /* Tell the destination to discard this page */
            if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) {
                /* For the unsent_pass we:
                 *     discard partially sent pages
                 * For the !unsent_pass (dirty) we:
                 *     discard partially dirty pages that were sent
                 *     (any partially sent pages were already discarded
                 *     by the previous unsent_pass)
                 */
                postcopy_discard_send_range(ms, pds, fixup_start_addr,
                                            host_ratio);
            }

            /* Clean up the bitmap */
            for (page = fixup_start_addr;
                 page < fixup_start_addr + host_ratio; page++) {
                /* All pages in this host page are now not sent */
                set_bit(page, unsentmap);

                /*
                 * Remark them as dirty, updating the count for any pages
                 * that weren't previously dirty.
                 */
                migration_dirty_pages += !test_and_set_bit(page, bitmap);
            }
        }

        if (unsent_pass) {
            /* Find the next sent page for the next iteration */
            run_start = find_next_zero_bit(unsentmap, last + 1,
                                           run_start);
        } else {
            /* Find the next dirty page for the next iteration */
            run_start = find_next_bit(bitmap, last + 1, run_start);
        }
    }
}

/*
 * Utility for the outgoing postcopy code.
 *
 * Discard any partially sent host-page size chunks, mark any partially
 * dirty host-page size chunks as all dirty.
 *
 * Returns: 0 on success
 */
static int postcopy_chunk_hostpages(MigrationState *ms)
{
    struct RAMBlock *block;

    if (qemu_host_page_size == TARGET_PAGE_SIZE) {
        /* Easy case - TPS==HPS - nothing to be done */
        return 0;
    }

    /* Easiest way to make sure we don't resume in the middle of a host-page */
    last_seen_block = NULL;
    last_sent_block = NULL;
    last_offset     = 0;

    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
        unsigned long first = block->offset >> TARGET_PAGE_BITS;

        PostcopyDiscardState *pds =
                         postcopy_discard_send_init(ms, first, block->idstr);

        /* First pass: Discard all partially sent host pages */
        postcopy_chunk_hostpages_pass(ms, true, block, pds);
        /*
         * Second pass: Ensure that all partially dirty host pages are made
         * fully dirty.
         */
        postcopy_chunk_hostpages_pass(ms, false, block, pds);

        postcopy_discard_send_finish(ms, pds);
    } /* ram_list loop */

    return 0;
}

/*
 * Transmit the set of pages to be discarded after precopy to the target
 * these are pages that:
 *     a) Have been previously transmitted but are now dirty again
 *     b) Pages that have never been transmitted, this ensures that
 *        any pages on the destination that have been mapped by background
 *        tasks get discarded (transparent huge pages is the specific concern)
 * Hopefully this is pretty sparse
 */
int ram_postcopy_send_discard_bitmap(MigrationState *ms)
{
    int ret;
    unsigned long *bitmap, *unsentmap;

    rcu_read_lock();

    /* This should be our last sync, the src is now paused */
    migration_bitmap_sync();

    unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap;
    if (!unsentmap) {
        /* We don't have a safe way to resize the sentmap, so
         * if the bitmap was resized it will be NULL at this
         * point.
         */
        error_report("migration ram resized during precopy phase");
        rcu_read_unlock();
        return -EINVAL;
    }

    /* Deal with TPS != HPS */
    ret = postcopy_chunk_hostpages(ms);
    if (ret) {
        rcu_read_unlock();
        return ret;
    }

    /*
     * Update the unsentmap to be unsentmap = unsentmap | dirty
     */
    bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
    bitmap_or(unsentmap, unsentmap, bitmap,
               last_ram_offset() >> TARGET_PAGE_BITS);


    trace_ram_postcopy_send_discard_bitmap();
#ifdef DEBUG_POSTCOPY
    ram_debug_dump_bitmap(unsentmap, true);
#endif

    ret = postcopy_each_ram_send_discard(ms);
    rcu_read_unlock();

    return ret;
}

/*
 * At the start of the postcopy phase of migration, any now-dirty
 * precopied pages are discarded.
 *
 * start, length describe a byte address range within the RAMBlock
 *
 * Returns 0 on success.
 */
int ram_discard_range(MigrationIncomingState *mis,
                      const char *block_name,
                      uint64_t start, size_t length)
{
    int ret = -1;

    rcu_read_lock();
    RAMBlock *rb = qemu_ram_block_by_name(block_name);

    if (!rb) {
        error_report("ram_discard_range: Failed to find block '%s'",
                     block_name);
        goto err;
    }

    uint8_t *host_startaddr = rb->host + start;

    if ((uintptr_t)host_startaddr & (qemu_host_page_size - 1)) {
        error_report("ram_discard_range: Unaligned start address: %p",
                     host_startaddr);
        goto err;
    }

    if ((start + length) <= rb->used_length) {
        uint8_t *host_endaddr = host_startaddr + length;
        if ((uintptr_t)host_endaddr & (qemu_host_page_size - 1)) {
            error_report("ram_discard_range: Unaligned end address: %p",
                         host_endaddr);
            goto err;
        }
        ret = postcopy_ram_discard_range(mis, host_startaddr, length);
    } else {
        error_report("ram_discard_range: Overrun block '%s' (%" PRIu64
                     "/%zx/" RAM_ADDR_FMT")",
                     block_name, start, length, rb->used_length);
    }

err:
    rcu_read_unlock();

    return ret;
}


/* Each of ram_save_setup, ram_save_iterate and ram_save_complete has
 * long-running RCU critical section.  When rcu-reclaims in the code
 * start to become numerous it will be necessary to reduce the
 * granularity of these critical sections.
 */

static int ram_save_setup(QEMUFile *f, void *opaque)
{
    RAMBlock *block;
    int64_t ram_bitmap_pages; /* Size of bitmap in pages, including gaps */

    dirty_rate_high_cnt = 0;
    bitmap_sync_count = 0;
    migration_bitmap_sync_init();
    qemu_mutex_init(&migration_bitmap_mutex);

    if (migrate_use_xbzrle()) {
        XBZRLE_cache_lock();
        XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
                                  TARGET_PAGE_SIZE,
                                  TARGET_PAGE_SIZE);
        if (!XBZRLE.cache) {
            XBZRLE_cache_unlock();
            error_report("Error creating cache");
            return -1;
        }
        XBZRLE_cache_unlock();

        /* We prefer not to abort if there is no memory */
        XBZRLE.encoded_buf = g_try_malloc0(TARGET_PAGE_SIZE);
        if (!XBZRLE.encoded_buf) {
            error_report("Error allocating encoded_buf");
            return -1;
        }

        XBZRLE.current_buf = g_try_malloc(TARGET_PAGE_SIZE);
        if (!XBZRLE.current_buf) {
            error_report("Error allocating current_buf");
            g_free(XBZRLE.encoded_buf);
            XBZRLE.encoded_buf = NULL;
            return -1;
        }

        acct_clear();
    }

    /* For memory_global_dirty_log_start below.  */
    qemu_mutex_lock_iothread();

    qemu_mutex_lock_ramlist();
    rcu_read_lock();
    bytes_transferred = 0;
    reset_ram_globals();

    ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
    migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
    migration_bitmap_rcu->bmap = bitmap_new(ram_bitmap_pages);
    bitmap_set(migration_bitmap_rcu->bmap, 0, ram_bitmap_pages);

    if (migrate_postcopy_ram()) {
        migration_bitmap_rcu->unsentmap = bitmap_new(ram_bitmap_pages);
        bitmap_set(migration_bitmap_rcu->unsentmap, 0, ram_bitmap_pages);
    }

    /*
     * Count the total number of pages used by ram blocks not including any
     * gaps due to alignment or unplugs.
     */
    migration_dirty_pages = ram_bytes_total() >> TARGET_PAGE_BITS;

    memory_global_dirty_log_start();
    migration_bitmap_sync();
    qemu_mutex_unlock_ramlist();
    qemu_mutex_unlock_iothread();

    qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE);

    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
        qemu_put_byte(f, strlen(block->idstr));
        qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
        qemu_put_be64(f, block->used_length);
    }

    rcu_read_unlock();

    ram_control_before_iterate(f, RAM_CONTROL_SETUP);
    ram_control_after_iterate(f, RAM_CONTROL_SETUP);

    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);

    return 0;
}

static int ram_save_iterate(QEMUFile *f, void *opaque)
{
    int ret;
    int i;
    int64_t t0;
    int pages_sent = 0;

    rcu_read_lock();
    if (ram_list.version != last_version) {
        reset_ram_globals();
    }

    /* Read version before ram_list.blocks */
    smp_rmb();

    ram_control_before_iterate(f, RAM_CONTROL_ROUND);

    t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
    i = 0;
    while ((ret = qemu_file_rate_limit(f)) == 0) {
        int pages;

        pages = ram_find_and_save_block(f, false, &bytes_transferred);
        /* no more pages to sent */
        if (pages == 0) {
            break;
        }
        pages_sent += pages;
        acct_info.iterations++;

        /* we want to check in the 1st loop, just in case it was the 1st time
           and we had to sync the dirty bitmap.
           qemu_get_clock_ns() is a bit expensive, so we only check each some
           iterations
        */
        if ((i & 63) == 0) {
            uint64_t t1 = (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - t0) / 1000000;
            if (t1 > MAX_WAIT) {
                DPRINTF("big wait: %" PRIu64 " milliseconds, %d iterations\n",
                        t1, i);
                break;
            }
        }
        i++;
    }
    flush_compressed_data(f);
    rcu_read_unlock();

    /*
     * Must occur before EOS (or any QEMUFile operation)
     * because of RDMA protocol.
     */
    ram_control_after_iterate(f, RAM_CONTROL_ROUND);

    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
    bytes_transferred += 8;

    ret = qemu_file_get_error(f);
    if (ret < 0) {
        return ret;
    }

    return pages_sent;
}

/* Called with iothread lock */
static int ram_save_complete(QEMUFile *f, void *opaque)
{
    rcu_read_lock();

    if (!migration_in_postcopy(migrate_get_current())) {
        migration_bitmap_sync();
    }

    ram_control_before_iterate(f, RAM_CONTROL_FINISH);

    /* try transferring iterative blocks of memory */

    /* flush all remaining blocks regardless of rate limiting */
    while (true) {
        int pages;

        pages = ram_find_and_save_block(f, true, &bytes_transferred);
        /* no more blocks to sent */
        if (pages == 0) {
            break;
        }
    }

    flush_compressed_data(f);
    ram_control_after_iterate(f, RAM_CONTROL_FINISH);

    rcu_read_unlock();

    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);

    return 0;
}

static void ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
                             uint64_t *non_postcopiable_pending,
                             uint64_t *postcopiable_pending)
{
    uint64_t remaining_size;

    remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;

    if (!migration_in_postcopy(migrate_get_current()) &&
        remaining_size < max_size) {
        qemu_mutex_lock_iothread();
        rcu_read_lock();
        migration_bitmap_sync();
        rcu_read_unlock();
        qemu_mutex_unlock_iothread();
        remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
    }

    /* We can do postcopy, and all the data is postcopiable */
    *postcopiable_pending += remaining_size;
}

static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
{
    unsigned int xh_len;
    int xh_flags;
    uint8_t *loaded_data;

    if (!xbzrle_decoded_buf) {
        xbzrle_decoded_buf = g_malloc(TARGET_PAGE_SIZE);
    }
    loaded_data = xbzrle_decoded_buf;

    /* extract RLE header */
    xh_flags = qemu_get_byte(f);
    xh_len = qemu_get_be16(f);

    if (xh_flags != ENCODING_FLAG_XBZRLE) {
        error_report("Failed to load XBZRLE page - wrong compression!");
        return -1;
    }

    if (xh_len > TARGET_PAGE_SIZE) {
        error_report("Failed to load XBZRLE page - len overflow!");
        return -1;
    }
    /* load data and decode */
    qemu_get_buffer_in_place(f, &loaded_data, xh_len);

    /* decode RLE */
    if (xbzrle_decode_buffer(loaded_data, xh_len, host,
                             TARGET_PAGE_SIZE) == -1) {
        error_report("Failed to load XBZRLE page - decode error!");
        return -1;
    }

    return 0;
}

/* Must be called from within a rcu critical section.
 * Returns a pointer from within the RCU-protected ram_list.
 */
/*
 * Read a RAMBlock ID from the stream f.
 *
 * f: Stream to read from
 * flags: Page flags (mostly to see if it's a continuation of previous block)
 */
static inline RAMBlock *ram_block_from_stream(QEMUFile *f,
                                              int flags)
{
    static RAMBlock *block = NULL;
    char id[256];
    uint8_t len;

    if (flags & RAM_SAVE_FLAG_CONTINUE) {
        if (!block) {
            error_report("Ack, bad migration stream!");
            return NULL;
        }
        return block;
    }

    len = qemu_get_byte(f);
    qemu_get_buffer(f, (uint8_t *)id, len);
    id[len] = 0;

    block = qemu_ram_block_by_name(id);
    if (!block) {
        error_report("Can't find block %s", id);
        return NULL;
    }

    return block;
}

static inline void *host_from_ram_block_offset(RAMBlock *block,
                                               ram_addr_t offset)
{
    if (!offset_in_ramblock(block, offset)) {
        return NULL;
    }

    return block->host + offset;
}

/*
 * If a page (or a whole RDMA chunk) has been
 * determined to be zero, then zap it.
 */
void ram_handle_compressed(void *host, uint8_t ch, uint64_t size)
{
    if (ch != 0 || !is_zero_range(host, size)) {
        memset(host, ch, size);
    }
}

static void *do_data_decompress(void *opaque)
{
    DecompressParam *param = opaque;
    unsigned long pagesize;

    while (!quit_decomp_thread) {
        qemu_mutex_lock(&param->mutex);
        while (!param->start && !quit_decomp_thread) {
            qemu_cond_wait(&param->cond, &param->mutex);
            pagesize = TARGET_PAGE_SIZE;
            if (!quit_decomp_thread) {
                /* uncompress() will return failed in some case, especially
                 * when the page is dirted when doing the compression, it's
                 * not a problem because the dirty page will be retransferred
                 * and uncompress() won't break the data in other pages.
                 */
                uncompress((Bytef *)param->des, &pagesize,
                           (const Bytef *)param->compbuf, param->len);
            }
            param->start = false;
        }
        qemu_mutex_unlock(&param->mutex);
    }

    return NULL;
}

void migrate_decompress_threads_create(void)
{
    int i, thread_count;

    thread_count = migrate_decompress_threads();
    decompress_threads = g_new0(QemuThread, thread_count);
    decomp_param = g_new0(DecompressParam, thread_count);
    quit_decomp_thread = false;
    for (i = 0; i < thread_count; i++) {
        qemu_mutex_init(&decomp_param[i].mutex);
        qemu_cond_init(&decomp_param[i].cond);
        decomp_param[i].compbuf = g_malloc0(compressBound(TARGET_PAGE_SIZE));
        qemu_thread_create(decompress_threads + i, "decompress",
                           do_data_decompress, decomp_param + i,
                           QEMU_THREAD_JOINABLE);
    }
}

void migrate_decompress_threads_join(void)
{
    int i, thread_count;

    quit_decomp_thread = true;
    thread_count = migrate_decompress_threads();
    for (i = 0; i < thread_count; i++) {
        qemu_mutex_lock(&decomp_param[i].mutex);
        qemu_cond_signal(&decomp_param[i].cond);
        qemu_mutex_unlock(&decomp_param[i].mutex);
    }
    for (i = 0; i < thread_count; i++) {
        qemu_thread_join(decompress_threads + i);
        qemu_mutex_destroy(&decomp_param[i].mutex);
        qemu_cond_destroy(&decomp_param[i].cond);
        g_free(decomp_param[i].compbuf);
    }
    g_free(decompress_threads);
    g_free(decomp_param);
    decompress_threads = NULL;
    decomp_param = NULL;
}

static void decompress_data_with_multi_threads(QEMUFile *f,
                                               void *host, int len)
{
    int idx, thread_count;

    thread_count = migrate_decompress_threads();
    while (true) {
        for (idx = 0; idx < thread_count; idx++) {
            if (!decomp_param[idx].start) {
                qemu_get_buffer(f, decomp_param[idx].compbuf, len);
                decomp_param[idx].des = host;
                decomp_param[idx].len = len;
                start_decompression(&decomp_param[idx]);
                break;
            }
        }
        if (idx < thread_count) {
            break;
        }
    }
}

/*
 * Allocate data structures etc needed by incoming migration with postcopy-ram
 * postcopy-ram's similarly names postcopy_ram_incoming_init does the work
 */
int ram_postcopy_incoming_init(MigrationIncomingState *mis)
{
    size_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;

    return postcopy_ram_incoming_init(mis, ram_pages);
}

/*
 * Called in postcopy mode by ram_load().
 * rcu_read_lock is taken prior to this being called.
 */
static int ram_load_postcopy(QEMUFile *f)
{
    int flags = 0, ret = 0;
    bool place_needed = false;
    bool matching_page_sizes = qemu_host_page_size == TARGET_PAGE_SIZE;
    MigrationIncomingState *mis = migration_incoming_get_current();
    /* Temporary page that is later 'placed' */
    void *postcopy_host_page = postcopy_get_tmp_page(mis);
    void *last_host = NULL;
    bool all_zero = false;

    while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
        ram_addr_t addr;
        void *host = NULL;
        void *page_buffer = NULL;
        void *place_source = NULL;
        uint8_t ch;

        addr = qemu_get_be64(f);
        flags = addr & ~TARGET_PAGE_MASK;
        addr &= TARGET_PAGE_MASK;

        trace_ram_load_postcopy_loop((uint64_t)addr, flags);
        place_needed = false;
        if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE)) {
            RAMBlock *block = ram_block_from_stream(f, flags);

            host = host_from_ram_block_offset(block, addr);
            if (!host) {
                error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
                ret = -EINVAL;
                break;
            }
            page_buffer = host;
            /*
             * Postcopy requires that we place whole host pages atomically.
             * To make it atomic, the data is read into a temporary page
             * that's moved into place later.
             * The migration protocol uses,  possibly smaller, target-pages
             * however the source ensures it always sends all the components
             * of a host page in order.
             */
            page_buffer = postcopy_host_page +
                          ((uintptr_t)host & ~qemu_host_page_mask);
            /* If all TP are zero then we can optimise the place */
            if (!((uintptr_t)host & ~qemu_host_page_mask)) {
                all_zero = true;
            } else {
                /* not the 1st TP within the HP */
                if (host != (last_host + TARGET_PAGE_SIZE)) {
                    error_report("Non-sequential target page %p/%p",
                                  host, last_host);
                    ret = -EINVAL;
                    break;
                }
            }


            /*
             * If it's the last part of a host page then we place the host
             * page
             */
            place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) &
                                     ~qemu_host_page_mask) == 0;
            place_source = postcopy_host_page;
        }
        last_host = host;

        switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
        case RAM_SAVE_FLAG_COMPRESS:
            ch = qemu_get_byte(f);
            memset(page_buffer, ch, TARGET_PAGE_SIZE);
            if (ch) {
                all_zero = false;
            }
            break;

        case RAM_SAVE_FLAG_PAGE:
            all_zero = false;
            if (!place_needed || !matching_page_sizes) {
                qemu_get_buffer(f, page_buffer, TARGET_PAGE_SIZE);
            } else {
                /* Avoids the qemu_file copy during postcopy, which is
                 * going to do a copy later; can only do it when we
                 * do this read in one go (matching page sizes)
                 */
                qemu_get_buffer_in_place(f, (uint8_t **)&place_source,
                                         TARGET_PAGE_SIZE);
            }
            break;
        case RAM_SAVE_FLAG_EOS:
            /* normal exit */
            break;
        default:
            error_report("Unknown combination of migration flags: %#x"
                         " (postcopy mode)", flags);
            ret = -EINVAL;
        }

        if (place_needed) {
            /* This gets called at the last target page in the host page */
            if (all_zero) {
                ret = postcopy_place_page_zero(mis,
                                               host + TARGET_PAGE_SIZE -
                                               qemu_host_page_size);
            } else {
                ret = postcopy_place_page(mis, host + TARGET_PAGE_SIZE -
                                               qemu_host_page_size,
                                               place_source);
            }
        }
        if (!ret) {
            ret = qemu_file_get_error(f);
        }
    }

    return ret;
}

static int ram_load(QEMUFile *f, void *opaque, int version_id)
{
    int flags = 0, ret = 0;
    static uint64_t seq_iter;
    int len = 0;
    /*
     * If system is running in postcopy mode, page inserts to host memory must
     * be atomic
     */
    bool postcopy_running = postcopy_state_get() >= POSTCOPY_INCOMING_LISTENING;

    seq_iter++;

    if (version_id != 4) {
        ret = -EINVAL;
    }

    /* This RCU critical section can be very long running.
     * When RCU reclaims in the code start to become numerous,
     * it will be necessary to reduce the granularity of this
     * critical section.
     */
    rcu_read_lock();

    if (postcopy_running) {
        ret = ram_load_postcopy(f);
    }

    while (!postcopy_running && !ret && !(flags & RAM_SAVE_FLAG_EOS)) {
        ram_addr_t addr, total_ram_bytes;
        void *host = NULL;
        uint8_t ch;

        addr = qemu_get_be64(f);
        flags = addr & ~TARGET_PAGE_MASK;
        addr &= TARGET_PAGE_MASK;

        if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE |
                     RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) {
            RAMBlock *block = ram_block_from_stream(f, flags);

            host = host_from_ram_block_offset(block, addr);
            if (!host) {
                error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
                ret = -EINVAL;
                break;
            }
        }

        switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
        case RAM_SAVE_FLAG_MEM_SIZE:
            /* Synchronize RAM block list */
            total_ram_bytes = addr;
            while (!ret && total_ram_bytes) {
                RAMBlock *block;
                char id[256];
                ram_addr_t length;

                len = qemu_get_byte(f);
                qemu_get_buffer(f, (uint8_t *)id, len);
                id[len] = 0;
                length = qemu_get_be64(f);

                block = qemu_ram_block_by_name(id);
                if (block) {
                    if (length != block->used_length) {
                        Error *local_err = NULL;

                        ret = qemu_ram_resize(block->offset, length,
                                              &local_err);
                        if (local_err) {
                            error_report_err(local_err);
                        }
                    }
                    ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG,
                                          block->idstr);
                } else {
                    error_report("Unknown ramblock \"%s\", cannot "
                                 "accept migration", id);
                    ret = -EINVAL;
                }

                total_ram_bytes -= length;
            }
            break;

        case RAM_SAVE_FLAG_COMPRESS:
            ch = qemu_get_byte(f);
            ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
            break;

        case RAM_SAVE_FLAG_PAGE:
            qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
            break;

        case RAM_SAVE_FLAG_COMPRESS_PAGE:
            len = qemu_get_be32(f);
            if (len < 0 || len > compressBound(TARGET_PAGE_SIZE)) {
                error_report("Invalid compressed data length: %d", len);
                ret = -EINVAL;
                break;
            }
            decompress_data_with_multi_threads(f, host, len);
            break;

        case RAM_SAVE_FLAG_XBZRLE:
            if (load_xbzrle(f, addr, host) < 0) {
                error_report("Failed to decompress XBZRLE page at "
                             RAM_ADDR_FMT, addr);
                ret = -EINVAL;
                break;
            }
            break;
        case RAM_SAVE_FLAG_EOS:
            /* normal exit */
            break;
        default:
            if (flags & RAM_SAVE_FLAG_HOOK) {
                ram_control_load_hook(f, RAM_CONTROL_HOOK, NULL);
            } else {
                error_report("Unknown combination of migration flags: %#x",
                             flags);
                ret = -EINVAL;
            }
        }
        if (!ret) {
            ret = qemu_file_get_error(f);
        }
    }

    rcu_read_unlock();
    DPRINTF("Completed load of VM with exit code %d seq iteration "
            "%" PRIu64 "\n", ret, seq_iter);
    return ret;
}

static SaveVMHandlers savevm_ram_handlers = {
    .save_live_setup = ram_save_setup,
    .save_live_iterate = ram_save_iterate,
    .save_live_complete_postcopy = ram_save_complete,
    .save_live_complete_precopy = ram_save_complete,
    .save_live_pending = ram_save_pending,
    .load_state = ram_load,
    .cleanup = ram_migration_cleanup,
};

void ram_mig_init(void)
{
    qemu_mutex_init(&XBZRLE.lock);
    register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, NULL);
}