Training courses

Kernel and Embedded Linux

Bootlin training courses

Embedded Linux, kernel,
Yocto Project, Buildroot, real-time,
graphics, boot time, debugging...

Bootlin logo

Elixir Cross Referencer

   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
/******************************************************************************
 * grant_table.c
 *
 * Granting foreign access to our memory reservation.
 *
 * Copyright (c) 2005-2006, Christopher Clark
 * Copyright (c) 2004-2005, K A Fraser
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (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.
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/memblock.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/hardirq.h>
#include <linux/workqueue.h>
#include <linux/ratelimit.h>
#include <linux/moduleparam.h>
#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
#include <linux/dma-mapping.h>
#endif

#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/page.h>
#include <xen/grant_table.h>
#include <xen/interface/memory.h>
#include <xen/hvc-console.h>
#include <xen/swiotlb-xen.h>
#include <xen/balloon.h>
#ifdef CONFIG_X86
#include <asm/xen/cpuid.h>
#endif
#include <xen/mem-reservation.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/interface.h>

#include <asm/pgtable.h>
#include <asm/sync_bitops.h>

/* External tools reserve first few grant table entries. */
#define NR_RESERVED_ENTRIES 8
#define GNTTAB_LIST_END 0xffffffff

static grant_ref_t **gnttab_list;
static unsigned int nr_grant_frames;
static int gnttab_free_count;
static grant_ref_t gnttab_free_head;
static DEFINE_SPINLOCK(gnttab_list_lock);
struct grant_frames xen_auto_xlat_grant_frames;
static unsigned int xen_gnttab_version;
module_param_named(version, xen_gnttab_version, uint, 0);

static union {
	struct grant_entry_v1 *v1;
	union grant_entry_v2 *v2;
	void *addr;
} gnttab_shared;

/*This is a structure of function pointers for grant table*/
struct gnttab_ops {
	/*
	 * Version of the grant interface.
	 */
	unsigned int version;
	/*
	 * Grant refs per grant frame.
	 */
	unsigned int grefs_per_grant_frame;
	/*
	 * Mapping a list of frames for storing grant entries. Frames parameter
	 * is used to store grant table address when grant table being setup,
	 * nr_gframes is the number of frames to map grant table. Returning
	 * GNTST_okay means success and negative value means failure.
	 */
	int (*map_frames)(xen_pfn_t *frames, unsigned int nr_gframes);
	/*
	 * Release a list of frames which are mapped in map_frames for grant
	 * entry status.
	 */
	void (*unmap_frames)(void);
	/*
	 * Introducing a valid entry into the grant table, granting the frame of
	 * this grant entry to domain for accessing or transfering. Ref
	 * parameter is reference of this introduced grant entry, domid is id of
	 * granted domain, frame is the page frame to be granted, and flags is
	 * status of the grant entry to be updated.
	 */
	void (*update_entry)(grant_ref_t ref, domid_t domid,
			     unsigned long frame, unsigned flags);
	/*
	 * Stop granting a grant entry to domain for accessing. Ref parameter is
	 * reference of a grant entry whose grant access will be stopped,
	 * readonly is not in use in this function. If the grant entry is
	 * currently mapped for reading or writing, just return failure(==0)
	 * directly and don't tear down the grant access. Otherwise, stop grant
	 * access for this entry and return success(==1).
	 */
	int (*end_foreign_access_ref)(grant_ref_t ref, int readonly);
	/*
	 * Stop granting a grant entry to domain for transfer. Ref parameter is
	 * reference of a grant entry whose grant transfer will be stopped. If
	 * tranfer has not started, just reclaim the grant entry and return
	 * failure(==0). Otherwise, wait for the transfer to complete and then
	 * return the frame.
	 */
	unsigned long (*end_foreign_transfer_ref)(grant_ref_t ref);
	/*
	 * Query the status of a grant entry. Ref parameter is reference of
	 * queried grant entry, return value is the status of queried entry.
	 * Detailed status(writing/reading) can be gotten from the return value
	 * by bit operations.
	 */
	int (*query_foreign_access)(grant_ref_t ref);
};

struct unmap_refs_callback_data {
	struct completion completion;
	int result;
};

static const struct gnttab_ops *gnttab_interface;

/* This reflects status of grant entries, so act as a global value. */
static grant_status_t *grstatus;

static struct gnttab_free_callback *gnttab_free_callback_list;

static int gnttab_expand(unsigned int req_entries);

#define RPP (PAGE_SIZE / sizeof(grant_ref_t))
#define SPP (PAGE_SIZE / sizeof(grant_status_t))

static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
{
	return &gnttab_list[(entry) / RPP][(entry) % RPP];
}
/* This can be used as an l-value */
#define gnttab_entry(entry) (*__gnttab_entry(entry))

static int get_free_entries(unsigned count)
{
	unsigned long flags;
	int ref, rc = 0;
	grant_ref_t head;

	spin_lock_irqsave(&gnttab_list_lock, flags);

	if ((gnttab_free_count < count) &&
	    ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
		spin_unlock_irqrestore(&gnttab_list_lock, flags);
		return rc;
	}

	ref = head = gnttab_free_head;
	gnttab_free_count -= count;
	while (count-- > 1)
		head = gnttab_entry(head);
	gnttab_free_head = gnttab_entry(head);
	gnttab_entry(head) = GNTTAB_LIST_END;

	spin_unlock_irqrestore(&gnttab_list_lock, flags);

	return ref;
}

static void do_free_callbacks(void)
{
	struct gnttab_free_callback *callback, *next;

	callback = gnttab_free_callback_list;
	gnttab_free_callback_list = NULL;

	while (callback != NULL) {
		next = callback->next;
		if (gnttab_free_count >= callback->count) {
			callback->next = NULL;
			callback->fn(callback->arg);
		} else {
			callback->next = gnttab_free_callback_list;
			gnttab_free_callback_list = callback;
		}
		callback = next;
	}
}

static inline void check_free_callbacks(void)
{
	if (unlikely(gnttab_free_callback_list))
		do_free_callbacks();
}

static void put_free_entry(grant_ref_t ref)
{
	unsigned long flags;
	spin_lock_irqsave(&gnttab_list_lock, flags);
	gnttab_entry(ref) = gnttab_free_head;
	gnttab_free_head = ref;
	gnttab_free_count++;
	check_free_callbacks();
	spin_unlock_irqrestore(&gnttab_list_lock, flags);
}

/*
 * Following applies to gnttab_update_entry_v1 and gnttab_update_entry_v2.
 * Introducing a valid entry into the grant table:
 *  1. Write ent->domid.
 *  2. Write ent->frame:
 *      GTF_permit_access:   Frame to which access is permitted.
 *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
 *                           frame, or zero if none.
 *  3. Write memory barrier (WMB).
 *  4. Write ent->flags, inc. valid type.
 */
static void gnttab_update_entry_v1(grant_ref_t ref, domid_t domid,
				   unsigned long frame, unsigned flags)
{
	gnttab_shared.v1[ref].domid = domid;
	gnttab_shared.v1[ref].frame = frame;
	wmb();
	gnttab_shared.v1[ref].flags = flags;
}

static void gnttab_update_entry_v2(grant_ref_t ref, domid_t domid,
				   unsigned long frame, unsigned int flags)
{
	gnttab_shared.v2[ref].hdr.domid = domid;
	gnttab_shared.v2[ref].full_page.frame = frame;
	wmb();	/* Hypervisor concurrent accesses. */
	gnttab_shared.v2[ref].hdr.flags = GTF_permit_access | flags;
}

/*
 * Public grant-issuing interface functions
 */
void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
				     unsigned long frame, int readonly)
{
	gnttab_interface->update_entry(ref, domid, frame,
			   GTF_permit_access | (readonly ? GTF_readonly : 0));
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);

int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
				int readonly)
{
	int ref;

	ref = get_free_entries(1);
	if (unlikely(ref < 0))
		return -ENOSPC;

	gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);

	return ref;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);

static int gnttab_query_foreign_access_v1(grant_ref_t ref)
{
	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
}

static int gnttab_query_foreign_access_v2(grant_ref_t ref)
{
	return grstatus[ref] & (GTF_reading|GTF_writing);
}

int gnttab_query_foreign_access(grant_ref_t ref)
{
	return gnttab_interface->query_foreign_access(ref);
}
EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);

static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref, int readonly)
{
	u16 flags, nflags;
	u16 *pflags;

	pflags = &gnttab_shared.v1[ref].flags;
	nflags = *pflags;
	do {
		flags = nflags;
		if (flags & (GTF_reading|GTF_writing))
			return 0;
	} while ((nflags = sync_cmpxchg(pflags, flags, 0)) != flags);

	return 1;
}

static int gnttab_end_foreign_access_ref_v2(grant_ref_t ref, int readonly)
{
	gnttab_shared.v2[ref].hdr.flags = 0;
	mb();	/* Concurrent access by hypervisor. */
	if (grstatus[ref] & (GTF_reading|GTF_writing)) {
		return 0;
	} else {
		/*
		 * The read of grstatus needs to have acquire semantics.
		 *  On x86, reads already have that, and we just need to
		 * protect against compiler reorderings.
		 * On other architectures we may need a full barrier.
		 */
#ifdef CONFIG_X86
		barrier();
#else
		mb();
#endif
	}

	return 1;
}

static inline int _gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
{
	return gnttab_interface->end_foreign_access_ref(ref, readonly);
}

int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
{
	if (_gnttab_end_foreign_access_ref(ref, readonly))
		return 1;
	pr_warn("WARNING: g.e. %#x still in use!\n", ref);
	return 0;
}
EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);

struct deferred_entry {
	struct list_head list;
	grant_ref_t ref;
	bool ro;
	uint16_t warn_delay;
	struct page *page;
};
static LIST_HEAD(deferred_list);
static void gnttab_handle_deferred(struct timer_list *);
static DEFINE_TIMER(deferred_timer, gnttab_handle_deferred);

static void gnttab_handle_deferred(struct timer_list *unused)
{
	unsigned int nr = 10;
	struct deferred_entry *first = NULL;
	unsigned long flags;

	spin_lock_irqsave(&gnttab_list_lock, flags);
	while (nr--) {
		struct deferred_entry *entry
			= list_first_entry(&deferred_list,
					   struct deferred_entry, list);

		if (entry == first)
			break;
		list_del(&entry->list);
		spin_unlock_irqrestore(&gnttab_list_lock, flags);
		if (_gnttab_end_foreign_access_ref(entry->ref, entry->ro)) {
			put_free_entry(entry->ref);
			if (entry->page) {
				pr_debug("freeing g.e. %#x (pfn %#lx)\n",
					 entry->ref, page_to_pfn(entry->page));
				put_page(entry->page);
			} else
				pr_info("freeing g.e. %#x\n", entry->ref);
			kfree(entry);
			entry = NULL;
		} else {
			if (!--entry->warn_delay)
				pr_info("g.e. %#x still pending\n", entry->ref);
			if (!first)
				first = entry;
		}
		spin_lock_irqsave(&gnttab_list_lock, flags);
		if (entry)
			list_add_tail(&entry->list, &deferred_list);
		else if (list_empty(&deferred_list))
			break;
	}
	if (!list_empty(&deferred_list) && !timer_pending(&deferred_timer)) {
		deferred_timer.expires = jiffies + HZ;
		add_timer(&deferred_timer);
	}
	spin_unlock_irqrestore(&gnttab_list_lock, flags);
}

static void gnttab_add_deferred(grant_ref_t ref, bool readonly,
				struct page *page)
{
	struct deferred_entry *entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
	const char *what = KERN_WARNING "leaking";

	if (entry) {
		unsigned long flags;

		entry->ref = ref;
		entry->ro = readonly;
		entry->page = page;
		entry->warn_delay = 60;
		spin_lock_irqsave(&gnttab_list_lock, flags);
		list_add_tail(&entry->list, &deferred_list);
		if (!timer_pending(&deferred_timer)) {
			deferred_timer.expires = jiffies + HZ;
			add_timer(&deferred_timer);
		}
		spin_unlock_irqrestore(&gnttab_list_lock, flags);
		what = KERN_DEBUG "deferring";
	}
	printk("%s g.e. %#x (pfn %#lx)\n",
	       what, ref, page ? page_to_pfn(page) : -1);
}

void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
			       unsigned long page)
{
	if (gnttab_end_foreign_access_ref(ref, readonly)) {
		put_free_entry(ref);
		if (page != 0)
			put_page(virt_to_page(page));
	} else
		gnttab_add_deferred(ref, readonly,
				    page ? virt_to_page(page) : NULL);
}
EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);

int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)
{
	int ref;

	ref = get_free_entries(1);
	if (unlikely(ref < 0))
		return -ENOSPC;
	gnttab_grant_foreign_transfer_ref(ref, domid, pfn);

	return ref;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);

void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,
				       unsigned long pfn)
{
	gnttab_interface->update_entry(ref, domid, pfn, GTF_accept_transfer);
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);

static unsigned long gnttab_end_foreign_transfer_ref_v1(grant_ref_t ref)
{
	unsigned long frame;
	u16           flags;
	u16          *pflags;

	pflags = &gnttab_shared.v1[ref].flags;

	/*
	 * If a transfer is not even yet started, try to reclaim the grant
	 * reference and return failure (== 0).
	 */
	while (!((flags = *pflags) & GTF_transfer_committed)) {
		if (sync_cmpxchg(pflags, flags, 0) == flags)
			return 0;
		cpu_relax();
	}

	/* If a transfer is in progress then wait until it is completed. */
	while (!(flags & GTF_transfer_completed)) {
		flags = *pflags;
		cpu_relax();
	}

	rmb();	/* Read the frame number /after/ reading completion status. */
	frame = gnttab_shared.v1[ref].frame;
	BUG_ON(frame == 0);

	return frame;
}

static unsigned long gnttab_end_foreign_transfer_ref_v2(grant_ref_t ref)
{
	unsigned long frame;
	u16           flags;
	u16          *pflags;

	pflags = &gnttab_shared.v2[ref].hdr.flags;

	/*
	 * If a transfer is not even yet started, try to reclaim the grant
	 * reference and return failure (== 0).
	 */
	while (!((flags = *pflags) & GTF_transfer_committed)) {
		if (sync_cmpxchg(pflags, flags, 0) == flags)
			return 0;
		cpu_relax();
	}

	/* If a transfer is in progress then wait until it is completed. */
	while (!(flags & GTF_transfer_completed)) {
		flags = *pflags;
		cpu_relax();
	}

	rmb();  /* Read the frame number /after/ reading completion status. */
	frame = gnttab_shared.v2[ref].full_page.frame;
	BUG_ON(frame == 0);

	return frame;
}

unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
{
	return gnttab_interface->end_foreign_transfer_ref(ref);
}
EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);

unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)
{
	unsigned long frame = gnttab_end_foreign_transfer_ref(ref);
	put_free_entry(ref);
	return frame;
}
EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);

void gnttab_free_grant_reference(grant_ref_t ref)
{
	put_free_entry(ref);
}
EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);

void gnttab_free_grant_references(grant_ref_t head)
{
	grant_ref_t ref;
	unsigned long flags;
	int count = 1;
	if (head == GNTTAB_LIST_END)
		return;
	spin_lock_irqsave(&gnttab_list_lock, flags);
	ref = head;
	while (gnttab_entry(ref) != GNTTAB_LIST_END) {
		ref = gnttab_entry(ref);
		count++;
	}
	gnttab_entry(ref) = gnttab_free_head;
	gnttab_free_head = head;
	gnttab_free_count += count;
	check_free_callbacks();
	spin_unlock_irqrestore(&gnttab_list_lock, flags);
}
EXPORT_SYMBOL_GPL(gnttab_free_grant_references);

int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
{
	int h = get_free_entries(count);

	if (h < 0)
		return -ENOSPC;

	*head = h;

	return 0;
}
EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);

int gnttab_empty_grant_references(const grant_ref_t *private_head)
{
	return (*private_head == GNTTAB_LIST_END);
}
EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);

int gnttab_claim_grant_reference(grant_ref_t *private_head)
{
	grant_ref_t g = *private_head;
	if (unlikely(g == GNTTAB_LIST_END))
		return -ENOSPC;
	*private_head = gnttab_entry(g);
	return g;
}
EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);

void gnttab_release_grant_reference(grant_ref_t *private_head,
				    grant_ref_t release)
{
	gnttab_entry(release) = *private_head;
	*private_head = release;
}
EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);

void gnttab_request_free_callback(struct gnttab_free_callback *callback,
				  void (*fn)(void *), void *arg, u16 count)
{
	unsigned long flags;
	struct gnttab_free_callback *cb;

	spin_lock_irqsave(&gnttab_list_lock, flags);

	/* Check if the callback is already on the list */
	cb = gnttab_free_callback_list;
	while (cb) {
		if (cb == callback)
			goto out;
		cb = cb->next;
	}

	callback->fn = fn;
	callback->arg = arg;
	callback->count = count;
	callback->next = gnttab_free_callback_list;
	gnttab_free_callback_list = callback;
	check_free_callbacks();
out:
	spin_unlock_irqrestore(&gnttab_list_lock, flags);
}
EXPORT_SYMBOL_GPL(gnttab_request_free_callback);

void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
{
	struct gnttab_free_callback **pcb;
	unsigned long flags;

	spin_lock_irqsave(&gnttab_list_lock, flags);
	for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
		if (*pcb == callback) {
			*pcb = callback->next;
			break;
		}
	}
	spin_unlock_irqrestore(&gnttab_list_lock, flags);
}
EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);

static unsigned int gnttab_frames(unsigned int frames, unsigned int align)
{
	return (frames * gnttab_interface->grefs_per_grant_frame + align - 1) /
	       align;
}

static int grow_gnttab_list(unsigned int more_frames)
{
	unsigned int new_nr_grant_frames, extra_entries, i;
	unsigned int nr_glist_frames, new_nr_glist_frames;
	unsigned int grefs_per_frame;

	BUG_ON(gnttab_interface == NULL);
	grefs_per_frame = gnttab_interface->grefs_per_grant_frame;

	new_nr_grant_frames = nr_grant_frames + more_frames;
	extra_entries = more_frames * grefs_per_frame;

	nr_glist_frames = gnttab_frames(nr_grant_frames, RPP);
	new_nr_glist_frames = gnttab_frames(new_nr_grant_frames, RPP);
	for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
		if (!gnttab_list[i])
			goto grow_nomem;
	}


	for (i = grefs_per_frame * nr_grant_frames;
	     i < grefs_per_frame * new_nr_grant_frames - 1; i++)
		gnttab_entry(i) = i + 1;

	gnttab_entry(i) = gnttab_free_head;
	gnttab_free_head = grefs_per_frame * nr_grant_frames;
	gnttab_free_count += extra_entries;

	nr_grant_frames = new_nr_grant_frames;

	check_free_callbacks();

	return 0;

grow_nomem:
	while (i-- > nr_glist_frames)
		free_page((unsigned long) gnttab_list[i]);
	return -ENOMEM;
}

static unsigned int __max_nr_grant_frames(void)
{
	struct gnttab_query_size query;
	int rc;

	query.dom = DOMID_SELF;

	rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
	if ((rc < 0) || (query.status != GNTST_okay))
		return 4; /* Legacy max supported number of frames */

	return query.max_nr_frames;
}

unsigned int gnttab_max_grant_frames(void)
{
	unsigned int xen_max = __max_nr_grant_frames();
	static unsigned int boot_max_nr_grant_frames;

	/* First time, initialize it properly. */
	if (!boot_max_nr_grant_frames)
		boot_max_nr_grant_frames = __max_nr_grant_frames();

	if (xen_max > boot_max_nr_grant_frames)
		return boot_max_nr_grant_frames;
	return xen_max;
}
EXPORT_SYMBOL_GPL(gnttab_max_grant_frames);

int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
{
	xen_pfn_t *pfn;
	unsigned int max_nr_gframes = __max_nr_grant_frames();
	unsigned int i;
	void *vaddr;

	if (xen_auto_xlat_grant_frames.count)
		return -EINVAL;

	vaddr = xen_remap(addr, XEN_PAGE_SIZE * max_nr_gframes);
	if (vaddr == NULL) {
		pr_warn("Failed to ioremap gnttab share frames (addr=%pa)!\n",
			&addr);
		return -ENOMEM;
	}
	pfn = kcalloc(max_nr_gframes, sizeof(pfn[0]), GFP_KERNEL);
	if (!pfn) {
		xen_unmap(vaddr);
		return -ENOMEM;
	}
	for (i = 0; i < max_nr_gframes; i++)
		pfn[i] = XEN_PFN_DOWN(addr) + i;

	xen_auto_xlat_grant_frames.vaddr = vaddr;
	xen_auto_xlat_grant_frames.pfn = pfn;
	xen_auto_xlat_grant_frames.count = max_nr_gframes;

	return 0;
}
EXPORT_SYMBOL_GPL(gnttab_setup_auto_xlat_frames);

void gnttab_free_auto_xlat_frames(void)
{
	if (!xen_auto_xlat_grant_frames.count)
		return;
	kfree(xen_auto_xlat_grant_frames.pfn);
	xen_unmap(xen_auto_xlat_grant_frames.vaddr);

	xen_auto_xlat_grant_frames.pfn = NULL;
	xen_auto_xlat_grant_frames.count = 0;
	xen_auto_xlat_grant_frames.vaddr = NULL;
}
EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);

int gnttab_pages_set_private(int nr_pages, struct page **pages)
{
	int i;

	for (i = 0; i < nr_pages; i++) {
#if BITS_PER_LONG < 64
		struct xen_page_foreign *foreign;

		foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
		if (!foreign)
			return -ENOMEM;

		set_page_private(pages[i], (unsigned long)foreign);
#endif
		SetPagePrivate(pages[i]);
	}

	return 0;
}
EXPORT_SYMBOL_GPL(gnttab_pages_set_private);

/**
 * gnttab_alloc_pages - alloc pages suitable for grant mapping into
 * @nr_pages: number of pages to alloc
 * @pages: returns the pages
 */
int gnttab_alloc_pages(int nr_pages, struct page **pages)
{
	int ret;

	ret = alloc_xenballooned_pages(nr_pages, pages);
	if (ret < 0)
		return ret;

	ret = gnttab_pages_set_private(nr_pages, pages);
	if (ret < 0)
		gnttab_free_pages(nr_pages, pages);

	return ret;
}
EXPORT_SYMBOL_GPL(gnttab_alloc_pages);

void gnttab_pages_clear_private(int nr_pages, struct page **pages)
{
	int i;

	for (i = 0; i < nr_pages; i++) {
		if (PagePrivate(pages[i])) {
#if BITS_PER_LONG < 64
			kfree((void *)page_private(pages[i]));
#endif
			ClearPagePrivate(pages[i]);
		}
	}
}
EXPORT_SYMBOL_GPL(gnttab_pages_clear_private);

/**
 * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
 * @nr_pages; number of pages to free
 * @pages: the pages
 */
void gnttab_free_pages(int nr_pages, struct page **pages)
{
	gnttab_pages_clear_private(nr_pages, pages);
	free_xenballooned_pages(nr_pages, pages);
}
EXPORT_SYMBOL_GPL(gnttab_free_pages);

#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
/**
 * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
 * @args: arguments to the function
 */
int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
{
	unsigned long pfn, start_pfn;
	size_t size;
	int i, ret;

	size = args->nr_pages << PAGE_SHIFT;
	if (args->coherent)
		args->vaddr = dma_alloc_coherent(args->dev, size,
						 &args->dev_bus_addr,
						 GFP_KERNEL | __GFP_NOWARN);
	else
		args->vaddr = dma_alloc_wc(args->dev, size,
					   &args->dev_bus_addr,
					   GFP_KERNEL | __GFP_NOWARN);
	if (!args->vaddr) {
		pr_debug("Failed to allocate DMA buffer of size %zu\n", size);
		return -ENOMEM;
	}

	start_pfn = __phys_to_pfn(args->dev_bus_addr);
	for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
			pfn++, i++) {
		struct page *page = pfn_to_page(pfn);

		args->pages[i] = page;
		args->frames[i] = xen_page_to_gfn(page);
		xenmem_reservation_scrub_page(page);
	}

	xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);

	ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
	if (ret != args->nr_pages) {
		pr_debug("Failed to decrease reservation for DMA buffer\n");
		ret = -EFAULT;
		goto fail;
	}

	ret = gnttab_pages_set_private(args->nr_pages, args->pages);
	if (ret < 0)
		goto fail;

	return 0;

fail:
	gnttab_dma_free_pages(args);
	return ret;
}
EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);

/**
 * gnttab_dma_free_pages - free DMAable pages
 * @args: arguments to the function
 */
int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
{
	size_t size;
	int i, ret;

	gnttab_pages_clear_private(args->nr_pages, args->pages);

	for (i = 0; i < args->nr_pages; i++)
		args->frames[i] = page_to_xen_pfn(args->pages[i]);

	ret = xenmem_reservation_increase(args->nr_pages, args->frames);
	if (ret != args->nr_pages) {
		pr_debug("Failed to increase reservation for DMA buffer\n");
		ret = -EFAULT;
	} else {
		ret = 0;
	}

	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
					     args->frames);

	size = args->nr_pages << PAGE_SHIFT;
	if (args->coherent)
		dma_free_coherent(args->dev, size,
				  args->vaddr, args->dev_bus_addr);
	else
		dma_free_wc(args->dev, size,
			    args->vaddr, args->dev_bus_addr);
	return ret;
}
EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
#endif

/* Handling of paged out grant targets (GNTST_eagain) */
#define MAX_DELAY 256
static inline void
gnttab_retry_eagain_gop(unsigned int cmd, void *gop, int16_t *status,
						const char *func)
{
	unsigned delay = 1;

	do {
		BUG_ON(HYPERVISOR_grant_table_op(cmd, gop, 1));
		if (*status == GNTST_eagain)
			msleep(delay++);
	} while ((*status == GNTST_eagain) && (delay < MAX_DELAY));

	if (delay >= MAX_DELAY) {
		pr_err("%s: %s eagain grant\n", func, current->comm);
		*status = GNTST_bad_page;
	}
}

void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count)
{
	struct gnttab_map_grant_ref *op;

	if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, batch, count))
		BUG();
	for (op = batch; op < batch + count; op++)
		if (op->status == GNTST_eagain)
			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, op,
						&op->status, __func__);
}
EXPORT_SYMBOL_GPL(gnttab_batch_map);

void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count)
{
	struct gnttab_copy *op;

	if (HYPERVISOR_grant_table_op(GNTTABOP_copy, batch, count))
		BUG();
	for (op = batch; op < batch + count; op++)
		if (op->status == GNTST_eagain)
			gnttab_retry_eagain_gop(GNTTABOP_copy, op,
						&op->status, __func__);
}
EXPORT_SYMBOL_GPL(gnttab_batch_copy);

void gnttab_foreach_grant_in_range(struct page *page,
				   unsigned int offset,
				   unsigned int len,
				   xen_grant_fn_t fn,
				   void *data)
{
	unsigned int goffset;
	unsigned int glen;
	unsigned long xen_pfn;

	len = min_t(unsigned int, PAGE_SIZE - offset, len);
	goffset = xen_offset_in_page(offset);

	xen_pfn = page_to_xen_pfn(page) + XEN_PFN_DOWN(offset);

	while (len) {
		glen = min_t(unsigned int, XEN_PAGE_SIZE - goffset, len);
		fn(pfn_to_gfn(xen_pfn), goffset, glen, data);

		goffset = 0;
		xen_pfn++;
		len -= glen;
	}
}
EXPORT_SYMBOL_GPL(gnttab_foreach_grant_in_range);

void gnttab_foreach_grant(struct page **pages,
			  unsigned int nr_grefs,
			  xen_grant_fn_t fn,
			  void *data)
{
	unsigned int goffset = 0;
	unsigned long xen_pfn = 0;
	unsigned int i;

	for (i = 0; i < nr_grefs; i++) {
		if ((i % XEN_PFN_PER_PAGE) == 0) {
			xen_pfn = page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
			goffset = 0;
		}

		fn(pfn_to_gfn(xen_pfn), goffset, XEN_PAGE_SIZE, data);

		goffset += XEN_PAGE_SIZE;
		xen_pfn++;
	}
}

int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
		    struct gnttab_map_grant_ref *kmap_ops,
		    struct page **pages, unsigned int count)
{
	int i, ret;

	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);
	if (ret)
		return ret;

	for (i = 0; i < count; i++) {
		switch (map_ops[i].status) {
		case GNTST_okay:
		{
			struct xen_page_foreign *foreign;

			SetPageForeign(pages[i]);
			foreign = xen_page_foreign(pages[i]);
			foreign->domid = map_ops[i].dom;
			foreign->gref = map_ops[i].ref;
			break;
		}

		case GNTST_no_device_space:
			pr_warn_ratelimited("maptrack limit reached, can't map all guest pages\n");
			break;

		case GNTST_eagain:
			/* Retry eagain maps */
			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref,
						map_ops + i,
						&map_ops[i].status, __func__);
			/* Test status in next loop iteration. */
			i--;
			break;

		default:
			break;
		}
	}

	return set_foreign_p2m_mapping(map_ops, kmap_ops, pages, count);
}
EXPORT_SYMBOL_GPL(gnttab_map_refs);

int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
		      struct gnttab_unmap_grant_ref *kunmap_ops,
		      struct page **pages, unsigned int count)
{
	unsigned int i;
	int ret;

	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
	if (ret)
		return ret;

	for (i = 0; i < count; i++)
		ClearPageForeign(pages[i]);

	return clear_foreign_p2m_mapping(unmap_ops, kunmap_ops, pages, count);
}
EXPORT_SYMBOL_GPL(gnttab_unmap_refs);

#define GNTTAB_UNMAP_REFS_DELAY 5

static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item);

static void gnttab_unmap_work(struct work_struct *work)
{
	struct gntab_unmap_queue_data
		*unmap_data = container_of(work, 
					   struct gntab_unmap_queue_data,
					   gnttab_work.work);
	if (unmap_data->age != UINT_MAX)
		unmap_data->age++;
	__gnttab_unmap_refs_async(unmap_data);
}

static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
{
	int ret;
	int pc;

	for (pc = 0; pc < item->count; pc++) {
		if (page_count(item->pages[pc]) > 1) {
			unsigned long delay = GNTTAB_UNMAP_REFS_DELAY * (item->age + 1);
			schedule_delayed_work(&item->gnttab_work,
					      msecs_to_jiffies(delay));
			return;
		}
	}

	ret = gnttab_unmap_refs(item->unmap_ops, item->kunmap_ops,
				item->pages, item->count);
	item->done(ret, item);
}

void gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
{
	INIT_DELAYED_WORK(&item->gnttab_work, gnttab_unmap_work);
	item->age = 0;

	__gnttab_unmap_refs_async(item);
}
EXPORT_SYMBOL_GPL(gnttab_unmap_refs_async);

static void unmap_refs_callback(int result,
		struct gntab_unmap_queue_data *data)
{
	struct unmap_refs_callback_data *d = data->data;

	d->result = result;
	complete(&d->completion);
}

int gnttab_unmap_refs_sync(struct gntab_unmap_queue_data *item)
{
	struct unmap_refs_callback_data data;

	init_completion(&data.completion);
	item->data = &data;
	item->done = &unmap_refs_callback;
	gnttab_unmap_refs_async(item);
	wait_for_completion(&data.completion);

	return data.result;
}
EXPORT_SYMBOL_GPL(gnttab_unmap_refs_sync);

static unsigned int nr_status_frames(unsigned int nr_grant_frames)
{
	BUG_ON(gnttab_interface == NULL);
	return gnttab_frames(nr_grant_frames, SPP);
}

static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)
{
	int rc;

	rc = arch_gnttab_map_shared(frames, nr_gframes,
				    gnttab_max_grant_frames(),
				    &gnttab_shared.addr);
	BUG_ON(rc);

	return 0;
}

static void gnttab_unmap_frames_v1(void)
{
	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
}

static int gnttab_map_frames_v2(xen_pfn_t *frames, unsigned int nr_gframes)
{
	uint64_t *sframes;
	unsigned int nr_sframes;
	struct gnttab_get_status_frames getframes;
	int rc;

	nr_sframes = nr_status_frames(nr_gframes);

	/* No need for kzalloc as it is initialized in following hypercall
	 * GNTTABOP_get_status_frames.
	 */
	sframes = kmalloc_array(nr_sframes, sizeof(uint64_t), GFP_ATOMIC);
	if (!sframes)
		return -ENOMEM;

	getframes.dom        = DOMID_SELF;
	getframes.nr_frames  = nr_sframes;
	set_xen_guest_handle(getframes.frame_list, sframes);

	rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
				       &getframes, 1);
	if (rc == -ENOSYS) {
		kfree(sframes);
		return -ENOSYS;
	}

	BUG_ON(rc || getframes.status);

	rc = arch_gnttab_map_status(sframes, nr_sframes,
				    nr_status_frames(gnttab_max_grant_frames()),
				    &grstatus);
	BUG_ON(rc);
	kfree(sframes);

	rc = arch_gnttab_map_shared(frames, nr_gframes,
				    gnttab_max_grant_frames(),
				    &gnttab_shared.addr);
	BUG_ON(rc);

	return 0;
}

static void gnttab_unmap_frames_v2(void)
{
	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
	arch_gnttab_unmap(grstatus, nr_status_frames(nr_grant_frames));
}

static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
{
	struct gnttab_setup_table setup;
	xen_pfn_t *frames;
	unsigned int nr_gframes = end_idx + 1;
	int rc;

	if (xen_feature(XENFEAT_auto_translated_physmap)) {
		struct xen_add_to_physmap xatp;
		unsigned int i = end_idx;
		rc = 0;
		BUG_ON(xen_auto_xlat_grant_frames.count < nr_gframes);
		/*
		 * Loop backwards, so that the first hypercall has the largest
		 * index, ensuring that the table will grow only once.
		 */
		do {
			xatp.domid = DOMID_SELF;
			xatp.idx = i;
			xatp.space = XENMAPSPACE_grant_table;
			xatp.gpfn = xen_auto_xlat_grant_frames.pfn[i];
			rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
			if (rc != 0) {
				pr_warn("grant table add_to_physmap failed, err=%d\n",
					rc);
				break;
			}
		} while (i-- > start_idx);

		return rc;
	}

	/* No need for kzalloc as it is initialized in following hypercall
	 * GNTTABOP_setup_table.
	 */
	frames = kmalloc_array(nr_gframes, sizeof(unsigned long), GFP_ATOMIC);
	if (!frames)
		return -ENOMEM;

	setup.dom        = DOMID_SELF;
	setup.nr_frames  = nr_gframes;
	set_xen_guest_handle(setup.frame_list, frames);

	rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
	if (rc == -ENOSYS) {
		kfree(frames);
		return -ENOSYS;
	}

	BUG_ON(rc || setup.status);

	rc = gnttab_interface->map_frames(frames, nr_gframes);

	kfree(frames);

	return rc;
}

static const struct gnttab_ops gnttab_v1_ops = {
	.version			= 1,
	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
					  sizeof(struct grant_entry_v1),
	.map_frames			= gnttab_map_frames_v1,
	.unmap_frames			= gnttab_unmap_frames_v1,
	.update_entry			= gnttab_update_entry_v1,
	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v1,
	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v1,
	.query_foreign_access		= gnttab_query_foreign_access_v1,
};

static const struct gnttab_ops gnttab_v2_ops = {
	.version			= 2,
	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
					  sizeof(union grant_entry_v2),
	.map_frames			= gnttab_map_frames_v2,
	.unmap_frames			= gnttab_unmap_frames_v2,
	.update_entry			= gnttab_update_entry_v2,
	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,
	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v2,
	.query_foreign_access		= gnttab_query_foreign_access_v2,
};

static bool gnttab_need_v2(void)
{
#ifdef CONFIG_X86
	uint32_t base, width;

	if (xen_pv_domain()) {
		base = xen_cpuid_base();
		if (cpuid_eax(base) < 5)
			return false;	/* Information not available, use V1. */
		width = cpuid_ebx(base + 5) &
			XEN_CPUID_MACHINE_ADDRESS_WIDTH_MASK;
		return width > 32 + PAGE_SHIFT;
	}
#endif
	return !!(max_possible_pfn >> 32);
}

static void gnttab_request_version(void)
{
	long rc;
	struct gnttab_set_version gsv;

	if (gnttab_need_v2())
		gsv.version = 2;
	else
		gsv.version = 1;

	/* Boot parameter overrides automatic selection. */
	if (xen_gnttab_version >= 1 && xen_gnttab_version <= 2)
		gsv.version = xen_gnttab_version;

	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
	if (rc == 0 && gsv.version == 2)
		gnttab_interface = &gnttab_v2_ops;
	else
		gnttab_interface = &gnttab_v1_ops;
	pr_info("Grant tables using version %d layout\n",
		gnttab_interface->version);
}

static int gnttab_setup(void)
{
	unsigned int max_nr_gframes;

	max_nr_gframes = gnttab_max_grant_frames();
	if (max_nr_gframes < nr_grant_frames)
		return -ENOSYS;

	if (xen_feature(XENFEAT_auto_translated_physmap) && gnttab_shared.addr == NULL) {
		gnttab_shared.addr = xen_auto_xlat_grant_frames.vaddr;
		if (gnttab_shared.addr == NULL) {
			pr_warn("gnttab share frames is not mapped!\n");
			return -ENOMEM;
		}
	}
	return gnttab_map(0, nr_grant_frames - 1);
}

int gnttab_resume(void)
{
	gnttab_request_version();
	return gnttab_setup();
}

int gnttab_suspend(void)
{
	if (!xen_feature(XENFEAT_auto_translated_physmap))
		gnttab_interface->unmap_frames();
	return 0;
}

static int gnttab_expand(unsigned int req_entries)
{
	int rc;
	unsigned int cur, extra;

	BUG_ON(gnttab_interface == NULL);
	cur = nr_grant_frames;
	extra = ((req_entries + gnttab_interface->grefs_per_grant_frame - 1) /
		 gnttab_interface->grefs_per_grant_frame);
	if (cur + extra > gnttab_max_grant_frames()) {
		pr_warn_ratelimited("xen/grant-table: max_grant_frames reached"
				    " cur=%u extra=%u limit=%u"
				    " gnttab_free_count=%u req_entries=%u\n",
				    cur, extra, gnttab_max_grant_frames(),
				    gnttab_free_count, req_entries);
		return -ENOSPC;
	}

	rc = gnttab_map(cur, cur + extra - 1);
	if (rc == 0)
		rc = grow_gnttab_list(extra);

	return rc;
}

int gnttab_init(void)
{
	int i;
	unsigned long max_nr_grant_frames;
	unsigned int max_nr_glist_frames, nr_glist_frames;
	unsigned int nr_init_grefs;
	int ret;

	gnttab_request_version();
	max_nr_grant_frames = gnttab_max_grant_frames();
	nr_grant_frames = 1;

	/* Determine the maximum number of frames required for the
	 * grant reference free list on the current hypervisor.
	 */
	BUG_ON(gnttab_interface == NULL);
	max_nr_glist_frames = (max_nr_grant_frames *
			       gnttab_interface->grefs_per_grant_frame / RPP);

	gnttab_list = kmalloc_array(max_nr_glist_frames,
				    sizeof(grant_ref_t *),
				    GFP_KERNEL);
	if (gnttab_list == NULL)
		return -ENOMEM;

	nr_glist_frames = gnttab_frames(nr_grant_frames, RPP);
	for (i = 0; i < nr_glist_frames; i++) {
		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
		if (gnttab_list[i] == NULL) {
			ret = -ENOMEM;
			goto ini_nomem;
		}
	}

	ret = arch_gnttab_init(max_nr_grant_frames,
			       nr_status_frames(max_nr_grant_frames));
	if (ret < 0)
		goto ini_nomem;

	if (gnttab_setup() < 0) {
		ret = -ENODEV;
		goto ini_nomem;
	}

	nr_init_grefs = nr_grant_frames *
			gnttab_interface->grefs_per_grant_frame;

	for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
		gnttab_entry(i) = i + 1;

	gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
	gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
	gnttab_free_head  = NR_RESERVED_ENTRIES;

	printk("Grant table initialized\n");
	return 0;

 ini_nomem:
	for (i--; i >= 0; i--)
		free_page((unsigned long)gnttab_list[i]);
	kfree(gnttab_list);
	return ret;
}
EXPORT_SYMBOL_GPL(gnttab_init);

static int __gnttab_init(void)
{
	if (!xen_domain())
		return -ENODEV;

	/* Delay grant-table initialization in the PV on HVM case */
	if (xen_hvm_domain() && !xen_pvh_domain())
		return 0;

	return gnttab_init();
}
/* Starts after core_initcall so that xen_pvh_gnttab_setup can be called
 * beforehand to initialize xen_auto_xlat_grant_frames. */
core_initcall_sync(__gnttab_init);