summaryrefslogtreecommitdiff
path: root/drivers/xen/grant-table.c
blob: b91f14e831648e68093a02f804f82e4113325360 (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
/******************************************************************************
 * 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.
 */

#include <linux/module.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 <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 <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
#define GREFS_PER_GRANT_FRAME \
(grant_table_version == 1 ?                      \
(PAGE_SIZE / sizeof(struct grant_entry_v1)) :   \
(PAGE_SIZE / sizeof(union grant_entry_v2)))

static grant_ref_t **gnttab_list;
static unsigned int nr_grant_frames;
static unsigned int boot_max_nr_grant_frames;
static int gnttab_free_count;
static grant_ref_t gnttab_free_head;
static DEFINE_SPINLOCK(gnttab_list_lock);
unsigned long xen_hvm_resume_frames;
EXPORT_SYMBOL_GPL(xen_hvm_resume_frames);

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 {
	/*
	 * 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);
	/*
	 * Grant a domain to access a range of bytes within the page referred by
	 * an available grant entry. Ref parameter is reference of a grant entry
	 * which will be sub-page accessed, domid is id of grantee domain, frame
	 * is frame address of subpage grant, flags is grant type and flag
	 * information, page_off is offset of the range of bytes, and length is
	 * length of bytes to be accessed.
	 */
	void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,
				     unsigned long frame, int flags,
				     unsigned page_off, unsigned length);
	/*
	 * Redirect an available grant entry on domain A to another grant
	 * reference of domain B, then allow domain C to use grant reference
	 * of domain B transitively. Ref parameter is an available grant entry
	 * reference on domain A, domid is id of domain C which accesses grant
	 * entry transitively, flags is grant type and flag information,
	 * trans_domid is id of domain B whose grant entry is finally accessed
	 * transitively, trans_gref is grant entry transitive reference of
	 * domain B.
	 */
	void (*update_trans_entry)(grant_ref_t ref, domid_t domid, int flags,
				   domid_t trans_domid, grant_ref_t trans_gref);
};

static struct gnttab_ops *gnttab_interface;

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

static int grant_table_version;

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 flags)
{
	gnttab_shared.v2[ref].hdr.domid = domid;
	gnttab_shared.v2[ref].full_page.frame = frame;
	wmb();
	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 void gnttab_update_subpage_entry_v2(grant_ref_t ref, domid_t domid,
					   unsigned long frame, int flags,
					   unsigned page_off, unsigned length)
{
	gnttab_shared.v2[ref].sub_page.frame = frame;
	gnttab_shared.v2[ref].sub_page.page_off = page_off;
	gnttab_shared.v2[ref].sub_page.length = length;
	gnttab_shared.v2[ref].hdr.domid = domid;
	wmb();
	gnttab_shared.v2[ref].hdr.flags =
				GTF_permit_access | GTF_sub_page | flags;
}

int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
					    unsigned long frame, int flags,
					    unsigned page_off,
					    unsigned length)
{
	if (flags & (GTF_accept_transfer | GTF_reading |
		     GTF_writing | GTF_transitive))
		return -EPERM;

	if (gnttab_interface->update_subpage_entry == NULL)
		return -ENOSYS;

	gnttab_interface->update_subpage_entry(ref, domid, frame, flags,
					       page_off, length);

	return 0;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage_ref);

int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
					int flags, unsigned page_off,
					unsigned length)
{
	int ref, rc;

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

	rc = gnttab_grant_foreign_access_subpage_ref(ref, domid, frame, flags,
						     page_off, length);
	if (rc < 0) {
		put_free_entry(ref);
		return rc;
	}

	return ref;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);

bool gnttab_subpage_grants_available(void)
{
	return gnttab_interface->update_subpage_entry != NULL;
}
EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);

static void gnttab_update_trans_entry_v2(grant_ref_t ref, domid_t domid,
					 int flags, domid_t trans_domid,
					 grant_ref_t trans_gref)
{
	gnttab_shared.v2[ref].transitive.trans_domid = trans_domid;
	gnttab_shared.v2[ref].transitive.gref = trans_gref;
	gnttab_shared.v2[ref].hdr.domid = domid;
	wmb();
	gnttab_shared.v2[ref].hdr.flags =
				GTF_permit_access | GTF_transitive | flags;
}

int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
					  int flags, domid_t trans_domid,
					  grant_ref_t trans_gref)
{
	if (flags & (GTF_accept_transfer | GTF_reading |
		     GTF_writing | GTF_sub_page))
		return -EPERM;

	if (gnttab_interface->update_trans_entry == NULL)
		return -ENOSYS;

	gnttab_interface->update_trans_entry(ref, domid, flags, trans_domid,
					     trans_gref);

	return 0;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans_ref);

int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
				      domid_t trans_domid,
				      grant_ref_t trans_gref)
{
	int ref, rc;

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

	rc = gnttab_grant_foreign_access_trans_ref(ref, domid, flags,
						   trans_domid, trans_gref);
	if (rc < 0) {
		put_free_entry(ref);
		return rc;
	}

	return ref;
}
EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans);

bool gnttab_trans_grants_available(void)
{
	return gnttab_interface->update_trans_entry != NULL;
}
EXPORT_SYMBOL_GPL(gnttab_trans_grants_available);

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();
	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(unsigned long);
static DEFINE_TIMER(deferred_timer, gnttab_handle_deferred, 0, 0);

static void gnttab_handle_deferred(unsigned long 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));
				__free_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)
			free_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;
	spin_lock_irqsave(&gnttab_list_lock, flags);
	if (callback->next)
		goto out;
	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 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;

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

	nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
	new_nr_glist_frames =
		(new_nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / 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_GRANT_FRAME * nr_grant_frames;
	     i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)
		gnttab_entry(i) = i + 1;

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

	nr_grant_frames = new_nr_grant_frames;

	check_free_callbacks();

	return 0;

grow_nomem:
	for ( ; i >= nr_glist_frames; i--)
		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();

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

/* 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) {
		printk(KERN_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);

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;
	bool lazy = false;
	pte_t *pte;
	unsigned long mfn;

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

	/* Retry eagain maps */
	for (i = 0; i < count; i++)
		if (map_ops[i].status == GNTST_eagain)
			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
						&map_ops[i].status, __func__);

	if (xen_feature(XENFEAT_auto_translated_physmap))
		return ret;

	if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
		arch_enter_lazy_mmu_mode();
		lazy = true;
	}

	for (i = 0; i < count; i++) {
		/* Do not add to override if the map failed. */
		if (map_ops[i].status)
			continue;

		if (map_ops[i].flags & GNTMAP_contains_pte) {
			pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
				(map_ops[i].host_addr & ~PAGE_MASK));
			mfn = pte_mfn(*pte);
		} else {
			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
		}
		ret = m2p_add_override(mfn, pages[i], kmap_ops ?
				       &kmap_ops[i] : NULL);
		if (ret)
			return ret;
	}

	if (lazy)
		arch_leave_lazy_mmu_mode();

	return ret;
}
EXPORT_SYMBOL_GPL(gnttab_map_refs);

int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
		      struct gnttab_map_grant_ref *kmap_ops,
		      struct page **pages, unsigned int count)
{
	int i, ret;
	bool lazy = false;

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

	if (xen_feature(XENFEAT_auto_translated_physmap))
		return ret;

	if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
		arch_enter_lazy_mmu_mode();
		lazy = true;
	}

	for (i = 0; i < count; i++) {
		ret = m2p_remove_override(pages[i], kmap_ops ?
				       &kmap_ops[i] : NULL);
		if (ret)
			return ret;
	}

	if (lazy)
		arch_leave_lazy_mmu_mode();

	return ret;
}
EXPORT_SYMBOL_GPL(gnttab_unmap_refs);

static unsigned nr_status_frames(unsigned nr_grant_frames)
{
	return (nr_grant_frames * GREFS_PER_GRANT_FRAME + SPP - 1) / 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(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_hvm_domain()) {
		struct xen_add_to_physmap xatp;
		unsigned int i = end_idx;
		rc = 0;
		/*
		 * 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_hvm_resume_frames >> PAGE_SHIFT) + i;
			rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
			if (rc != 0) {
				printk(KERN_WARNING
						"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(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 struct gnttab_ops gnttab_v1_ops = {
	.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 struct gnttab_ops gnttab_v2_ops = {
	.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,
	.update_subpage_entry		= gnttab_update_subpage_entry_v2,
	.update_trans_entry		= gnttab_update_trans_entry_v2,
};

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

	if (xen_hvm_domain())
		gsv.version = 1;
	else
		gsv.version = 2;
	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
	if (rc == 0 && gsv.version == 2) {
		grant_table_version = 2;
		gnttab_interface = &gnttab_v2_ops;
	} else if (grant_table_version == 2) {
		/*
		 * If we've already used version 2 features,
		 * but then suddenly discover that they're not
		 * available (e.g. migrating to an older
		 * version of Xen), almost unbounded badness
		 * can happen.
		 */
		panic("we need grant tables version 2, but only version 1 is available");
	} else {
		grant_table_version = 1;
		gnttab_interface = &gnttab_v1_ops;
	}
	printk(KERN_INFO "Grant tables using version %d layout.\n",
		grant_table_version);
}

int gnttab_resume(void)
{
	unsigned int max_nr_gframes;

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

	if (xen_pv_domain())
		return gnttab_map(0, nr_grant_frames - 1);

	if (gnttab_shared.addr == NULL) {
		gnttab_shared.addr = ioremap(xen_hvm_resume_frames,
						PAGE_SIZE * max_nr_gframes);
		if (gnttab_shared.addr == NULL) {
			printk(KERN_WARNING
					"Failed to ioremap gnttab share frames!");
			return -ENOMEM;
		}
	}

	gnttab_map(0, nr_grant_frames - 1);

	return 0;
}

int gnttab_suspend(void)
{
	gnttab_interface->unmap_frames();
	return 0;
}

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

	cur = nr_grant_frames;
	extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) /
		 GREFS_PER_GRANT_FRAME);
	if (cur + extra > gnttab_max_grant_frames())
		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 int max_nr_glist_frames, nr_glist_frames;
	unsigned int nr_init_grefs;
	int ret;

	nr_grant_frames = 1;
	boot_max_nr_grant_frames = __max_nr_grant_frames();

	/* Determine the maximum number of frames required for the
	 * grant reference free list on the current hypervisor.
	 */
	max_nr_glist_frames = (boot_max_nr_grant_frames *
			       GREFS_PER_GRANT_FRAME / RPP);

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

	nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / 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;
		}
	}

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

	nr_init_grefs = nr_grant_frames * 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 __devinit __gnttab_init(void)
{
	/* Delay grant-table initialization in the PV on HVM case */
	if (xen_hvm_domain())
		return 0;

	if (!xen_pv_domain())
		return -ENODEV;

	return gnttab_init();
}

core_initcall(__gnttab_init);