summaryrefslogtreecommitdiff
path: root/arch/x86/kvm/mmu/tdp_mmu.c
blob: 6c63f2d1675f9d60885f9baa1176f5e6550bf8f3 (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
// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include "mmu.h"
#include "mmu_internal.h"
#include "mmutrace.h"
#include "tdp_iter.h"
#include "tdp_mmu.h"
#include "spte.h"

#include <asm/cmpxchg.h>
#include <trace/events/kvm.h>

/* Initializes the TDP MMU for the VM, if enabled. */
int kvm_mmu_init_tdp_mmu(struct kvm *kvm)
{
	struct workqueue_struct *wq;

	wq = alloc_workqueue("kvm", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 0);
	if (!wq)
		return -ENOMEM;

	INIT_LIST_HEAD(&kvm->arch.tdp_mmu_roots);
	spin_lock_init(&kvm->arch.tdp_mmu_pages_lock);
	kvm->arch.tdp_mmu_zap_wq = wq;
	return 1;
}

/* Arbitrarily returns true so that this may be used in if statements. */
static __always_inline bool kvm_lockdep_assert_mmu_lock_held(struct kvm *kvm,
							     bool shared)
{
	if (shared)
		lockdep_assert_held_read(&kvm->mmu_lock);
	else
		lockdep_assert_held_write(&kvm->mmu_lock);

	return true;
}

void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
{
	/*
	 * Invalidate all roots, which besides the obvious, schedules all roots
	 * for zapping and thus puts the TDP MMU's reference to each root, i.e.
	 * ultimately frees all roots.
	 */
	kvm_tdp_mmu_invalidate_all_roots(kvm);

	/*
	 * Destroying a workqueue also first flushes the workqueue, i.e. no
	 * need to invoke kvm_tdp_mmu_zap_invalidated_roots().
	 */
	destroy_workqueue(kvm->arch.tdp_mmu_zap_wq);

	WARN_ON(atomic64_read(&kvm->arch.tdp_mmu_pages));
	WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots));

	/*
	 * Ensure that all the outstanding RCU callbacks to free shadow pages
	 * can run before the VM is torn down.  Work items on tdp_mmu_zap_wq
	 * can call kvm_tdp_mmu_put_root and create new callbacks.
	 */
	rcu_barrier();
}

static void tdp_mmu_free_sp(struct kvm_mmu_page *sp)
{
	free_page((unsigned long)sp->spt);
	kmem_cache_free(mmu_page_header_cache, sp);
}

/*
 * This is called through call_rcu in order to free TDP page table memory
 * safely with respect to other kernel threads that may be operating on
 * the memory.
 * By only accessing TDP MMU page table memory in an RCU read critical
 * section, and freeing it after a grace period, lockless access to that
 * memory won't use it after it is freed.
 */
static void tdp_mmu_free_sp_rcu_callback(struct rcu_head *head)
{
	struct kvm_mmu_page *sp = container_of(head, struct kvm_mmu_page,
					       rcu_head);

	tdp_mmu_free_sp(sp);
}

static void tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root,
			     bool shared);

static void tdp_mmu_zap_root_work(struct work_struct *work)
{
	struct kvm_mmu_page *root = container_of(work, struct kvm_mmu_page,
						 tdp_mmu_async_work);
	struct kvm *kvm = root->tdp_mmu_async_data;

	read_lock(&kvm->mmu_lock);

	/*
	 * A TLB flush is not necessary as KVM performs a local TLB flush when
	 * allocating a new root (see kvm_mmu_load()), and when migrating vCPU
	 * to a different pCPU.  Note, the local TLB flush on reuse also
	 * invalidates any paging-structure-cache entries, i.e. TLB entries for
	 * intermediate paging structures, that may be zapped, as such entries
	 * are associated with the ASID on both VMX and SVM.
	 */
	tdp_mmu_zap_root(kvm, root, true);

	/*
	 * Drop the refcount using kvm_tdp_mmu_put_root() to test its logic for
	 * avoiding an infinite loop.  By design, the root is reachable while
	 * it's being asynchronously zapped, thus a different task can put its
	 * last reference, i.e. flowing through kvm_tdp_mmu_put_root() for an
	 * asynchronously zapped root is unavoidable.
	 */
	kvm_tdp_mmu_put_root(kvm, root, true);

	read_unlock(&kvm->mmu_lock);
}

static void tdp_mmu_schedule_zap_root(struct kvm *kvm, struct kvm_mmu_page *root)
{
	root->tdp_mmu_async_data = kvm;
	INIT_WORK(&root->tdp_mmu_async_work, tdp_mmu_zap_root_work);
	queue_work(kvm->arch.tdp_mmu_zap_wq, &root->tdp_mmu_async_work);
}

void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root,
			  bool shared)
{
	kvm_lockdep_assert_mmu_lock_held(kvm, shared);

	if (!refcount_dec_and_test(&root->tdp_mmu_root_count))
		return;

	/*
	 * The TDP MMU itself holds a reference to each root until the root is
	 * explicitly invalidated, i.e. the final reference should be never be
	 * put for a valid root.
	 */
	KVM_BUG_ON(!is_tdp_mmu_page(root) || !root->role.invalid, kvm);

	spin_lock(&kvm->arch.tdp_mmu_pages_lock);
	list_del_rcu(&root->link);
	spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
	call_rcu(&root->rcu_head, tdp_mmu_free_sp_rcu_callback);
}

/*
 * Returns the next root after @prev_root (or the first root if @prev_root is
 * NULL).  A reference to the returned root is acquired, and the reference to
 * @prev_root is released (the caller obviously must hold a reference to
 * @prev_root if it's non-NULL).
 *
 * If @only_valid is true, invalid roots are skipped.
 *
 * Returns NULL if the end of tdp_mmu_roots was reached.
 */
static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
					      struct kvm_mmu_page *prev_root,
					      bool shared, bool only_valid)
{
	struct kvm_mmu_page *next_root;

	rcu_read_lock();

	if (prev_root)
		next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
						  &prev_root->link,
						  typeof(*prev_root), link);
	else
		next_root = list_first_or_null_rcu(&kvm->arch.tdp_mmu_roots,
						   typeof(*next_root), link);

	while (next_root) {
		if ((!only_valid || !next_root->role.invalid) &&
		    kvm_tdp_mmu_get_root(next_root))
			break;

		next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
				&next_root->link, typeof(*next_root), link);
	}

	rcu_read_unlock();

	if (prev_root)
		kvm_tdp_mmu_put_root(kvm, prev_root, shared);

	return next_root;
}

/*
 * Note: this iterator gets and puts references to the roots it iterates over.
 * This makes it safe to release the MMU lock and yield within the loop, but
 * if exiting the loop early, the caller must drop the reference to the most
 * recent root. (Unless keeping a live reference is desirable.)
 *
 * If shared is set, this function is operating under the MMU lock in read
 * mode. In the unlikely event that this thread must free a root, the lock
 * will be temporarily dropped and reacquired in write mode.
 */
#define __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, _only_valid)\
	for (_root = tdp_mmu_next_root(_kvm, NULL, _shared, _only_valid);	\
	     _root;								\
	     _root = tdp_mmu_next_root(_kvm, _root, _shared, _only_valid))	\
		if (kvm_lockdep_assert_mmu_lock_held(_kvm, _shared) &&		\
		    kvm_mmu_page_as_id(_root) != _as_id) {			\
		} else

#define for_each_valid_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared)	\
	__for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, true)

#define for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id)			\
	__for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, false, false)

/*
 * Iterate over all TDP MMU roots.  Requires that mmu_lock be held for write,
 * the implication being that any flow that holds mmu_lock for read is
 * inherently yield-friendly and should use the yield-safe variant above.
 * Holding mmu_lock for write obviates the need for RCU protection as the list
 * is guaranteed to be stable.
 */
#define for_each_tdp_mmu_root(_kvm, _root, _as_id)			\
	list_for_each_entry(_root, &_kvm->arch.tdp_mmu_roots, link)	\
		if (kvm_lockdep_assert_mmu_lock_held(_kvm, false) &&	\
		    kvm_mmu_page_as_id(_root) != _as_id) {		\
		} else

static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu)
{
	struct kvm_mmu_page *sp;

	sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
	sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);

	return sp;
}

static void tdp_mmu_init_sp(struct kvm_mmu_page *sp, tdp_ptep_t sptep,
			    gfn_t gfn, union kvm_mmu_page_role role)
{
	INIT_LIST_HEAD(&sp->possible_nx_huge_page_link);

	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);

	sp->role = role;
	sp->gfn = gfn;
	sp->ptep = sptep;
	sp->tdp_mmu_page = true;

	trace_kvm_mmu_get_page(sp, true);
}

static void tdp_mmu_init_child_sp(struct kvm_mmu_page *child_sp,
				  struct tdp_iter *iter)
{
	struct kvm_mmu_page *parent_sp;
	union kvm_mmu_page_role role;

	parent_sp = sptep_to_sp(rcu_dereference(iter->sptep));

	role = parent_sp->role;
	role.level--;

	tdp_mmu_init_sp(child_sp, iter->sptep, iter->gfn, role);
}

hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
{
	union kvm_mmu_page_role role = vcpu->arch.mmu->root_role;
	struct kvm *kvm = vcpu->kvm;
	struct kvm_mmu_page *root;

	lockdep_assert_held_write(&kvm->mmu_lock);

	/*
	 * Check for an existing root before allocating a new one.  Note, the
	 * role check prevents consuming an invalid root.
	 */
	for_each_tdp_mmu_root(kvm, root, kvm_mmu_role_as_id(role)) {
		if (root->role.word == role.word &&
		    kvm_tdp_mmu_get_root(root))
			goto out;
	}

	root = tdp_mmu_alloc_sp(vcpu);
	tdp_mmu_init_sp(root, NULL, 0, role);

	/*
	 * TDP MMU roots are kept until they are explicitly invalidated, either
	 * by a memslot update or by the destruction of the VM.  Initialize the
	 * refcount to two; one reference for the vCPU, and one reference for
	 * the TDP MMU itself, which is held until the root is invalidated and
	 * is ultimately put by tdp_mmu_zap_root_work().
	 */
	refcount_set(&root->tdp_mmu_root_count, 2);

	spin_lock(&kvm->arch.tdp_mmu_pages_lock);
	list_add_rcu(&root->link, &kvm->arch.tdp_mmu_roots);
	spin_unlock(&kvm->arch.tdp_mmu_pages_lock);

out:
	return __pa(root->spt);
}

static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
				u64 old_spte, u64 new_spte, int level,
				bool shared);

static void tdp_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
	kvm_account_pgtable_pages((void *)sp->spt, +1);
	atomic64_inc(&kvm->arch.tdp_mmu_pages);
}

static void tdp_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
	kvm_account_pgtable_pages((void *)sp->spt, -1);
	atomic64_dec(&kvm->arch.tdp_mmu_pages);
}

/**
 * tdp_mmu_unlink_sp() - Remove a shadow page from the list of used pages
 *
 * @kvm: kvm instance
 * @sp: the page to be removed
 * @shared: This operation may not be running under the exclusive use of
 *	    the MMU lock and the operation must synchronize with other
 *	    threads that might be adding or removing pages.
 */
static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp,
			      bool shared)
{
	tdp_unaccount_mmu_page(kvm, sp);

	if (!sp->nx_huge_page_disallowed)
		return;

	if (shared)
		spin_lock(&kvm->arch.tdp_mmu_pages_lock);
	else
		lockdep_assert_held_write(&kvm->mmu_lock);

	sp->nx_huge_page_disallowed = false;
	untrack_possible_nx_huge_page(kvm, sp);

	if (shared)
		spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
}

/**
 * handle_removed_pt() - handle a page table removed from the TDP structure
 *
 * @kvm: kvm instance
 * @pt: the page removed from the paging structure
 * @shared: This operation may not be running under the exclusive use
 *	    of the MMU lock and the operation must synchronize with other
 *	    threads that might be modifying SPTEs.
 *
 * Given a page table that has been removed from the TDP paging structure,
 * iterates through the page table to clear SPTEs and free child page tables.
 *
 * Note that pt is passed in as a tdp_ptep_t, but it does not need RCU
 * protection. Since this thread removed it from the paging structure,
 * this thread will be responsible for ensuring the page is freed. Hence the
 * early rcu_dereferences in the function.
 */
static void handle_removed_pt(struct kvm *kvm, tdp_ptep_t pt, bool shared)
{
	struct kvm_mmu_page *sp = sptep_to_sp(rcu_dereference(pt));
	int level = sp->role.level;
	gfn_t base_gfn = sp->gfn;
	int i;

	trace_kvm_mmu_prepare_zap_page(sp);

	tdp_mmu_unlink_sp(kvm, sp, shared);

	for (i = 0; i < SPTE_ENT_PER_PAGE; i++) {
		tdp_ptep_t sptep = pt + i;
		gfn_t gfn = base_gfn + i * KVM_PAGES_PER_HPAGE(level);
		u64 old_spte;

		if (shared) {
			/*
			 * Set the SPTE to a nonpresent value that other
			 * threads will not overwrite. If the SPTE was
			 * already marked as removed then another thread
			 * handling a page fault could overwrite it, so
			 * set the SPTE until it is set from some other
			 * value to the removed SPTE value.
			 */
			for (;;) {
				old_spte = kvm_tdp_mmu_write_spte_atomic(sptep, REMOVED_SPTE);
				if (!is_removed_spte(old_spte))
					break;
				cpu_relax();
			}
		} else {
			/*
			 * If the SPTE is not MMU-present, there is no backing
			 * page associated with the SPTE and so no side effects
			 * that need to be recorded, and exclusive ownership of
			 * mmu_lock ensures the SPTE can't be made present.
			 * Note, zapping MMIO SPTEs is also unnecessary as they
			 * are guarded by the memslots generation, not by being
			 * unreachable.
			 */
			old_spte = kvm_tdp_mmu_read_spte(sptep);
			if (!is_shadow_present_pte(old_spte))
				continue;

			/*
			 * Use the common helper instead of a raw WRITE_ONCE as
			 * the SPTE needs to be updated atomically if it can be
			 * modified by a different vCPU outside of mmu_lock.
			 * Even though the parent SPTE is !PRESENT, the TLB
			 * hasn't yet been flushed, and both Intel and AMD
			 * document that A/D assists can use upper-level PxE
			 * entries that are cached in the TLB, i.e. the CPU can
			 * still access the page and mark it dirty.
			 *
			 * No retry is needed in the atomic update path as the
			 * sole concern is dropping a Dirty bit, i.e. no other
			 * task can zap/remove the SPTE as mmu_lock is held for
			 * write.  Marking the SPTE as a removed SPTE is not
			 * strictly necessary for the same reason, but using
			 * the remove SPTE value keeps the shared/exclusive
			 * paths consistent and allows the handle_changed_spte()
			 * call below to hardcode the new value to REMOVED_SPTE.
			 *
			 * Note, even though dropping a Dirty bit is the only
			 * scenario where a non-atomic update could result in a
			 * functional bug, simply checking the Dirty bit isn't
			 * sufficient as a fast page fault could read the upper
			 * level SPTE before it is zapped, and then make this
			 * target SPTE writable, resume the guest, and set the
			 * Dirty bit between reading the SPTE above and writing
			 * it here.
			 */
			old_spte = kvm_tdp_mmu_write_spte(sptep, old_spte,
							  REMOVED_SPTE, level);
		}
		handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn,
				    old_spte, REMOVED_SPTE, level, shared);
	}

	call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback);
}

/**
 * handle_changed_spte - handle bookkeeping associated with an SPTE change
 * @kvm: kvm instance
 * @as_id: the address space of the paging structure the SPTE was a part of
 * @gfn: the base GFN that was mapped by the SPTE
 * @old_spte: The value of the SPTE before the change
 * @new_spte: The value of the SPTE after the change
 * @level: the level of the PT the SPTE is part of in the paging structure
 * @shared: This operation may not be running under the exclusive use of
 *	    the MMU lock and the operation must synchronize with other
 *	    threads that might be modifying SPTEs.
 *
 * Handle bookkeeping that might result from the modification of a SPTE.  Note,
 * dirty logging updates are handled in common code, not here (see make_spte()
 * and fast_pf_fix_direct_spte()).
 */
static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
				u64 old_spte, u64 new_spte, int level,
				bool shared)
{
	bool was_present = is_shadow_present_pte(old_spte);
	bool is_present = is_shadow_present_pte(new_spte);
	bool was_leaf = was_present && is_last_spte(old_spte, level);
	bool is_leaf = is_present && is_last_spte(new_spte, level);
	bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);

	WARN_ON_ONCE(level > PT64_ROOT_MAX_LEVEL);
	WARN_ON_ONCE(level < PG_LEVEL_4K);
	WARN_ON_ONCE(gfn & (KVM_PAGES_PER_HPAGE(level) - 1));

	/*
	 * If this warning were to trigger it would indicate that there was a
	 * missing MMU notifier or a race with some notifier handler.
	 * A present, leaf SPTE should never be directly replaced with another
	 * present leaf SPTE pointing to a different PFN. A notifier handler
	 * should be zapping the SPTE before the main MM's page table is
	 * changed, or the SPTE should be zeroed, and the TLBs flushed by the
	 * thread before replacement.
	 */
	if (was_leaf && is_leaf && pfn_changed) {
		pr_err("Invalid SPTE change: cannot replace a present leaf\n"
		       "SPTE with another present leaf SPTE mapping a\n"
		       "different PFN!\n"
		       "as_id: %d gfn: %llx old_spte: %llx new_spte: %llx level: %d",
		       as_id, gfn, old_spte, new_spte, level);

		/*
		 * Crash the host to prevent error propagation and guest data
		 * corruption.
		 */
		BUG();
	}

	if (old_spte == new_spte)
		return;

	trace_kvm_tdp_mmu_spte_changed(as_id, gfn, level, old_spte, new_spte);

	if (is_leaf)
		check_spte_writable_invariants(new_spte);

	/*
	 * The only times a SPTE should be changed from a non-present to
	 * non-present state is when an MMIO entry is installed/modified/
	 * removed. In that case, there is nothing to do here.
	 */
	if (!was_present && !is_present) {
		/*
		 * If this change does not involve a MMIO SPTE or removed SPTE,
		 * it is unexpected. Log the change, though it should not
		 * impact the guest since both the former and current SPTEs
		 * are nonpresent.
		 */
		if (WARN_ON_ONCE(!is_mmio_spte(old_spte) &&
				 !is_mmio_spte(new_spte) &&
				 !is_removed_spte(new_spte)))
			pr_err("Unexpected SPTE change! Nonpresent SPTEs\n"
			       "should not be replaced with another,\n"
			       "different nonpresent SPTE, unless one or both\n"
			       "are MMIO SPTEs, or the new SPTE is\n"
			       "a temporary removed SPTE.\n"
			       "as_id: %d gfn: %llx old_spte: %llx new_spte: %llx level: %d",
			       as_id, gfn, old_spte, new_spte, level);
		return;
	}

	if (is_leaf != was_leaf)
		kvm_update_page_stats(kvm, level, is_leaf ? 1 : -1);

	if (was_leaf && is_dirty_spte(old_spte) &&
	    (!is_present || !is_dirty_spte(new_spte) || pfn_changed))
		kvm_set_pfn_dirty(spte_to_pfn(old_spte));

	/*
	 * Recursively handle child PTs if the change removed a subtree from
	 * the paging structure.  Note the WARN on the PFN changing without the
	 * SPTE being converted to a hugepage (leaf) or being zapped.  Shadow
	 * pages are kernel allocations and should never be migrated.
	 */
	if (was_present && !was_leaf &&
	    (is_leaf || !is_present || WARN_ON_ONCE(pfn_changed)))
		handle_removed_pt(kvm, spte_to_child_pt(old_spte, level), shared);

	if (was_leaf && is_accessed_spte(old_spte) &&
	    (!is_present || !is_accessed_spte(new_spte) || pfn_changed))
		kvm_set_pfn_accessed(spte_to_pfn(old_spte));
}

/*
 * tdp_mmu_set_spte_atomic - Set a TDP MMU SPTE atomically
 * and handle the associated bookkeeping.  Do not mark the page dirty
 * in KVM's dirty bitmaps.
 *
 * If setting the SPTE fails because it has changed, iter->old_spte will be
 * refreshed to the current value of the spte.
 *
 * @kvm: kvm instance
 * @iter: a tdp_iter instance currently on the SPTE that should be set
 * @new_spte: The value the SPTE should be set to
 * Return:
 * * 0      - If the SPTE was set.
 * * -EBUSY - If the SPTE cannot be set. In this case this function will have
 *            no side-effects other than setting iter->old_spte to the last
 *            known value of the spte.
 */
static inline int tdp_mmu_set_spte_atomic(struct kvm *kvm,
					  struct tdp_iter *iter,
					  u64 new_spte)
{
	u64 *sptep = rcu_dereference(iter->sptep);

	/*
	 * The caller is responsible for ensuring the old SPTE is not a REMOVED
	 * SPTE.  KVM should never attempt to zap or manipulate a REMOVED SPTE,
	 * and pre-checking before inserting a new SPTE is advantageous as it
	 * avoids unnecessary work.
	 */
	WARN_ON_ONCE(iter->yielded || is_removed_spte(iter->old_spte));

	lockdep_assert_held_read(&kvm->mmu_lock);

	/*
	 * Note, fast_pf_fix_direct_spte() can also modify TDP MMU SPTEs and
	 * does not hold the mmu_lock.  On failure, i.e. if a different logical
	 * CPU modified the SPTE, try_cmpxchg64() updates iter->old_spte with
	 * the current value, so the caller operates on fresh data, e.g. if it
	 * retries tdp_mmu_set_spte_atomic()
	 */
	if (!try_cmpxchg64(sptep, &iter->old_spte, new_spte))
		return -EBUSY;

	handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
			    new_spte, iter->level, true);

	return 0;
}

static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
					  struct tdp_iter *iter)
{
	int ret;

	/*
	 * Freeze the SPTE by setting it to a special,
	 * non-present value. This will stop other threads from
	 * immediately installing a present entry in its place
	 * before the TLBs are flushed.
	 */
	ret = tdp_mmu_set_spte_atomic(kvm, iter, REMOVED_SPTE);
	if (ret)
		return ret;

	kvm_flush_remote_tlbs_gfn(kvm, iter->gfn, iter->level);

	/*
	 * No other thread can overwrite the removed SPTE as they must either
	 * wait on the MMU lock or use tdp_mmu_set_spte_atomic() which will not
	 * overwrite the special removed SPTE value. No bookkeeping is needed
	 * here since the SPTE is going from non-present to non-present.  Use
	 * the raw write helper to avoid an unnecessary check on volatile bits.
	 */
	__kvm_tdp_mmu_write_spte(iter->sptep, 0);

	return 0;
}


/*
 * tdp_mmu_set_spte - Set a TDP MMU SPTE and handle the associated bookkeeping
 * @kvm:	      KVM instance
 * @as_id:	      Address space ID, i.e. regular vs. SMM
 * @sptep:	      Pointer to the SPTE
 * @old_spte:	      The current value of the SPTE
 * @new_spte:	      The new value that will be set for the SPTE
 * @gfn:	      The base GFN that was (or will be) mapped by the SPTE
 * @level:	      The level _containing_ the SPTE (its parent PT's level)
 *
 * Returns the old SPTE value, which _may_ be different than @old_spte if the
 * SPTE had voldatile bits.
 */
static u64 tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep,
			    u64 old_spte, u64 new_spte, gfn_t gfn, int level)
{
	lockdep_assert_held_write(&kvm->mmu_lock);

	/*
	 * No thread should be using this function to set SPTEs to or from the
	 * temporary removed SPTE value.
	 * If operating under the MMU lock in read mode, tdp_mmu_set_spte_atomic
	 * should be used. If operating under the MMU lock in write mode, the
	 * use of the removed SPTE should not be necessary.
	 */
	WARN_ON_ONCE(is_removed_spte(old_spte) || is_removed_spte(new_spte));

	old_spte = kvm_tdp_mmu_write_spte(sptep, old_spte, new_spte, level);

	handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level, false);
	return old_spte;
}

static inline void tdp_mmu_iter_set_spte(struct kvm *kvm, struct tdp_iter *iter,
					 u64 new_spte)
{
	WARN_ON_ONCE(iter->yielded);
	iter->old_spte = tdp_mmu_set_spte(kvm, iter->as_id, iter->sptep,
					  iter->old_spte, new_spte,
					  iter->gfn, iter->level);
}

#define tdp_root_for_each_pte(_iter, _root, _start, _end) \
	for_each_tdp_pte(_iter, _root, _start, _end)

#define tdp_root_for_each_leaf_pte(_iter, _root, _start, _end)	\
	tdp_root_for_each_pte(_iter, _root, _start, _end)		\
		if (!is_shadow_present_pte(_iter.old_spte) ||		\
		    !is_last_spte(_iter.old_spte, _iter.level))		\
			continue;					\
		else

#define tdp_mmu_for_each_pte(_iter, _mmu, _start, _end)		\
	for_each_tdp_pte(_iter, root_to_sp(_mmu->root.hpa), _start, _end)

/*
 * Yield if the MMU lock is contended or this thread needs to return control
 * to the scheduler.
 *
 * If this function should yield and flush is set, it will perform a remote
 * TLB flush before yielding.
 *
 * If this function yields, iter->yielded is set and the caller must skip to
 * the next iteration, where tdp_iter_next() will reset the tdp_iter's walk
 * over the paging structures to allow the iterator to continue its traversal
 * from the paging structure root.
 *
 * Returns true if this function yielded.
 */
static inline bool __must_check tdp_mmu_iter_cond_resched(struct kvm *kvm,
							  struct tdp_iter *iter,
							  bool flush, bool shared)
{
	WARN_ON_ONCE(iter->yielded);

	/* Ensure forward progress has been made before yielding. */
	if (iter->next_last_level_gfn == iter->yielded_gfn)
		return false;

	if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
		if (flush)
			kvm_flush_remote_tlbs(kvm);

		rcu_read_unlock();

		if (shared)
			cond_resched_rwlock_read(&kvm->mmu_lock);
		else
			cond_resched_rwlock_write(&kvm->mmu_lock);

		rcu_read_lock();

		WARN_ON_ONCE(iter->gfn > iter->next_last_level_gfn);

		iter->yielded = true;
	}

	return iter->yielded;
}

static inline gfn_t tdp_mmu_max_gfn_exclusive(void)
{
	/*
	 * Bound TDP MMU walks at host.MAXPHYADDR.  KVM disallows memslots with
	 * a gpa range that would exceed the max gfn, and KVM does not create
	 * MMIO SPTEs for "impossible" gfns, instead sending such accesses down
	 * the slow emulation path every time.
	 */
	return kvm_mmu_max_gfn() + 1;
}

static void __tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root,
			       bool shared, int zap_level)
{
	struct tdp_iter iter;

	gfn_t end = tdp_mmu_max_gfn_exclusive();
	gfn_t start = 0;

	for_each_tdp_pte_min_level(iter, root, zap_level, start, end) {
retry:
		if (tdp_mmu_iter_cond_resched(kvm, &iter, false, shared))
			continue;

		if (!is_shadow_present_pte(iter.old_spte))
			continue;

		if (iter.level > zap_level)
			continue;

		if (!shared)
			tdp_mmu_iter_set_spte(kvm, &iter, 0);
		else if (tdp_mmu_set_spte_atomic(kvm, &iter, 0))
			goto retry;
	}
}

static void tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root,
			     bool shared)
{

	/*
	 * The root must have an elevated refcount so that it's reachable via
	 * mmu_notifier callbacks, which allows this path to yield and drop
	 * mmu_lock.  When handling an unmap/release mmu_notifier command, KVM
	 * must drop all references to relevant pages prior to completing the
	 * callback.  Dropping mmu_lock with an unreachable root would result
	 * in zapping SPTEs after a relevant mmu_notifier callback completes
	 * and lead to use-after-free as zapping a SPTE triggers "writeback" of
	 * dirty accessed bits to the SPTE's associated struct page.
	 */
	WARN_ON_ONCE(!refcount_read(&root->tdp_mmu_root_count));

	kvm_lockdep_assert_mmu_lock_held(kvm, shared);

	rcu_read_lock();

	/*
	 * To avoid RCU stalls due to recursively removing huge swaths of SPs,
	 * split the zap into two passes.  On the first pass, zap at the 1gb
	 * level, and then zap top-level SPs on the second pass.  "1gb" is not
	 * arbitrary, as KVM must be able to zap a 1gb shadow page without
	 * inducing a stall to allow in-place replacement with a 1gb hugepage.
	 *
	 * Because zapping a SP recurses on its children, stepping down to
	 * PG_LEVEL_4K in the iterator itself is unnecessary.
	 */
	__tdp_mmu_zap_root(kvm, root, shared, PG_LEVEL_1G);
	__tdp_mmu_zap_root(kvm, root, shared, root->role.level);

	rcu_read_unlock();
}

bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
{
	u64 old_spte;

	/*
	 * This helper intentionally doesn't allow zapping a root shadow page,
	 * which doesn't have a parent page table and thus no associated entry.
	 */
	if (WARN_ON_ONCE(!sp->ptep))
		return false;

	old_spte = kvm_tdp_mmu_read_spte(sp->ptep);
	if (WARN_ON_ONCE(!is_shadow_present_pte(old_spte)))
		return false;

	tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte, 0,
			 sp->gfn, sp->role.level + 1);

	return true;
}

/*
 * If can_yield is true, will release the MMU lock and reschedule if the
 * scheduler needs the CPU or there is contention on the MMU lock. If this
 * function cannot yield, it will not release the MMU lock or reschedule and
 * the caller must ensure it does not supply too large a GFN range, or the
 * operation can cause a soft lockup.
 */
static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root,
			      gfn_t start, gfn_t end, bool can_yield, bool flush)
{
	struct tdp_iter iter;

	end = min(end, tdp_mmu_max_gfn_exclusive());

	lockdep_assert_held_write(&kvm->mmu_lock);

	rcu_read_lock();

	for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end) {
		if (can_yield &&
		    tdp_mmu_iter_cond_resched(kvm, &iter, flush, false)) {
			flush = false;
			continue;
		}

		if (!is_shadow_present_pte(iter.old_spte) ||
		    !is_last_spte(iter.old_spte, iter.level))
			continue;

		tdp_mmu_iter_set_spte(kvm, &iter, 0);
		flush = true;
	}

	rcu_read_unlock();

	/*
	 * Because this flow zaps _only_ leaf SPTEs, the caller doesn't need
	 * to provide RCU protection as no 'struct kvm_mmu_page' will be freed.
	 */
	return flush;
}

/*
 * Zap leaf SPTEs for the range of gfns, [start, end), for all roots. Returns
 * true if a TLB flush is needed before releasing the MMU lock, i.e. if one or
 * more SPTEs were zapped since the MMU lock was last acquired.
 */
bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, int as_id, gfn_t start, gfn_t end,
			   bool can_yield, bool flush)
{
	struct kvm_mmu_page *root;

	for_each_tdp_mmu_root_yield_safe(kvm, root, as_id)
		flush = tdp_mmu_zap_leafs(kvm, root, start, end, can_yield, flush);

	return flush;
}

void kvm_tdp_mmu_zap_all(struct kvm *kvm)
{
	struct kvm_mmu_page *root;
	int i;

	/*
	 * Zap all roots, including invalid roots, as all SPTEs must be dropped
	 * before returning to the caller.  Zap directly even if the root is
	 * also being zapped by a worker.  Walking zapped top-level SPTEs isn't
	 * all that expensive and mmu_lock is already held, which means the
	 * worker has yielded, i.e. flushing the work instead of zapping here
	 * isn't guaranteed to be any faster.
	 *
	 * A TLB flush is unnecessary, KVM zaps everything if and only the VM
	 * is being destroyed or the userspace VMM has exited.  In both cases,
	 * KVM_RUN is unreachable, i.e. no vCPUs will ever service the request.
	 */
	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
		for_each_tdp_mmu_root_yield_safe(kvm, root, i)
			tdp_mmu_zap_root(kvm, root, false);
	}
}

/*
 * Zap all invalidated roots to ensure all SPTEs are dropped before the "fast
 * zap" completes.
 */
void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
{
	flush_workqueue(kvm->arch.tdp_mmu_zap_wq);
}

/*
 * Mark each TDP MMU root as invalid to prevent vCPUs from reusing a root that
 * is about to be zapped, e.g. in response to a memslots update.  The actual
 * zapping is performed asynchronously.  Using a separate workqueue makes it
 * easy to ensure that the destruction is performed before the "fast zap"
 * completes, without keeping a separate list of invalidated roots; the list is
 * effectively the list of work items in the workqueue.
 *
 * Note, the asynchronous worker is gifted the TDP MMU's reference.
 * See kvm_tdp_mmu_get_vcpu_root_hpa().
 */
void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm)
{
	struct kvm_mmu_page *root;

	/*
	 * mmu_lock must be held for write to ensure that a root doesn't become
	 * invalid while there are active readers (invalidating a root while
	 * there are active readers may or may not be problematic in practice,
	 * but it's uncharted territory and not supported).
	 *
	 * Waive the assertion if there are no users of @kvm, i.e. the VM is
	 * being destroyed after all references have been put, or if no vCPUs
	 * have been created (which means there are no roots), i.e. the VM is
	 * being destroyed in an error path of KVM_CREATE_VM.
	 */
	if (IS_ENABLED(CONFIG_PROVE_LOCKING) &&
	    refcount_read(&kvm->users_count) && kvm->created_vcpus)
		lockdep_assert_held_write(&kvm->mmu_lock);

	/*
	 * As above, mmu_lock isn't held when destroying the VM!  There can't
	 * be other references to @kvm, i.e. nothing else can invalidate roots
	 * or be consuming roots, but walking the list of roots does need to be
	 * guarded against roots being deleted by the asynchronous zap worker.
	 */
	rcu_read_lock();

	list_for_each_entry_rcu(root, &kvm->arch.tdp_mmu_roots, link) {
		if (!root->role.invalid) {
			root->role.invalid = true;
			tdp_mmu_schedule_zap_root(kvm, root);
		}
	}

	rcu_read_unlock();
}

/*
 * Installs a last-level SPTE to handle a TDP page fault.
 * (NPT/EPT violation/misconfiguration)
 */
static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
					  struct kvm_page_fault *fault,
					  struct tdp_iter *iter)
{
	struct kvm_mmu_page *sp = sptep_to_sp(rcu_dereference(iter->sptep));
	u64 new_spte;
	int ret = RET_PF_FIXED;
	bool wrprot = false;

	if (WARN_ON_ONCE(sp->role.level != fault->goal_level))
		return RET_PF_RETRY;

	if (unlikely(!fault->slot))
		new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL);
	else
		wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn,
					 fault->pfn, iter->old_spte, fault->prefetch, true,
					 fault->map_writable, &new_spte);

	if (new_spte == iter->old_spte)
		ret = RET_PF_SPURIOUS;
	else if (tdp_mmu_set_spte_atomic(vcpu->kvm, iter, new_spte))
		return RET_PF_RETRY;
	else if (is_shadow_present_pte(iter->old_spte) &&
		 !is_last_spte(iter->old_spte, iter->level))
		kvm_flush_remote_tlbs_gfn(vcpu->kvm, iter->gfn, iter->level);

	/*
	 * If the page fault was caused by a write but the page is write
	 * protected, emulation is needed. If the emulation was skipped,
	 * the vCPU would have the same fault again.
	 */
	if (wrprot) {
		if (fault->write)
			ret = RET_PF_EMULATE;
	}

	/* If a MMIO SPTE is installed, the MMIO will need to be emulated. */
	if (unlikely(is_mmio_spte(new_spte))) {
		vcpu->stat.pf_mmio_spte_created++;
		trace_mark_mmio_spte(rcu_dereference(iter->sptep), iter->gfn,
				     new_spte);
		ret = RET_PF_EMULATE;
	} else {
		trace_kvm_mmu_set_spte(iter->level, iter->gfn,
				       rcu_dereference(iter->sptep));
	}

	return ret;
}

/*
 * tdp_mmu_link_sp - Replace the given spte with an spte pointing to the
 * provided page table.
 *
 * @kvm: kvm instance
 * @iter: a tdp_iter instance currently on the SPTE that should be set
 * @sp: The new TDP page table to install.
 * @shared: This operation is running under the MMU lock in read mode.
 *
 * Returns: 0 if the new page table was installed. Non-0 if the page table
 *          could not be installed (e.g. the atomic compare-exchange failed).
 */
static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
			   struct kvm_mmu_page *sp, bool shared)
{
	u64 spte = make_nonleaf_spte(sp->spt, !kvm_ad_enabled());
	int ret = 0;

	if (shared) {
		ret = tdp_mmu_set_spte_atomic(kvm, iter, spte);
		if (ret)
			return ret;
	} else {
		tdp_mmu_iter_set_spte(kvm, iter, spte);
	}

	tdp_account_mmu_page(kvm, sp);

	return 0;
}

static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter,
				   struct kvm_mmu_page *sp, bool shared);

/*
 * Handle a TDP page fault (NPT/EPT violation/misconfiguration) by installing
 * page tables and SPTEs to translate the faulting guest physical address.
 */
int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
	struct kvm_mmu *mmu = vcpu->arch.mmu;
	struct kvm *kvm = vcpu->kvm;
	struct tdp_iter iter;
	struct kvm_mmu_page *sp;
	int ret = RET_PF_RETRY;

	kvm_mmu_hugepage_adjust(vcpu, fault);

	trace_kvm_mmu_spte_requested(fault);

	rcu_read_lock();

	tdp_mmu_for_each_pte(iter, mmu, fault->gfn, fault->gfn + 1) {
		int r;

		if (fault->nx_huge_page_workaround_enabled)
			disallowed_hugepage_adjust(fault, iter.old_spte, iter.level);

		/*
		 * If SPTE has been frozen by another thread, just give up and
		 * retry, avoiding unnecessary page table allocation and free.
		 */
		if (is_removed_spte(iter.old_spte))
			goto retry;

		if (iter.level == fault->goal_level)
			goto map_target_level;

		/* Step down into the lower level page table if it exists. */
		if (is_shadow_present_pte(iter.old_spte) &&
		    !is_large_pte(iter.old_spte))
			continue;

		/*
		 * The SPTE is either non-present or points to a huge page that
		 * needs to be split.
		 */
		sp = tdp_mmu_alloc_sp(vcpu);
		tdp_mmu_init_child_sp(sp, &iter);

		sp->nx_huge_page_disallowed = fault->huge_page_disallowed;

		if (is_shadow_present_pte(iter.old_spte))
			r = tdp_mmu_split_huge_page(kvm, &iter, sp, true);
		else
			r = tdp_mmu_link_sp(kvm, &iter, sp, true);

		/*
		 * Force the guest to retry if installing an upper level SPTE
		 * failed, e.g. because a different task modified the SPTE.
		 */
		if (r) {
			tdp_mmu_free_sp(sp);
			goto retry;
		}

		if (fault->huge_page_disallowed &&
		    fault->req_level >= iter.level) {
			spin_lock(&kvm->arch.tdp_mmu_pages_lock);
			if (sp->nx_huge_page_disallowed)
				track_possible_nx_huge_page(kvm, sp);
			spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
		}
	}

	/*
	 * The walk aborted before reaching the target level, e.g. because the
	 * iterator detected an upper level SPTE was frozen during traversal.
	 */
	WARN_ON_ONCE(iter.level == fault->goal_level);
	goto retry;

map_target_level:
	ret = tdp_mmu_map_handle_target_level(vcpu, fault, &iter);

retry:
	rcu_read_unlock();
	return ret;
}

bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range,
				 bool flush)
{
	return kvm_tdp_mmu_zap_leafs(kvm, range->slot->as_id, range->start,
				     range->end, range->may_block, flush);
}

typedef bool (*tdp_handler_t)(struct kvm *kvm, struct tdp_iter *iter,
			      struct kvm_gfn_range *range);

static __always_inline bool kvm_tdp_mmu_handle_gfn(struct kvm *kvm,
						   struct kvm_gfn_range *range,
						   tdp_handler_t handler)
{
	struct kvm_mmu_page *root;
	struct tdp_iter iter;
	bool ret = false;

	/*
	 * Don't support rescheduling, none of the MMU notifiers that funnel
	 * into this helper allow blocking; it'd be dead, wasteful code.
	 */
	for_each_tdp_mmu_root(kvm, root, range->slot->as_id) {
		rcu_read_lock();

		tdp_root_for_each_leaf_pte(iter, root, range->start, range->end)
			ret |= handler(kvm, &iter, range);

		rcu_read_unlock();
	}

	return ret;
}

/*
 * Mark the SPTEs range of GFNs [start, end) unaccessed and return non-zero
 * if any of the GFNs in the range have been accessed.
 *
 * No need to mark the corresponding PFN as accessed as this call is coming
 * from the clear_young() or clear_flush_young() notifier, which uses the
 * return value to determine if the page has been accessed.
 */
static bool age_gfn_range(struct kvm *kvm, struct tdp_iter *iter,
			  struct kvm_gfn_range *range)
{
	u64 new_spte;

	/* If we have a non-accessed entry we don't need to change the pte. */
	if (!is_accessed_spte(iter->old_spte))
		return false;

	if (spte_ad_enabled(iter->old_spte)) {
		iter->old_spte = tdp_mmu_clear_spte_bits(iter->sptep,
							 iter->old_spte,
							 shadow_accessed_mask,
							 iter->level);
		new_spte = iter->old_spte & ~shadow_accessed_mask;
	} else {
		/*
		 * Capture the dirty status of the page, so that it doesn't get
		 * lost when the SPTE is marked for access tracking.
		 */
		if (is_writable_pte(iter->old_spte))
			kvm_set_pfn_dirty(spte_to_pfn(iter->old_spte));

		new_spte = mark_spte_for_access_track(iter->old_spte);
		iter->old_spte = kvm_tdp_mmu_write_spte(iter->sptep,
							iter->old_spte, new_spte,
							iter->level);
	}

	trace_kvm_tdp_mmu_spte_changed(iter->as_id, iter->gfn, iter->level,
				       iter->old_spte, new_spte);
	return true;
}

bool kvm_tdp_mmu_age_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
{
	return kvm_tdp_mmu_handle_gfn(kvm, range, age_gfn_range);
}

static bool test_age_gfn(struct kvm *kvm, struct tdp_iter *iter,
			 struct kvm_gfn_range *range)
{
	return is_accessed_spte(iter->old_spte);
}

bool kvm_tdp_mmu_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
	return kvm_tdp_mmu_handle_gfn(kvm, range, test_age_gfn);
}

static bool set_spte_gfn(struct kvm *kvm, struct tdp_iter *iter,
			 struct kvm_gfn_range *range)
{
	u64 new_spte;

	/* Huge pages aren't expected to be modified without first being zapped. */
	WARN_ON_ONCE(pte_huge(range->arg.pte) || range->start + 1 != range->end);

	if (iter->level != PG_LEVEL_4K ||
	    !is_shadow_present_pte(iter->old_spte))
		return false;

	/*
	 * Note, when changing a read-only SPTE, it's not strictly necessary to
	 * zero the SPTE before setting the new PFN, but doing so preserves the
	 * invariant that the PFN of a present * leaf SPTE can never change.
	 * See handle_changed_spte().
	 */
	tdp_mmu_iter_set_spte(kvm, iter, 0);

	if (!pte_write(range->arg.pte)) {
		new_spte = kvm_mmu_changed_pte_notifier_make_spte(iter->old_spte,
								  pte_pfn(range->arg.pte));

		tdp_mmu_iter_set_spte(kvm, iter, new_spte);
	}

	return true;
}

/*
 * Handle the changed_pte MMU notifier for the TDP MMU.
 * data is a pointer to the new pte_t mapping the HVA specified by the MMU
 * notifier.
 * Returns non-zero if a flush is needed before releasing the MMU lock.
 */
bool kvm_tdp_mmu_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
	/*
	 * No need to handle the remote TLB flush under RCU protection, the
	 * target SPTE _must_ be a leaf SPTE, i.e. cannot result in freeing a
	 * shadow page. See the WARN on pfn_changed in handle_changed_spte().
	 */
	return kvm_tdp_mmu_handle_gfn(kvm, range, set_spte_gfn);
}

/*
 * Remove write access from all SPTEs at or above min_level that map GFNs
 * [start, end). Returns true if an SPTE has been changed and the TLBs need to
 * be flushed.
 */
static bool wrprot_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
			     gfn_t start, gfn_t end, int min_level)
{
	struct tdp_iter iter;
	u64 new_spte;
	bool spte_set = false;

	rcu_read_lock();

	BUG_ON(min_level > KVM_MAX_HUGEPAGE_LEVEL);

	for_each_tdp_pte_min_level(iter, root, min_level, start, end) {
retry:
		if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true))
			continue;

		if (!is_shadow_present_pte(iter.old_spte) ||
		    !is_last_spte(iter.old_spte, iter.level) ||
		    !(iter.old_spte & PT_WRITABLE_MASK))
			continue;

		new_spte = iter.old_spte & ~PT_WRITABLE_MASK;

		if (tdp_mmu_set_spte_atomic(kvm, &iter, new_spte))
			goto retry;

		spte_set = true;
	}

	rcu_read_unlock();
	return spte_set;
}

/*
 * Remove write access from all the SPTEs mapping GFNs in the memslot. Will
 * only affect leaf SPTEs down to min_level.
 * Returns true if an SPTE has been changed and the TLBs need to be flushed.
 */
bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm,
			     const struct kvm_memory_slot *slot, int min_level)
{
	struct kvm_mmu_page *root;
	bool spte_set = false;

	lockdep_assert_held_read(&kvm->mmu_lock);

	for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, true)
		spte_set |= wrprot_gfn_range(kvm, root, slot->base_gfn,
			     slot->base_gfn + slot->npages, min_level);

	return spte_set;
}

static struct kvm_mmu_page *__tdp_mmu_alloc_sp_for_split(gfp_t gfp)
{
	struct kvm_mmu_page *sp;

	gfp |= __GFP_ZERO;

	sp = kmem_cache_alloc(mmu_page_header_cache, gfp);
	if (!sp)
		return NULL;

	sp->spt = (void *)__get_free_page(gfp);
	if (!sp->spt) {
		kmem_cache_free(mmu_page_header_cache, sp);
		return NULL;
	}

	return sp;
}

static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(struct kvm *kvm,
						       struct tdp_iter *iter,
						       bool shared)
{
	struct kvm_mmu_page *sp;

	/*
	 * Since we are allocating while under the MMU lock we have to be
	 * careful about GFP flags. Use GFP_NOWAIT to avoid blocking on direct
	 * reclaim and to avoid making any filesystem callbacks (which can end
	 * up invoking KVM MMU notifiers, resulting in a deadlock).
	 *
	 * If this allocation fails we drop the lock and retry with reclaim
	 * allowed.
	 */
	sp = __tdp_mmu_alloc_sp_for_split(GFP_NOWAIT | __GFP_ACCOUNT);
	if (sp)
		return sp;

	rcu_read_unlock();

	if (shared)
		read_unlock(&kvm->mmu_lock);
	else
		write_unlock(&kvm->mmu_lock);

	iter->yielded = true;
	sp = __tdp_mmu_alloc_sp_for_split(GFP_KERNEL_ACCOUNT);

	if (shared)
		read_lock(&kvm->mmu_lock);
	else
		write_lock(&kvm->mmu_lock);

	rcu_read_lock();

	return sp;
}

/* Note, the caller is responsible for initializing @sp. */
static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter,
				   struct kvm_mmu_page *sp, bool shared)
{
	const u64 huge_spte = iter->old_spte;
	const int level = iter->level;
	int ret, i;

	/*
	 * No need for atomics when writing to sp->spt since the page table has
	 * not been linked in yet and thus is not reachable from any other CPU.
	 */
	for (i = 0; i < SPTE_ENT_PER_PAGE; i++)
		sp->spt[i] = make_huge_page_split_spte(kvm, huge_spte, sp->role, i);

	/*
	 * Replace the huge spte with a pointer to the populated lower level
	 * page table. Since we are making this change without a TLB flush vCPUs
	 * will see a mix of the split mappings and the original huge mapping,
	 * depending on what's currently in their TLB. This is fine from a
	 * correctness standpoint since the translation will be the same either
	 * way.
	 */
	ret = tdp_mmu_link_sp(kvm, iter, sp, shared);
	if (ret)
		goto out;

	/*
	 * tdp_mmu_link_sp_atomic() will handle subtracting the huge page we
	 * are overwriting from the page stats. But we have to manually update
	 * the page stats with the new present child pages.
	 */
	kvm_update_page_stats(kvm, level - 1, SPTE_ENT_PER_PAGE);

out:
	trace_kvm_mmu_split_huge_page(iter->gfn, huge_spte, level, ret);
	return ret;
}

static int tdp_mmu_split_huge_pages_root(struct kvm *kvm,
					 struct kvm_mmu_page *root,
					 gfn_t start, gfn_t end,
					 int target_level, bool shared)
{
	struct kvm_mmu_page *sp = NULL;
	struct tdp_iter iter;
	int ret = 0;

	rcu_read_lock();

	/*
	 * Traverse the page table splitting all huge pages above the target
	 * level into one lower level. For example, if we encounter a 1GB page
	 * we split it into 512 2MB pages.
	 *
	 * Since the TDP iterator uses a pre-order traversal, we are guaranteed
	 * to visit an SPTE before ever visiting its children, which means we
	 * will correctly recursively split huge pages that are more than one
	 * level above the target level (e.g. splitting a 1GB to 512 2MB pages,
	 * and then splitting each of those to 512 4KB pages).
	 */
	for_each_tdp_pte_min_level(iter, root, target_level + 1, start, end) {
retry:
		if (tdp_mmu_iter_cond_resched(kvm, &iter, false, shared))
			continue;

		if (!is_shadow_present_pte(iter.old_spte) || !is_large_pte(iter.old_spte))
			continue;

		if (!sp) {
			sp = tdp_mmu_alloc_sp_for_split(kvm, &iter, shared);
			if (!sp) {
				ret = -ENOMEM;
				trace_kvm_mmu_split_huge_page(iter.gfn,
							      iter.old_spte,
							      iter.level, ret);
				break;
			}

			if (iter.yielded)
				continue;
		}

		tdp_mmu_init_child_sp(sp, &iter);

		if (tdp_mmu_split_huge_page(kvm, &iter, sp, shared))
			goto retry;

		sp = NULL;
	}

	rcu_read_unlock();

	/*
	 * It's possible to exit the loop having never used the last sp if, for
	 * example, a vCPU doing HugePage NX splitting wins the race and
	 * installs its own sp in place of the last sp we tried to split.
	 */
	if (sp)
		tdp_mmu_free_sp(sp);

	return ret;
}


/*
 * Try to split all huge pages mapped by the TDP MMU down to the target level.
 */
void kvm_tdp_mmu_try_split_huge_pages(struct kvm *kvm,
				      const struct kvm_memory_slot *slot,
				      gfn_t start, gfn_t end,
				      int target_level, bool shared)
{
	struct kvm_mmu_page *root;
	int r = 0;

	kvm_lockdep_assert_mmu_lock_held(kvm, shared);

	for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, shared) {
		r = tdp_mmu_split_huge_pages_root(kvm, root, start, end, target_level, shared);
		if (r) {
			kvm_tdp_mmu_put_root(kvm, root, shared);
			break;
		}
	}
}

/*
 * Clear the dirty status of all the SPTEs mapping GFNs in the memslot. If
 * AD bits are enabled, this will involve clearing the dirty bit on each SPTE.
 * If AD bits are not enabled, this will require clearing the writable bit on
 * each SPTE. Returns true if an SPTE has been changed and the TLBs need to
 * be flushed.
 */
static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
			   gfn_t start, gfn_t end)
{
	u64 dbit = kvm_ad_enabled() ? shadow_dirty_mask : PT_WRITABLE_MASK;
	struct tdp_iter iter;
	bool spte_set = false;

	rcu_read_lock();

	tdp_root_for_each_leaf_pte(iter, root, start, end) {
retry:
		if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true))
			continue;

		if (!is_shadow_present_pte(iter.old_spte))
			continue;

		KVM_MMU_WARN_ON(kvm_ad_enabled() &&
				spte_ad_need_write_protect(iter.old_spte));

		if (!(iter.old_spte & dbit))
			continue;

		if (tdp_mmu_set_spte_atomic(kvm, &iter, iter.old_spte & ~dbit))
			goto retry;

		spte_set = true;
	}

	rcu_read_unlock();
	return spte_set;
}

/*
 * Clear the dirty status of all the SPTEs mapping GFNs in the memslot. If
 * AD bits are enabled, this will involve clearing the dirty bit on each SPTE.
 * If AD bits are not enabled, this will require clearing the writable bit on
 * each SPTE. Returns true if an SPTE has been changed and the TLBs need to
 * be flushed.
 */
bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm,
				  const struct kvm_memory_slot *slot)
{
	struct kvm_mmu_page *root;
	bool spte_set = false;

	lockdep_assert_held_read(&kvm->mmu_lock);

	for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, true)
		spte_set |= clear_dirty_gfn_range(kvm, root, slot->base_gfn,
				slot->base_gfn + slot->npages);

	return spte_set;
}

/*
 * Clears the dirty status of all the 4k SPTEs mapping GFNs for which a bit is
 * set in mask, starting at gfn. The given memslot is expected to contain all
 * the GFNs represented by set bits in the mask. If AD bits are enabled,
 * clearing the dirty status will involve clearing the dirty bit on each SPTE
 * or, if AD bits are not enabled, clearing the writable bit on each SPTE.
 */
static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root,
				  gfn_t gfn, unsigned long mask, bool wrprot)
{
	u64 dbit = (wrprot || !kvm_ad_enabled()) ? PT_WRITABLE_MASK :
						   shadow_dirty_mask;
	struct tdp_iter iter;

	lockdep_assert_held_write(&kvm->mmu_lock);

	rcu_read_lock();

	tdp_root_for_each_leaf_pte(iter, root, gfn + __ffs(mask),
				    gfn + BITS_PER_LONG) {
		if (!mask)
			break;

		KVM_MMU_WARN_ON(kvm_ad_enabled() &&
				spte_ad_need_write_protect(iter.old_spte));

		if (iter.level > PG_LEVEL_4K ||
		    !(mask & (1UL << (iter.gfn - gfn))))
			continue;

		mask &= ~(1UL << (iter.gfn - gfn));

		if (!(iter.old_spte & dbit))
			continue;

		iter.old_spte = tdp_mmu_clear_spte_bits(iter.sptep,
							iter.old_spte, dbit,
							iter.level);

		trace_kvm_tdp_mmu_spte_changed(iter.as_id, iter.gfn, iter.level,
					       iter.old_spte,
					       iter.old_spte & ~dbit);
		kvm_set_pfn_dirty(spte_to_pfn(iter.old_spte));
	}

	rcu_read_unlock();
}

/*
 * Clears the dirty status of all the 4k SPTEs mapping GFNs for which a bit is
 * set in mask, starting at gfn. The given memslot is expected to contain all
 * the GFNs represented by set bits in the mask. If AD bits are enabled,
 * clearing the dirty status will involve clearing the dirty bit on each SPTE
 * or, if AD bits are not enabled, clearing the writable bit on each SPTE.
 */
void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm,
				       struct kvm_memory_slot *slot,
				       gfn_t gfn, unsigned long mask,
				       bool wrprot)
{
	struct kvm_mmu_page *root;

	for_each_tdp_mmu_root(kvm, root, slot->as_id)
		clear_dirty_pt_masked(kvm, root, gfn, mask, wrprot);
}

static void zap_collapsible_spte_range(struct kvm *kvm,
				       struct kvm_mmu_page *root,
				       const struct kvm_memory_slot *slot)
{
	gfn_t start = slot->base_gfn;
	gfn_t end = start + slot->npages;
	struct tdp_iter iter;
	int max_mapping_level;

	rcu_read_lock();

	for_each_tdp_pte_min_level(iter, root, PG_LEVEL_2M, start, end) {
retry:
		if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true))
			continue;

		if (iter.level > KVM_MAX_HUGEPAGE_LEVEL ||
		    !is_shadow_present_pte(iter.old_spte))
			continue;

		/*
		 * Don't zap leaf SPTEs, if a leaf SPTE could be replaced with
		 * a large page size, then its parent would have been zapped
		 * instead of stepping down.
		 */
		if (is_last_spte(iter.old_spte, iter.level))
			continue;

		/*
		 * If iter.gfn resides outside of the slot, i.e. the page for
		 * the current level overlaps but is not contained by the slot,
		 * then the SPTE can't be made huge.  More importantly, trying
		 * to query that info from slot->arch.lpage_info will cause an
		 * out-of-bounds access.
		 */
		if (iter.gfn < start || iter.gfn >= end)
			continue;

		max_mapping_level = kvm_mmu_max_mapping_level(kvm, slot,
							      iter.gfn, PG_LEVEL_NUM);
		if (max_mapping_level < iter.level)
			continue;

		/* Note, a successful atomic zap also does a remote TLB flush. */
		if (tdp_mmu_zap_spte_atomic(kvm, &iter))
			goto retry;
	}

	rcu_read_unlock();
}

/*
 * Zap non-leaf SPTEs (and free their associated page tables) which could
 * be replaced by huge pages, for GFNs within the slot.
 */
void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
				       const struct kvm_memory_slot *slot)
{
	struct kvm_mmu_page *root;

	lockdep_assert_held_read(&kvm->mmu_lock);

	for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, true)
		zap_collapsible_spte_range(kvm, root, slot);
}

/*
 * Removes write access on the last level SPTE mapping this GFN and unsets the
 * MMU-writable bit to ensure future writes continue to be intercepted.
 * Returns true if an SPTE was set and a TLB flush is needed.
 */
static bool write_protect_gfn(struct kvm *kvm, struct kvm_mmu_page *root,
			      gfn_t gfn, int min_level)
{
	struct tdp_iter iter;
	u64 new_spte;
	bool spte_set = false;

	BUG_ON(min_level > KVM_MAX_HUGEPAGE_LEVEL);

	rcu_read_lock();

	for_each_tdp_pte_min_level(iter, root, min_level, gfn, gfn + 1) {
		if (!is_shadow_present_pte(iter.old_spte) ||
		    !is_last_spte(iter.old_spte, iter.level))
			continue;

		new_spte = iter.old_spte &
			~(PT_WRITABLE_MASK | shadow_mmu_writable_mask);

		if (new_spte == iter.old_spte)
			break;

		tdp_mmu_iter_set_spte(kvm, &iter, new_spte);
		spte_set = true;
	}

	rcu_read_unlock();

	return spte_set;
}

/*
 * Removes write access on the last level SPTE mapping this GFN and unsets the
 * MMU-writable bit to ensure future writes continue to be intercepted.
 * Returns true if an SPTE was set and a TLB flush is needed.
 */
bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm,
				   struct kvm_memory_slot *slot, gfn_t gfn,
				   int min_level)
{
	struct kvm_mmu_page *root;
	bool spte_set = false;

	lockdep_assert_held_write(&kvm->mmu_lock);
	for_each_tdp_mmu_root(kvm, root, slot->as_id)
		spte_set |= write_protect_gfn(kvm, root, gfn, min_level);

	return spte_set;
}

/*
 * Return the level of the lowest level SPTE added to sptes.
 * That SPTE may be non-present.
 *
 * Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}.
 */
int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
			 int *root_level)
{
	struct tdp_iter iter;
	struct kvm_mmu *mmu = vcpu->arch.mmu;
	gfn_t gfn = addr >> PAGE_SHIFT;
	int leaf = -1;

	*root_level = vcpu->arch.mmu->root_role.level;

	tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
		leaf = iter.level;
		sptes[leaf] = iter.old_spte;
	}

	return leaf;
}

/*
 * Returns the last level spte pointer of the shadow page walk for the given
 * gpa, and sets *spte to the spte value. This spte may be non-preset. If no
 * walk could be performed, returns NULL and *spte does not contain valid data.
 *
 * Contract:
 *  - Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}.
 *  - The returned sptep must not be used after kvm_tdp_mmu_walk_lockless_end.
 *
 * WARNING: This function is only intended to be called during fast_page_fault.
 */
u64 *kvm_tdp_mmu_fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, u64 addr,
					u64 *spte)
{
	struct tdp_iter iter;
	struct kvm_mmu *mmu = vcpu->arch.mmu;
	gfn_t gfn = addr >> PAGE_SHIFT;
	tdp_ptep_t sptep = NULL;

	tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
		*spte = iter.old_spte;
		sptep = iter.sptep;
	}

	/*
	 * Perform the rcu_dereference to get the raw spte pointer value since
	 * we are passing it up to fast_page_fault, which is shared with the
	 * legacy MMU and thus does not retain the TDP MMU-specific __rcu
	 * annotation.
	 *
	 * This is safe since fast_page_fault obeys the contracts of this
	 * function as well as all TDP MMU contracts around modifying SPTEs
	 * outside of mmu_lock.
	 */
	return rcu_dereference(sptep);
}