summaryrefslogtreecommitdiff
path: root/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
blob: a4aa9500fa179f2c8ff9cf857703e085aea54ba1 (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
// SPDX-License-Identifier: MIT
/*
 * Copyright © 2021 Intel Corporation
 */

#include <linux/shmem_fs.h>

#include <drm/ttm/ttm_bo_driver.h>
#include <drm/ttm/ttm_placement.h>
#include <drm/drm_buddy.h>

#include "i915_drv.h"
#include "i915_ttm_buddy_manager.h"
#include "intel_memory_region.h"
#include "intel_region_ttm.h"

#include "gem/i915_gem_mman.h"
#include "gem/i915_gem_object.h"
#include "gem/i915_gem_region.h"
#include "gem/i915_gem_ttm.h"
#include "gem/i915_gem_ttm_move.h"
#include "gem/i915_gem_ttm_pm.h"
#include "gt/intel_gpu_commands.h"

#define I915_TTM_PRIO_PURGE     0
#define I915_TTM_PRIO_NO_PAGES  1
#define I915_TTM_PRIO_HAS_PAGES 2
#define I915_TTM_PRIO_NEEDS_CPU_ACCESS 3

/*
 * Size of struct ttm_place vector in on-stack struct ttm_placement allocs
 */
#define I915_TTM_MAX_PLACEMENTS INTEL_REGION_UNKNOWN

/**
 * struct i915_ttm_tt - TTM page vector with additional private information
 * @ttm: The base TTM page vector.
 * @dev: The struct device used for dma mapping and unmapping.
 * @cached_rsgt: The cached scatter-gather table.
 * @is_shmem: Set if using shmem.
 * @filp: The shmem file, if using shmem backend.
 *
 * Note that DMA may be going on right up to the point where the page-
 * vector is unpopulated in delayed destroy. Hence keep the
 * scatter-gather table mapped and cached up to that point. This is
 * different from the cached gem object io scatter-gather table which
 * doesn't have an associated dma mapping.
 */
struct i915_ttm_tt {
	struct ttm_tt ttm;
	struct device *dev;
	struct i915_refct_sgt cached_rsgt;

	bool is_shmem;
	struct file *filp;
};

static const struct ttm_place sys_placement_flags = {
	.fpfn = 0,
	.lpfn = 0,
	.mem_type = I915_PL_SYSTEM,
	.flags = 0,
};

static struct ttm_placement i915_sys_placement = {
	.num_placement = 1,
	.placement = &sys_placement_flags,
	.num_busy_placement = 1,
	.busy_placement = &sys_placement_flags,
};

/**
 * i915_ttm_sys_placement - Return the struct ttm_placement to be
 * used for an object in system memory.
 *
 * Rather than making the struct extern, use this
 * function.
 *
 * Return: A pointer to a static variable for sys placement.
 */
struct ttm_placement *i915_ttm_sys_placement(void)
{
	return &i915_sys_placement;
}

static int i915_ttm_err_to_gem(int err)
{
	/* Fastpath */
	if (likely(!err))
		return 0;

	switch (err) {
	case -EBUSY:
		/*
		 * TTM likes to convert -EDEADLK to -EBUSY, and wants us to
		 * restart the operation, since we don't record the contending
		 * lock. We use -EAGAIN to restart.
		 */
		return -EAGAIN;
	case -ENOSPC:
		/*
		 * Memory type / region is full, and we can't evict.
		 * Except possibly system, that returns -ENOMEM;
		 */
		return -ENXIO;
	default:
		break;
	}

	return err;
}

static enum ttm_caching
i915_ttm_select_tt_caching(const struct drm_i915_gem_object *obj)
{
	/*
	 * Objects only allowed in system get cached cpu-mappings, or when
	 * evicting lmem-only buffers to system for swapping. Other objects get
	 * WC mapping for now. Even if in system.
	 */
	if (obj->mm.n_placements <= 1)
		return ttm_cached;

	return ttm_write_combined;
}

static void
i915_ttm_place_from_region(const struct intel_memory_region *mr,
			   struct ttm_place *place,
			   resource_size_t offset,
			   resource_size_t size,
			   unsigned int flags)
{
	memset(place, 0, sizeof(*place));
	place->mem_type = intel_region_to_ttm_type(mr);

	if (mr->type == INTEL_MEMORY_SYSTEM)
		return;

	if (flags & I915_BO_ALLOC_CONTIGUOUS)
		place->flags |= TTM_PL_FLAG_CONTIGUOUS;
	if (offset != I915_BO_INVALID_OFFSET) {
		place->fpfn = offset >> PAGE_SHIFT;
		place->lpfn = place->fpfn + (size >> PAGE_SHIFT);
	} else if (mr->io_size && mr->io_size < mr->total) {
		if (flags & I915_BO_ALLOC_GPU_ONLY) {
			place->flags |= TTM_PL_FLAG_TOPDOWN;
		} else {
			place->fpfn = 0;
			place->lpfn = mr->io_size >> PAGE_SHIFT;
		}
	}
}

static void
i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj,
			    struct ttm_place *requested,
			    struct ttm_place *busy,
			    struct ttm_placement *placement)
{
	unsigned int num_allowed = obj->mm.n_placements;
	unsigned int flags = obj->flags;
	unsigned int i;

	placement->num_placement = 1;
	i915_ttm_place_from_region(num_allowed ? obj->mm.placements[0] :
				   obj->mm.region, requested, obj->bo_offset,
				   obj->base.size, flags);

	/* Cache this on object? */
	placement->num_busy_placement = num_allowed;
	for (i = 0; i < placement->num_busy_placement; ++i)
		i915_ttm_place_from_region(obj->mm.placements[i], busy + i,
					   obj->bo_offset, obj->base.size, flags);

	if (num_allowed == 0) {
		*busy = *requested;
		placement->num_busy_placement = 1;
	}

	placement->placement = requested;
	placement->busy_placement = busy;
}

static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
				      struct ttm_tt *ttm,
				      struct ttm_operation_ctx *ctx)
{
	struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
	struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
	const unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
	const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
	struct file *filp = i915_tt->filp;
	struct sgt_iter sgt_iter;
	struct sg_table *st;
	struct page *page;
	unsigned long i;
	int err;

	if (!filp) {
		struct address_space *mapping;
		gfp_t mask;

		filp = shmem_file_setup("i915-shmem-tt", size, VM_NORESERVE);
		if (IS_ERR(filp))
			return PTR_ERR(filp);

		mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;

		mapping = filp->f_mapping;
		mapping_set_gfp_mask(mapping, mask);
		GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM));

		i915_tt->filp = filp;
	}

	st = &i915_tt->cached_rsgt.table;
	err = shmem_sg_alloc_table(i915, st, size, mr, filp->f_mapping,
				   max_segment);
	if (err)
		return err;

	err = dma_map_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL,
			      DMA_ATTR_SKIP_CPU_SYNC);
	if (err)
		goto err_free_st;

	i = 0;
	for_each_sgt_page(page, sgt_iter, st)
		ttm->pages[i++] = page;

	if (ttm->page_flags & TTM_TT_FLAG_SWAPPED)
		ttm->page_flags &= ~TTM_TT_FLAG_SWAPPED;

	return 0;

err_free_st:
	shmem_sg_free_table(st, filp->f_mapping, false, false);

	return err;
}

static void i915_ttm_tt_shmem_unpopulate(struct ttm_tt *ttm)
{
	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
	bool backup = ttm->page_flags & TTM_TT_FLAG_SWAPPED;
	struct sg_table *st = &i915_tt->cached_rsgt.table;

	shmem_sg_free_table(st, file_inode(i915_tt->filp)->i_mapping,
			    backup, backup);
}

static void i915_ttm_tt_release(struct kref *ref)
{
	struct i915_ttm_tt *i915_tt =
		container_of(ref, typeof(*i915_tt), cached_rsgt.kref);
	struct sg_table *st = &i915_tt->cached_rsgt.table;

	GEM_WARN_ON(st->sgl);

	kfree(i915_tt);
}

static const struct i915_refct_sgt_ops tt_rsgt_ops = {
	.release = i915_ttm_tt_release
};

static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
					 uint32_t page_flags)
{
	struct drm_i915_private *i915 = container_of(bo->bdev, typeof(*i915),
						     bdev);
	struct ttm_resource_manager *man =
		ttm_manager_type(bo->bdev, bo->resource->mem_type);
	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
	unsigned long ccs_pages = 0;
	enum ttm_caching caching;
	struct i915_ttm_tt *i915_tt;
	int ret;

	if (!obj)
		return NULL;

	i915_tt = kzalloc(sizeof(*i915_tt), GFP_KERNEL);
	if (!i915_tt)
		return NULL;

	if (obj->flags & I915_BO_ALLOC_CPU_CLEAR &&
	    man->use_tt)
		page_flags |= TTM_TT_FLAG_ZERO_ALLOC;

	caching = i915_ttm_select_tt_caching(obj);
	if (i915_gem_object_is_shrinkable(obj) && caching == ttm_cached) {
		page_flags |= TTM_TT_FLAG_EXTERNAL |
			      TTM_TT_FLAG_EXTERNAL_MAPPABLE;
		i915_tt->is_shmem = true;
	}

	if (i915_gem_object_needs_ccs_pages(obj))
		ccs_pages = DIV_ROUND_UP(DIV_ROUND_UP(bo->base.size,
						      NUM_BYTES_PER_CCS_BYTE),
					 PAGE_SIZE);

	ret = ttm_tt_init(&i915_tt->ttm, bo, page_flags, caching, ccs_pages);
	if (ret)
		goto err_free;

	__i915_refct_sgt_init(&i915_tt->cached_rsgt, bo->base.size,
			      &tt_rsgt_ops);

	i915_tt->dev = obj->base.dev->dev;

	return &i915_tt->ttm;

err_free:
	kfree(i915_tt);
	return NULL;
}

static int i915_ttm_tt_populate(struct ttm_device *bdev,
				struct ttm_tt *ttm,
				struct ttm_operation_ctx *ctx)
{
	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);

	if (i915_tt->is_shmem)
		return i915_ttm_tt_shmem_populate(bdev, ttm, ctx);

	return ttm_pool_alloc(&bdev->pool, ttm, ctx);
}

static void i915_ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
{
	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
	struct sg_table *st = &i915_tt->cached_rsgt.table;

	if (st->sgl)
		dma_unmap_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL, 0);

	if (i915_tt->is_shmem) {
		i915_ttm_tt_shmem_unpopulate(ttm);
	} else {
		sg_free_table(st);
		ttm_pool_free(&bdev->pool, ttm);
	}
}

static void i915_ttm_tt_destroy(struct ttm_device *bdev, struct ttm_tt *ttm)
{
	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);

	if (i915_tt->filp)
		fput(i915_tt->filp);

	ttm_tt_fini(ttm);
	i915_refct_sgt_put(&i915_tt->cached_rsgt);
}

static bool i915_ttm_eviction_valuable(struct ttm_buffer_object *bo,
				       const struct ttm_place *place)
{
	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);

	if (!obj)
		return false;

	/*
	 * EXTERNAL objects should never be swapped out by TTM, instead we need
	 * to handle that ourselves. TTM will already skip such objects for us,
	 * but we would like to avoid grabbing locks for no good reason.
	 */
	if (bo->ttm && bo->ttm->page_flags & TTM_TT_FLAG_EXTERNAL)
		return false;

	/* Will do for now. Our pinned objects are still on TTM's LRU lists */
	if (!i915_gem_object_evictable(obj))
		return false;

	return ttm_bo_eviction_valuable(bo, place);
}

static void i915_ttm_evict_flags(struct ttm_buffer_object *bo,
				 struct ttm_placement *placement)
{
	*placement = i915_sys_placement;
}

/**
 * i915_ttm_free_cached_io_rsgt - Free object cached LMEM information
 * @obj: The GEM object
 * This function frees any LMEM-related information that is cached on
 * the object. For example the radix tree for fast page lookup and the
 * cached refcounted sg-table
 */
void i915_ttm_free_cached_io_rsgt(struct drm_i915_gem_object *obj)
{
	struct radix_tree_iter iter;
	void __rcu **slot;

	if (!obj->ttm.cached_io_rsgt)
		return;

	rcu_read_lock();
	radix_tree_for_each_slot(slot, &obj->ttm.get_io_page.radix, &iter, 0)
		radix_tree_delete(&obj->ttm.get_io_page.radix, iter.index);
	rcu_read_unlock();

	i915_refct_sgt_put(obj->ttm.cached_io_rsgt);
	obj->ttm.cached_io_rsgt = NULL;
}

/**
 * i915_ttm_purge - Clear an object of its memory
 * @obj: The object
 *
 * This function is called to clear an object of it's memory when it is
 * marked as not needed anymore.
 *
 * Return: 0 on success, negative error code on failure.
 */
int i915_ttm_purge(struct drm_i915_gem_object *obj)
{
	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
	struct i915_ttm_tt *i915_tt =
		container_of(bo->ttm, typeof(*i915_tt), ttm);
	struct ttm_operation_ctx ctx = {
		.interruptible = true,
		.no_wait_gpu = false,
	};
	struct ttm_placement place = {};
	int ret;

	if (obj->mm.madv == __I915_MADV_PURGED)
		return 0;

	ret = ttm_bo_validate(bo, &place, &ctx);
	if (ret)
		return ret;

	if (bo->ttm && i915_tt->filp) {
		/*
		 * The below fput(which eventually calls shmem_truncate) might
		 * be delayed by worker, so when directly called to purge the
		 * pages(like by the shrinker) we should try to be more
		 * aggressive and release the pages immediately.
		 */
		shmem_truncate_range(file_inode(i915_tt->filp),
				     0, (loff_t)-1);
		fput(fetch_and_zero(&i915_tt->filp));
	}

	obj->write_domain = 0;
	obj->read_domains = 0;
	i915_ttm_adjust_gem_after_move(obj);
	i915_ttm_free_cached_io_rsgt(obj);
	obj->mm.madv = __I915_MADV_PURGED;

	return 0;
}

static int i915_ttm_shrink(struct drm_i915_gem_object *obj, unsigned int flags)
{
	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
	struct i915_ttm_tt *i915_tt =
		container_of(bo->ttm, typeof(*i915_tt), ttm);
	struct ttm_operation_ctx ctx = {
		.interruptible = true,
		.no_wait_gpu = flags & I915_GEM_OBJECT_SHRINK_NO_GPU_WAIT,
	};
	struct ttm_placement place = {};
	int ret;

	if (!bo->ttm || bo->resource->mem_type != TTM_PL_SYSTEM)
		return 0;

	GEM_BUG_ON(!i915_tt->is_shmem);

	if (!i915_tt->filp)
		return 0;

	ret = ttm_bo_wait_ctx(bo, &ctx);
	if (ret)
		return ret;

	switch (obj->mm.madv) {
	case I915_MADV_DONTNEED:
		return i915_ttm_purge(obj);
	case __I915_MADV_PURGED:
		return 0;
	}

	if (bo->ttm->page_flags & TTM_TT_FLAG_SWAPPED)
		return 0;

	bo->ttm->page_flags |= TTM_TT_FLAG_SWAPPED;
	ret = ttm_bo_validate(bo, &place, &ctx);
	if (ret) {
		bo->ttm->page_flags &= ~TTM_TT_FLAG_SWAPPED;
		return ret;
	}

	if (flags & I915_GEM_OBJECT_SHRINK_WRITEBACK)
		__shmem_writeback(obj->base.size, i915_tt->filp->f_mapping);

	return 0;
}

static void i915_ttm_delete_mem_notify(struct ttm_buffer_object *bo)
{
	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
	intel_wakeref_t wakeref = 0;

	if (bo->resource && likely(obj)) {
		/* ttm_bo_release() already has dma_resv_lock */
		if (i915_ttm_cpu_maps_iomem(bo->resource))
			wakeref = intel_runtime_pm_get(&to_i915(obj->base.dev)->runtime_pm);

		__i915_gem_object_pages_fini(obj);

		if (wakeref)
			intel_runtime_pm_put(&to_i915(obj->base.dev)->runtime_pm, wakeref);

		i915_ttm_free_cached_io_rsgt(obj);
	}
}

static struct i915_refct_sgt *i915_ttm_tt_get_st(struct ttm_tt *ttm)
{
	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
	struct sg_table *st;
	int ret;

	if (i915_tt->cached_rsgt.table.sgl)
		return i915_refct_sgt_get(&i915_tt->cached_rsgt);

	st = &i915_tt->cached_rsgt.table;
	ret = sg_alloc_table_from_pages_segment(st,
			ttm->pages, ttm->num_pages,
			0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
			i915_sg_segment_size(i915_tt->dev), GFP_KERNEL);
	if (ret) {
		st->sgl = NULL;
		return ERR_PTR(ret);
	}

	ret = dma_map_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL, 0);
	if (ret) {
		sg_free_table(st);
		return ERR_PTR(ret);
	}

	return i915_refct_sgt_get(&i915_tt->cached_rsgt);
}

/**
 * i915_ttm_resource_get_st - Get a refcounted sg-table pointing to the
 * resource memory
 * @obj: The GEM object used for sg-table caching
 * @res: The struct ttm_resource for which an sg-table is requested.
 *
 * This function returns a refcounted sg-table representing the memory
 * pointed to by @res. If @res is the object's current resource it may also
 * cache the sg_table on the object or attempt to access an already cached
 * sg-table. The refcounted sg-table needs to be put when no-longer in use.
 *
 * Return: A valid pointer to a struct i915_refct_sgt or error pointer on
 * failure.
 */
struct i915_refct_sgt *
i915_ttm_resource_get_st(struct drm_i915_gem_object *obj,
			 struct ttm_resource *res)
{
	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
	u32 page_alignment;

	if (!i915_ttm_gtt_binds_lmem(res))
		return i915_ttm_tt_get_st(bo->ttm);

	page_alignment = bo->page_alignment << PAGE_SHIFT;
	if (!page_alignment)
		page_alignment = obj->mm.region->min_page_size;

	/*
	 * If CPU mapping differs, we need to add the ttm_tt pages to
	 * the resulting st. Might make sense for GGTT.
	 */
	GEM_WARN_ON(!i915_ttm_cpu_maps_iomem(res));
	if (bo->resource == res) {
		if (!obj->ttm.cached_io_rsgt) {
			struct i915_refct_sgt *rsgt;

			rsgt = intel_region_ttm_resource_to_rsgt(obj->mm.region,
								 res,
								 page_alignment);
			if (IS_ERR(rsgt))
				return rsgt;

			obj->ttm.cached_io_rsgt = rsgt;
		}
		return i915_refct_sgt_get(obj->ttm.cached_io_rsgt);
	}

	return intel_region_ttm_resource_to_rsgt(obj->mm.region, res,
						 page_alignment);
}

static int i915_ttm_truncate(struct drm_i915_gem_object *obj)
{
	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
	int err;

	WARN_ON_ONCE(obj->mm.madv == I915_MADV_WILLNEED);

	err = i915_ttm_move_notify(bo);
	if (err)
		return err;

	return i915_ttm_purge(obj);
}

static void i915_ttm_swap_notify(struct ttm_buffer_object *bo)
{
	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
	int ret;

	if (!obj)
		return;

	ret = i915_ttm_move_notify(bo);
	GEM_WARN_ON(ret);
	GEM_WARN_ON(obj->ttm.cached_io_rsgt);
	if (!ret && obj->mm.madv != I915_MADV_WILLNEED)
		i915_ttm_purge(obj);
}

/**
 * i915_ttm_resource_mappable - Return true if the ttm resource is CPU
 * accessible.
 * @res: The TTM resource to check.
 *
 * This is interesting on small-BAR systems where we may encounter lmem objects
 * that can't be accessed via the CPU.
 */
bool i915_ttm_resource_mappable(struct ttm_resource *res)
{
	struct i915_ttm_buddy_resource *bman_res = to_ttm_buddy_resource(res);

	if (!i915_ttm_cpu_maps_iomem(res))
		return true;

	return bman_res->used_visible_size == bman_res->base.num_pages;
}

static int i915_ttm_io_mem_reserve(struct ttm_device *bdev, struct ttm_resource *mem)
{
	struct drm_i915_gem_object *obj = i915_ttm_to_gem(mem->bo);
	bool unknown_state;

	if (!obj)
		return -EINVAL;

	if (!kref_get_unless_zero(&obj->base.refcount))
		return -EINVAL;

	assert_object_held(obj);

	unknown_state = i915_gem_object_has_unknown_state(obj);
	i915_gem_object_put(obj);
	if (unknown_state)
		return -EINVAL;

	if (!i915_ttm_cpu_maps_iomem(mem))
		return 0;

	if (!i915_ttm_resource_mappable(mem))
		return -EINVAL;

	mem->bus.caching = ttm_write_combined;
	mem->bus.is_iomem = true;

	return 0;
}

static unsigned long i915_ttm_io_mem_pfn(struct ttm_buffer_object *bo,
					 unsigned long page_offset)
{
	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
	struct scatterlist *sg;
	unsigned long base;
	unsigned int ofs;

	GEM_BUG_ON(!obj);
	GEM_WARN_ON(bo->ttm);

	base = obj->mm.region->iomap.base - obj->mm.region->region.start;
	sg = __i915_gem_object_get_sg(obj, &obj->ttm.get_io_page, page_offset, &ofs, true);

	return ((base + sg_dma_address(sg)) >> PAGE_SHIFT) + ofs;
}

/*
 * All callbacks need to take care not to downcast a struct ttm_buffer_object
 * without checking its subclass, since it might be a TTM ghost object.
 */
static struct ttm_device_funcs i915_ttm_bo_driver = {
	.ttm_tt_create = i915_ttm_tt_create,
	.ttm_tt_populate = i915_ttm_tt_populate,
	.ttm_tt_unpopulate = i915_ttm_tt_unpopulate,
	.ttm_tt_destroy = i915_ttm_tt_destroy,
	.eviction_valuable = i915_ttm_eviction_valuable,
	.evict_flags = i915_ttm_evict_flags,
	.move = i915_ttm_move,
	.swap_notify = i915_ttm_swap_notify,
	.delete_mem_notify = i915_ttm_delete_mem_notify,
	.io_mem_reserve = i915_ttm_io_mem_reserve,
	.io_mem_pfn = i915_ttm_io_mem_pfn,
};

/**
 * i915_ttm_driver - Return a pointer to the TTM device funcs
 *
 * Return: Pointer to statically allocated TTM device funcs.
 */
struct ttm_device_funcs *i915_ttm_driver(void)
{
	return &i915_ttm_bo_driver;
}

static int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
				struct ttm_placement *placement)
{
	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
	struct ttm_operation_ctx ctx = {
		.interruptible = true,
		.no_wait_gpu = false,
	};
	int real_num_busy;
	int ret;

	/* First try only the requested placement. No eviction. */
	real_num_busy = fetch_and_zero(&placement->num_busy_placement);
	ret = ttm_bo_validate(bo, placement, &ctx);
	if (ret) {
		ret = i915_ttm_err_to_gem(ret);
		/*
		 * Anything that wants to restart the operation gets to
		 * do that.
		 */
		if (ret == -EDEADLK || ret == -EINTR || ret == -ERESTARTSYS ||
		    ret == -EAGAIN)
			return ret;

		/*
		 * If the initial attempt fails, allow all accepted placements,
		 * evicting if necessary.
		 */
		placement->num_busy_placement = real_num_busy;
		ret = ttm_bo_validate(bo, placement, &ctx);
		if (ret)
			return i915_ttm_err_to_gem(ret);
	}

	if (bo->ttm && !ttm_tt_is_populated(bo->ttm)) {
		ret = ttm_tt_populate(bo->bdev, bo->ttm, &ctx);
		if (ret)
			return ret;

		i915_ttm_adjust_domains_after_move(obj);
		i915_ttm_adjust_gem_after_move(obj);
	}

	if (!i915_gem_object_has_pages(obj)) {
		struct i915_refct_sgt *rsgt =
			i915_ttm_resource_get_st(obj, bo->resource);

		if (IS_ERR(rsgt))
			return PTR_ERR(rsgt);

		GEM_BUG_ON(obj->mm.rsgt);
		obj->mm.rsgt = rsgt;
		__i915_gem_object_set_pages(obj, &rsgt->table,
					    i915_sg_dma_sizes(rsgt->table.sgl));
	}

	GEM_BUG_ON(bo->ttm && ((obj->base.size >> PAGE_SHIFT) < bo->ttm->num_pages));
	i915_ttm_adjust_lru(obj);
	return ret;
}

static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
{
	struct ttm_place requested, busy[I915_TTM_MAX_PLACEMENTS];
	struct ttm_placement placement;

	GEM_BUG_ON(obj->mm.n_placements > I915_TTM_MAX_PLACEMENTS);

	/* Move to the requested placement. */
	i915_ttm_placement_from_obj(obj, &requested, busy, &placement);

	return __i915_ttm_get_pages(obj, &placement);
}

/**
 * DOC: Migration vs eviction
 *
 * GEM migration may not be the same as TTM migration / eviction. If
 * the TTM core decides to evict an object it may be evicted to a
 * TTM memory type that is not in the object's allowable GEM regions, or
 * in fact theoretically to a TTM memory type that doesn't correspond to
 * a GEM memory region. In that case the object's GEM region is not
 * updated, and the data is migrated back to the GEM region at
 * get_pages time. TTM may however set up CPU ptes to the object even
 * when it is evicted.
 * Gem forced migration using the i915_ttm_migrate() op, is allowed even
 * to regions that are not in the object's list of allowable placements.
 */
static int __i915_ttm_migrate(struct drm_i915_gem_object *obj,
			      struct intel_memory_region *mr,
			      unsigned int flags)
{
	struct ttm_place requested;
	struct ttm_placement placement;
	int ret;

	i915_ttm_place_from_region(mr, &requested, obj->bo_offset,
				   obj->base.size, flags);
	placement.num_placement = 1;
	placement.num_busy_placement = 1;
	placement.placement = &requested;
	placement.busy_placement = &requested;

	ret = __i915_ttm_get_pages(obj, &placement);
	if (ret)
		return ret;

	/*
	 * Reinitialize the region bindings. This is primarily
	 * required for objects where the new region is not in
	 * its allowable placements.
	 */
	if (obj->mm.region != mr) {
		i915_gem_object_release_memory_region(obj);
		i915_gem_object_init_memory_region(obj, mr);
	}

	return 0;
}

static int i915_ttm_migrate(struct drm_i915_gem_object *obj,
			    struct intel_memory_region *mr,
			    unsigned int flags)
{
	return __i915_ttm_migrate(obj, mr, flags);
}

static void i915_ttm_put_pages(struct drm_i915_gem_object *obj,
			       struct sg_table *st)
{
	/*
	 * We're currently not called from a shrinker, so put_pages()
	 * typically means the object is about to destroyed, or called
	 * from move_notify(). So just avoid doing much for now.
	 * If the object is not destroyed next, The TTM eviction logic
	 * and shrinkers will move it out if needed.
	 */

	if (obj->mm.rsgt)
		i915_refct_sgt_put(fetch_and_zero(&obj->mm.rsgt));
}

/**
 * i915_ttm_adjust_lru - Adjust an object's position on relevant LRU lists.
 * @obj: The object
 */
void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj)
{
	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
	struct i915_ttm_tt *i915_tt =
		container_of(bo->ttm, typeof(*i915_tt), ttm);
	bool shrinkable =
		bo->ttm && i915_tt->filp && ttm_tt_is_populated(bo->ttm);

	/*
	 * Don't manipulate the TTM LRUs while in TTM bo destruction.
	 * We're called through i915_ttm_delete_mem_notify().
	 */
	if (!kref_read(&bo->kref))
		return;

	/*
	 * We skip managing the shrinker LRU in set_pages() and just manage
	 * everything here. This does at least solve the issue with having
	 * temporary shmem mappings(like with evicted lmem) not being visible to
	 * the shrinker. Only our shmem objects are shrinkable, everything else
	 * we keep as unshrinkable.
	 *
	 * To make sure everything plays nice we keep an extra shrink pin in TTM
	 * if the underlying pages are not currently shrinkable. Once we release
	 * our pin, like when the pages are moved to shmem, the pages will then
	 * be added to the shrinker LRU, assuming the caller isn't also holding
	 * a pin.
	 *
	 * TODO: consider maybe also bumping the shrinker list here when we have
	 * already unpinned it, which should give us something more like an LRU.
	 *
	 * TODO: There is a small window of opportunity for this function to
	 * get called from eviction after we've dropped the last GEM refcount,
	 * but before the TTM deleted flag is set on the object. Avoid
	 * adjusting the shrinker list in such cases, since the object is
	 * not available to the shrinker anyway due to its zero refcount.
	 * To fix this properly we should move to a TTM shrinker LRU list for
	 * these objects.
	 */
	if (kref_get_unless_zero(&obj->base.refcount)) {
		if (shrinkable != obj->mm.ttm_shrinkable) {
			if (shrinkable) {
				if (obj->mm.madv == I915_MADV_WILLNEED)
					__i915_gem_object_make_shrinkable(obj);
				else
					__i915_gem_object_make_purgeable(obj);
			} else {
				i915_gem_object_make_unshrinkable(obj);
			}

			obj->mm.ttm_shrinkable = shrinkable;
		}
		i915_gem_object_put(obj);
	}

	/*
	 * Put on the correct LRU list depending on the MADV status
	 */
	spin_lock(&bo->bdev->lru_lock);
	if (shrinkable) {
		/* Try to keep shmem_tt from being considered for shrinking. */
		bo->priority = TTM_MAX_BO_PRIORITY - 1;
	} else if (obj->mm.madv != I915_MADV_WILLNEED) {
		bo->priority = I915_TTM_PRIO_PURGE;
	} else if (!i915_gem_object_has_pages(obj)) {
		bo->priority = I915_TTM_PRIO_NO_PAGES;
	} else {
		struct ttm_resource_manager *man =
			ttm_manager_type(bo->bdev, bo->resource->mem_type);

		/*
		 * If we need to place an LMEM resource which doesn't need CPU
		 * access then we should try not to victimize mappable objects
		 * first, since we likely end up stealing more of the mappable
		 * portion. And likewise when we try to find space for a mappble
		 * object, we know not to ever victimize objects that don't
		 * occupy any mappable pages.
		 */
		if (i915_ttm_cpu_maps_iomem(bo->resource) &&
		    i915_ttm_buddy_man_visible_size(man) < man->size &&
		    !(obj->flags & I915_BO_ALLOC_GPU_ONLY))
			bo->priority = I915_TTM_PRIO_NEEDS_CPU_ACCESS;
		else
			bo->priority = I915_TTM_PRIO_HAS_PAGES;
	}

	ttm_bo_move_to_lru_tail(bo);
	spin_unlock(&bo->bdev->lru_lock);
}

/*
 * TTM-backed gem object destruction requires some clarification.
 * Basically we have two possibilities here. We can either rely on the
 * i915 delayed destruction and put the TTM object when the object
 * is idle. This would be detected by TTM which would bypass the
 * TTM delayed destroy handling. The other approach is to put the TTM
 * object early and rely on the TTM destroyed handling, and then free
 * the leftover parts of the GEM object once TTM's destroyed list handling is
 * complete. For now, we rely on the latter for two reasons:
 * a) TTM can evict an object even when it's on the delayed destroy list,
 * which in theory allows for complete eviction.
 * b) There is work going on in TTM to allow freeing an object even when
 * it's not idle, and using the TTM destroyed list handling could help us
 * benefit from that.
 */
static void i915_ttm_delayed_free(struct drm_i915_gem_object *obj)
{
	GEM_BUG_ON(!obj->ttm.created);

	ttm_bo_put(i915_gem_to_ttm(obj));
}

static vm_fault_t vm_fault_ttm(struct vm_fault *vmf)
{
	struct vm_area_struct *area = vmf->vma;
	struct ttm_buffer_object *bo = area->vm_private_data;
	struct drm_device *dev = bo->base.dev;
	struct drm_i915_gem_object *obj;
	intel_wakeref_t wakeref = 0;
	vm_fault_t ret;
	int idx;

	obj = i915_ttm_to_gem(bo);
	if (!obj)
		return VM_FAULT_SIGBUS;

	/* Sanity check that we allow writing into this object */
	if (unlikely(i915_gem_object_is_readonly(obj) &&
		     area->vm_flags & VM_WRITE))
		return VM_FAULT_SIGBUS;

	ret = ttm_bo_vm_reserve(bo, vmf);
	if (ret)
		return ret;

	if (obj->mm.madv != I915_MADV_WILLNEED) {
		dma_resv_unlock(bo->base.resv);
		return VM_FAULT_SIGBUS;
	}

	if (i915_ttm_cpu_maps_iomem(bo->resource))
		wakeref = intel_runtime_pm_get(&to_i915(obj->base.dev)->runtime_pm);

	if (!i915_ttm_resource_mappable(bo->resource)) {
		int err = -ENODEV;
		int i;

		for (i = 0; i < obj->mm.n_placements; i++) {
			struct intel_memory_region *mr = obj->mm.placements[i];
			unsigned int flags;

			if (!mr->io_size && mr->type != INTEL_MEMORY_SYSTEM)
				continue;

			flags = obj->flags;
			flags &= ~I915_BO_ALLOC_GPU_ONLY;
			err = __i915_ttm_migrate(obj, mr, flags);
			if (!err)
				break;
		}

		if (err) {
			drm_dbg(dev, "Unable to make resource CPU accessible\n");
			dma_resv_unlock(bo->base.resv);
			ret = VM_FAULT_SIGBUS;
			goto out_rpm;
		}
	}

	if (drm_dev_enter(dev, &idx)) {
		ret = ttm_bo_vm_fault_reserved(vmf, vmf->vma->vm_page_prot,
					       TTM_BO_VM_NUM_PREFAULT);
		drm_dev_exit(idx);
	} else {
		ret = ttm_bo_vm_dummy_page(vmf, vmf->vma->vm_page_prot);
	}

	if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
		goto out_rpm;

	/* ttm_bo_vm_reserve() already has dma_resv_lock */
	if (ret == VM_FAULT_NOPAGE && wakeref && !obj->userfault_count) {
		obj->userfault_count = 1;
		mutex_lock(&to_gt(to_i915(obj->base.dev))->lmem_userfault_lock);
		list_add(&obj->userfault_link, &to_gt(to_i915(obj->base.dev))->lmem_userfault_list);
		mutex_unlock(&to_gt(to_i915(obj->base.dev))->lmem_userfault_lock);
	}

	if (wakeref & CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND)
		intel_wakeref_auto(&to_gt(to_i915(obj->base.dev))->userfault_wakeref,
				   msecs_to_jiffies_timeout(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND));

	i915_ttm_adjust_lru(obj);

	dma_resv_unlock(bo->base.resv);

out_rpm:
	if (wakeref)
		intel_runtime_pm_put(&to_i915(obj->base.dev)->runtime_pm, wakeref);

	return ret;
}

static int
vm_access_ttm(struct vm_area_struct *area, unsigned long addr,
	      void *buf, int len, int write)
{
	struct drm_i915_gem_object *obj =
		i915_ttm_to_gem(area->vm_private_data);

	if (i915_gem_object_is_readonly(obj) && write)
		return -EACCES;

	return ttm_bo_vm_access(area, addr, buf, len, write);
}

static void ttm_vm_open(struct vm_area_struct *vma)
{
	struct drm_i915_gem_object *obj =
		i915_ttm_to_gem(vma->vm_private_data);

	GEM_BUG_ON(!obj);
	i915_gem_object_get(obj);
}

static void ttm_vm_close(struct vm_area_struct *vma)
{
	struct drm_i915_gem_object *obj =
		i915_ttm_to_gem(vma->vm_private_data);

	GEM_BUG_ON(!obj);
	i915_gem_object_put(obj);
}

static const struct vm_operations_struct vm_ops_ttm = {
	.fault = vm_fault_ttm,
	.access = vm_access_ttm,
	.open = ttm_vm_open,
	.close = ttm_vm_close,
};

static u64 i915_ttm_mmap_offset(struct drm_i915_gem_object *obj)
{
	/* The ttm_bo must be allocated with I915_BO_ALLOC_USER */
	GEM_BUG_ON(!drm_mm_node_allocated(&obj->base.vma_node.vm_node));

	return drm_vma_node_offset_addr(&obj->base.vma_node);
}

static void i915_ttm_unmap_virtual(struct drm_i915_gem_object *obj)
{
	ttm_bo_unmap_virtual(i915_gem_to_ttm(obj));
}

static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
	.name = "i915_gem_object_ttm",
	.flags = I915_GEM_OBJECT_IS_SHRINKABLE |
		 I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST,

	.get_pages = i915_ttm_get_pages,
	.put_pages = i915_ttm_put_pages,
	.truncate = i915_ttm_truncate,
	.shrink = i915_ttm_shrink,

	.adjust_lru = i915_ttm_adjust_lru,
	.delayed_free = i915_ttm_delayed_free,
	.migrate = i915_ttm_migrate,

	.mmap_offset = i915_ttm_mmap_offset,
	.unmap_virtual = i915_ttm_unmap_virtual,
	.mmap_ops = &vm_ops_ttm,
};

void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
{
	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);

	i915_gem_object_release_memory_region(obj);
	mutex_destroy(&obj->ttm.get_io_page.lock);

	if (obj->ttm.created) {
		/*
		 * We freely manage the shrinker LRU outide of the mm.pages life
		 * cycle. As a result when destroying the object we should be
		 * extra paranoid and ensure we remove it from the LRU, before
		 * we free the object.
		 *
		 * Touching the ttm_shrinkable outside of the object lock here
		 * should be safe now that the last GEM object ref was dropped.
		 */
		if (obj->mm.ttm_shrinkable)
			i915_gem_object_make_unshrinkable(obj);

		i915_ttm_backup_free(obj);

		/* This releases all gem object bindings to the backend. */
		__i915_gem_free_object(obj);

		call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
	} else {
		__i915_gem_object_fini(obj);
	}
}

/**
 * __i915_gem_ttm_object_init - Initialize a ttm-backed i915 gem object
 * @mem: The initial memory region for the object.
 * @obj: The gem object.
 * @size: Object size in bytes.
 * @flags: gem object flags.
 *
 * Return: 0 on success, negative error code on failure.
 */
int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
			       struct drm_i915_gem_object *obj,
			       resource_size_t offset,
			       resource_size_t size,
			       resource_size_t page_size,
			       unsigned int flags)
{
	static struct lock_class_key lock_class;
	struct drm_i915_private *i915 = mem->i915;
	struct ttm_operation_ctx ctx = {
		.interruptible = true,
		.no_wait_gpu = false,
	};
	enum ttm_bo_type bo_type;
	int ret;

	drm_gem_private_object_init(&i915->drm, &obj->base, size);
	i915_gem_object_init(obj, &i915_gem_ttm_obj_ops, &lock_class, flags);

	obj->bo_offset = offset;

	/* Don't put on a region list until we're either locked or fully initialized. */
	obj->mm.region = mem;
	INIT_LIST_HEAD(&obj->mm.region_link);

	INIT_RADIX_TREE(&obj->ttm.get_io_page.radix, GFP_KERNEL | __GFP_NOWARN);
	mutex_init(&obj->ttm.get_io_page.lock);
	bo_type = (obj->flags & I915_BO_ALLOC_USER) ? ttm_bo_type_device :
		ttm_bo_type_kernel;

	obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);

	/* Forcing the page size is kernel internal only */
	GEM_BUG_ON(page_size && obj->mm.n_placements);

	/*
	 * Keep an extra shrink pin to prevent the object from being made
	 * shrinkable too early. If the ttm_tt is ever allocated in shmem, we
	 * drop the pin. The TTM backend manages the shrinker LRU itself,
	 * outside of the normal mm.pages life cycle.
	 */
	i915_gem_object_make_unshrinkable(obj);

	/*
	 * If this function fails, it will call the destructor, but
	 * our caller still owns the object. So no freeing in the
	 * destructor until obj->ttm.created is true.
	 * Similarly, in delayed_destroy, we can't call ttm_bo_put()
	 * until successful initialization.
	 */
	ret = ttm_bo_init_reserved(&i915->bdev, i915_gem_to_ttm(obj), bo_type,
				   &i915_sys_placement, page_size >> PAGE_SHIFT,
				   &ctx, NULL, NULL, i915_ttm_bo_destroy);
	if (ret)
		return i915_ttm_err_to_gem(ret);

	obj->ttm.created = true;
	i915_gem_object_release_memory_region(obj);
	i915_gem_object_init_memory_region(obj, mem);
	i915_ttm_adjust_domains_after_move(obj);
	i915_ttm_adjust_gem_after_move(obj);
	i915_gem_object_unlock(obj);

	return 0;
}

static const struct intel_memory_region_ops ttm_system_region_ops = {
	.init_object = __i915_gem_ttm_object_init,
	.release = intel_region_ttm_fini,
};

struct intel_memory_region *
i915_gem_ttm_system_setup(struct drm_i915_private *i915,
			  u16 type, u16 instance)
{
	struct intel_memory_region *mr;

	mr = intel_memory_region_create(i915, 0,
					totalram_pages() << PAGE_SHIFT,
					PAGE_SIZE, 0, 0,
					type, instance,
					&ttm_system_region_ops);
	if (IS_ERR(mr))
		return mr;

	intel_memory_region_set_name(mr, "system-ttm");
	return mr;
}