1 // SPDX-License-Identifier: MIT
2 /*
3  * Copyright © 2021 Intel Corporation
4  */
5 
6 #include <drm/ttm/ttm_tt.h>
7 
8 #include "i915_deps.h"
9 #include "i915_drv.h"
10 #include "intel_memory_region.h"
11 #include "intel_region_ttm.h"
12 
13 #include "gem/i915_gem_object.h"
14 #include "gem/i915_gem_region.h"
15 #include "gem/i915_gem_ttm.h"
16 #include "gem/i915_gem_ttm_move.h"
17 
18 #include "gt/intel_engine_pm.h"
19 #include "gt/intel_gt.h"
20 #include "gt/intel_migrate.h"
21 
22 /**
23  * DOC: Selftest failure modes for failsafe migration:
24  *
25  * For fail_gpu_migration, the gpu blit scheduled is always a clear blit
26  * rather than a copy blit, and then we force the failure paths as if
27  * the blit fence returned an error.
28  *
29  * For fail_work_allocation we fail the kmalloc of the async worker, we
30  * sync the gpu blit. If it then fails, or fail_gpu_migration is set to
31  * true, then a memcpy operation is performed sync.
32  */
33 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
34 static bool fail_gpu_migration;
35 static bool fail_work_allocation;
36 static bool ban_memcpy;
37 
38 void i915_ttm_migrate_set_failure_modes(bool gpu_migration,
39 					bool work_allocation)
40 {
41 	fail_gpu_migration = gpu_migration;
42 	fail_work_allocation = work_allocation;
43 }
44 
45 void i915_ttm_migrate_set_ban_memcpy(bool ban)
46 {
47 	ban_memcpy = ban;
48 }
49 #endif
50 
51 static enum i915_cache_level
52 i915_ttm_cache_level(struct drm_i915_private *i915, struct ttm_resource *res,
53 		     struct ttm_tt *ttm)
54 {
55 	return ((HAS_LLC(i915) || HAS_SNOOP(i915)) &&
56 		!i915_ttm_gtt_binds_lmem(res) &&
57 		ttm->caching == ttm_cached) ? I915_CACHE_LLC :
58 		I915_CACHE_NONE;
59 }
60 
61 static struct intel_memory_region *
62 i915_ttm_region(struct ttm_device *bdev, int ttm_mem_type)
63 {
64 	struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
65 
66 	/* There's some room for optimization here... */
67 	GEM_BUG_ON(ttm_mem_type != I915_PL_SYSTEM &&
68 		   ttm_mem_type < I915_PL_LMEM0);
69 	if (ttm_mem_type == I915_PL_SYSTEM)
70 		return intel_memory_region_lookup(i915, INTEL_MEMORY_SYSTEM,
71 						  0);
72 
73 	return intel_memory_region_lookup(i915, INTEL_MEMORY_LOCAL,
74 					  ttm_mem_type - I915_PL_LMEM0);
75 }
76 
77 /**
78  * i915_ttm_adjust_domains_after_move - Adjust the GEM domains after a
79  * TTM move
80  * @obj: The gem object
81  */
82 void i915_ttm_adjust_domains_after_move(struct drm_i915_gem_object *obj)
83 {
84 	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
85 
86 	if (i915_ttm_cpu_maps_iomem(bo->resource) || bo->ttm->caching != ttm_cached) {
87 		obj->write_domain = I915_GEM_DOMAIN_WC;
88 		obj->read_domains = I915_GEM_DOMAIN_WC;
89 	} else {
90 		obj->write_domain = I915_GEM_DOMAIN_CPU;
91 		obj->read_domains = I915_GEM_DOMAIN_CPU;
92 	}
93 }
94 
95 /**
96  * i915_ttm_adjust_gem_after_move - Adjust the GEM state after a TTM move
97  * @obj: The gem object
98  *
99  * Adjusts the GEM object's region, mem_flags and cache coherency after a
100  * TTM move.
101  */
102 void i915_ttm_adjust_gem_after_move(struct drm_i915_gem_object *obj)
103 {
104 	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
105 	unsigned int cache_level;
106 	unsigned int mem_flags;
107 	unsigned int i;
108 	int mem_type;
109 
110 	/*
111 	 * We might have been purged (or swapped out) if the resource is NULL,
112 	 * in which case the SYSTEM placement is the closest match to describe
113 	 * the current domain. If the object is ever used in this state then we
114 	 * will require moving it again.
115 	 */
116 	if (!bo->resource) {
117 		mem_flags = I915_BO_FLAG_STRUCT_PAGE;
118 		mem_type = I915_PL_SYSTEM;
119 		cache_level = I915_CACHE_NONE;
120 	} else {
121 		mem_flags = i915_ttm_cpu_maps_iomem(bo->resource) ? I915_BO_FLAG_IOMEM :
122 			I915_BO_FLAG_STRUCT_PAGE;
123 		mem_type = bo->resource->mem_type;
124 		cache_level = i915_ttm_cache_level(to_i915(bo->base.dev), bo->resource,
125 						   bo->ttm);
126 	}
127 
128 	/*
129 	 * If object was moved to an allowable region, update the object
130 	 * region to consider it migrated. Note that if it's currently not
131 	 * in an allowable region, it's evicted and we don't update the
132 	 * object region.
133 	 */
134 	if (intel_region_to_ttm_type(obj->mm.region) != mem_type) {
135 		for (i = 0; i < obj->mm.n_placements; ++i) {
136 			struct intel_memory_region *mr = obj->mm.placements[i];
137 
138 			if (intel_region_to_ttm_type(mr) == mem_type &&
139 			    mr != obj->mm.region) {
140 				i915_gem_object_release_memory_region(obj);
141 				i915_gem_object_init_memory_region(obj, mr);
142 				break;
143 			}
144 		}
145 	}
146 
147 	obj->mem_flags &= ~(I915_BO_FLAG_STRUCT_PAGE | I915_BO_FLAG_IOMEM);
148 	obj->mem_flags |= mem_flags;
149 
150 	i915_gem_object_set_cache_coherency(obj, cache_level);
151 }
152 
153 /**
154  * i915_ttm_move_notify - Prepare an object for move
155  * @bo: The ttm buffer object.
156  *
157  * This function prepares an object for move by removing all GPU bindings,
158  * removing all CPU mapings and finally releasing the pages sg-table.
159  *
160  * Return: 0 if successful, negative error code on error.
161  */
162 int i915_ttm_move_notify(struct ttm_buffer_object *bo)
163 {
164 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
165 	int ret;
166 
167 	/*
168 	 * Note: The async unbinding here will actually transform the
169 	 * blocking wait for unbind into a wait before finally submitting
170 	 * evict / migration blit and thus stall the migration timeline
171 	 * which may not be good for overall throughput. We should make
172 	 * sure we await the unbind fences *after* the migration blit
173 	 * instead of *before* as we currently do.
174 	 */
175 	ret = i915_gem_object_unbind(obj, I915_GEM_OBJECT_UNBIND_ACTIVE |
176 				     I915_GEM_OBJECT_UNBIND_ASYNC);
177 	if (ret)
178 		return ret;
179 
180 	ret = __i915_gem_object_put_pages(obj);
181 	if (ret)
182 		return ret;
183 
184 	return 0;
185 }
186 
187 static struct dma_fence *i915_ttm_accel_move(struct ttm_buffer_object *bo,
188 					     bool clear,
189 					     struct ttm_resource *dst_mem,
190 					     struct ttm_tt *dst_ttm,
191 					     struct sg_table *dst_st,
192 					     const struct i915_deps *deps)
193 {
194 	struct drm_i915_private *i915 = container_of(bo->bdev, typeof(*i915),
195 						     bdev);
196 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
197 	struct i915_request *rq;
198 	struct ttm_tt *src_ttm = bo->ttm;
199 	enum i915_cache_level src_level, dst_level;
200 	int ret;
201 
202 	if (!to_gt(i915)->migrate.context || intel_gt_is_wedged(to_gt(i915)))
203 		return ERR_PTR(-EINVAL);
204 
205 	/* With fail_gpu_migration, we always perform a GPU clear. */
206 	if (I915_SELFTEST_ONLY(fail_gpu_migration))
207 		clear = true;
208 
209 	dst_level = i915_ttm_cache_level(i915, dst_mem, dst_ttm);
210 	if (clear) {
211 		if (bo->type == ttm_bo_type_kernel &&
212 		    !I915_SELFTEST_ONLY(fail_gpu_migration))
213 			return ERR_PTR(-EINVAL);
214 
215 		intel_engine_pm_get(to_gt(i915)->migrate.context->engine);
216 		ret = intel_context_migrate_clear(to_gt(i915)->migrate.context, deps,
217 						  dst_st->sgl, dst_level,
218 						  i915_ttm_gtt_binds_lmem(dst_mem),
219 						  0, &rq);
220 	} else {
221 		struct i915_refct_sgt *src_rsgt =
222 			i915_ttm_resource_get_st(obj, bo->resource);
223 
224 		if (IS_ERR(src_rsgt))
225 			return ERR_CAST(src_rsgt);
226 
227 		src_level = i915_ttm_cache_level(i915, bo->resource, src_ttm);
228 		intel_engine_pm_get(to_gt(i915)->migrate.context->engine);
229 		ret = intel_context_migrate_copy(to_gt(i915)->migrate.context,
230 						 deps, src_rsgt->table.sgl,
231 						 src_level,
232 						 i915_ttm_gtt_binds_lmem(bo->resource),
233 						 dst_st->sgl, dst_level,
234 						 i915_ttm_gtt_binds_lmem(dst_mem),
235 						 &rq);
236 
237 		i915_refct_sgt_put(src_rsgt);
238 	}
239 
240 	intel_engine_pm_put(to_gt(i915)->migrate.context->engine);
241 
242 	if (ret && rq) {
243 		i915_request_wait(rq, 0, MAX_SCHEDULE_TIMEOUT);
244 		i915_request_put(rq);
245 	}
246 
247 	return ret ? ERR_PTR(ret) : &rq->fence;
248 }
249 
250 /**
251  * struct i915_ttm_memcpy_arg - argument for the bo memcpy functionality.
252  * @_dst_iter: Storage space for the destination kmap iterator.
253  * @_src_iter: Storage space for the source kmap iterator.
254  * @dst_iter: Pointer to the destination kmap iterator.
255  * @src_iter: Pointer to the source kmap iterator.
256  * @num_pages: Number of pages
257  * @clear: Whether to clear instead of copy.
258  * @src_rsgt: Refcounted scatter-gather list of source memory.
259  * @dst_rsgt: Refcounted scatter-gather list of destination memory.
260  */
261 struct i915_ttm_memcpy_arg {
262 	union {
263 		struct ttm_kmap_iter_tt tt;
264 		struct ttm_kmap_iter_iomap io;
265 	} _dst_iter,
266 	_src_iter;
267 	struct ttm_kmap_iter *dst_iter;
268 	struct ttm_kmap_iter *src_iter;
269 	unsigned long num_pages;
270 	bool clear;
271 	struct i915_refct_sgt *src_rsgt;
272 	struct i915_refct_sgt *dst_rsgt;
273 };
274 
275 /**
276  * struct i915_ttm_memcpy_work - Async memcpy worker under a dma-fence.
277  * @fence: The dma-fence.
278  * @work: The work struct use for the memcpy work.
279  * @lock: The fence lock. Not used to protect anything else ATM.
280  * @irq_work: Low latency worker to signal the fence since it can't be done
281  * from the callback for lockdep reasons.
282  * @cb: Callback for the accelerated migration fence.
283  * @arg: The argument for the memcpy functionality.
284  * @i915: The i915 pointer.
285  * @obj: The GEM object.
286  * @memcpy_allowed: Instead of processing the @arg, and falling back to memcpy
287  * or memset, we wedge the device and set the @obj unknown_state, to prevent
288  * further access to the object with the CPU or GPU.  On some devices we might
289  * only be permitted to use the blitter engine for such operations.
290  */
291 struct i915_ttm_memcpy_work {
292 	struct dma_fence fence;
293 	struct work_struct work;
294 	spinlock_t lock;
295 	struct irq_work irq_work;
296 	struct dma_fence_cb cb;
297 	struct i915_ttm_memcpy_arg arg;
298 	struct drm_i915_private *i915;
299 	struct drm_i915_gem_object *obj;
300 	bool memcpy_allowed;
301 };
302 
303 static void i915_ttm_move_memcpy(struct i915_ttm_memcpy_arg *arg)
304 {
305 	ttm_move_memcpy(arg->clear, arg->num_pages,
306 			arg->dst_iter, arg->src_iter);
307 }
308 
309 static void i915_ttm_memcpy_init(struct i915_ttm_memcpy_arg *arg,
310 				 struct ttm_buffer_object *bo, bool clear,
311 				 struct ttm_resource *dst_mem,
312 				 struct ttm_tt *dst_ttm,
313 				 struct i915_refct_sgt *dst_rsgt)
314 {
315 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
316 	struct intel_memory_region *dst_reg, *src_reg;
317 
318 	dst_reg = i915_ttm_region(bo->bdev, dst_mem->mem_type);
319 	src_reg = i915_ttm_region(bo->bdev, bo->resource->mem_type);
320 	GEM_BUG_ON(!dst_reg || !src_reg);
321 
322 	arg->dst_iter = !i915_ttm_cpu_maps_iomem(dst_mem) ?
323 		ttm_kmap_iter_tt_init(&arg->_dst_iter.tt, dst_ttm) :
324 		ttm_kmap_iter_iomap_init(&arg->_dst_iter.io, &dst_reg->iomap,
325 					 &dst_rsgt->table, dst_reg->region.start);
326 
327 	arg->src_iter = !i915_ttm_cpu_maps_iomem(bo->resource) ?
328 		ttm_kmap_iter_tt_init(&arg->_src_iter.tt, bo->ttm) :
329 		ttm_kmap_iter_iomap_init(&arg->_src_iter.io, &src_reg->iomap,
330 					 &obj->ttm.cached_io_rsgt->table,
331 					 src_reg->region.start);
332 	arg->clear = clear;
333 	arg->num_pages = bo->base.size >> PAGE_SHIFT;
334 
335 	arg->dst_rsgt = i915_refct_sgt_get(dst_rsgt);
336 	arg->src_rsgt = clear ? NULL :
337 		i915_ttm_resource_get_st(obj, bo->resource);
338 }
339 
340 static void i915_ttm_memcpy_release(struct i915_ttm_memcpy_arg *arg)
341 {
342 	i915_refct_sgt_put(arg->src_rsgt);
343 	i915_refct_sgt_put(arg->dst_rsgt);
344 }
345 
346 static void __memcpy_work(struct work_struct *work)
347 {
348 	struct i915_ttm_memcpy_work *copy_work =
349 		container_of(work, typeof(*copy_work), work);
350 	struct i915_ttm_memcpy_arg *arg = &copy_work->arg;
351 	bool cookie;
352 
353 	/*
354 	 * FIXME: We need to take a closer look here. We should be able to plonk
355 	 * this into the fence critical section.
356 	 */
357 	if (!copy_work->memcpy_allowed) {
358 		struct intel_gt *gt;
359 		unsigned int id;
360 
361 		for_each_gt(gt, copy_work->i915, id)
362 			intel_gt_set_wedged(gt);
363 	}
364 
365 	cookie = dma_fence_begin_signalling();
366 
367 	if (copy_work->memcpy_allowed) {
368 		i915_ttm_move_memcpy(arg);
369 	} else {
370 		/*
371 		 * Prevent further use of the object. Any future GTT binding or
372 		 * CPU access is not allowed once we signal the fence. Outside
373 		 * of the fence critical section, we then also then wedge the gpu
374 		 * to indicate the device is not functional.
375 		 *
376 		 * The below dma_fence_signal() is our write-memory-barrier.
377 		 */
378 		copy_work->obj->mm.unknown_state = true;
379 	}
380 
381 	dma_fence_end_signalling(cookie);
382 
383 	dma_fence_signal(&copy_work->fence);
384 
385 	i915_ttm_memcpy_release(arg);
386 	i915_gem_object_put(copy_work->obj);
387 	dma_fence_put(&copy_work->fence);
388 }
389 
390 static void __memcpy_irq_work(struct irq_work *irq_work)
391 {
392 	struct i915_ttm_memcpy_work *copy_work =
393 		container_of(irq_work, typeof(*copy_work), irq_work);
394 	struct i915_ttm_memcpy_arg *arg = &copy_work->arg;
395 
396 	dma_fence_signal(&copy_work->fence);
397 	i915_ttm_memcpy_release(arg);
398 	i915_gem_object_put(copy_work->obj);
399 	dma_fence_put(&copy_work->fence);
400 }
401 
402 static void __memcpy_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
403 {
404 	struct i915_ttm_memcpy_work *copy_work =
405 		container_of(cb, typeof(*copy_work), cb);
406 
407 	if (unlikely(fence->error || I915_SELFTEST_ONLY(fail_gpu_migration))) {
408 		INIT_WORK(&copy_work->work, __memcpy_work);
409 		queue_work(system_unbound_wq, &copy_work->work);
410 	} else {
411 		init_irq_work(&copy_work->irq_work, __memcpy_irq_work);
412 		irq_work_queue(&copy_work->irq_work);
413 	}
414 }
415 
416 static const char *get_driver_name(struct dma_fence *fence)
417 {
418 	return "i915_ttm_memcpy_work";
419 }
420 
421 static const char *get_timeline_name(struct dma_fence *fence)
422 {
423 	return "unbound";
424 }
425 
426 static const struct dma_fence_ops dma_fence_memcpy_ops = {
427 	.get_driver_name = get_driver_name,
428 	.get_timeline_name = get_timeline_name,
429 };
430 
431 static struct dma_fence *
432 i915_ttm_memcpy_work_arm(struct i915_ttm_memcpy_work *work,
433 			 struct dma_fence *dep)
434 {
435 	int ret;
436 
437 	spin_lock_init(&work->lock);
438 	dma_fence_init(&work->fence, &dma_fence_memcpy_ops, &work->lock, 0, 0);
439 	dma_fence_get(&work->fence);
440 	ret = dma_fence_add_callback(dep, &work->cb, __memcpy_cb);
441 	if (ret) {
442 		if (ret != -ENOENT)
443 			dma_fence_wait(dep, false);
444 
445 		return ERR_PTR(I915_SELFTEST_ONLY(fail_gpu_migration) ? -EINVAL :
446 			       dep->error);
447 	}
448 
449 	return &work->fence;
450 }
451 
452 static bool i915_ttm_memcpy_allowed(struct ttm_buffer_object *bo,
453 				    struct ttm_resource *dst_mem)
454 {
455 	if (i915_gem_object_needs_ccs_pages(i915_ttm_to_gem(bo)))
456 		return false;
457 
458 	if (!(i915_ttm_resource_mappable(bo->resource) &&
459 	      i915_ttm_resource_mappable(dst_mem)))
460 		return false;
461 
462 	return I915_SELFTEST_ONLY(ban_memcpy) ? false : true;
463 }
464 
465 static struct dma_fence *
466 __i915_ttm_move(struct ttm_buffer_object *bo,
467 		const struct ttm_operation_ctx *ctx, bool clear,
468 		struct ttm_resource *dst_mem, struct ttm_tt *dst_ttm,
469 		struct i915_refct_sgt *dst_rsgt, bool allow_accel,
470 		const struct i915_deps *move_deps)
471 {
472 	const bool memcpy_allowed = i915_ttm_memcpy_allowed(bo, dst_mem);
473 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
474 	struct drm_i915_private *i915 = to_i915(bo->base.dev);
475 	struct i915_ttm_memcpy_work *copy_work = NULL;
476 	struct i915_ttm_memcpy_arg _arg, *arg = &_arg;
477 	struct dma_fence *fence = ERR_PTR(-EINVAL);
478 
479 	if (allow_accel) {
480 		fence = i915_ttm_accel_move(bo, clear, dst_mem, dst_ttm,
481 					    &dst_rsgt->table, move_deps);
482 
483 		/*
484 		 * We only need to intercept the error when moving to lmem.
485 		 * When moving to system, TTM or shmem will provide us with
486 		 * cleared pages.
487 		 */
488 		if (!IS_ERR(fence) && !i915_ttm_gtt_binds_lmem(dst_mem) &&
489 		    !I915_SELFTEST_ONLY(fail_gpu_migration ||
490 					fail_work_allocation))
491 			goto out;
492 	}
493 
494 	/* If we've scheduled gpu migration. Try to arm error intercept. */
495 	if (!IS_ERR(fence)) {
496 		struct dma_fence *dep = fence;
497 
498 		if (!I915_SELFTEST_ONLY(fail_work_allocation))
499 			copy_work = kzalloc(sizeof(*copy_work), GFP_KERNEL);
500 
501 		if (copy_work) {
502 			copy_work->i915 = i915;
503 			copy_work->memcpy_allowed = memcpy_allowed;
504 			copy_work->obj = i915_gem_object_get(obj);
505 			arg = &copy_work->arg;
506 			if (memcpy_allowed)
507 				i915_ttm_memcpy_init(arg, bo, clear, dst_mem,
508 						     dst_ttm, dst_rsgt);
509 
510 			fence = i915_ttm_memcpy_work_arm(copy_work, dep);
511 		} else {
512 			dma_fence_wait(dep, false);
513 			fence = ERR_PTR(I915_SELFTEST_ONLY(fail_gpu_migration) ?
514 					-EINVAL : fence->error);
515 		}
516 		dma_fence_put(dep);
517 
518 		if (!IS_ERR(fence))
519 			goto out;
520 	} else {
521 		int err = PTR_ERR(fence);
522 
523 		if (err == -EINTR || err == -ERESTARTSYS || err == -EAGAIN)
524 			return fence;
525 
526 		if (move_deps) {
527 			err = i915_deps_sync(move_deps, ctx);
528 			if (err)
529 				return ERR_PTR(err);
530 		}
531 	}
532 
533 	/* Error intercept failed or no accelerated migration to start with */
534 
535 	if (memcpy_allowed) {
536 		if (!copy_work)
537 			i915_ttm_memcpy_init(arg, bo, clear, dst_mem, dst_ttm,
538 					     dst_rsgt);
539 		i915_ttm_move_memcpy(arg);
540 		i915_ttm_memcpy_release(arg);
541 	}
542 	if (copy_work)
543 		i915_gem_object_put(copy_work->obj);
544 	kfree(copy_work);
545 
546 	return memcpy_allowed ? NULL : ERR_PTR(-EIO);
547 out:
548 	if (!fence && copy_work) {
549 		i915_ttm_memcpy_release(arg);
550 		i915_gem_object_put(copy_work->obj);
551 		kfree(copy_work);
552 	}
553 
554 	return fence;
555 }
556 
557 /**
558  * i915_ttm_move - The TTM move callback used by i915.
559  * @bo: The buffer object.
560  * @evict: Whether this is an eviction.
561  * @ctx: Pointer to a struct ttm_operation_ctx indicating how the waits should be
562  *       performed if waiting
563  * @dst_mem: The destination ttm resource.
564  * @hop: If we need multihop, what temporary memory type to move to.
565  *
566  * Return: 0 if successful, negative error code otherwise.
567  */
568 int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
569 		  struct ttm_operation_ctx *ctx,
570 		  struct ttm_resource *dst_mem,
571 		  struct ttm_place *hop)
572 {
573 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
574 	struct ttm_resource_manager *dst_man =
575 		ttm_manager_type(bo->bdev, dst_mem->mem_type);
576 	struct dma_fence *migration_fence = NULL;
577 	struct ttm_tt *ttm = bo->ttm;
578 	struct i915_refct_sgt *dst_rsgt;
579 	bool clear;
580 	int ret;
581 
582 	if (GEM_WARN_ON(i915_ttm_is_ghost_object(bo))) {
583 		ttm_bo_move_null(bo, dst_mem);
584 		return 0;
585 	}
586 
587 	if (!bo->resource) {
588 		if (dst_mem->mem_type != TTM_PL_SYSTEM) {
589 			hop->mem_type = TTM_PL_SYSTEM;
590 			hop->flags = TTM_PL_FLAG_TEMPORARY;
591 			return -EMULTIHOP;
592 		}
593 
594 		/*
595 		 * This is only reached when first creating the object, or if
596 		 * the object was purged or swapped out (pipeline-gutting). For
597 		 * the former we can safely skip all of the below since we are
598 		 * only using a dummy SYSTEM placement here. And with the latter
599 		 * we will always re-enter here with bo->resource set correctly
600 		 * (as per the above), since this is part of a multi-hop
601 		 * sequence, where at the end we can do the move for real.
602 		 *
603 		 * The special case here is when the dst_mem is TTM_PL_SYSTEM,
604 		 * which doens't require any kind of move, so it should be safe
605 		 * to skip all the below and call ttm_bo_move_null() here, where
606 		 * the caller in __i915_ttm_get_pages() will take care of the
607 		 * rest, since we should have a valid ttm_tt.
608 		 */
609 		ttm_bo_move_null(bo, dst_mem);
610 		return 0;
611 	}
612 
613 	ret = i915_ttm_move_notify(bo);
614 	if (ret)
615 		return ret;
616 
617 	if (obj->mm.madv != I915_MADV_WILLNEED) {
618 		i915_ttm_purge(obj);
619 		ttm_resource_free(bo, &dst_mem);
620 		return 0;
621 	}
622 
623 	/* Populate ttm with pages if needed. Typically system memory. */
624 	if (ttm && (dst_man->use_tt || (ttm->page_flags & TTM_TT_FLAG_SWAPPED))) {
625 		ret = ttm_tt_populate(bo->bdev, ttm, ctx);
626 		if (ret)
627 			return ret;
628 	}
629 
630 	dst_rsgt = i915_ttm_resource_get_st(obj, dst_mem);
631 	if (IS_ERR(dst_rsgt))
632 		return PTR_ERR(dst_rsgt);
633 
634 	clear = !i915_ttm_cpu_maps_iomem(bo->resource) && (!ttm || !ttm_tt_is_populated(ttm));
635 	if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC))) {
636 		struct i915_deps deps;
637 
638 		i915_deps_init(&deps, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
639 		ret = i915_deps_add_resv(&deps, bo->base.resv, ctx);
640 		if (ret) {
641 			i915_refct_sgt_put(dst_rsgt);
642 			return ret;
643 		}
644 
645 		migration_fence = __i915_ttm_move(bo, ctx, clear, dst_mem, ttm,
646 						  dst_rsgt, true, &deps);
647 		i915_deps_fini(&deps);
648 	}
649 
650 	/* We can possibly get an -ERESTARTSYS here */
651 	if (IS_ERR(migration_fence)) {
652 		i915_refct_sgt_put(dst_rsgt);
653 		return PTR_ERR(migration_fence);
654 	}
655 
656 	if (migration_fence) {
657 		if (I915_SELFTEST_ONLY(evict && fail_gpu_migration))
658 			ret = -EIO; /* never feed non-migrate fences into ttm */
659 		else
660 			ret = ttm_bo_move_accel_cleanup(bo, migration_fence, evict,
661 							true, dst_mem);
662 		if (ret) {
663 			dma_fence_wait(migration_fence, false);
664 			ttm_bo_move_sync_cleanup(bo, dst_mem);
665 		}
666 		dma_fence_put(migration_fence);
667 	} else {
668 		ttm_bo_move_sync_cleanup(bo, dst_mem);
669 	}
670 
671 	i915_ttm_adjust_domains_after_move(obj);
672 	i915_ttm_free_cached_io_rsgt(obj);
673 
674 	if (i915_ttm_gtt_binds_lmem(dst_mem) || i915_ttm_cpu_maps_iomem(dst_mem)) {
675 		obj->ttm.cached_io_rsgt = dst_rsgt;
676 		obj->ttm.get_io_page.sg_pos = dst_rsgt->table.sgl;
677 		obj->ttm.get_io_page.sg_idx = 0;
678 	} else {
679 		i915_refct_sgt_put(dst_rsgt);
680 	}
681 
682 	i915_ttm_adjust_lru(obj);
683 	i915_ttm_adjust_gem_after_move(obj);
684 	return 0;
685 }
686 
687 /**
688  * i915_gem_obj_copy_ttm - Copy the contents of one ttm-based gem object to
689  * another
690  * @dst: The destination object
691  * @src: The source object
692  * @allow_accel: Allow using the blitter. Otherwise TTM memcpy is used.
693  * @intr: Whether to perform waits interruptible:
694  *
695  * Note: The caller is responsible for assuring that the underlying
696  * TTM objects are populated if needed and locked.
697  *
698  * Return: Zero on success. Negative error code on error. If @intr == true,
699  * then it may return -ERESTARTSYS or -EINTR.
700  */
701 int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst,
702 			  struct drm_i915_gem_object *src,
703 			  bool allow_accel, bool intr)
704 {
705 	struct ttm_buffer_object *dst_bo = i915_gem_to_ttm(dst);
706 	struct ttm_buffer_object *src_bo = i915_gem_to_ttm(src);
707 	struct ttm_operation_ctx ctx = {
708 		.interruptible = intr,
709 	};
710 	struct i915_refct_sgt *dst_rsgt;
711 	struct dma_fence *copy_fence;
712 	struct i915_deps deps;
713 	int ret;
714 
715 	assert_object_held(dst);
716 	assert_object_held(src);
717 
718 	if (GEM_WARN_ON(!src_bo->resource || !dst_bo->resource))
719 		return -EINVAL;
720 
721 	i915_deps_init(&deps, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
722 
723 	ret = dma_resv_reserve_fences(src_bo->base.resv, 1);
724 	if (ret)
725 		return ret;
726 
727 	ret = dma_resv_reserve_fences(dst_bo->base.resv, 1);
728 	if (ret)
729 		return ret;
730 
731 	ret = i915_deps_add_resv(&deps, dst_bo->base.resv, &ctx);
732 	if (ret)
733 		return ret;
734 
735 	ret = i915_deps_add_resv(&deps, src_bo->base.resv, &ctx);
736 	if (ret)
737 		return ret;
738 
739 	dst_rsgt = i915_ttm_resource_get_st(dst, dst_bo->resource);
740 	copy_fence = __i915_ttm_move(src_bo, &ctx, false, dst_bo->resource,
741 				     dst_bo->ttm, dst_rsgt, allow_accel,
742 				     &deps);
743 
744 	i915_deps_fini(&deps);
745 	i915_refct_sgt_put(dst_rsgt);
746 	if (IS_ERR_OR_NULL(copy_fence))
747 		return PTR_ERR_OR_ZERO(copy_fence);
748 
749 	dma_resv_add_fence(dst_bo->base.resv, copy_fence, DMA_RESV_USAGE_WRITE);
750 	dma_resv_add_fence(src_bo->base.resv, copy_fence, DMA_RESV_USAGE_READ);
751 	dma_fence_put(copy_fence);
752 
753 	return 0;
754 }
755