drivers/gpu/drm/i915/gem/i915_gem_object.c - linux - Git at Google

 /*
  * Copyright © 2017 Intel Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice (including the next
  * paragraph) shall be included in all copies or substantial portions of the
  * Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  * IN THE SOFTWARE.
  *
  */

 #include <linux/sched/mm.h>

 #include "display/intel_frontbuffer.h"
 #include "gt/intel_gt.h"
 #include "i915_drv.h"
 #include "i915_gem_clflush.h"
 #include "i915_gem_context.h"
 #include "i915_gem_mman.h"
 #include "i915_gem_object.h"
 #include "i915_globals.h"
 #include "i915_trace.h"

 static struct i915_global_object {
 	struct i915_global base;
 	struct kmem_cache *slab_objects;
 } global;

 struct drm_i915_gem_object *i915_gem_object_alloc(void)
 {
 	return kmem_cache_zalloc(global.slab_objects, GFP_KERNEL);
 }

 void i915_gem_object_free(struct drm_i915_gem_object *obj)
 {
 	return kmem_cache_free(global.slab_objects, obj);
 }

 void i915_gem_object_init(struct drm_i915_gem_object *obj,
 			  const struct drm_i915_gem_object_ops *ops,
 			  struct lock_class_key *key)
 {
 	__mutex_init(&obj->mm.lock, ops->name ?: "obj->mm.lock", key);

 	spin_lock_init(&obj->vma.lock);
 	INIT_LIST_HEAD(&obj->vma.list);

 	INIT_LIST_HEAD(&obj->mm.link);

 	INIT_LIST_HEAD(&obj->lut_list);
 	spin_lock_init(&obj->lut_lock);

 	spin_lock_init(&obj->mmo.lock);
 	obj->mmo.offsets = RB_ROOT;

 	init_rcu_head(&obj->rcu);

 	obj->ops = ops;

 	obj->mm.madv = I915_MADV_WILLNEED;
 	INIT_RADIX_TREE(&obj->mm.get_page.radix, GFP_KERNEL | __GFP_NOWARN);
 	mutex_init(&obj->mm.get_page.lock);

 	if (IS_ENABLED(CONFIG_LOCKDEP) && i915_gem_object_is_shrinkable(obj))
 		i915_gem_shrinker_taints_mutex(to_i915(obj->base.dev),
 					       &obj->mm.lock);
 }

 /**
  * Mark up the object's coherency levels for a given cache_level
  * @obj: #drm_i915_gem_object
  * @cache_level: cache level
  */
 void i915_gem_object_set_cache_coherency(struct drm_i915_gem_object *obj,
 					 unsigned int cache_level)
 {
 	obj->cache_level = cache_level;

 	if (cache_level != I915_CACHE_NONE)
 		obj->cache_coherent = (I915_BO_CACHE_COHERENT_FOR_READ |
 				       I915_BO_CACHE_COHERENT_FOR_WRITE);
 	else if (HAS_LLC(to_i915(obj->base.dev)))
 		obj->cache_coherent = I915_BO_CACHE_COHERENT_FOR_READ;
 	else
 		obj->cache_coherent = 0;

 	obj->cache_dirty =
 		!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE);
 }

 void i915_gem_close_object(struct drm_gem_object *gem, struct drm_file *file)
 {
 	struct drm_i915_gem_object *obj = to_intel_bo(gem);
 	struct drm_i915_file_private *fpriv = file->driver_priv;
 	struct i915_lut_handle bookmark = {};
 	struct i915_mmap_offset *mmo, *mn;
 	struct i915_lut_handle *lut, *ln;
 	LIST_HEAD(close);

 	spin_lock(&obj->lut_lock);
 	list_for_each_entry_safe(lut, ln, &obj->lut_list, obj_link) {
 		struct i915_gem_context *ctx = lut->ctx;

 		if (ctx && ctx->file_priv == fpriv) {
 			i915_gem_context_get(ctx);
 			list_move(&lut->obj_link, &close);
 		}

 		/* Break long locks, and carefully continue on from this spot */
 		if (&ln->obj_link != &obj->lut_list) {
 			list_add_tail(&bookmark.obj_link, &ln->obj_link);
 			if (cond_resched_lock(&obj->lut_lock))
 				list_safe_reset_next(&bookmark, ln, obj_link);
 			__list_del_entry(&bookmark.obj_link);
 		}
 	}
 	spin_unlock(&obj->lut_lock);

 	spin_lock(&obj->mmo.lock);
 	rbtree_postorder_for_each_entry_safe(mmo, mn, &obj->mmo.offsets, offset)
 		drm_vma_node_revoke(&mmo->vma_node, file);
 	spin_unlock(&obj->mmo.lock);

 	list_for_each_entry_safe(lut, ln, &close, obj_link) {
 		struct i915_gem_context *ctx = lut->ctx;
 		struct i915_vma *vma;

 		/*
 		 * We allow the process to have multiple handles to the same
 		 * vma, in the same fd namespace, by virtue of flink/open.
 		 */

 		mutex_lock(&ctx->lut_mutex);
 		vma = radix_tree_delete(&ctx->handles_vma, lut->handle);
 		if (vma) {
 			GEM_BUG_ON(vma->obj != obj);
 			GEM_BUG_ON(!atomic_read(&vma->open_count));
 			i915_vma_close(vma);
 		}
 		mutex_unlock(&ctx->lut_mutex);

 		i915_gem_context_put(lut->ctx);
 		i915_lut_handle_free(lut);
 		i915_gem_object_put(obj);
 	}
 }

 static void __i915_gem_free_object_rcu(struct rcu_head *head)
 {
 	struct drm_i915_gem_object *obj =
 		container_of(head, typeof(*obj), rcu);
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);

 	dma_resv_fini(&obj->base._resv);
 	i915_gem_object_free(obj);

 	GEM_BUG_ON(!atomic_read(&i915->mm.free_count));
 	atomic_dec(&i915->mm.free_count);
 }

 static void __i915_gem_object_free_mmaps(struct drm_i915_gem_object *obj)
 {
 	/* Skip serialisation and waking the device if known to be not used. */

 	if (obj->userfault_count)
 		i915_gem_object_release_mmap_gtt(obj);

 	if (!RB_EMPTY_ROOT(&obj->mmo.offsets)) {
 		struct i915_mmap_offset *mmo, *mn;

 		i915_gem_object_release_mmap_offset(obj);

 		rbtree_postorder_for_each_entry_safe(mmo, mn,
 						     &obj->mmo.offsets,
 						     offset) {
 			drm_vma_offset_remove(obj->base.dev->vma_offset_manager,
 					      &mmo->vma_node);
 			kfree(mmo);
 		}
 		obj->mmo.offsets = RB_ROOT;
 	}
 }

 static void __i915_gem_free_objects(struct drm_i915_private *i915,
 				    struct llist_node *freed)
 {
 	struct drm_i915_gem_object *obj, *on;

 	llist_for_each_entry_safe(obj, on, freed, freed) {
 		trace_i915_gem_object_destroy(obj);

 		if (!list_empty(&obj->vma.list)) {
 			struct i915_vma *vma;

 			/*
 			 * Note that the vma keeps an object reference while
 			 * it is active, so it *should* not sleep while we
 			 * destroy it. Our debug code errs insits it *might*.
 			 * For the moment, play along.
 			 */
 			spin_lock(&obj->vma.lock);
 			while ((vma = list_first_entry_or_null(&obj->vma.list,
 							       struct i915_vma,
 							       obj_link))) {
 				GEM_BUG_ON(vma->obj != obj);
 				spin_unlock(&obj->vma.lock);

 				__i915_vma_put(vma);

 				spin_lock(&obj->vma.lock);
 			}
 			spin_unlock(&obj->vma.lock);
 		}

 		__i915_gem_object_free_mmaps(obj);

 		GEM_BUG_ON(!list_empty(&obj->lut_list));

 		atomic_set(&obj->mm.pages_pin_count, 0);
 		__i915_gem_object_put_pages(obj);
 		GEM_BUG_ON(i915_gem_object_has_pages(obj));
 		bitmap_free(obj->bit_17);

 		if (obj->base.import_attach)
 			drm_prime_gem_destroy(&obj->base, NULL);

 		drm_gem_free_mmap_offset(&obj->base);

 		if (obj->ops->release)
 			obj->ops->release(obj);

 		/* But keep the pointer alive for RCU-protected lookups */
 		call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
 		cond_resched();
 	}
 }

 void i915_gem_flush_free_objects(struct drm_i915_private *i915)
 {
 	struct llist_node *freed = llist_del_all(&i915->mm.free_list);

 	if (unlikely(freed))
 		__i915_gem_free_objects(i915, freed);
 }

 static void __i915_gem_free_work(struct work_struct *work)
 {
 	struct drm_i915_private *i915 =
 		container_of(work, struct drm_i915_private, mm.free_work);

 	i915_gem_flush_free_objects(i915);
 }

 void i915_gem_free_object(struct drm_gem_object *gem_obj)
 {
 	struct drm_i915_gem_object *obj = to_intel_bo(gem_obj);
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);

 	GEM_BUG_ON(i915_gem_object_is_framebuffer(obj));

 	/*
 	 * Before we free the object, make sure any pure RCU-only
 	 * read-side critical sections are complete, e.g.
 	 * i915_gem_busy_ioctl(). For the corresponding synchronized
 	 * lookup see i915_gem_object_lookup_rcu().
 	 */
 	atomic_inc(&i915->mm.free_count);

 	/*
 	 * This serializes freeing with the shrinker. Since the free
 	 * is delayed, first by RCU then by the workqueue, we want the
 	 * shrinker to be able to free pages of unreferenced objects,
 	 * or else we may oom whilst there are plenty of deferred
 	 * freed objects.
 	 */
 	i915_gem_object_make_unshrinkable(obj);

 	/*
 	 * Since we require blocking on struct_mutex to unbind the freed
 	 * object from the GPU before releasing resources back to the
 	 * system, we can not do that directly from the RCU callback (which may
 	 * be a softirq context), but must instead then defer that work onto a
 	 * kthread. We use the RCU callback rather than move the freed object
 	 * directly onto the work queue so that we can mix between using the
 	 * worker and performing frees directly from subsequent allocations for
 	 * crude but effective memory throttling.
 	 */
 	if (llist_add(&obj->freed, &i915->mm.free_list))
 		queue_work(i915->wq, &i915->mm.free_work);
 }

 static bool gpu_write_needs_clflush(struct drm_i915_gem_object *obj)
 {
 	return !(obj->cache_level == I915_CACHE_NONE ||
 		 obj->cache_level == I915_CACHE_WT);
 }

 void
 i915_gem_object_flush_write_domain(struct drm_i915_gem_object *obj,
 				   unsigned int flush_domains)
 {
 	struct i915_vma *vma;

 	assert_object_held(obj);

 	if (!(obj->write_domain & flush_domains))
 		return;

 	switch (obj->write_domain) {
 	case I915_GEM_DOMAIN_GTT:
 		spin_lock(&obj->vma.lock);
 		for_each_ggtt_vma(vma, obj) {
 			if (i915_vma_unset_ggtt_write(vma))
 				intel_gt_flush_ggtt_writes(vma->vm->gt);
 		}
 		spin_unlock(&obj->vma.lock);

 		i915_gem_object_flush_frontbuffer(obj, ORIGIN_CPU);
 		break;

 	case I915_GEM_DOMAIN_WC:
 		wmb();
 		break;

 	case I915_GEM_DOMAIN_CPU:
 		i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
 		break;

 	case I915_GEM_DOMAIN_RENDER:
 		if (gpu_write_needs_clflush(obj))
 			obj->cache_dirty = true;
 		break;
 	}

 	obj->write_domain = 0;
 }

 void __i915_gem_object_flush_frontbuffer(struct drm_i915_gem_object *obj,
 					 enum fb_op_origin origin)
 {
 	struct intel_frontbuffer *front;

 	front = __intel_frontbuffer_get(obj);
 	if (front) {
 		intel_frontbuffer_flush(front, origin);
 		intel_frontbuffer_put(front);
 	}
 }

 void __i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj,
 					      enum fb_op_origin origin)
 {
 	struct intel_frontbuffer *front;

 	front = __intel_frontbuffer_get(obj);
 	if (front) {
 		intel_frontbuffer_invalidate(front, origin);
 		intel_frontbuffer_put(front);
 	}
 }

 void i915_gem_init__objects(struct drm_i915_private *i915)
 {
 	INIT_WORK(&i915->mm.free_work, __i915_gem_free_work);
 }

 static void i915_global_objects_shrink(void)
 {
 	kmem_cache_shrink(global.slab_objects);
 }

 static void i915_global_objects_exit(void)
 {
 	kmem_cache_destroy(global.slab_objects);
 }

 static struct i915_global_object global = { {
 	.shrink = i915_global_objects_shrink,
 	.exit = i915_global_objects_exit,
 } };

 int __init i915_global_objects_init(void)
 {
 	global.slab_objects =
 		KMEM_CACHE(drm_i915_gem_object, SLAB_HWCACHE_ALIGN);
 	if (!global.slab_objects)
 		return -ENOMEM;

 	i915_global_register(&global.base);
 	return 0;
 }

 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftests/huge_gem_object.c"
 #include "selftests/huge_pages.c"
 #include "selftests/i915_gem_object.c"
 #include "selftests/i915_gem_coherency.c"
 #endif
	/*
	* Copyright © 2017 Intel Corporation
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the "Software"),
	* to deal in the Software without restriction, including without limitation
	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	* and/or sell copies of the Software, and to permit persons to whom the
	* Software is furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice (including the next
	* paragraph) shall be included in all copies or substantial portions of the
	* Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
	* IN THE SOFTWARE.
	*
	*/

	#include <linux/sched/mm.h>

	#include "display/intel_frontbuffer.h"
	#include "gt/intel_gt.h"
	#include "i915_drv.h"
	#include "i915_gem_clflush.h"
	#include "i915_gem_context.h"
	#include "i915_gem_mman.h"
	#include "i915_gem_object.h"
	#include "i915_globals.h"
	#include "i915_trace.h"

	static struct i915_global_object {
	struct i915_global base;
	struct kmem_cache *slab_objects;
	} global;

	struct drm_i915_gem_object *i915_gem_object_alloc(void)
	{
	return kmem_cache_zalloc(global.slab_objects, GFP_KERNEL);
	}

	void i915_gem_object_free(struct drm_i915_gem_object *obj)
	{
	return kmem_cache_free(global.slab_objects, obj);
	}

	void i915_gem_object_init(struct drm_i915_gem_object *obj,
	const struct drm_i915_gem_object_ops *ops,
	struct lock_class_key *key)
	{
	__mutex_init(&obj->mm.lock, ops->name ?: "obj->mm.lock", key);

	spin_lock_init(&obj->vma.lock);
	INIT_LIST_HEAD(&obj->vma.list);

	INIT_LIST_HEAD(&obj->mm.link);

	INIT_LIST_HEAD(&obj->lut_list);
	spin_lock_init(&obj->lut_lock);

	spin_lock_init(&obj->mmo.lock);
	obj->mmo.offsets = RB_ROOT;

	init_rcu_head(&obj->rcu);

	obj->ops = ops;

	obj->mm.madv = I915_MADV_WILLNEED;
	INIT_RADIX_TREE(&obj->mm.get_page.radix, GFP_KERNEL \| __GFP_NOWARN);
	mutex_init(&obj->mm.get_page.lock);

	if (IS_ENABLED(CONFIG_LOCKDEP) && i915_gem_object_is_shrinkable(obj))
	i915_gem_shrinker_taints_mutex(to_i915(obj->base.dev),
	&obj->mm.lock);
	}

	/**
	* Mark up the object's coherency levels for a given cache_level
	* @obj: #drm_i915_gem_object
	* @cache_level: cache level
	*/
	void i915_gem_object_set_cache_coherency(struct drm_i915_gem_object *obj,
	unsigned int cache_level)
	{
	obj->cache_level = cache_level;

	if (cache_level != I915_CACHE_NONE)
	obj->cache_coherent = (I915_BO_CACHE_COHERENT_FOR_READ \|
	I915_BO_CACHE_COHERENT_FOR_WRITE);
	else if (HAS_LLC(to_i915(obj->base.dev)))
	obj->cache_coherent = I915_BO_CACHE_COHERENT_FOR_READ;
	else
	obj->cache_coherent = 0;

	obj->cache_dirty =
	!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE);
	}

	void i915_gem_close_object(struct drm_gem_object gem, struct drm_file file)
	{
	struct drm_i915_gem_object *obj = to_intel_bo(gem);
	struct drm_i915_file_private *fpriv = file->driver_priv;
	struct i915_lut_handle bookmark = {};
	struct i915_mmap_offset mmo, mn;
	struct i915_lut_handle lut, ln;
	LIST_HEAD(close);

	spin_lock(&obj->lut_lock);
	list_for_each_entry_safe(lut, ln, &obj->lut_list, obj_link) {
	struct i915_gem_context *ctx = lut->ctx;

	if (ctx && ctx->file_priv == fpriv) {
	i915_gem_context_get(ctx);
	list_move(&lut->obj_link, &close);
	}

	/* Break long locks, and carefully continue on from this spot */
	if (&ln->obj_link != &obj->lut_list) {
	list_add_tail(&bookmark.obj_link, &ln->obj_link);
	if (cond_resched_lock(&obj->lut_lock))
	list_safe_reset_next(&bookmark, ln, obj_link);
	__list_del_entry(&bookmark.obj_link);
	}
	}
	spin_unlock(&obj->lut_lock);

	spin_lock(&obj->mmo.lock);
	rbtree_postorder_for_each_entry_safe(mmo, mn, &obj->mmo.offsets, offset)
	drm_vma_node_revoke(&mmo->vma_node, file);
	spin_unlock(&obj->mmo.lock);

	list_for_each_entry_safe(lut, ln, &close, obj_link) {
	struct i915_gem_context *ctx = lut->ctx;
	struct i915_vma *vma;

	/*
	* We allow the process to have multiple handles to the same
	* vma, in the same fd namespace, by virtue of flink/open.
	*/

	mutex_lock(&ctx->lut_mutex);
	vma = radix_tree_delete(&ctx->handles_vma, lut->handle);
	if (vma) {
	GEM_BUG_ON(vma->obj != obj);
	GEM_BUG_ON(!atomic_read(&vma->open_count));
	i915_vma_close(vma);
	}
	mutex_unlock(&ctx->lut_mutex);

	i915_gem_context_put(lut->ctx);
	i915_lut_handle_free(lut);
	i915_gem_object_put(obj);
	}
	}

	static void __i915_gem_free_object_rcu(struct rcu_head *head)
	{
	struct drm_i915_gem_object *obj =
	container_of(head, typeof(*obj), rcu);
	struct drm_i915_private *i915 = to_i915(obj->base.dev);

	dma_resv_fini(&obj->base._resv);
	i915_gem_object_free(obj);

	GEM_BUG_ON(!atomic_read(&i915->mm.free_count));
	atomic_dec(&i915->mm.free_count);
	}

	static void __i915_gem_object_free_mmaps(struct drm_i915_gem_object *obj)
	{
	/* Skip serialisation and waking the device if known to be not used. */

	if (obj->userfault_count)
	i915_gem_object_release_mmap_gtt(obj);

	if (!RB_EMPTY_ROOT(&obj->mmo.offsets)) {
	struct i915_mmap_offset mmo, mn;

	i915_gem_object_release_mmap_offset(obj);

	rbtree_postorder_for_each_entry_safe(mmo, mn,
	&obj->mmo.offsets,
	offset) {
	drm_vma_offset_remove(obj->base.dev->vma_offset_manager,
	&mmo->vma_node);
	kfree(mmo);
	}
	obj->mmo.offsets = RB_ROOT;
	}
	}

	static void __i915_gem_free_objects(struct drm_i915_private *i915,
	struct llist_node *freed)
	{
	struct drm_i915_gem_object obj, on;

	llist_for_each_entry_safe(obj, on, freed, freed) {
	trace_i915_gem_object_destroy(obj);

	if (!list_empty(&obj->vma.list)) {
	struct i915_vma *vma;

	/*
	* Note that the vma keeps an object reference while
	* it is active, so it should not sleep while we
	* destroy it. Our debug code errs insits it might.
	* For the moment, play along.
	*/
	spin_lock(&obj->vma.lock);
	while ((vma = list_first_entry_or_null(&obj->vma.list,
	struct i915_vma,
	obj_link))) {
	GEM_BUG_ON(vma->obj != obj);
	spin_unlock(&obj->vma.lock);

	__i915_vma_put(vma);

	spin_lock(&obj->vma.lock);
	}
	spin_unlock(&obj->vma.lock);
	}

	__i915_gem_object_free_mmaps(obj);

	GEM_BUG_ON(!list_empty(&obj->lut_list));

	atomic_set(&obj->mm.pages_pin_count, 0);
	__i915_gem_object_put_pages(obj);
	GEM_BUG_ON(i915_gem_object_has_pages(obj));
	bitmap_free(obj->bit_17);

	if (obj->base.import_attach)
	drm_prime_gem_destroy(&obj->base, NULL);

	drm_gem_free_mmap_offset(&obj->base);

	if (obj->ops->release)
	obj->ops->release(obj);

	/* But keep the pointer alive for RCU-protected lookups */
	call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
	cond_resched();
	}
	}

	void i915_gem_flush_free_objects(struct drm_i915_private *i915)
	{
	struct llist_node *freed = llist_del_all(&i915->mm.free_list);

	if (unlikely(freed))
	__i915_gem_free_objects(i915, freed);
	}

	static void __i915_gem_free_work(struct work_struct *work)
	{
	struct drm_i915_private *i915 =
	container_of(work, struct drm_i915_private, mm.free_work);

	i915_gem_flush_free_objects(i915);
	}

	void i915_gem_free_object(struct drm_gem_object *gem_obj)
	{
	struct drm_i915_gem_object *obj = to_intel_bo(gem_obj);
	struct drm_i915_private *i915 = to_i915(obj->base.dev);

	GEM_BUG_ON(i915_gem_object_is_framebuffer(obj));

	/*
	* Before we free the object, make sure any pure RCU-only
	* read-side critical sections are complete, e.g.
	* i915_gem_busy_ioctl(). For the corresponding synchronized
	* lookup see i915_gem_object_lookup_rcu().
	*/
	atomic_inc(&i915->mm.free_count);

	/*
	* This serializes freeing with the shrinker. Since the free
	* is delayed, first by RCU then by the workqueue, we want the
	* shrinker to be able to free pages of unreferenced objects,
	* or else we may oom whilst there are plenty of deferred
	* freed objects.
	*/
	i915_gem_object_make_unshrinkable(obj);

	/*
	* Since we require blocking on struct_mutex to unbind the freed
	* object from the GPU before releasing resources back to the
	* system, we can not do that directly from the RCU callback (which may
	* be a softirq context), but must instead then defer that work onto a
	* kthread. We use the RCU callback rather than move the freed object
	* directly onto the work queue so that we can mix between using the
	* worker and performing frees directly from subsequent allocations for
	* crude but effective memory throttling.
	*/
	if (llist_add(&obj->freed, &i915->mm.free_list))
	queue_work(i915->wq, &i915->mm.free_work);
	}

	static bool gpu_write_needs_clflush(struct drm_i915_gem_object *obj)
	{
	return !(obj->cache_level == I915_CACHE_NONE \|\|
	obj->cache_level == I915_CACHE_WT);
	}

	void
	i915_gem_object_flush_write_domain(struct drm_i915_gem_object *obj,
	unsigned int flush_domains)
	{
	struct i915_vma *vma;

	assert_object_held(obj);

	if (!(obj->write_domain & flush_domains))
	return;

	switch (obj->write_domain) {
	case I915_GEM_DOMAIN_GTT:
	spin_lock(&obj->vma.lock);
	for_each_ggtt_vma(vma, obj) {
	if (i915_vma_unset_ggtt_write(vma))
	intel_gt_flush_ggtt_writes(vma->vm->gt);
	}
	spin_unlock(&obj->vma.lock);

	i915_gem_object_flush_frontbuffer(obj, ORIGIN_CPU);
	break;

	case I915_GEM_DOMAIN_WC:
	wmb();
	break;

	case I915_GEM_DOMAIN_CPU:
	i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
	break;

	case I915_GEM_DOMAIN_RENDER:
	if (gpu_write_needs_clflush(obj))
	obj->cache_dirty = true;
	break;
	}

	obj->write_domain = 0;
	}

	void __i915_gem_object_flush_frontbuffer(struct drm_i915_gem_object *obj,
	enum fb_op_origin origin)
	{
	struct intel_frontbuffer *front;

	front = __intel_frontbuffer_get(obj);
	if (front) {
	intel_frontbuffer_flush(front, origin);
	intel_frontbuffer_put(front);
	}
	}

	void __i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj,
	enum fb_op_origin origin)
	{
	struct intel_frontbuffer *front;

	front = __intel_frontbuffer_get(obj);
	if (front) {
	intel_frontbuffer_invalidate(front, origin);
	intel_frontbuffer_put(front);
	}
	}

	void i915_gem_init__objects(struct drm_i915_private *i915)
	{
	INIT_WORK(&i915->mm.free_work, __i915_gem_free_work);
	}

	static void i915_global_objects_shrink(void)
	{
	kmem_cache_shrink(global.slab_objects);
	}

	static void i915_global_objects_exit(void)
	{
	kmem_cache_destroy(global.slab_objects);
	}

	static struct i915_global_object global = { {
	.shrink = i915_global_objects_shrink,
	.exit = i915_global_objects_exit,
	} };

	int __init i915_global_objects_init(void)
	{
	global.slab_objects =
	KMEM_CACHE(drm_i915_gem_object, SLAB_HWCACHE_ALIGN);
	if (!global.slab_objects)
	return -ENOMEM;

	i915_global_register(&global.base);
	return 0;
	}

	#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
	#include "selftests/huge_gem_object.c"
	#include "selftests/huge_pages.c"
	#include "selftests/i915_gem_object.c"
	#include "selftests/i915_gem_coherency.c"
	#endif