drivers/gpu/drm/i915/i915_gem_evict.c - linux - Git at Google

 /*
  * Copyright © 2008-2010 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.
  *
  * Authors:
  *    Eric Anholt <eric@anholt.net>
  *    Chris Wilson <chris@chris-wilson.co.uuk>
  *
  */

 #include "gem/i915_gem_context.h"
 #include "gt/intel_gt.h"
 #include "gt/intel_gt_requests.h"

 #include "i915_drv.h"
 #include "i915_gem_evict.h"
 #include "i915_trace.h"

 I915_SELFTEST_DECLARE(static struct igt_evict_ctl {
 	bool fail_if_busy:1;
 } igt_evict_ctl;)

 static bool dying_vma(struct i915_vma *vma)
 {
 	return !kref_read(&vma->obj->base.refcount);
 }

 static int ggtt_flush(struct i915_address_space *vm)
 {
 	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
 	struct intel_gt *gt;
 	int ret = 0;

 	list_for_each_entry(gt, &ggtt->gt_list, ggtt_link) {
 		/*
 		 * Not everything in the GGTT is tracked via vma (otherwise we
 		 * could evict as required with minimal stalling) so we are forced
 		 * to idle the GPU and explicitly retire outstanding requests in
 		 * the hopes that we can then remove contexts and the like only
 		 * bound by their active reference.
 		 */
 		ret = intel_gt_wait_for_idle(gt, MAX_SCHEDULE_TIMEOUT);
 		if (ret)
 			return ret;
 	}
 	return ret;
 }

 static bool grab_vma(struct i915_vma *vma, struct i915_gem_ww_ctx *ww)
 {
 	/*
 	 * We add the extra refcount so the object doesn't drop to zero until
 	 * after ungrab_vma(), this way trylock is always paired with unlock.
 	 */
 	if (i915_gem_object_get_rcu(vma->obj)) {
 		if (!i915_gem_object_trylock(vma->obj, ww)) {
 			i915_gem_object_put(vma->obj);
 			return false;
 		}
 	} else {
 		/* Dead objects don't need pins */
 		atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
 	}

 	return true;
 }

 static void ungrab_vma(struct i915_vma *vma)
 {
 	if (dying_vma(vma))
 		return;

 	i915_gem_object_unlock(vma->obj);
 	i915_gem_object_put(vma->obj);
 }

 static bool
 mark_free(struct drm_mm_scan *scan,
 	  struct i915_gem_ww_ctx *ww,
 	  struct i915_vma *vma,
 	  unsigned int flags,
 	  struct list_head *unwind)
 {
 	if (i915_vma_is_pinned(vma))
 		return false;

 	if (!grab_vma(vma, ww))
 		return false;

 	list_add(&vma->evict_link, unwind);
 	return drm_mm_scan_add_block(scan, &vma->node);
 }

 static bool defer_evict(struct i915_vma *vma)
 {
 	if (i915_vma_is_active(vma))
 		return true;

 	if (i915_vma_is_scanout(vma))
 		return true;

 	return false;
 }

 /**
  * i915_gem_evict_something - Evict vmas to make room for binding a new one
  * @vm: address space to evict from
  * @ww: An optional struct i915_gem_ww_ctx.
  * @min_size: size of the desired free space
  * @alignment: alignment constraint of the desired free space
  * @color: color for the desired space
  * @start: start (inclusive) of the range from which to evict objects
  * @end: end (exclusive) of the range from which to evict objects
  * @flags: additional flags to control the eviction algorithm
  *
  * This function will try to evict vmas until a free space satisfying the
  * requirements is found. Callers must check first whether any such hole exists
  * already before calling this function.
  *
  * This function is used by the object/vma binding code.
  *
  * Since this function is only used to free up virtual address space it only
  * ignores pinned vmas, and not object where the backing storage itself is
  * pinned. Hence obj->pages_pin_count does not protect against eviction.
  *
  * To clarify: This is for freeing up virtual address space, not for freeing
  * memory in e.g. the shrinker.
  */
 int
 i915_gem_evict_something(struct i915_address_space *vm,
 			 struct i915_gem_ww_ctx *ww,
 			 u64 min_size, u64 alignment,
 			 unsigned long color,
 			 u64 start, u64 end,
 			 unsigned flags)
 {
 	struct drm_mm_scan scan;
 	struct list_head eviction_list;
 	struct i915_vma *vma, *next;
 	struct drm_mm_node *node;
 	enum drm_mm_insert_mode mode;
 	struct i915_vma *active;
 	struct intel_gt *gt;
 	int ret;

 	lockdep_assert_held(&vm->mutex);
 	trace_i915_gem_evict(vm, min_size, alignment, flags);

 	/*
 	 * The goal is to evict objects and amalgamate space in rough LRU order.
 	 * Since both active and inactive objects reside on the same list,
 	 * in a mix of creation and last scanned order, as we process the list
 	 * we sort it into inactive/active, which keeps the active portion
 	 * in a rough MRU order.
 	 *
 	 * The retirement sequence is thus:
 	 *   1. Inactive objects (already retired, random order)
 	 *   2. Active objects (will stall on unbinding, oldest scanned first)
 	 */
 	mode = DRM_MM_INSERT_BEST;
 	if (flags & PIN_HIGH)
 		mode = DRM_MM_INSERT_HIGH;
 	if (flags & PIN_MAPPABLE)
 		mode = DRM_MM_INSERT_LOW;
 	drm_mm_scan_init_with_range(&scan, &vm->mm,
 				    min_size, alignment, color,
 				    start, end, mode);

 	if (i915_is_ggtt(vm)) {
 		struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);

 		list_for_each_entry(gt, &ggtt->gt_list, ggtt_link)
 			intel_gt_retire_requests(gt);
 	} else {
 		intel_gt_retire_requests(vm->gt);
 	}

 search_again:
 	active = NULL;
 	INIT_LIST_HEAD(&eviction_list);
 	list_for_each_entry_safe(vma, next, &vm->bound_list, vm_link) {
 		if (vma == active) { /* now seen this vma twice */
 			if (flags & PIN_NONBLOCK)
 				break;

 			active = ERR_PTR(-EAGAIN);
 		}

 		/*
 		 * We keep this list in a rough least-recently scanned order
 		 * of active elements (inactive elements are cheap to reap).
 		 * New entries are added to the end, and we move anything we
 		 * scan to the end. The assumption is that the working set
 		 * of applications is either steady state (and thanks to the
 		 * userspace bo cache it almost always is) or volatile and
 		 * frequently replaced after a frame, which are self-evicting!
 		 * Given that assumption, the MRU order of the scan list is
 		 * fairly static, and keeping it in least-recently scan order
 		 * is suitable.
 		 *
 		 * To notice when we complete one full cycle, we record the
 		 * first active element seen, before moving it to the tail.
 		 */
 		if (active != ERR_PTR(-EAGAIN) && defer_evict(vma)) {
 			if (!active)
 				active = vma;

 			list_move_tail(&vma->vm_link, &vm->bound_list);
 			continue;
 		}

 		if (mark_free(&scan, ww, vma, flags, &eviction_list))
 			goto found;
 	}

 	/* Nothing found, clean up and bail out! */
 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
 		ret = drm_mm_scan_remove_block(&scan, &vma->node);
 		BUG_ON(ret);
 		ungrab_vma(vma);
 	}

 	/*
 	 * Can we unpin some objects such as idle hw contents,
 	 * or pending flips? But since only the GGTT has global entries
 	 * such as scanouts, rinbuffers and contexts, we can skip the
 	 * purge when inspecting per-process local address spaces.
 	 */
 	if (!i915_is_ggtt(vm) || flags & PIN_NONBLOCK)
 		return -ENOSPC;

 	/*
 	 * Not everything in the GGTT is tracked via VMA using
 	 * i915_vma_move_to_active(), otherwise we could evict as required
 	 * with minimal stalling. Instead we are forced to idle the GPU and
 	 * explicitly retire outstanding requests which will then remove
 	 * the pinning for active objects such as contexts and ring,
 	 * enabling us to evict them on the next iteration.
 	 *
 	 * To ensure that all user contexts are evictable, we perform
 	 * a switch to the perma-pinned kernel context. This all also gives
 	 * us a termination condition, when the last retired context is
 	 * the kernel's there is no more we can evict.
 	 */
 	if (I915_SELFTEST_ONLY(igt_evict_ctl.fail_if_busy))
 		return -EBUSY;

 	ret = ggtt_flush(vm);
 	if (ret)
 		return ret;

 	cond_resched();

 	flags |= PIN_NONBLOCK;
 	goto search_again;

 found:
 	/* drm_mm doesn't allow any other other operations while
 	 * scanning, therefore store to-be-evicted objects on a
 	 * temporary list and take a reference for all before
 	 * calling unbind (which may remove the active reference
 	 * of any of our objects, thus corrupting the list).
 	 */
 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
 		if (drm_mm_scan_remove_block(&scan, &vma->node)) {
 			__i915_vma_pin(vma);
 		} else {
 			list_del(&vma->evict_link);
 			ungrab_vma(vma);
 		}
 	}

 	/* Unbinding will emit any required flushes */
 	ret = 0;
 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
 		__i915_vma_unpin(vma);
 		if (ret == 0)
 			ret = __i915_vma_unbind(vma);
 		ungrab_vma(vma);
 	}

 	while (ret == 0 && (node = drm_mm_scan_color_evict(&scan))) {
 		vma = container_of(node, struct i915_vma, node);

 		/* If we find any non-objects (!vma), we cannot evict them */
 		if (vma->node.color != I915_COLOR_UNEVICTABLE &&
 		    grab_vma(vma, ww)) {
 			ret = __i915_vma_unbind(vma);
 			ungrab_vma(vma);
 		} else {
 			ret = -ENOSPC;
 		}
 	}

 	return ret;
 }

 /**
  * i915_gem_evict_for_node - Evict vmas to make room for binding a new one
  * @vm: address space to evict from
  * @ww: An optional struct i915_gem_ww_ctx.
  * @target: range (and color) to evict for
  * @flags: additional flags to control the eviction algorithm
  *
  * This function will try to evict vmas that overlap the target node.
  *
  * To clarify: This is for freeing up virtual address space, not for freeing
  * memory in e.g. the shrinker.
  */
 int i915_gem_evict_for_node(struct i915_address_space *vm,
 			    struct i915_gem_ww_ctx *ww,
 			    struct drm_mm_node *target,
 			    unsigned int flags)
 {
 	LIST_HEAD(eviction_list);
 	struct drm_mm_node *node;
 	u64 start = target->start;
 	u64 end = start + target->size;
 	struct i915_vma *vma, *next;
 	int ret = 0;

 	lockdep_assert_held(&vm->mutex);
 	GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE));
 	GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE));

 	trace_i915_gem_evict_node(vm, target, flags);

 	/*
 	 * Retire before we search the active list. Although we have
 	 * reasonable accuracy in our retirement lists, we may have
 	 * a stray pin (preventing eviction) that can only be resolved by
 	 * retiring.
 	 */
 	if (i915_is_ggtt(vm)) {
 		struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
 		struct intel_gt *gt;

 		list_for_each_entry(gt, &ggtt->gt_list, ggtt_link)
 			intel_gt_retire_requests(gt);
 	} else {
 		intel_gt_retire_requests(vm->gt);
 	}

 	if (i915_vm_has_cache_coloring(vm)) {
 		/* Expand search to cover neighbouring guard pages (or lack!) */
 		if (start)
 			start -= I915_GTT_PAGE_SIZE;

 		/* Always look at the page afterwards to avoid the end-of-GTT */
 		end += I915_GTT_PAGE_SIZE;
 	}
 	GEM_BUG_ON(start >= end);

 	drm_mm_for_each_node_in_range(node, &vm->mm, start, end) {
 		/* If we find any non-objects (!vma), we cannot evict them */
 		if (node->color == I915_COLOR_UNEVICTABLE) {
 			ret = -ENOSPC;
 			break;
 		}

 		GEM_BUG_ON(!drm_mm_node_allocated(node));
 		vma = container_of(node, typeof(*vma), node);

 		/*
 		 * If we are using coloring to insert guard pages between
 		 * different cache domains within the address space, we have
 		 * to check whether the objects on either side of our range
 		 * abutt and conflict. If they are in conflict, then we evict
 		 * those as well to make room for our guard pages.
 		 */
 		if (i915_vm_has_cache_coloring(vm)) {
 			if (node->start + node->size == target->start) {
 				if (node->color == target->color)
 					continue;
 			}
 			if (node->start == target->start + target->size) {
 				if (node->color == target->color)
 					continue;
 			}
 		}

 		if (i915_vma_is_pinned(vma)) {
 			ret = -ENOSPC;
 			break;
 		}

 		if (flags & PIN_NONBLOCK && i915_vma_is_active(vma)) {
 			ret = -ENOSPC;
 			break;
 		}

 		if (!grab_vma(vma, ww)) {
 			ret = -ENOSPC;
 			break;
 		}

 		/*
 		 * Never show fear in the face of dragons!
 		 *
 		 * We cannot directly remove this node from within this
 		 * iterator and as with i915_gem_evict_something() we employ
 		 * the vma pin_count in order to prevent the action of
 		 * unbinding one vma from freeing (by dropping its active
 		 * reference) another in our eviction list.
 		 */
 		__i915_vma_pin(vma);
 		list_add(&vma->evict_link, &eviction_list);
 	}

 	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
 		__i915_vma_unpin(vma);
 		if (ret == 0)
 			ret = __i915_vma_unbind(vma);

 		ungrab_vma(vma);
 	}

 	return ret;
 }

 /**
  * i915_gem_evict_vm - Evict all idle vmas from a vm
  * @vm: Address space to cleanse
  * @ww: An optional struct i915_gem_ww_ctx. If not NULL, i915_gem_evict_vm
  * will be able to evict vma's locked by the ww as well.
  * @busy_bo: Optional pointer to struct drm_i915_gem_object. If not NULL, then
  * in the event i915_gem_evict_vm() is unable to trylock an object for eviction,
  * then @busy_bo will point to it. -EBUSY is also returned. The caller must drop
  * the vm->mutex, before trying again to acquire the contended lock. The caller
  * also owns a reference to the object.
  *
  * This function evicts all vmas from a vm.
  *
  * This is used by the execbuf code as a last-ditch effort to defragment the
  * address space.
  *
  * To clarify: This is for freeing up virtual address space, not for freeing
  * memory in e.g. the shrinker.
  */
 int i915_gem_evict_vm(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww,
 		      struct drm_i915_gem_object **busy_bo)
 {
 	int ret = 0;

 	lockdep_assert_held(&vm->mutex);
 	trace_i915_gem_evict_vm(vm);

 	/* Switch back to the default context in order to unpin
 	 * the existing context objects. However, such objects only
 	 * pin themselves inside the global GTT and performing the
 	 * switch otherwise is ineffective.
 	 */
 	if (i915_is_ggtt(vm)) {
 		ret = ggtt_flush(vm);
 		if (ret)
 			return ret;
 	}

 	do {
 		struct i915_vma *vma, *vn;
 		LIST_HEAD(eviction_list);
 		LIST_HEAD(locked_eviction_list);

 		list_for_each_entry(vma, &vm->bound_list, vm_link) {
 			if (i915_vma_is_pinned(vma))
 				continue;

 			/*
 			 * If we already own the lock, trylock fails. In case
 			 * the resv is shared among multiple objects, we still
 			 * need the object ref.
 			 */
 			if (!i915_gem_object_get_rcu(vma->obj) ||
 			    (ww && (dma_resv_locking_ctx(vma->obj->base.resv) == &ww->ctx))) {
 				__i915_vma_pin(vma);
 				list_add(&vma->evict_link, &locked_eviction_list);
 				continue;
 			}

 			if (!i915_gem_object_trylock(vma->obj, ww)) {
 				if (busy_bo) {
 					*busy_bo = vma->obj; /* holds ref */
 					ret = -EBUSY;
 					break;
 				}
 				i915_gem_object_put(vma->obj);
 				continue;
 			}

 			__i915_vma_pin(vma);
 			list_add(&vma->evict_link, &eviction_list);
 		}
 		if (list_empty(&eviction_list) && list_empty(&locked_eviction_list))
 			break;

 		/* Unbind locked objects first, before unlocking the eviction_list */
 		list_for_each_entry_safe(vma, vn, &locked_eviction_list, evict_link) {
 			__i915_vma_unpin(vma);

 			if (ret == 0) {
 				ret = __i915_vma_unbind(vma);
 				if (ret != -EINTR) /* "Get me out of here!" */
 					ret = 0;
 			}
 			if (!dying_vma(vma))
 				i915_gem_object_put(vma->obj);
 		}

 		list_for_each_entry_safe(vma, vn, &eviction_list, evict_link) {
 			__i915_vma_unpin(vma);
 			if (ret == 0) {
 				ret = __i915_vma_unbind(vma);
 				if (ret != -EINTR) /* "Get me out of here!" */
 					ret = 0;
 			}

 			i915_gem_object_unlock(vma->obj);
 			i915_gem_object_put(vma->obj);
 		}
 	} while (ret == 0);

 	return ret;
 }

 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftests/i915_gem_evict.c"
 #endif
	/*
	* Copyright © 2008-2010 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.
	*
	* Authors:
	* Eric Anholt <eric@anholt.net>
	* Chris Wilson <chris@chris-wilson.co.uuk>
	*
	*/

	#include "gem/i915_gem_context.h"
	#include "gt/intel_gt.h"
	#include "gt/intel_gt_requests.h"

	#include "i915_drv.h"
	#include "i915_gem_evict.h"
	#include "i915_trace.h"

	I915_SELFTEST_DECLARE(static struct igt_evict_ctl {
	bool fail_if_busy:1;
	} igt_evict_ctl;)

	static bool dying_vma(struct i915_vma *vma)
	{
	return !kref_read(&vma->obj->base.refcount);
	}

	static int ggtt_flush(struct i915_address_space *vm)
	{
	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
	struct intel_gt *gt;
	int ret = 0;

	list_for_each_entry(gt, &ggtt->gt_list, ggtt_link) {
	/*
	* Not everything in the GGTT is tracked via vma (otherwise we
	* could evict as required with minimal stalling) so we are forced
	* to idle the GPU and explicitly retire outstanding requests in
	* the hopes that we can then remove contexts and the like only
	* bound by their active reference.
	*/
	ret = intel_gt_wait_for_idle(gt, MAX_SCHEDULE_TIMEOUT);
	if (ret)
	return ret;
	}
	return ret;
	}

	static bool grab_vma(struct i915_vma vma, struct i915_gem_ww_ctx ww)
	{
	/*
	* We add the extra refcount so the object doesn't drop to zero until
	* after ungrab_vma(), this way trylock is always paired with unlock.
	*/
	if (i915_gem_object_get_rcu(vma->obj)) {
	if (!i915_gem_object_trylock(vma->obj, ww)) {
	i915_gem_object_put(vma->obj);
	return false;
	}
	} else {
	/* Dead objects don't need pins */
	atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
	}

	return true;
	}

	static void ungrab_vma(struct i915_vma *vma)
	{
	if (dying_vma(vma))
	return;

	i915_gem_object_unlock(vma->obj);
	i915_gem_object_put(vma->obj);
	}

	static bool
	mark_free(struct drm_mm_scan *scan,
	struct i915_gem_ww_ctx *ww,
	struct i915_vma *vma,
	unsigned int flags,
	struct list_head *unwind)
	{
	if (i915_vma_is_pinned(vma))
	return false;

	if (!grab_vma(vma, ww))
	return false;

	list_add(&vma->evict_link, unwind);
	return drm_mm_scan_add_block(scan, &vma->node);
	}

	static bool defer_evict(struct i915_vma *vma)
	{
	if (i915_vma_is_active(vma))
	return true;

	if (i915_vma_is_scanout(vma))
	return true;

	return false;
	}

	/**
	* i915_gem_evict_something - Evict vmas to make room for binding a new one
	* @vm: address space to evict from
	* @ww: An optional struct i915_gem_ww_ctx.
	* @min_size: size of the desired free space
	* @alignment: alignment constraint of the desired free space
	* @color: color for the desired space
	* @start: start (inclusive) of the range from which to evict objects
	* @end: end (exclusive) of the range from which to evict objects
	* @flags: additional flags to control the eviction algorithm
	*
	* This function will try to evict vmas until a free space satisfying the
	* requirements is found. Callers must check first whether any such hole exists
	* already before calling this function.
	*
	* This function is used by the object/vma binding code.
	*
	* Since this function is only used to free up virtual address space it only
	* ignores pinned vmas, and not object where the backing storage itself is
	* pinned. Hence obj->pages_pin_count does not protect against eviction.
	*
	* To clarify: This is for freeing up virtual address space, not for freeing
	* memory in e.g. the shrinker.
	*/
	int
	i915_gem_evict_something(struct i915_address_space *vm,
	struct i915_gem_ww_ctx *ww,
	u64 min_size, u64 alignment,
	unsigned long color,
	u64 start, u64 end,
	unsigned flags)
	{
	struct drm_mm_scan scan;
	struct list_head eviction_list;
	struct i915_vma vma, next;
	struct drm_mm_node *node;
	enum drm_mm_insert_mode mode;
	struct i915_vma *active;
	struct intel_gt *gt;
	int ret;

	lockdep_assert_held(&vm->mutex);
	trace_i915_gem_evict(vm, min_size, alignment, flags);

	/*
	* The goal is to evict objects and amalgamate space in rough LRU order.
	* Since both active and inactive objects reside on the same list,
	* in a mix of creation and last scanned order, as we process the list
	* we sort it into inactive/active, which keeps the active portion
	* in a rough MRU order.
	*
	* The retirement sequence is thus:
	* 1. Inactive objects (already retired, random order)
	* 2. Active objects (will stall on unbinding, oldest scanned first)
	*/
	mode = DRM_MM_INSERT_BEST;
	if (flags & PIN_HIGH)
	mode = DRM_MM_INSERT_HIGH;
	if (flags & PIN_MAPPABLE)
	mode = DRM_MM_INSERT_LOW;
	drm_mm_scan_init_with_range(&scan, &vm->mm,
	min_size, alignment, color,
	start, end, mode);

	if (i915_is_ggtt(vm)) {
	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);

	list_for_each_entry(gt, &ggtt->gt_list, ggtt_link)
	intel_gt_retire_requests(gt);
	} else {
	intel_gt_retire_requests(vm->gt);
	}

	search_again:
	active = NULL;
	INIT_LIST_HEAD(&eviction_list);
	list_for_each_entry_safe(vma, next, &vm->bound_list, vm_link) {
	if (vma == active) { /* now seen this vma twice */
	if (flags & PIN_NONBLOCK)
	break;

	active = ERR_PTR(-EAGAIN);
	}

	/*
	* We keep this list in a rough least-recently scanned order
	* of active elements (inactive elements are cheap to reap).
	* New entries are added to the end, and we move anything we
	* scan to the end. The assumption is that the working set
	* of applications is either steady state (and thanks to the
	* userspace bo cache it almost always is) or volatile and
	* frequently replaced after a frame, which are self-evicting!
	* Given that assumption, the MRU order of the scan list is
	* fairly static, and keeping it in least-recently scan order
	* is suitable.
	*
	* To notice when we complete one full cycle, we record the
	* first active element seen, before moving it to the tail.
	*/
	if (active != ERR_PTR(-EAGAIN) && defer_evict(vma)) {
	if (!active)
	active = vma;

	list_move_tail(&vma->vm_link, &vm->bound_list);
	continue;
	}

	if (mark_free(&scan, ww, vma, flags, &eviction_list))
	goto found;
	}

	/* Nothing found, clean up and bail out! */
	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
	ret = drm_mm_scan_remove_block(&scan, &vma->node);
	BUG_ON(ret);
	ungrab_vma(vma);
	}

	/*
	* Can we unpin some objects such as idle hw contents,
	* or pending flips? But since only the GGTT has global entries
	* such as scanouts, rinbuffers and contexts, we can skip the
	* purge when inspecting per-process local address spaces.
	*/
	if (!i915_is_ggtt(vm) \|\| flags & PIN_NONBLOCK)
	return -ENOSPC;

	/*
	* Not everything in the GGTT is tracked via VMA using
	* i915_vma_move_to_active(), otherwise we could evict as required
	* with minimal stalling. Instead we are forced to idle the GPU and
	* explicitly retire outstanding requests which will then remove
	* the pinning for active objects such as contexts and ring,
	* enabling us to evict them on the next iteration.
	*
	* To ensure that all user contexts are evictable, we perform
	* a switch to the perma-pinned kernel context. This all also gives
	* us a termination condition, when the last retired context is
	* the kernel's there is no more we can evict.
	*/
	if (I915_SELFTEST_ONLY(igt_evict_ctl.fail_if_busy))
	return -EBUSY;

	ret = ggtt_flush(vm);
	if (ret)
	return ret;

	cond_resched();

	flags \|= PIN_NONBLOCK;
	goto search_again;

	found:
	/* drm_mm doesn't allow any other other operations while
	* scanning, therefore store to-be-evicted objects on a
	* temporary list and take a reference for all before
	* calling unbind (which may remove the active reference
	* of any of our objects, thus corrupting the list).
	*/
	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
	if (drm_mm_scan_remove_block(&scan, &vma->node)) {
	__i915_vma_pin(vma);
	} else {
	list_del(&vma->evict_link);
	ungrab_vma(vma);
	}
	}

	/* Unbinding will emit any required flushes */
	ret = 0;
	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
	__i915_vma_unpin(vma);
	if (ret == 0)
	ret = __i915_vma_unbind(vma);
	ungrab_vma(vma);
	}

	while (ret == 0 && (node = drm_mm_scan_color_evict(&scan))) {
	vma = container_of(node, struct i915_vma, node);

	/* If we find any non-objects (!vma), we cannot evict them */
	if (vma->node.color != I915_COLOR_UNEVICTABLE &&
	grab_vma(vma, ww)) {
	ret = __i915_vma_unbind(vma);
	ungrab_vma(vma);
	} else {
	ret = -ENOSPC;
	}
	}

	return ret;
	}

	/**
	* i915_gem_evict_for_node - Evict vmas to make room for binding a new one
	* @vm: address space to evict from
	* @ww: An optional struct i915_gem_ww_ctx.
	* @target: range (and color) to evict for
	* @flags: additional flags to control the eviction algorithm
	*
	* This function will try to evict vmas that overlap the target node.
	*
	* To clarify: This is for freeing up virtual address space, not for freeing
	* memory in e.g. the shrinker.
	*/
	int i915_gem_evict_for_node(struct i915_address_space *vm,
	struct i915_gem_ww_ctx *ww,
	struct drm_mm_node *target,
	unsigned int flags)
	{
	LIST_HEAD(eviction_list);
	struct drm_mm_node *node;
	u64 start = target->start;
	u64 end = start + target->size;
	struct i915_vma vma, next;
	int ret = 0;

	lockdep_assert_held(&vm->mutex);
	GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE));
	GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE));

	trace_i915_gem_evict_node(vm, target, flags);

	/*
	* Retire before we search the active list. Although we have
	* reasonable accuracy in our retirement lists, we may have
	* a stray pin (preventing eviction) that can only be resolved by
	* retiring.
	*/
	if (i915_is_ggtt(vm)) {
	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
	struct intel_gt *gt;

	list_for_each_entry(gt, &ggtt->gt_list, ggtt_link)
	intel_gt_retire_requests(gt);
	} else {
	intel_gt_retire_requests(vm->gt);
	}

	if (i915_vm_has_cache_coloring(vm)) {
	/* Expand search to cover neighbouring guard pages (or lack!) */
	if (start)
	start -= I915_GTT_PAGE_SIZE;

	/* Always look at the page afterwards to avoid the end-of-GTT */
	end += I915_GTT_PAGE_SIZE;
	}
	GEM_BUG_ON(start >= end);

	drm_mm_for_each_node_in_range(node, &vm->mm, start, end) {
	/* If we find any non-objects (!vma), we cannot evict them */
	if (node->color == I915_COLOR_UNEVICTABLE) {
	ret = -ENOSPC;
	break;
	}

	GEM_BUG_ON(!drm_mm_node_allocated(node));
	vma = container_of(node, typeof(*vma), node);

	/*
	* If we are using coloring to insert guard pages between
	* different cache domains within the address space, we have
	* to check whether the objects on either side of our range
	* abutt and conflict. If they are in conflict, then we evict
	* those as well to make room for our guard pages.
	*/
	if (i915_vm_has_cache_coloring(vm)) {
	if (node->start + node->size == target->start) {
	if (node->color == target->color)
	continue;
	}
	if (node->start == target->start + target->size) {
	if (node->color == target->color)
	continue;
	}
	}

	if (i915_vma_is_pinned(vma)) {
	ret = -ENOSPC;
	break;
	}

	if (flags & PIN_NONBLOCK && i915_vma_is_active(vma)) {
	ret = -ENOSPC;
	break;
	}

	if (!grab_vma(vma, ww)) {
	ret = -ENOSPC;
	break;
	}

	/*
	* Never show fear in the face of dragons!
	*
	* We cannot directly remove this node from within this
	* iterator and as with i915_gem_evict_something() we employ
	* the vma pin_count in order to prevent the action of
	* unbinding one vma from freeing (by dropping its active
	* reference) another in our eviction list.
	*/
	__i915_vma_pin(vma);
	list_add(&vma->evict_link, &eviction_list);
	}

	list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
	__i915_vma_unpin(vma);
	if (ret == 0)
	ret = __i915_vma_unbind(vma);

	ungrab_vma(vma);
	}

	return ret;
	}

	/**
	* i915_gem_evict_vm - Evict all idle vmas from a vm
	* @vm: Address space to cleanse
	* @ww: An optional struct i915_gem_ww_ctx. If not NULL, i915_gem_evict_vm
	* will be able to evict vma's locked by the ww as well.
	* @busy_bo: Optional pointer to struct drm_i915_gem_object. If not NULL, then
	* in the event i915_gem_evict_vm() is unable to trylock an object for eviction,
	* then @busy_bo will point to it. -EBUSY is also returned. The caller must drop
	* the vm->mutex, before trying again to acquire the contended lock. The caller
	* also owns a reference to the object.
	*
	* This function evicts all vmas from a vm.
	*
	* This is used by the execbuf code as a last-ditch effort to defragment the
	* address space.
	*
	* To clarify: This is for freeing up virtual address space, not for freeing
	* memory in e.g. the shrinker.
	*/
	int i915_gem_evict_vm(struct i915_address_space vm, struct i915_gem_ww_ctx ww,
	struct drm_i915_gem_object **busy_bo)
	{
	int ret = 0;

	lockdep_assert_held(&vm->mutex);
	trace_i915_gem_evict_vm(vm);

	/* Switch back to the default context in order to unpin
	* the existing context objects. However, such objects only
	* pin themselves inside the global GTT and performing the
	* switch otherwise is ineffective.
	*/
	if (i915_is_ggtt(vm)) {
	ret = ggtt_flush(vm);
	if (ret)
	return ret;
	}

	do {
	struct i915_vma vma, vn;
	LIST_HEAD(eviction_list);
	LIST_HEAD(locked_eviction_list);

	list_for_each_entry(vma, &vm->bound_list, vm_link) {
	if (i915_vma_is_pinned(vma))
	continue;

	/*
	* If we already own the lock, trylock fails. In case
	* the resv is shared among multiple objects, we still
	* need the object ref.
	*/
	if (!i915_gem_object_get_rcu(vma->obj) \|\|
	(ww && (dma_resv_locking_ctx(vma->obj->base.resv) == &ww->ctx))) {
	__i915_vma_pin(vma);
	list_add(&vma->evict_link, &locked_eviction_list);
	continue;
	}

	if (!i915_gem_object_trylock(vma->obj, ww)) {
	if (busy_bo) {
	busy_bo = vma->obj; / holds ref */
	ret = -EBUSY;
	break;
	}
	i915_gem_object_put(vma->obj);
	continue;
	}

	__i915_vma_pin(vma);
	list_add(&vma->evict_link, &eviction_list);
	}
	if (list_empty(&eviction_list) && list_empty(&locked_eviction_list))
	break;

	/* Unbind locked objects first, before unlocking the eviction_list */
	list_for_each_entry_safe(vma, vn, &locked_eviction_list, evict_link) {
	__i915_vma_unpin(vma);

	if (ret == 0) {
	ret = __i915_vma_unbind(vma);
	if (ret != -EINTR) /* "Get me out of here!" */
	ret = 0;
	}
	if (!dying_vma(vma))
	i915_gem_object_put(vma->obj);
	}

	list_for_each_entry_safe(vma, vn, &eviction_list, evict_link) {
	__i915_vma_unpin(vma);
	if (ret == 0) {
	ret = __i915_vma_unbind(vma);
	if (ret != -EINTR) /* "Get me out of here!" */
	ret = 0;
	}

	i915_gem_object_unlock(vma->obj);
	i915_gem_object_put(vma->obj);
	}
	} while (ret == 0);

	return ret;
	}

	#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
	#include "selftests/i915_gem_evict.c"
	#endif