text: /*
   * 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 <drm/i915_drm.h>
  
  #include "i915_drv.h"
  #include "intel_drv.h"
  #include "i915_trace.h"
  
  I915_SELFTEST_DECLARE(static struct igt_evict_ctl {
  	bool fail_if_busy:1;
  } igt_evict_ctl;)
  
  static bool ggtt_is_idle(struct drm_i915_private *i915)
  {
  	return !i915->gt.active_requests;
  }
  
  static int ggtt_flush(struct drm_i915_private *i915)
  {
  	int err;
  
  	/*
  	 * 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.
  	 */
  	err = i915_gem_switch_to_kernel_context(i915, i915->gt.active_engines);
  	if (err)
  		return err;
  
  	err = i915_gem_wait_for_idle(i915,
  				     I915_WAIT_INTERRUPTIBLE |
  				     I915_WAIT_LOCKED,
  				     MAX_SCHEDULE_TIMEOUT);
  	if (err)
  		return err;
  
  	GEM_BUG_ON(!ggtt_is_idle(i915));
  	return 0;
  }
  
  static bool
  mark_free(struct drm_mm_scan *scan,
  	  struct i915_vma *vma,
  	  unsigned int flags,
  	  struct list_head *unwind)
  {
  	if (i915_vma_is_pinned(vma))
  		return false;
  
  	if (flags & PIN_NONFAULT && i915_vma_has_userfault(vma))
  		return false;
  
  	list_add(&vma->evict_link, unwind);
  	return drm_mm_scan_add_block(scan, &vma->node);
  }
  
  /**
   * i915_gem_evict_something - Evict vmas to make room for binding a new one
   * @vm: address space to evict from
   * @min_size: size of the desired free space
   * @alignment: alignment constraint of the desired free space
   * @cache_level: cache_level 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,
  			 u64 min_size, u64 alignment,
  			 unsigned cache_level,
  			 u64 start, u64 end,
  			 unsigned flags)
  {
  	struct drm_i915_private *dev_priv = vm->i915;
  	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;
  	int ret;
  
  	lockdep_assert_held(&vm->i915->drm.struct_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, cache_level,
  				    start, end, mode);
  
  	/*
  	 * 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 (!(flags & PIN_NONBLOCK))
  		i915_retire_requests(dev_priv);
  
  search_again:
  	active = NULL;
  	INIT_LIST_HEAD(&eviction_list);
  	list_for_each_entry_safe(vma, next, &vm->bound_list, vm_link) {
  		/*
  		 * 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 (i915_vma_is_active(vma)) {
  			if (vma == active) {
  				if (flags & PIN_NONBLOCK)
  					break;
  
  				active = ERR_PTR(-EAGAIN);
  			}
  
  			if (active != ERR_PTR(-EAGAIN)) {
  				if (!active)
  					active = vma;
  
  				list_move_tail(&vma->vm_link, &vm->bound_list);
  				continue;
  			}
  		}
  
  		if (mark_free(&scan, 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);
  	}
  
  	/*
  	 * 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 (!ggtt_is_idle(dev_priv)) {
  		if (I915_SELFTEST_ONLY(igt_evict_ctl.fail_if_busy))
  			return -EBUSY;
  
  		ret = ggtt_flush(dev_priv);
  		if (ret)
  			return ret;
  
  		cond_resched();
  		goto search_again;
  	}
  
  	/*
  	 * If we still have pending pageflip completions, drop
  	 * back to userspace to give our workqueues time to
  	 * acquire our locks and unpin the old scanouts.
  	 */
  	return intel_has_pending_fb_unpin(dev_priv) ? -EAGAIN : -ENOSPC;
  
  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);
  	}
  
  	/* 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);
  	}
  
  	while (ret == 0 && (node = drm_mm_scan_color_evict(&scan))) {
  		vma = container_of(node, struct i915_vma, node);
  		ret = i915_vma_unbind(vma);
  	}
  
  	return ret;
  }
  
  /**
   * i915_gem_evict_for_vma - Evict vmas to make room for binding a new one
   * @vm: address space to evict from
   * @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 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;
  	bool check_color;
  	int ret = 0;
  
  	lockdep_assert_held(&vm->i915->drm.struct_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 (!(flags & PIN_NONBLOCK))
  		i915_retire_requests(vm->i915);
  
  	check_color = vm->mm.color_adjust;
  	if (check_color) {
  		/* 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(!node->allocated);
  		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 (check_color) {
  			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 (flags & PIN_NONBLOCK &&
  		    (i915_vma_is_pinned(vma) || i915_vma_is_active(vma))) {
  			ret = -ENOSPC;
  			break;
  		}
  
  		if (flags & PIN_NONFAULT && i915_vma_has_userfault(vma)) {
  			ret = -ENOSPC;
  			break;
  		}
  
  		/* Overlap of objects in the same batch? */
  		if (i915_vma_is_pinned(vma)) {
  			ret = -ENOSPC;
  			if (vma->exec_flags &&
  			    *vma->exec_flags & EXEC_OBJECT_PINNED)
  				ret = -EINVAL;
  			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);
  	}
  
  	return ret;
  }
  
  /**
   * i915_gem_evict_vm - Evict all idle vmas from a vm
   * @vm: Address space to cleanse
   *
   * 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 list_head eviction_list;
  	struct i915_vma *vma, *next;
  	int ret;
  
  	lockdep_assert_held(&vm->i915->drm.struct_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->i915);
  		if (ret)
  			return ret;
  	}
  
  	INIT_LIST_HEAD(&eviction_list);
  	mutex_lock(&vm->mutex);
  	list_for_each_entry(vma, &vm->bound_list, vm_link) {
  		if (i915_vma_is_pinned(vma))
  			continue;
  
  		__i915_vma_pin(vma);
  		list_add(&vma->evict_link, &eviction_list);
  	}
  	mutex_unlock(&vm->mutex);
  
  	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);
  	}
  	return ret;
  }
  
  #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
  #include "selftests/i915_gem_evict.c"
  #endif
  