drm/i915: Add i915_vma_unbind_unlocked, and take obj lock for i915_vma_unbind, v2.

We want to remove more members of i915_vma, which requires the locking to
be held more often.

Start requiring gem object lock for i915_vma_unbind, as it's one of the
callers that may unpin pages.

Some special care is needed when evicting, because the last reference to
the object may be held by the VMA, so after __i915_vma_unbind, vma may be
garbage, and we need to cache vma->obj before unlocking.

Changes since v1:
- Make trylock failing a WARN. (Matt)
- Remove double i915_vma_wait_for_bind() (Matt)
- Move atomic_set to right before mutex_unlock(), to make it more clear
  they belong together. (Matt)

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220114132320.109030-5-maarten.lankhorst@linux.intel.com

1 files changed, 42 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index da7f54b6fa38..536b0995b595 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -129,22 +129,51 @@ void i915_ggtt_suspend_vm(struct i915_address_space *vm)
 
 	drm_WARN_ON(&vm->i915->drm, !vm->is_ggtt && !vm->is_dpt);
 
+retry:
+	i915_gem_drain_freed_objects(vm->i915);
+
 	mutex_lock(&vm->mutex);
 
 	/* Skip rewriting PTE on VMA unbind. */
 	open = atomic_xchg(&vm->open, 0);
 
 	list_for_each_entry_safe(vma, vn, &vm->bound_list, vm_link) {
+		struct drm_i915_gem_object *obj = vma->obj;
+
 		GEM_BUG_ON(!drm_mm_node_allocated(&vma->node));
-		i915_vma_wait_for_bind(vma);
 
-		if (i915_vma_is_pinned(vma))
+		if (i915_vma_is_pinned(vma) || !i915_vma_is_bound(vma, I915_VMA_GLOBAL_BIND))
 			continue;
 
+		/* unlikely to race when GPU is idle, so no worry about slowpath.. */
+		if (WARN_ON(!i915_gem_object_trylock(obj, NULL))) {
+			/*
+			 * No dead objects should appear here, GPU should be
+			 * completely idle, and userspace suspended
+			 */
+			i915_gem_object_get(obj);
+
+			atomic_set(&vm->open, open);
+			mutex_unlock(&vm->mutex);
+
+			i915_gem_object_lock(obj, NULL);
+			open = i915_vma_unbind(vma);
+			i915_gem_object_unlock(obj);
+
+			GEM_WARN_ON(open);
+
+			i915_gem_object_put(obj);
+			goto retry;
+		}
+
 		if (!i915_vma_is_bound(vma, I915_VMA_GLOBAL_BIND)) {
+			i915_vma_wait_for_bind(vma);
+
 			__i915_vma_evict(vma, false);
 			drm_mm_remove_node(&vma->node);
 		}
+
+		i915_gem_object_unlock(obj);
 	}
 
 	vm->clear_range(vm, 0, vm->total);
@@ -746,11 +775,21 @@ static void ggtt_cleanup_hw(struct i915_ggtt *ggtt)
 	atomic_set(&ggtt->vm.open, 0);
 
 	flush_workqueue(ggtt->vm.i915->wq);
+	i915_gem_drain_freed_objects(ggtt->vm.i915);
 
 	mutex_lock(&ggtt->vm.mutex);
 
-	list_for_each_entry_safe(vma, vn, &ggtt->vm.bound_list, vm_link)
+	list_for_each_entry_safe(vma, vn, &ggtt->vm.bound_list, vm_link) {
+		struct drm_i915_gem_object *obj = vma->obj;
+		bool trylock;
+
+		trylock = i915_gem_object_trylock(obj, NULL);
+		WARN_ON(!trylock);
+
 		WARN_ON(__i915_vma_unbind(vma));
+		if (trylock)
+			i915_gem_object_unlock(obj);
+	}
 
 	if (drm_mm_node_allocated(&ggtt->error_capture))
 		drm_mm_remove_node(&ggtt->error_capture);