drm/i915: Defer pin calls in buffer pool until first use by caller.

We need to take the obj lock to pin pages, so wait until the callers
have done so, before making the object unshrinkable.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210323155059.628690-30-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -1349,6 +1349,7 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
 		err = PTR_ERR(cmd);
 		goto err_pool;
 	}
+	intel_gt_buffer_pool_mark_used(pool);
 
 	memset32(cmd, 0, pool->obj->base.size / sizeof(u32));
 
@@ -2644,6 +2645,7 @@ static int eb_parse(struct i915_execbuffer *eb)
 		err = PTR_ERR(shadow);
 		goto err;
 	}
+	intel_gt_buffer_pool_mark_used(pool);
 	i915_gem_object_set_readonly(shadow->obj);
 	shadow->private = pool;
 

drivers/gpu/drm/i915/gem/i915_gem_object_blt.c

@@ -55,6 +55,9 @@ struct i915_vma *intel_emit_vma_fill_blt(struct intel_context *ce,
 	if (unlikely(err))
 		goto out_put;
 
+	/* we pinned the pool, mark it as such */
+	intel_gt_buffer_pool_mark_used(pool);
+
 	cmd = i915_gem_object_pin_map(pool->obj, pool->type);
 	if (IS_ERR(cmd)) {
 		err = PTR_ERR(cmd);
@@ -277,6 +280,9 @@ struct i915_vma *intel_emit_vma_copy_blt(struct intel_context *ce,
 	if (unlikely(err))
 		goto out_put;
 
+	/* we pinned the pool, mark it as such */
+	intel_gt_buffer_pool_mark_used(pool);
+
 	cmd = i915_gem_object_pin_map(pool->obj, pool->type);
 	if (IS_ERR(cmd)) {
 		err = PTR_ERR(cmd);

drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c

@@ -98,28 +98,6 @@ static void pool_free_work(struct work_struct *wrk)
 				      round_jiffies_up_relative(HZ));
 }
 
-static int pool_active(struct i915_active *ref)
-{
-	struct intel_gt_buffer_pool_node *node =
-		container_of(ref, typeof(*node), active);
-	struct dma_resv *resv = node->obj->base.resv;
-	int err;
-
-	if (dma_resv_trylock(resv)) {
-		dma_resv_add_excl_fence(resv, NULL);
-		dma_resv_unlock(resv);
-	}
-
-	err = i915_gem_object_pin_pages(node->obj);
-	if (err)
-		return err;
-
-	/* Hide this pinned object from the shrinker until retired */
-	i915_gem_object_make_unshrinkable(node->obj);
-
-	return 0;
-}
-
 __i915_active_call
 static void pool_retire(struct i915_active *ref)
 {
@@ -129,10 +107,13 @@ static void pool_retire(struct i915_active *ref)
 	struct list_head *list = bucket_for_size(pool, node->obj->base.size);
 	unsigned long flags;
 
-	i915_gem_object_unpin_pages(node->obj);
+	if (node->pinned) {
+		i915_gem_object_unpin_pages(node->obj);
 
-	/* Return this object to the shrinker pool */
-	i915_gem_object_make_purgeable(node->obj);
+		/* Return this object to the shrinker pool */
+		i915_gem_object_make_purgeable(node->obj);
+		node->pinned = false;
+	}
 
 	GEM_BUG_ON(node->age);
 	spin_lock_irqsave(&pool->lock, flags);
@@ -144,6 +125,19 @@ static void pool_retire(struct i915_active *ref)
 			      round_jiffies_up_relative(HZ));
 }
 
+void intel_gt_buffer_pool_mark_used(struct intel_gt_buffer_pool_node *node)
+{
+	assert_object_held(node->obj);
+
+	if (node->pinned)
+		return;
+
+	__i915_gem_object_pin_pages(node->obj);
+	/* Hide this pinned object from the shrinker until retired */
+	i915_gem_object_make_unshrinkable(node->obj);
+	node->pinned = true;
+}
+
 static struct intel_gt_buffer_pool_node *
 node_create(struct intel_gt_buffer_pool *pool, size_t sz,
 	    enum i915_map_type type)
@@ -159,7 +153,8 @@ node_create(struct intel_gt_buffer_pool *pool, size_t sz,
 
 	node->age = 0;
 	node->pool = pool;
-	i915_active_init(&node->active, pool_active, pool_retire);
+	node->pinned = false;
+	i915_active_init(&node->active, NULL, pool_retire);
 
 	obj = i915_gem_object_create_internal(gt->i915, sz);
 	if (IS_ERR(obj)) {

drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.h

@@ -18,10 +18,15 @@ struct intel_gt_buffer_pool_node *
 intel_gt_get_buffer_pool(struct intel_gt *gt, size_t size,
 			 enum i915_map_type type);
 
+void intel_gt_buffer_pool_mark_used(struct intel_gt_buffer_pool_node *node);
+
 static inline int
 intel_gt_buffer_pool_mark_active(struct intel_gt_buffer_pool_node *node,
 				 struct i915_request *rq)
 {
+	/* did we call mark_used? */
+	GEM_WARN_ON(!node->pinned);
+
 	return i915_active_add_request(&node->active, rq);
 }
 

drivers/gpu/drm/i915/gt/intel_gt_buffer_pool_types.h

@@ -31,6 +31,7 @@ struct intel_gt_buffer_pool_node {
 	};
 	unsigned long age;
 	enum i915_map_type type;
+	u32 pinned;
 };
 
 #endif /* INTEL_GT_BUFFER_POOL_TYPES_H */