drm/i915: Tidy batch pool logic

Move the madvise logic out of the execbuffer main path into the
relatively rare allocation path, making the execbuffer manipulation less
fragile.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -869,6 +869,9 @@ static u32 *copy_batch(struct drm_i915_gem_object *dest_obj,
 	    batch_len + batch_start_offset > src_obj->base.size)
 		return ERR_PTR(-E2BIG);
 
+	if (WARN_ON(dest_obj->pages_pin_count == 0))
+		return ERR_PTR(-ENODEV);
+
 	ret = i915_gem_obj_prepare_shmem_read(src_obj, &needs_clflush);
 	if (ret) {
 		DRM_DEBUG_DRIVER("CMD: failed to prepare shadow batch\n");
@@ -882,13 +885,6 @@ static u32 *copy_batch(struct drm_i915_gem_object *dest_obj,
 		goto unpin_src;
 	}
 
-	ret = i915_gem_object_get_pages(dest_obj);
-	if (ret) {
-		DRM_DEBUG_DRIVER("CMD: Failed to get pages for shadow batch\n");
-		goto unmap_src;
-	}
-	i915_gem_object_pin_pages(dest_obj);
-
 	ret = i915_gem_object_set_to_cpu_domain(dest_obj, true);
 	if (ret) {
 		DRM_DEBUG_DRIVER("CMD: Failed to set shadow batch to CPU\n");
@@ -898,7 +894,6 @@ static u32 *copy_batch(struct drm_i915_gem_object *dest_obj,
 	dst = vmap_batch(dest_obj, 0, batch_len);
 	if (!dst) {
 		DRM_DEBUG_DRIVER("CMD: Failed to vmap shadow batch\n");
-		i915_gem_object_unpin_pages(dest_obj);
 		ret = -ENOMEM;
 		goto unmap_src;
 	}
@@ -1129,7 +1124,6 @@ int i915_parse_cmds(struct intel_engine_cs *ring,
 	}
 
 	vunmap(batch_base);
-	i915_gem_object_unpin_pages(shadow_batch_obj);
 
 	return ret;
 }

drivers/gpu/drm/i915/i915_gem_batch_pool.c

@@ -67,25 +67,23 @@ void i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool)
 					 struct drm_i915_gem_object,
 					 batch_pool_list);
 
-		WARN_ON(obj->active);
-
-		list_del_init(&obj->batch_pool_list);
+		list_del(&obj->batch_pool_list);
 		drm_gem_object_unreference(&obj->base);
 	}
 }
 
 /**
- * i915_gem_batch_pool_get() - select a buffer from the pool
+ * i915_gem_batch_pool_get() - allocate a buffer from the pool
  * @pool: the batch buffer pool
  * @size: the minimum desired size of the returned buffer
  *
- * Finds or allocates a batch buffer in the pool with at least the requested
- * size. The caller is responsible for any domain, active/inactive, or
- * purgeability management for the returned buffer.
+ * Returns an inactive buffer from @pool with at least @size bytes,
+ * with the pages pinned. The caller must i915_gem_object_unpin_pages()
+ * on the returned object.
  *
  * Note: Callers must hold the struct_mutex
  *
- * Return: the selected batch buffer object
+ * Return: the buffer object or an error pointer
  */
 struct drm_i915_gem_object *
 i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
@@ -98,7 +96,6 @@ i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
 
 	list_for_each_entry_safe(tmp, next,
 				 &pool->cache_list, batch_pool_list) {
-
 		if (tmp->active)
 			continue;
 
@@ -114,25 +111,27 @@ i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
 		 * but not 'too much' bigger. A better way to do this
 		 * might be to bucket the pool objects based on size.
 		 */
-		if (tmp->base.size >= size &&
-		    tmp->base.size <= (2 * size)) {
+		if (tmp->base.size >= size && tmp->base.size <= 2 * size) {
 			obj = tmp;
 			break;
 		}
 	}
 
-	if (!obj) {
+	if (obj == NULL) {
+		int ret;
+
 		obj = i915_gem_alloc_object(pool->dev, size);
-		if (!obj)
+		if (obj == NULL)
 			return ERR_PTR(-ENOMEM);
 
-		list_add_tail(&obj->batch_pool_list, &pool->cache_list);
-	}
-	else
-		/* Keep list in LRU order */
-		list_move_tail(&obj->batch_pool_list, &pool->cache_list);
+		ret = i915_gem_object_get_pages(obj);
+		if (ret)
+			return ERR_PTR(ret);
 
-	obj->madv = I915_MADV_WILLNEED;
+		obj->madv = I915_MADV_DONTNEED;
+	}
 
+	list_move_tail(&obj->batch_pool_list, &pool->cache_list);
+	i915_gem_object_pin_pages(obj);
 	return obj;
 }

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -37,7 +37,6 @@
 #define  __EXEC_OBJECT_HAS_FENCE (1<<30)
 #define  __EXEC_OBJECT_NEEDS_MAP (1<<29)
 #define  __EXEC_OBJECT_NEEDS_BIAS (1<<28)
-#define  __EXEC_OBJECT_PURGEABLE (1<<27)
 
 #define BATCH_OFFSET_BIAS (256*1024)
 
@@ -224,12 +223,7 @@ i915_gem_execbuffer_unreserve_vma(struct i915_vma *vma)
 	if (entry->flags & __EXEC_OBJECT_HAS_PIN)
 		vma->pin_count--;
 
-	if (entry->flags & __EXEC_OBJECT_PURGEABLE)
-		obj->madv = I915_MADV_DONTNEED;
-
-	entry->flags &= ~(__EXEC_OBJECT_HAS_FENCE |
-			  __EXEC_OBJECT_HAS_PIN |
-			  __EXEC_OBJECT_PURGEABLE);
+	entry->flags &= ~(__EXEC_OBJECT_HAS_FENCE | __EXEC_OBJECT_HAS_PIN);
 }
 
 static void eb_destroy(struct eb_vmas *eb)
@@ -1165,11 +1159,13 @@ i915_gem_execbuffer_parse(struct intel_engine_cs *ring,
 	if (ret)
 		goto err;
 
+	i915_gem_object_unpin_pages(shadow_batch_obj);
+
 	memset(shadow_exec_entry, 0, sizeof(*shadow_exec_entry));
 
 	vma = i915_gem_obj_to_ggtt(shadow_batch_obj);
 	vma->exec_entry = shadow_exec_entry;
-	vma->exec_entry->flags = __EXEC_OBJECT_PURGEABLE | __EXEC_OBJECT_HAS_PIN;
+	vma->exec_entry->flags = __EXEC_OBJECT_HAS_PIN;
 	drm_gem_object_reference(&shadow_batch_obj->base);
 	list_add_tail(&vma->exec_list, &eb->vmas);
 
@@ -1178,6 +1174,7 @@ i915_gem_execbuffer_parse(struct intel_engine_cs *ring,
 	return shadow_batch_obj;
 
 err:
+	i915_gem_object_unpin_pages(shadow_batch_obj);
 	if (ret == -EACCES) /* unhandled chained batch */
 		return batch_obj;
 	else