drm/vmwgfx: Make user resource lookups reference-free during validation

Make the process of looking up a user resource and adding it to the
validation list reference-free unless when it's actually added to the
validation list where a single reference is taken.
This saves two locked atomic operations per command stream buffer object
handle lookup, unless there is a lookup cache hit.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -337,8 +337,6 @@ struct vmw_ctx_validation_info;
  * @last_query_ctx: Last context that submitted a query
  * @needs_post_query_barrier: Whether a query barrier is needed after
  * command submission
- * @error_resource: Pointer to hold a reference to the resource causing
- * an error
  * @staged_bindings: Cached per-context binding tracker
  * @staged_bindings_inuse: Whether the cached per-context binding tracker
  * is in use
@@ -365,7 +363,6 @@ struct vmw_sw_context{
 	struct vmw_res_cache_entry res_cache[vmw_res_max];
 	struct vmw_resource *last_query_ctx;
 	bool needs_post_query_barrier;
-	struct vmw_resource *error_resource;
 	struct vmw_ctx_binding_state *staged_bindings;
 	bool staged_bindings_inuse;
 	struct list_head staged_cmd_res;
@@ -698,6 +695,12 @@ extern int vmw_user_resource_lookup_handle(
 	uint32_t handle,
 	const struct vmw_user_resource_conv *converter,
 	struct vmw_resource **p_res);
+extern struct vmw_resource *
+vmw_user_resource_noref_lookup_handle(struct vmw_private *dev_priv,
+				      struct ttm_object_file *tfile,
+				      uint32_t handle,
+				      const struct vmw_user_resource_conv *
+				      converter);
 extern int vmw_stream_claim_ioctl(struct drm_device *dev, void *data,
 				  struct drm_file *file_priv);
 extern int vmw_stream_unref_ioctl(struct drm_device *dev, void *data,
@@ -716,6 +719,15 @@ extern int vmw_query_readback_all(struct vmw_buffer_object *dx_query_mob);
 extern void vmw_resource_evict_all(struct vmw_private *dev_priv);
 extern void vmw_resource_unbind_list(struct vmw_buffer_object *vbo);
 
+/**
+ * vmw_user_resource_noref_release - release a user resource pointer looked up
+ * without reference
+ */
+static inline void vmw_user_resource_noref_release(void)
+{
+	ttm_base_object_noref_release();
+}
+
 /**
  * Buffer object helper functions - vmwgfx_bo.c
  */

drivers/gpu/drm/vmwgfx/vmwgfx_resource.c

@@ -230,6 +230,41 @@ int vmw_user_resource_lookup_handle(struct vmw_private *dev_priv,
 	return ret;
 }
 
+/**
+ * vmw_user_resource_lookup_handle - lookup a struct resource from a
+ * TTM user-space handle and perform basic type checks
+ *
+ * @dev_priv:     Pointer to a device private struct
+ * @tfile:        Pointer to a struct ttm_object_file identifying the caller
+ * @handle:       The TTM user-space handle
+ * @converter:    Pointer to an object describing the resource type
+ * @p_res:        On successful return the location pointed to will contain
+ *                a pointer to a refcounted struct vmw_resource.
+ *
+ * If the handle can't be found or is associated with an incorrect resource
+ * type, -EINVAL will be returned.
+ */
+struct vmw_resource *
+vmw_user_resource_noref_lookup_handle(struct vmw_private *dev_priv,
+				      struct ttm_object_file *tfile,
+				      uint32_t handle,
+				      const struct vmw_user_resource_conv
+				      *converter)
+{
+	struct ttm_base_object *base;
+
+	base = ttm_base_object_noref_lookup(tfile, handle);
+	if (!base)
+		return ERR_PTR(-ESRCH);
+
+	if (unlikely(ttm_base_object_type(base) != converter->object_type)) {
+		ttm_base_object_noref_release();
+		return ERR_PTR(-EINVAL);
+	}
+
+	return converter->base_obj_to_res(base);
+}
+
 /**
  * Helper function that looks either a surface or bo.
  *