drm/i915: Allow parsing of unsized batches

commit 435e8fc0 upstream.

In "drm/i915: Add support for mandatory cmdparsing" we introduced the
concept of mandatory parsing. This allows the cmdparser to be invoked
even when user passes batch_len=0 to the execbuf ioctl's.

However, the cmdparser needs to know the extents of the buffer being
scanned. Refactor the code to ensure the cmdparser uses the actual
object size, instead of the incoming length, if user passes 0.
Signed-off-by: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Tyler Hicks <tyhicks@canonical.com>
Reviewed-by: Chris Wilson <chris.p.wilson@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -55,6 +55,7 @@ struct i915_execbuffer_params {
 	struct i915_vma			*batch;
 	u32				dispatch_flags;
 	u32				args_batch_start_offset;
+	u64				args_batch_len;
 	struct intel_engine_cs          *engine;
 	struct i915_gem_context         *ctx;
 	struct drm_i915_gem_request     *request;
@@ -1506,13 +1507,10 @@ execbuf_submit(struct i915_execbuffer_params *params,
 			return ret;
 	}
 
-	exec_len   = args->batch_len;
+	exec_len   = params->args_batch_len;
 	exec_start = params->batch->node.start +
 		     params->args_batch_start_offset;
 
-	if (exec_len == 0)
-		exec_len = params->batch->size - params->args_batch_start_offset;
-
 	ret = params->engine->emit_bb_start(params->request,
 					    exec_start, exec_len,
 					    params->dispatch_flags);
@@ -1748,6 +1746,10 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	}
 
 	params->args_batch_start_offset = args->batch_start_offset;
+	params->args_batch_len = args->batch_len;
+	if (args->batch_len == 0)
+		params->args_batch_len = params->batch->size - params->args_batch_start_offset;
+
 	if (intel_engine_requires_cmd_parser(engine) ||
 	    (intel_engine_using_cmd_parser(engine) && args->batch_len)) {
 		struct i915_vma *vma;
@@ -1755,8 +1757,8 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		vma = i915_gem_execbuffer_parse(engine, &shadow_exec_entry,
 						params->batch->obj,
 						eb, vm,
-						args->batch_start_offset,
-						args->batch_len);
+						params->args_batch_start_offset,
+						params->args_batch_len);
 		if (IS_ERR(vma)) {
 			ret = PTR_ERR(vma);
 			goto err;