drm/i915/gvt/kvmgt: return meaningful error for vgpu creating failure

The vgpu_create() routine we called returns meaningful errors to indicate
failures, so we'd better to pass it to our caller, the mdev framework,
whereby the sysfs is able to tell userspace what happened.
Signed-off-by: Jike Song <jike.song@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/kvmgt.c

@@ -398,6 +398,7 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
 	struct intel_vgpu_type *type;
 	struct device *pdev;
 	void *gvt;
+	int ret;
 
 	pdev = mdev_parent_dev(mdev);
 	gvt = kdev_to_i915(pdev)->gvt;
@@ -406,13 +407,15 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
 	if (!type) {
 		gvt_err("failed to find type %s to create\n",
 						kobject_name(kobj));
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out;
 	}
 
 	vgpu = intel_gvt_ops->vgpu_create(gvt, type);
 	if (IS_ERR_OR_NULL(vgpu)) {
-		gvt_err("create intel vgpu failed\n");
-		return -EINVAL;
+		ret = vgpu == NULL ? -EFAULT : PTR_ERR(vgpu);
+		gvt_err("failed to create intel vgpu: %d\n", ret);
+		goto out;
 	}
 
 	INIT_WORK(&vgpu->vdev.release_work, intel_vgpu_release_work);
@@ -422,7 +425,10 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
 
 	gvt_dbg_core("intel_vgpu_create succeeded for mdev: %s\n",
 		     dev_name(mdev_dev(mdev)));
-	return 0;
+	ret = 0;
+
+out:
+	return ret;
 }
 
 static int intel_vgpu_remove(struct mdev_device *mdev)