drm/virtio: implement blob resources: report blob mem to userspace

The stride field has never been used, so repurpose it to be
"blob_mem". This way, userspace can know the memory properties
of the blob if it's passed between userspace processes and
no suitable userspace API exists to transmit that knowledge.
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Acked-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200924003214.662-17-gurchetansingh@chromium.orgSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_ioctl.c

@@ -301,6 +301,9 @@ static int virtio_gpu_resource_info_ioctl(struct drm_device *dev, void *data,
 
 	ri->size = qobj->base.base.size;
 	ri->res_handle = qobj->hw_res_handle;
+	if (qobj->host3d_blob || qobj->guest_blob)
+		ri->blob_mem = qobj->blob_mem;
+
 	drm_gem_object_put(gobj);
 	return 0;
 }