drm/virtgpu api: host visible feature

This exposes the host visible feature to userspace.  Without it,
it is an error to specify BLOB_MEM_HOST3D with
BLOG_FLAG_USE_MAPPABLE.
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Acked-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Acked-by: Lingfeng Yang <lfy@google.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200924003214.662-6-gurchetansingh@chromium.orgSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

include/uapi/drm/virtgpu_drm.h

@@ -73,6 +73,7 @@ struct drm_virtgpu_execbuffer {
 #define VIRTGPU_PARAM_3D_FEATURES 1 /* do we have 3D features in the hw */
 #define VIRTGPU_PARAM_CAPSET_QUERY_FIX 2 /* do we have the capset fix */
 #define VIRTGPU_PARAM_RESOURCE_BLOB 3 /* DRM_VIRTGPU_RESOURCE_CREATE_BLOB */
+#define VIRTGPU_PARAM_HOST_VISIBLE 4 /* Host blob resources are mappable */
 
 struct drm_virtgpu_getparam {
 	__u64 param;