vhost-user-gpu: add a configuration flag for dmabuf usage

Let's inform VirtioGPUBase that vhost-user-gpu require DMABUF messages.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210204105232.834642-11-marcandre.lureau@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/display/vhost-user-gpu.c

@@ -547,6 +547,8 @@ vhost_user_gpu_device_realize(DeviceState *qdev, Error **errp)
         return;
     }
 
+    /* existing backend may send DMABUF, so let's add that requirement */
+    g->parent_obj.conf.flags |= 1 << VIRTIO_GPU_FLAG_DMABUF_ENABLED;
     if (virtio_has_feature(g->vhost->dev.features, VIRTIO_GPU_F_VIRGL)) {
         g->parent_obj.conf.flags |= 1 << VIRTIO_GPU_FLAG_VIRGL_ENABLED;
     }

include/hw/virtio/virtio-gpu.h

@@ -71,6 +71,7 @@ enum virtio_gpu_base_conf_flags {
     VIRTIO_GPU_FLAG_VIRGL_ENABLED = 1,
     VIRTIO_GPU_FLAG_STATS_ENABLED,
     VIRTIO_GPU_FLAG_EDID_ENABLED,
+    VIRTIO_GPU_FLAG_DMABUF_ENABLED,
 };
 
 #define virtio_gpu_virgl_enabled(_cfg) \
@@ -79,6 +80,8 @@ enum virtio_gpu_base_conf_flags {
     (_cfg.flags & (1 << VIRTIO_GPU_FLAG_STATS_ENABLED))
 #define virtio_gpu_edid_enabled(_cfg) \
     (_cfg.flags & (1 << VIRTIO_GPU_FLAG_EDID_ENABLED))
+#define virtio_gpu_dmabuf_enabled(_cfg) \
+    (_cfg.flags & (1 << VIRTIO_GPU_FLAG_DMABUF_ENABLED))
 
 struct virtio_gpu_base_conf {
     uint32_t max_outputs;