vhost-user-gpu: glFlush before notifying clients

For similar reasons as commit 3af16718 ("spice: flush on GL update
before notifying client"), vhost-user-gpu must ensure the GL state is
flushed before sharing its rendering result.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210312100108.2706195-3-marcandre.lureau@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

contrib/vhost-user-gpu/meson.build

@@ -2,7 +2,7 @@ if 'CONFIG_TOOLS' in config_host and 'CONFIG_VIRGL' in config_host \
     and 'CONFIG_GBM' in config_host and 'CONFIG_LINUX' in config_host \
     and pixman.found()
   executable('vhost-user-gpu', files('vhost-user-gpu.c', 'virgl.c', 'vugbm.c'),
-             dependencies: [qemuutil, pixman, gbm, virgl, vhost_user],
+             dependencies: [qemuutil, pixman, gbm, virgl, vhost_user, opengl],
              install: true,
              install_dir: get_option('libexecdir'))
 

contrib/vhost-user-gpu/virgl.c

@@ -16,6 +16,8 @@
 #include <virglrenderer.h>
 #include "virgl.h"
 
+#include <epoxy/gl.h>
+
 void
 vg_virgl_update_cursor_data(VuGpu *g, uint32_t resource_id,
                             gpointer data)
@@ -372,6 +374,7 @@ virgl_cmd_resource_flush(VuGpu *g,
 
     VUGPU_FILL_CMD(rf);
 
+    glFlush();
     if (!rf.resource_id) {
         g_debug("bad resource id for flush..?");
         return;