void vrend_sync_make_current(virgl_gl_context gl_cxt) {
   GLsync sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
   vrend_clicbs->make_current(gl_cxt);
   glWaitSync(sync, 0, GL_TIMEOUT_IGNORED);
   glDeleteSync(sync);
}
void vrend_sync_make_current(virgl_gl_context gl_cxt) {
   GLsync sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
   vrend_clicbs->make_current(gl_cxt);
   glWaitSync(sync, 0, GL_TIMEOUT_IGNORED);
   glDeleteSync(sync);
}