xvdi_ring_get_response
rsp = xvdi_ring_get_response(ring->ri_ring);
blkif_response_t *rsp = xvdi_ring_get_response(vdp->xs_ring);
while (resp = xvdi_ring_get_response(xbr)) {
void* xvdi_ring_get_response(xendev_ring_t *);