IBM Z uses ccw devices and the case for 'virtio-blk-ccw' with devicemapper doesn't properly work. It requires a special handling. That probably requires changes in govmm, the agent and the runtime. I saw from #1113 that you might plan to drop the 'virtio-blk'' option. Therefore, I don't know if it's worthy to implement this functionality. The option 'virtio-scsi' works.