UBLKSRV_CMD_BUF_OFFSET
end = UBLKSRV_CMD_BUF_OFFSET + ub->dev_info.nr_hw_queues * max_sz;
if (phys_off < UBLKSRV_CMD_BUF_OFFSET || phys_off >= end)
q_id = (phys_off - UBLKSRV_CMD_BUF_OFFSET) / max_sz;
off = UBLKSRV_CMD_BUF_OFFSET + q->q_id * ublk_queue_max_cmd_buf_sz();