QMP> {
QMP>   "execute":"blockdev-add",
QMP>   "arguments":{
QMP>     "driver":"qcow2",
QMP>     "node-name":"node1",
QMP>     "file":{
QMP>       "driver":"file",
QMP>       "filename":"/export/target.qcow2"
QMP>     },
QMP>     "backing":{
QMP>       "driver":"qcow2",
QMP>       "file":{
QMP>         "driver":"file",
QMP>         "filename":"/export/base.qcow2"
QMP>       }
QMP>     }
QMP>   }
QMP> }
{"return": {}}

QMP> { "execute": "query-block" }
{
  "return":[
    {
      "io-status":"ok",
      "device":"virtio0",
      "locked":false,
      "removable":false,
      "inserted":{
        "iops_rd":0,
        "detect_zeroes":"off",
        "image":{
          "virtual-size":41126400,
          "filename":"./base.qcow2",
          "cluster-size":65536,
          "format":"qcow2",
          "actual-size":19886080,
          "format-specific":{
            "type":"qcow2",
            "data":{
              "compat":"0.10",
              "refcount-bits":16
            }
          },
          "dirty-flag":false
        },
        "iops_wr":0,
        "ro":false,
        "node-name":"#block194",
        "backing_file_depth":0,
        "drv":"qcow2",
        "iops":0,
        "bps_wr":0,
        "write_threshold":0,
        "encrypted":false,
        "bps":0,
        "bps_rd":0,
        "cache":{
          "no-flush":false,
          "direct":false,
          "writeback":true
        },
        "file":"./base.qcow2",
        "encryption_key_missing":false
      },
      "type":"unknown"
    }
  ]
}