[RFC v2 0/6] hmp,qmp: Add some commands to introspect virtio devices

[Laurent Vivier]

This series introduces new QMP/HMP commands to dump the status
of a a virtio device at different levels.

1. Main command

 HMP Only:

     virtio [subcommand]

   Example:

    List all sub-commands:

    (qemu) virtio
    virtio query  -- List all available virtio devices
    virtio status path -- Display status of a given virtio device
    virtio queue-status path queue -- Display status of a given virtio queue
    virtio queue-element path queue [index] -- Display element of a given 
virtio queue

2. List available virtio devices in the machine

  HMP Form:

    virtio query

  Example:

    (qemu) virtio query
    /machine/peripheral-anon/device[3]/virtio-backend [virtio-net]
    /machine/peripheral-anon/device[1]/virtio-backend [virtio-serial]
    /machine/peripheral-anon/device[0]/virtio-backend [virtio-blk]

  QMP Form:

    { 'command': 'query-virtio', 'returns': ['VirtioInfo'] }

  Example:

  -> { "execute": "query-virtio" }
  <- { "return": [
         {
             "path": "/machine/peripheral-anon/device[3]/virtio-backend",
             "type": "virtio-net"
         },
         {
             "path": "/machine/peripheral-anon/device[1]/virtio-backend",
             "type": "virtio-serial"
         },
         {
             "path": "/machine/peripheral-anon/device[0]/virtio-backend",
             "type": "virtio-blk"
         }
       ]
     }

3. Display status of a given virtio device

  HMP Form:

    virtio status <path>

  Example:

    (qemu) virtio status /machine/peripheral-anon/device[3]/virtio-backend
    /machine/peripheral-anon/device[3]/virtio-backend:
      Device Id:        1
      Guest features:   event-idx, indirect-desc, version-1
                        ctrl-mac-addr, guest-announce, ctrl-vlan, ctrl-rx, 
ctrl-vq, status, mrg-rxbuf, host-ufo, host-ecn, host-tso6, host-tso4, 
guest-ufo, guest-ecn, guest-tso6, guest-tso4, mac, ctrl-guest-offloads, 
guest-csum, csum
      Host features:    event-idx, indirect-desc, bad-feature, version-1, 
any-layout, notify-on-empty
                        gso, ctrl-mac-addr, guest-announce, ctrl-rx-extra, 
ctrl-vlan, ctrl-rx, ctrl-vq, status, mrg-rxbuf, host-ufo, host-ecn, host-tso6, 
host-tso4, guest-ufo, guest-ecn, guest-tso6, guest-tso4, mac, 
ctrl-guest-offloads, guest-csum, csum
      Backend features:
      Endianness:       little
      VirtQueues:       3

  QMP Form:

    { 'command': 'virtio-status',
      'data': { 'path': 'str' },
      'returns': 'VirtioStatus'
    }

  Example:

  -> { "execute": "virtio-status",
       "arguments": {
           "path": "/machine/peripheral-anon/device[3]/virtio-backend"
       }
    }
  <- { "return": {
       "device-endian": "little",
       "device-id": 1,
       "backend-features": {
         "device": {
           "type": "virtio-net",
           "data": []
         },
         "unknown": 0,
         "transport": []
       },
       "num-vqs": 3,
       "guest-features": {
         "device": {
           "type": "virtio-net",
           "data": [ "ctrl-mac-addr", "guest-announce", "ctrl-vlan", "ctrl-rx",
                     "ctrl-vq", "status", "mrg-rxbuf", "host-ufo", "host-ecn",
                     "host-tso6", "host-tso4", "guest-ufo", "guest-ecn",
                     "guest-tso6", "guest-tso4", "mac", "ctrl-guest-offloads",
                     "guest-csum", "csum" ]
         },
         "unknown": 0,
         "transport": [ "event-idx", "indirect-desc", "version-1" ]
       },
       "host-features": {
         "device": {
           "type": "virtio-net",
           "data": [ "gso", "ctrl-mac-addr", "guest-announce", "ctrl-rx-extra",
                     "ctrl-vlan", "ctrl-rx", "ctrl-vq", "status", "mrg-rxbuf",
                     "host-ufo", "host-ecn", "host-tso6", "host-tso4",
                     "guest-ufo", "guest-ecn", "guest-tso6", "guest-tso4",
                     "mac", "ctrl-guest-offloads", "guest-csum", "csum" ]
           },
           "unknown": 0,
           "transport": [ "event-idx", "indirect-desc", "bad-feature",
                          "version-1", "any-layout", "notify-on-empty" ]
         }
       }
     }

4. Display status of a given virtio queue

  HMP Form:

    virtio queue-status <path> <queue>

  Example:

    (qemu) virtio queue-status 
/machine/peripheral-anon/device[3]/virtio-backend 0
    /machine/peripheral-anon/device[3]/virtio-backend:
      index:                0
      inuse:                0
      last_avail_idx:       61
      shadow_avail_idx:     292
      signalled_used:       61
      signalled_used_valid: 1
      VRing:
        num:         256
        num_default: 256
        align:       4096
        desc:        0x000000006c352000
        avail:       0x000000006c353000
        used:        0x000000006c353240

  QMP Form:

    { 'command': 'virtio-queue-status',
      'data': { 'path': 'str', 'queue': 'uint16' },
      'returns': 'VirtQueueStatus'
    }

  Example:

  -> { "execute": "virtio-queue-status",
       "arguments": {
           "path": "/machine/peripheral-anon/device[3]/virtio-backend",
           "queue": 0
       }
    }
  <- { "return": {
       "signalled_used": 373,
       "inuse": 0,
       "vring_desc": 864411648,
       "vring_num_default": 256,
       "signalled_used_valid": 1,
       "vring_avail": 864415744,
       "last_avail_idx": 373,
       "queue_index": 0,
       "vring_used": 864416320,
       "shadow_avail_idx": 619,
       "used_idx": 373,
       "vring_num": 256,
       "vring_align": 4096
       }
     }

5. Display element of a given virtio queue

  HMP Form:

    virtio queue-element <path> <queue> [index]

  Example:

    Dump the information of the head element of the first queue of
    the first virtio device::

      (qemu) virtio 
queue-element/machine/peripheral-anon/device[3]/virtio-backend 0
      index:  67
      ndescs: 1
      descs:  addr 0x6fe69800 len 1536 (write)

      (qemu) xp/128bx 0x6fe69800
      000000006fe69800: 0x02 0x00 0x00 0x00 0x00 0x00 0x00 0x00
      000000006fe69808: 0x00 0x00 0x01 0x00 0x52 0x54 0x00 0x12
      000000006fe69810: 0x34 0x56 0x52 0x54 0x00 0x09 0x51 0xde
      000000006fe69818: 0x08 0x00 0x45 0x00 0x00 0x4c 0x8f 0x32

    device[3] is a virtio-net device and we can see in the element buffer the
    MAC address of the card::

      [root@localhost ~]# ip link show ens4
      2: ens4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state 
UP m0
          link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff

    and the MAC address of the gateway::

      [root@localhost ~]# arp -a
      _gateway (192.168.122.1) at 52:54:00:09:51:de [ether] on ens4

  QMP Form:

    { 'command': 'virtio-queue-element',
      'data': { 'path': 'str', 'queue': 'uint16', '*index': 'uint16' },
      'returns': 'VirtioQueueElement'
    }

  Example:

  -> { "execute": "virtio-queue-element",
       "arguments": {
           "path": "/machine/peripheral-anon/device[3]/virtio-backend",
           "queue": 0
       }
    }
  -> { "return": {
          "index": 109,
          "ndescs": 1,
          "descs": [
              { "flags": [ "write" ], "len": 1536, "addr": 853145600 }
          ]
       }
    }

v2: introduce VirtioType enum
    use an enum for the endianness
    change field names to stick to naming conventions (s/_/-/)
    add a patch to decode feature bits
    don't check if the queue is empty to allow to displa old elements
    use enum for desc flags
    manage indirect desc
    decode device features in the HMP command

Laurent Vivier (6):
  qmp: add QMP command query-virtio
  qmp: add QMP command virtio-status
  qmp: decode feature bits in virtio-status
  qmp: add QMP command virtio-queue-status
  qmp: add QMP command virtio-queue-element
  hmp: add virtio commands

 Makefile                     |   2 +-
 Makefile.target              |   7 +-
 docs/system/monitor.rst      |   2 +
 hmp-commands-virtio.hx       | 160 +++++++++++
 hmp-commands.hx              |  10 +
 hw/block/virtio-blk.c        |  23 ++
 hw/char/virtio-serial-bus.c  |  11 +
 hw/display/virtio-gpu-base.c |  10 +
 hw/net/virtio-net.c          |  35 +++
 hw/scsi/virtio-scsi.c        |  12 +
 hw/virtio/Makefile.objs      |   2 +
 hw/virtio/virtio-balloon.c   |  13 +
 hw/virtio/virtio-iommu.c     |  14 +
 hw/virtio/virtio-stub.c      |  32 +++
 hw/virtio/virtio.c           | 537 +++++++++++++++++++++++++++++++++++
 include/hw/virtio/virtio.h   |  14 +
 include/monitor/hmp.h        |   4 +
 monitor/misc.c               |  17 ++
 qapi/Makefile.objs           |   2 +-
 qapi/qapi-schema.json        |   1 +
 qapi/virtio.json             | 502 ++++++++++++++++++++++++++++++++
 tests/qtest/qmp-cmd-test.c   |   1 +
 22 files changed, 1407 insertions(+), 4 deletions(-)
 create mode 100644 hmp-commands-virtio.hx
 create mode 100644 hw/virtio/virtio-stub.c
 create mode 100644 qapi/virtio.json

-- 
2.25.2