Re: [PATCH v9 7/8] qmp: add QMP command x-query-virtio-queue-element

[Markus Armbruster <armbru@redhat.com>]

Jonah Palmer <jonah.palmer@oracle.com> writes:

> From: Laurent Vivier <lvivier@redhat.com>
>
> This new command shows the information of a VirtQueue element.
>
> Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>

[...]

> diff --git a/qapi/virtio.json b/qapi/virtio.json
> index 0f65044..c57fbc5 100644
> --- a/qapi/virtio.json
> +++ b/qapi/virtio.json
> @@ -1061,3 +1061,180 @@
>  { 'command': 'x-query-virtio-vhost-queue-status',
>    'data': { 'path': 'str', 'queue': 'uint16' },
>    'returns': 'VirtVhostQueueStatus', 'features': [ 'unstable' ] }
> +
> +##
> +# @VirtioRingDescFlags:
> +#
> +# An enumeration of the virtio ring descriptor flags
> +#
> +# Since: 6.3
> +#
> +##
> +
> +{ 'enum': 'VirtioRingDescFlags',
> +  'data': [ 'next', 'write', 'indirect', 'avail', 'used' ]
> +}
> +
> +##
> +# @VirtioRingDesc:
> +#
> +# Information regarding the VRing descriptor area
> +#
> +# @addr: guest physical address of the descriptor data
> +#
> +# @len: length of the descriptor data
> +#
> +# @flags: list of descriptor flags
> +#
> +# Since: 6.3
> +#
> +##
> +
> +{ 'struct': 'VirtioRingDesc',
> +  'data': { 'addr': 'uint64',
> +            'len': 'uint32',
> +            'flags': [ 'VirtioRingDescFlags' ] } }
> +
> +##
> +# @VirtioRingAvail:
> +#
> +# Information regarding the avail VRing (also known as the driver
> +# area)
> +#
> +# @flags: VRingAvail flags
> +#
> +# @idx: VRingAvail index
> +#
> +# @ring: VRingAvail ring[] entry at provided index
> +#
> +# Since: 6.3
> +#
> +##
> +
> +{ 'struct': 'VirtioRingAvail',
> +  'data': { 'flags': 'uint16',
> +            'idx': 'uint16',
> +            'ring': 'uint16' } }
> +
> +##
> +# @VirtioRingUsed:
> +#
> +# Information regarding the used VRing (also known as the device
> +# area)
> +#
> +# @flags: VRingUsed flags
> +#
> +# @idx: VRingUsed index
> +#
> +# Since: 6.3
> +#
> +##
> +
> +{ 'struct': 'VirtioRingUsed',
> +  'data': { 'flags': 'uint16',
> +            'idx': 'uint16' } }
> +
> +##
> +# @VirtioQueueElement:
> +#
> +# Information regarding a VirtQueue VirtQueueElement including
> +# descriptor, driver, and device areas
> +#
> +# @device-name: name of the VirtIODevice which this VirtQueue belongs
> +#               to (for reference)
> +#
> +# @index: index of the element in the queue
> +#
> +# @ndescs: number of descriptors
> +#
> +# @descs: list of the descriptors

Can @ndescs ever be not equal to the length of @descs?

If no, it's redundant.

> +#
> +# @avail: VRingAvail info
> +#
> +# @used: VRingUsed info
> +#
> +# Since: 6.3
> +#
> +##
> +
> +{ 'struct': 'VirtioQueueElement',
> +  'data': { 'device-name': 'str',
> +            'index': 'uint32',
> +            'ndescs': 'uint32',
> +            'descs': [ 'VirtioRingDesc' ],
> +            'avail': 'VirtioRingAvail',
> +            'used': 'VirtioRingUsed' } }
> +
> +##
> +# @x-query-virtio-queue-element:
> +#
> +# Return the information about a VirtQueue VirtQueueElement (by
> +# default looks at the head of the queue)
> +#
> +# @path: VirtIODevice canonical QOM path
> +#
> +# @queue: VirtQueue index to examine
> +#
> +# @index: the index in the queue, by default head
> +#
> +# Features:
> +# @unstable: This command is meant for debugging.
> +#
> +# Returns: VirtioQueueElement information
> +#
> +# Since: 6.3
> +#
> +# Examples:
> +#
> +# 1. Introspect on virtio-net virtqueue 0 at index 5
> +#
> +# -> { "execute": "x-query-virtio-queue-element",
> +#      "arguments": { "path": "/machine/peripheral-anon/device[1]/virtio-backend",
> +#                     "queue": 0,
> +#                     "index": 5 }
> +#    }
> +# <- { "return": {
> +#         "index": 5,
> +#         "ndescs": 1,
> +#         "device-name": "virtio-net",
> +#         "descs": [ { "flags": ["write"], "len": 1536, "addr": 5257305600 } ],
> +#         "avail": { "idx": 256, "flags": 0, "ring": 5 },
> +#         "used": { "idx": 13, "flags": 0 } }
> +#    }
> +#
> +# 2. Introspect on virtio-crypto virtqueue 1 at head
> +#
> +# -> { "execute": "x-query-virtio-queue-element",
> +#      "arguments": { "path": "/machine/peripheral/crypto0/virtio-backend",
> +#                     "queue": 1 }
> +#    }
> +# <- { "return": {
> +#         "index": 0,
> +#         "ndescs": 1,
> +#         "device-name": "virtio-crypto",
> +#         "descs": [ { "flags": [], "len": 0, "addr": 8080268923184214134 } ],
> +#         "avail": { "idx": 280, "flags": 0, "ring": 0 },
> +#         "used": { "idx": 280, "flags": 0 } }
> +#    }
> +#
> +# 3. Introspect on virtio-scsi virtqueue 2 at head
> +#
> +# -> { "execute": "x-query-virtio-queue-element",
> +#      "arguments": { "path": "/machine/peripheral-anon/device[2]/virtio-backend",
> +#                     "queue": 2 }
> +#    }
> +# <- { "return": {
> +#         "index": 19,
> +#         "ndescs": 1,
> +#         "device-name": "virtio-scsi",
> +#         "descs": [ { "flags": ["used", "indirect", "write"], "len": 4099327944,
> +#                      "addr": 12055409292258155293 } ],
> +#         "avail": { "idx": 1147, "flags": 0, "ring": 19 },
> +#         "used": { "idx": 1147, "flags": 0 } }
> +#    }
> +#
> +##
> +
> +{ 'command': 'x-query-virtio-queue-element',
> +  'data': { 'path': 'str', 'queue': 'uint16', '*index': 'uint16' },
> +  'returns': 'VirtioQueueElement', 'features': [ 'unstable' ] }