Re: [PATCH v6 2/6] qmp: add QMP command x-debug-virtio-status

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jul 12, 2021 at 06:35:33AM -0400, Jonah Palmer wrote:
> From: Laurent Vivier <lvivier@redhat.com>
> 
> This new command shows the status of a VirtIODevice
> (features, endianness and number of virtqueues)
> 
> Next patch will improve output by decoding feature bits.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>

Do we want to also decode the device status?
E.g. does it have driver, need reset, etc etc?

Also, the internal broken flag?


> ---
>  hw/virtio/virtio-stub.c |  5 ++++
>  hw/virtio/virtio.c      | 50 ++++++++++++++++++++++++++++++++
>  qapi/virtio.json        | 76 +++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 131 insertions(+)
> 
> diff --git a/hw/virtio/virtio-stub.c b/hw/virtio/virtio-stub.c
> index d4a88f5..ddb592f 100644
> --- a/hw/virtio/virtio-stub.c
> +++ b/hw/virtio/virtio-stub.c
> @@ -12,3 +12,8 @@ VirtioInfoList *qmp_x_debug_query_virtio(Error **errp)
>  {
>      return qmp_virtio_unsupported(errp);
>  }
> +
> +VirtioStatus *qmp_x_debug_virtio_status(const char* path, Error **errp)
> +{
> +    return qmp_virtio_unsupported(errp);
> +}
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index f3fc1bb..222330a 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -3896,6 +3896,56 @@ VirtioInfoList *qmp_x_debug_query_virtio(Error **errp)
>      return list;
>  }
>  
> +static VirtIODevice *virtio_device_find(const char *path)
> +{
> +    VirtIODevice *vdev;
> +
> +    QTAILQ_FOREACH(vdev, &virtio_list, next) {
> +        DeviceState *dev = DEVICE(vdev);
> +
> +        if (strcmp(dev->canonical_path, path) != 0) {
> +            continue;
> +        }
> +        return vdev;
> +    }
> +
> +    return NULL;
> +}
> +
> +VirtioStatus *qmp_x_debug_virtio_status(const char* path, Error **errp)
> +{
> +    VirtIODevice *vdev;
> +    VirtioStatus *status;
> +
> +    vdev = virtio_device_find(path);
> +    if (vdev == NULL) {
> +        error_setg(errp, "Path %s is not a VirtIO device", path);
> +        return NULL;
> +    }
> +
> +    status = g_new0(VirtioStatus, 1);
> +    status->guest_features = vdev->guest_features;
> +    status->host_features = vdev->host_features;
> +    status->backend_features = vdev->backend_features;
> +    status->device_id = vdev->device_id;
> +
> +    switch (vdev->device_endian) {
> +    case VIRTIO_DEVICE_ENDIAN_LITTLE:
> +        status->device_endian = VIRTIO_STATUS_ENDIANNESS_LITTLE;
> +        break;
> +    case VIRTIO_DEVICE_ENDIAN_BIG:
> +        status->device_endian = VIRTIO_STATUS_ENDIANNESS_BIG;
> +        break;
> +    default:
> +        status->device_endian = VIRTIO_STATUS_ENDIANNESS_UNKNOWN;
> +        break;
> +    }
> +
> +    status->num_vqs = virtio_get_num_queues(vdev);
> +
> +    return status;
> +}
> +
>  static const TypeInfo virtio_device_info = {
>      .name = TYPE_VIRTIO_DEVICE,
>      .parent = TYPE_DEVICE,
> diff --git a/qapi/virtio.json b/qapi/virtio.json
> index 804adbe..4bd09c9 100644
> --- a/qapi/virtio.json
> +++ b/qapi/virtio.json
> @@ -70,3 +70,79 @@
>  ##
>  
>  { 'command': 'x-debug-query-virtio', 'returns': ['VirtioInfo'] }
> +
> +##
> +# @VirtioStatusEndianness:
> +#
> +# Enumeration of endianness for VirtioDevice
> +#
> +# Since: 6.1
> +##
> +{ 'enum': 'VirtioStatusEndianness',
> +  'data': [ 'unknown', 'little', 'big' ]
> +}
> +
> +##
> +# @VirtioStatus:
> +#
> +# @device-id: VirtIODevice status
> +#
> +# @device-endian: VirtIODevice device_endian
> +#
> +# @guest-features: VirtIODevice guest_features
> +#
> +# @host-features: VirtIODevice host_features
> +#
> +# @backend-features: VirtIODevice backend_features
> +#
> +# @num-vqs: number of VirtIODevice queues
> +#
> +# Since: 6.1
> +#
> +##
> +
> +{ 'struct': 'VirtioStatus',
> +  'data': {
> +    'device-id': 'int',
> +    'device-endian': 'VirtioStatusEndianness',
> +    'guest-features': 'uint64',
> +    'host-features': 'uint64',
> +    'backend-features': 'uint64',
> +    'num-vqs': 'uint16'
> +  }
> +}
> +
> +##
> +# @x-debug-virtio-status:
> +#
> +# Return the status of virtio device
> +#
> +# @path: QOBject path of the VirtIODevice
> +#
> +# Returns: status of the VirtIODevice
> +#
> +# Since: 6.1
> +#
> +# Example:
> +#
> +# -> { "execute": "x-debug-virtio-status",
> +#      "arguments": {
> +#          "path": "/machine/peripheral-anon/device[3]/virtio-backend"
> +#      }
> +#   }
> +# <- { "return": {
> +#          "backend-features": 0,
> +#          "guest-features": 5111807911,
> +#          "num-vqs": 3,
> +#          "host-features": 6337593319,
> +#          "device-endian": "little",
> +#          "device-id": 1
> +#      }
> +#    }
> +#
> +##
> +
> +{ 'command': 'x-debug-virtio-status',
> +  'data': { 'path': 'str' },
> +  'returns': 'VirtioStatus'
> +}
> -- 
> 1.8.3.1