Re: [RFC 1/2] qapi/virtio: introduce the "show-bits" argument for x-query-virtio-status

[Markus Armbruster <armbru@redhat.com>]

Hyman Huang <yong.huang@smartx.com> writes:

> This patch allows to display feature and status bits in virtio-status.
>
> An optional argument is introduced: show-bits. For example:
> {"execute": "x-query-virtio-status",
>  "arguments": {"path": "/machine/peripheral-anon/device[1]/virtio-backend",
>                "show-bits": true}
>
> Features and status bits could be helpful for applications to compare
> directly. For instance, when an upper application aims to ensure the
> virtio negotiation correctness between guest, QEMU, and OVS-DPDK, it use
> the "ovs-vsctl list interface" command to retrieve interface features
> (in number format) and the QMP command x-query-virtio-status to retrieve
> vhost-user net device features. If "show-bits" is added, the application
> can compare the two features directly; No need to encoding the features
> returned by the QMP command.
>
> This patch also serves as a preparation for the next one, which implements
> a vhost-user test case about acked features of vhost-user protocol.
>
> Note that since the matching HMP command is typically used for human,
> leave it unchanged.
>
> Signed-off-by: Hyman Huang <yong.huang@smartx.com>
> ---
>  hw/virtio/virtio-hmp-cmds.c |  2 +-
>  hw/virtio/virtio-qmp.c      | 21 +++++++++++++++-
>  qapi/virtio.json            | 49 ++++++++++++++++++++++++++++++++++---
>  3 files changed, 67 insertions(+), 5 deletions(-)
>
> diff --git a/hw/virtio/virtio-hmp-cmds.c b/hw/virtio/virtio-hmp-cmds.c
> index 477c97dea2..3774f3d4bf 100644
> --- a/hw/virtio/virtio-hmp-cmds.c
> +++ b/hw/virtio/virtio-hmp-cmds.c
> @@ -108,7 +108,7 @@ void hmp_virtio_status(Monitor *mon, const QDict *qdict)
>  {
>      Error *err = NULL;
>      const char *path = qdict_get_try_str(qdict, "path");
> -    VirtioStatus *s = qmp_x_query_virtio_status(path, &err);
> +    VirtioStatus *s = qmp_x_query_virtio_status(path, false, false, &err);
>  
>      if (err != NULL) {
>          hmp_handle_error(mon, err);
> diff --git a/hw/virtio/virtio-qmp.c b/hw/virtio/virtio-qmp.c
> index 1dd96ed20f..2e92bf28ac 100644
> --- a/hw/virtio/virtio-qmp.c
> +++ b/hw/virtio/virtio-qmp.c
> @@ -718,10 +718,15 @@ VirtIODevice *qmp_find_virtio_device(const char *path)
>      return VIRTIO_DEVICE(dev);
>  }
>  
> -VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
> +VirtioStatus *qmp_x_query_virtio_status(const char *path,
> +                                        bool has_show_bits,
> +                                        bool show_bits,
> +                                        Error **errp)
>  {
>      VirtIODevice *vdev;
>      VirtioStatus *status;
> +    bool display_bits =
> +        has_show_bits ? show_bits : false;

Since !has_show_bits implies !show_bits, you can simply use
if (show_bits).

>  
>      vdev = qmp_find_virtio_device(path);
>      if (vdev == NULL) {
> @@ -733,6 +738,11 @@ VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
>      status->name = g_strdup(vdev->name);
>      status->device_id = vdev->device_id;
>      status->vhost_started = vdev->vhost_started;
> +    if (display_bits) {
> +        status->guest_features_bits = vdev->guest_features;
> +        status->host_features_bits = vdev->host_features;
> +        status->backend_features_bits = vdev->backend_features;
> +    }
>      status->guest_features = qmp_decode_features(vdev->device_id,
>                                                   vdev->guest_features);
>      status->host_features = qmp_decode_features(vdev->device_id,
> @@ -753,6 +763,9 @@ VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
>      }
>  
>      status->num_vqs = virtio_get_num_queues(vdev);
> +    if (display_bits) {
> +        status->status_bits = vdev->status;
> +    }
>      status->status = qmp_decode_status(vdev->status);
>      status->isr = vdev->isr;
>      status->queue_sel = vdev->queue_sel;
> @@ -775,6 +788,12 @@ VirtioStatus *qmp_x_query_virtio_status(const char *path, Error **errp)
>          status->vhost_dev->n_tmp_sections = hdev->n_tmp_sections;
>          status->vhost_dev->nvqs = hdev->nvqs;
>          status->vhost_dev->vq_index = hdev->vq_index;
> +        if (display_bits) {
> +            status->vhost_dev->features_bits = hdev->features;
> +            status->vhost_dev->acked_features_bits = hdev->acked_features;
> +            status->vhost_dev->backend_features_bits = hdev->backend_features;
> +            status->vhost_dev->protocol_features_bits = hdev->protocol_features;
> +        }
>          status->vhost_dev->features =
>              qmp_decode_features(vdev->device_id, hdev->features);
>          status->vhost_dev->acked_features =
> diff --git a/qapi/virtio.json b/qapi/virtio.json
> index e6dcee7b83..608b841a89 100644
> --- a/qapi/virtio.json
> +++ b/qapi/virtio.json
> @@ -79,12 +79,20 @@
>  #
>  # @vq-index: vhost_dev vq_index
>  #
> +# @features-bits: vhost_dev features in decimal format

Say "encoded as a number".  The number is decimal just because the
transport is JSON.  We could have another transport some day.  Or
language bindings wrapping around the JSON transport.

> +#
>  # @features: vhost_dev features

Double-checking...  @feature-bits provides the exact same information as
@features, only in another encoding.  Correct?

Same for all the other new -bits.  Correct?

>  #
> +# @acked-features-bits: vhost_dev acked_features in decimal format
> +#
>  # @acked-features: vhost_dev acked_features
>  #
> +# @backend-features-bits: vhost_dev backend_features in decimal format
> +#
>  # @backend-features: vhost_dev backend_features
>  #
> +# @protocol-features-bits: vhost_dev protocol_features in decimal format
> +#
>  # @protocol-features: vhost_dev protocol_features
>  #
>  # @max-queues: vhost_dev max_queues
> @@ -102,9 +110,13 @@
>              'n-tmp-sections': 'int',
>              'nvqs': 'uint32',
>              'vq-index': 'int',
> +            'features-bits': 'uint64',
>              'features': 'VirtioDeviceFeatures',
> +            'acked-features-bits': 'uint64',
>              'acked-features': 'VirtioDeviceFeatures',
> +            'backend-features-bits': 'uint64',
>              'backend-features': 'VirtioDeviceFeatures',
> +            'protocol-features-bits': 'uint64',
>              'protocol-features': 'VhostDeviceProtocols',
>              'max-queues': 'uint64',
>              'backend-cap': 'uint64',
> @@ -124,10 +136,16 @@
>  #
>  # @vhost-started: VirtIODevice vhost_started flag
>  #
> +# @guest-features-bits: VirtIODevice guest_features in decimal format
> +#
>  # @guest-features: VirtIODevice guest_features
>  #
> +# @host-features-bits: VirtIODevice host_features in decimal format
> +#
>  # @host-features: VirtIODevice host_features
>  #
> +# @backend-features-bits: VirtIODevice backend_features in decimal format
> +#
>  # @backend-features: VirtIODevice backend_features
>  #
>  # @device-endian: VirtIODevice device_endian
> @@ -135,6 +153,9 @@
>  # @num-vqs: VirtIODevice virtqueue count.  This is the number of
>  #     active virtqueues being used by the VirtIODevice.
>  #
> +# @status-bits: VirtIODevice configuration status in decimal format
> +#     (VirtioDeviceStatus)
> +#
>  # @status: VirtIODevice configuration status (VirtioDeviceStatus)
>  #
>  # @isr: VirtIODevice ISR
> @@ -170,10 +191,14 @@
>              'device-id': 'uint16',
>              'vhost-started': 'bool',
>              'device-endian': 'str',
> +            'guest-features-bits': 'uint64',
>              'guest-features': 'VirtioDeviceFeatures',
> +            'host-features-bits': 'uint64',
>              'host-features': 'VirtioDeviceFeatures',
> +            'backend-features-bits': 'uint64',
>              'backend-features': 'VirtioDeviceFeatures',
>              'num-vqs': 'int',
> +            'status-bits': 'uint8',
>              'status': 'VirtioDeviceStatus',
>              'isr': 'uint8',
>              'queue-sel': 'uint16',
> @@ -195,6 +220,9 @@
>  #
>  # @path: Canonical QOM path of the VirtIODevice
>  #
> +# @show-bits: Whether to display the feature & status bits.
> +#     Default is disabled. (Since 8.2)

This makes the new members opt-in.  Why not include them always?

> +#
>  # Features:
>  #
>  # @unstable: This command is meant for debugging.
> @@ -208,7 +236,8 @@
>  # 1. Poll for the status of virtio-crypto (no vhost-crypto active)
>  #
>  # -> { "execute": "x-query-virtio-status",
> -#      "arguments": { "path": "/machine/peripheral/crypto0/virtio-backend" }
> +#      "arguments": { "path": "/machine/peripheral/crypto0/virtio-backend",
> +#                     "show-bits": true }
>  #    }
>  # <- { "return": {
>  #          "device-endian": "little",
> @@ -216,6 +245,7 @@
>  #          "disable-legacy-check": false,
>  #          "name": "virtio-crypto",
>  #          "started": true,
> +#          "guest-features-bits": 5100273664,
>  #          "device-id": 20,
>  #          "backend-features": {
>  #              "transports": [],
> @@ -241,6 +271,7 @@
>  #                  "VIRTIO_F_VERSION_1: Device compliant for v1 spec (legacy)"
>  #              ]
>  #          },
> +#          "host-features-bits": 6325010432,
>  #          "host-features": {
>  #              "unknown-dev-features": 1073741824,
>  #              "dev-features": [],
> @@ -252,9 +283,11 @@
>  #                  "VIRTIO_F_NOTIFY_ON_EMPTY: Notify when device runs out of avail. descs. on VQ"
>  #              ]
>  #          },
> +#          "backend-features-bits": 0,
>  #          "use-guest-notifier-mask": true,
>  #          "vm-running": true,
>  #          "queue-sel": 1,
> +#          "status-bits": 15,
>  #          "disabled": false,
>  #          "vhost-started": false,
>  #          "use-started": true
> @@ -264,7 +297,8 @@
>  # 2. Poll for the status of virtio-net (vhost-net is active)
>  #
>  # -> { "execute": "x-query-virtio-status",
> -#      "arguments": { "path": "/machine/peripheral-anon/device[1]/virtio-backend" }
> +#      "arguments": { "path": "/machine/peripheral-anon/device[1]/virtio-backend",
> +#                     "show-bits": true }
>  #    }
>  # <- { "return": {
>  #          "device-endian": "little",
> @@ -272,11 +306,13 @@
>  #          "disabled-legacy-check": false,
>  #          "name": "virtio-net",
>  #          "started": true,
> +#          "guest-features-bits": 5111807911,
>  #          "device-id": 1,
>  #          "vhost-dev": {
>  #              "n-tmp-sections": 4,
>  #              "n-mem-sections": 4,
>  #              "max-queues": 1,
> +#              "features-bits": 13908344832
>  #              "backend-cap": 2,
>  #              "log-size": 0,
>  #              "backend-features": {
> @@ -284,6 +320,8 @@
>  #                  "transports": []
>  #              },
>  #              "nvqs": 2,
> +#              "acked-features-bits": 5100306432,
> +#              "backend-features-bits": 0,
>  #              "protocol-features": {
>  #                  "protocols": []
>  #              },
> @@ -299,6 +337,7 @@
>  #                      "VIRTIO_F_VERSION_1: Device compliant for v1 spec (legacy)"
>  #                  ]
>  #              },
> +#              "protocol-features-bits": 0,
>  #              "features": {
>  #                  "dev-features": [
>  #                      "VHOST_F_LOG_ALL: Logging write descriptors supported",
> @@ -387,6 +426,7 @@
>  #                  "VIRTIO_F_VERSION_1: Device compliant for v1 spec (legacy)"
>  #             ]
>  #          },
> +#          "host-features-bits": 6337593319,
>  #          "host-features": {
>  #              "dev-features": [
>  #                  "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features negotiation supported",
> @@ -420,9 +460,11 @@
>  #                  "VIRTIO_F_NOTIFY_ON_EMPTY: Notify when device runs out of avail. descs. on VQ"
>  #             ]
>  #          },
> +#          "backend-features-bits": 6337593319,
>  #          "use-guest-notifier-mask": true,
>  #          "vm-running": true,
>  #          "queue-sel": 2,
> +#          "status-bits": 15,
>  #          "disabled": false,
>  #          "vhost-started": true,
>  #          "use-started": true
> @@ -430,7 +472,8 @@
>  #    }
>  ##
>  { 'command': 'x-query-virtio-status',
> -  'data': { 'path': 'str' },
> +  'data': { 'path': 'str',
> +            '*show-bits': 'bool'},
>    'returns': 'VirtioStatus',
>    'features': [ 'unstable' ] }