Re: [PATCH RFC 1/4] net: Introduce qmp cmd "query-netdev"

[Jason Wang <jasowang@redhat.com>]

On Tue, Nov 1, 2022 at 12:19 AM <huangy81@chinatelecom.cn> wrote:
>
> From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
>
> For netdev device that can offload virtio-net dataplane to slave,
> such as vhost-net, vhost-user and vhost-vdpa, exporting it's
> capability information and acked features would be more friendly for
> developers. These infomation can be analyzed and compare to slave
> capability provided by, eg dpdk or other slaves directly, helping to
> draw conclusions about if vm network interface works normally, if
> it vm can be migrated to another feature-compatible destination or
> whatever else.
>
> For developers who devote to offload virtio-net dataplane to DPU
> and make efforts to migrate vm lively from software-based source
> host to DPU-offload destination host smoothly, virtio-net feature
> compatibility is an serious issue, exporting the key capability
> and acked_features of netdev could also help to debug greatly.
>
> So we export out the key capabilities of netdev, which may affect
> the final negotiated virtio-net features, meanwhile, backed-up
> acked_features also exported, which is used to initialize or
> restore features negotiated between qemu and vhost slave when
> starting vhost_dev device.
>
> Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
> ---
>  net/net.c     | 44 +++++++++++++++++++++++++++++++++++++++
>  qapi/net.json | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 110 insertions(+)
>
> diff --git a/net/net.c b/net/net.c
> index 2db160e..5d11674 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -53,6 +53,7 @@
>  #include "sysemu/runstate.h"
>  #include "net/colo-compare.h"
>  #include "net/filter.h"
> +#include "net/vhost-user.h"
>  #include "qapi/string-output-visitor.h"
>
>  /* Net bridge is currently not supported for W32. */
> @@ -1224,6 +1225,49 @@ void qmp_netdev_del(const char *id, Error **errp)
>      }
>  }
>
> +static NetDevInfo *query_netdev(NetClientState *nc)
> +{
> +    NetDevInfo *info = NULL;
> +
> +    if (!nc || !nc->is_netdev) {
> +        return NULL;
> +    }
> +
> +    info = g_malloc0(sizeof(*info));
> +    info->name = g_strdup(nc->name);
> +    info->type = nc->info->type;
> +    info->ufo = nc->info->has_ufo;
> +    info->vnet_hdr = nc->info->has_vnet_hdr;
> +    info->vnet_hdr_len = nc->info->has_vnet_hdr_len;

So all the fields are virtio specific, I wonder if it's better to
rename the command as query-vhost or query-virtio?

Thanks

> +
> +    if (nc->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
> +        info->has_acked_features = true;
> +        info->acked_features = vhost_user_get_acked_features(nc);
> +    }
> +
> +    return info;
> +}
> +
> +NetDevInfoList *qmp_query_netdev(Error **errp)
> +{
> +    NetClientState *nc;
> +    NetDevInfo *info = NULL;
> +    NetDevInfoList *head = NULL, **tail = &head;
> +
> +    QTAILQ_FOREACH(nc, &net_clients, next) {
> +        if (nc->info->type == NET_CLIENT_DRIVER_NIC) {
> +            continue;
> +        }
> +
> +        info = query_netdev(nc);
> +        if (info) {
> +            QAPI_LIST_APPEND(tail, info);
> +        }
> +    }
> +
> +    return head;
> +}
> +
>  static void netfilter_print_info(Monitor *mon, NetFilterState *nf)
>  {
>      char *str;
> diff --git a/qapi/net.json b/qapi/net.json
> index dd088c0..76a6513 100644
> --- a/qapi/net.json
> +++ b/qapi/net.json
> @@ -631,6 +631,72 @@
>                         'if': 'CONFIG_VMNET' } } }
>
>  ##
> +# @NetDevInfo:
> +#
> +# NetDev information.  This structure describes a NetDev information, including
> +# capabilities and negotiated features.
> +#
> +# @name: The NetDev name.
> +#
> +# @type: Type of NetDev.
> +#
> +# @ufo: True if NetDev has ufo capability.
> +#
> +# @vnet-hdr: True if NetDev has vnet_hdr.
> +#
> +# @vnet-hdr-len: True if given length can be assigned to NetDev.
> +#
> +# @acked-features: Negotiated features with vhost slave device if device support
> +#                  dataplane offload.
> +#
> +# Since:  7.1
> +##
> +{'struct': 'NetDevInfo',
> + 'data': {
> +    'name': 'str',
> +    'type': 'NetClientDriver',
> +    'ufo':'bool',
> +    'vnet-hdr':'bool',
> +    'vnet-hdr-len':'bool',
> +    '*acked-features': 'uint64' } }
> +
> +##
> +# @query-netdev:
> +#
> +# Get a list of NetDevInfo for all virtual netdev peer devices.
> +#
> +# Returns: a list of @NetDevInfo describing each virtual netdev peer device.
> +#
> +# Since: 7.1
> +#
> +# Example:
> +#
> +# -> { "execute": "query-netdev" }
> +# <- {
> +#       "return":[
> +#          {
> +#             "name":"hostnet0",
> +#             "type":"vhost-user",
> +#             "ufo":true,
> +#             "vnet-hdr":true,
> +#             "vnet-hdr-len":true,
> +#             "acked-features":"5111807907",
> +#          },
> +#          {
> +#             "name":"hostnet1",
> +#             "type":"vhost-user",
> +#             "ufo":true,
> +#             "vnet-hdr":true,
> +#             "vnet-hdr-len":true,
> +#             "acked-features":"5111807907",
> +#          }
> +#       ]
> +#    }
> +#
> +##
> +{ 'command': 'query-netdev', 'returns': ['NetDevInfo'] }
> +
> +##
>  # @RxState:
>  #
>  # Packets receiving state
> --
> 1.8.3.1
>