Virtualization - Dec 2021 - [PATCH v1 6/7] vdpa: Add support for querying control virtqueue index

On Thu, Dec 9, 2021 at 4:15 AM Eli Cohen <elic at nvidia.com>
wrote:
>
> Add netlink attribute and callback function to query the control VQ
> index of a device.
>
> Example:
>
> $ vdpa dev config show vdpa-a
>   vdpa-a: mac 00:00:00:00:88:88 link up link_announce false max_vq_pairs 5
\
>   mtu 9000 ctrl_vq_idx 10

I still wonder about the motivation for this. And as discussed, the
ctrl_vq_idx varies depending on whether MQ is negotiated.

Thanks
>
> Signed-off-by: Eli Cohen <elic at nvidia.com>
> ---
> v0 -> v1:
> 1. Use logic defined in the spec to deduce virtqueue index.
>
>  drivers/vdpa/vdpa.c       | 25 +++++++++++++++++++++++++
>  include/uapi/linux/vdpa.h |  1 +
>  2 files changed, 26 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 3bf016e03512..b4d4b8a7ca4e 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -712,6 +712,27 @@ static int vdpa_nl_cmd_dev_get_dumpit(struct sk_buff
*msg, struct netlink_callba
>         return msg->len;
>  }
>
> +static int vdpa_dev_net_ctrl_vq_fill(struct vdpa_device *vdev,
> +                                    struct sk_buff *msg,
> +                                    struct virtio_net_config *config,
> +                                    u64 features)
> +{
> +       u16 N;
> +
> +       /* control VQ index, if available, is deduced according to the
logic
> +        * described in the virtio spec in section 5.1.2
> +        */
> +       if (!(features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ)))
> +               return 0;
> +
> +       if (features & BIT_ULL(VIRTIO_NET_F_MQ))
> +               N = le16_to_cpu(config->max_virtqueue_pairs);
> +       else
> +               N = 1;
> +
> +       return nla_put_u16(msg, VDPA_ATTR_DEV_CTRL_VQ_IDX, 2 * N);
> +}
> +
>  static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
>                                        struct sk_buff *msg, u64 features,
>                                        const struct virtio_net_config
*config)
> @@ -730,6 +751,7 @@ static int vdpa_dev_net_config_fill(struct vdpa_device
*vdev, struct sk_buff *ms
>         struct virtio_net_config config = {};
>         u64 features;
>         u16 val_u16;
> +       int err;
>
>         vdpa_get_config(vdev, 0, &config, sizeof(config));
>
> @@ -746,6 +768,9 @@ static int vdpa_dev_net_config_fill(struct vdpa_device
*vdev, struct sk_buff *ms
>                 return -EMSGSIZE;
>
>         features = vdev->config->get_driver_features(vdev);
> +       err = vdpa_dev_net_ctrl_vq_fill(vdev, msg, &config, features);
> +       if (err)
> +               return err;
>
>         return vdpa_dev_net_mq_config_fill(vdev, msg, features,
&config);
>  }
> diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h
> index a252f06f9dfd..2e3a7f89f42d 100644
> --- a/include/uapi/linux/vdpa.h
> +++ b/include/uapi/linux/vdpa.h
> @@ -34,6 +34,7 @@ enum vdpa_attr {
>         VDPA_ATTR_DEV_MAX_VQS,                  /* u32 */
>         VDPA_ATTR_DEV_MAX_VQ_SIZE,              /* u16 */
>         VDPA_ATTR_DEV_MIN_VQ_SIZE,              /* u16 */
> +       VDPA_ATTR_DEV_CTRL_VQ_IDX,              /* u16 */
>
>         VDPA_ATTR_DEV_NET_CFG_MACADDR,          /* binary */
>         VDPA_ATTR_DEV_NET_STATUS,               /* u8 */
> --
> 2.33.1
>