linux-kernel - Re: [PATCH v2 3/4] vdpa: show dev config as-is in "vdpa dev show" output

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Date:   Thu, 20 Oct 2022 13:25:55 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Si-Wei Liu <si-wei.liu@...cle.com>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] vdpa: show dev config as-is in "vdpa dev show" output

On Wed, Oct 19, 2022 at 8:56 AM Si-Wei Liu <si-wei.liu@...cle.com> wrote:
>
> Live migration of vdpa would typically require re-instate vdpa
> device with an idential set of configs on the destination node,
> same way as how source node created the device in the first
> place. In order to save orchestration software from memorizing
> and keeping track of vdpa config, it will be helpful if the vdpa
> tool provides the aids for exporting the initial configs from
> which vdpa device was created as-is. The "vdpa dev show" command
> seems to be the right vehicle for that. It is unlike the "vdpa dev
> config show" command output that usually goes with the live value
> in the device config space, which is not quite reliable subject to
> the dynamics of feature negotiation and possible change in device
> config space.
>
> Examples:
>
> 1) Create vDPA by default without any config attribute
>
> $ vdpa dev add mgmtdev pci/0000:41:04.2 name vdpa0
> $ vdpa dev show vdpa0
> vdpa0: type network mgmtdev pci/0000:41:04.2 vendor_id 5555 max_vqs 9 max_vq_size 256
> $ vdpa dev -jp show vdpa0
> {
>     "dev": {
>         "vdpa0": {
>             "type": "network",
>             "mgmtdev": "pci/0000:41:04.2",
>             "vendor_id": 5555,
>             "max_vqs": 9,
>             "max_vq_size": 256,
>         }
>     }
> }
>
> 2) Create vDPA with config attribute(s) specified
>
> $ vdpa dev add mgmtdev pci/0000:41:04.2 name vdpa0 \
>     mac e4:11:c6:d3:45:f0 max_vq_pairs 4
> $ vdpa dev show
> vdpa0: type network mgmtdev pci/0000:41:04.2 vendor_id 5555 max_vqs 9 max_vq_size 256
>   virtio_config: mac e4:11:c6:d3:45:f0 max_vq_pairs 4
> $ vdpa dev -jp show
> {
>     "dev": {
>         "vdpa0": {
>             "type": "network",
>             "mgmtdev": "pci/0000:41:04.2",
>             "vendor_id": 5555,
>             "max_vqs": 9,
>             "max_vq_size": 256,
>             "virtio_config": {
>                 "mac": "e4:11:c6:d3:45:f0",
>                 "max_vq_pairs": 4
>             }
>         }
>     }
> }
>
> Signed-off-by: Si-Wei Liu <si-wei.liu@...cle.com>
> ---
>  drivers/vdpa/vdpa.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 566c1c6..91eca6d 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -677,6 +677,41 @@ static int vdpa_nl_cmd_dev_del_set_doit(struct sk_buff *skb, struct genl_info *i
>  }
>
>  static int
> +vdpa_dev_cfgattrs_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 device_id)
> +{
> +       struct vdpa_dev_set_config *cfg = &vdev->vdev_cfg;
> +       int err = -EMSGSIZE;
> +
> +       if (!cfg->mask)
> +               return 0;
> +
> +       switch (device_id) {
> +       case VIRTIO_ID_NET:
> +               if ((cfg->mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MACADDR)) != 0 &&
> +                   nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR,
> +                           sizeof(cfg->net.mac), cfg->net.mac))
> +                       return err;
> +               if ((cfg->mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MTU)) != 0 &&
> +                   nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, cfg->net.mtu))
> +                       return err;
> +               if ((cfg->mask & BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP)) != 0 &&
> +                   nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MAX_VQP,
> +                               cfg->net.max_vq_pairs))
> +                       return err;
> +               break;

This makes me think if we can reuse the virtio_net_config structure
other than duplicate it slowly with a dedicated nested structure
inside vdpa_dev_set_config then we can reuse the
vdpa_dev_net_config_fill().

Thanks

> +       default:
> +               break;
> +       }
> +
> +       if ((cfg->mask & BIT_ULL(VDPA_ATTR_DEV_FEATURES)) != 0 &&
> +           nla_put_u64_64bit(msg, VDPA_ATTR_DEV_FEATURES,
> +                             cfg->device_features, VDPA_ATTR_PAD))
> +               return err;
> +
> +       return 0;
> +}
> +
> +static int
>  vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq,
>               int flags, struct netlink_ext_ack *extack)
>  {
> @@ -715,6 +750,10 @@ static int vdpa_nl_cmd_dev_del_set_doit(struct sk_buff *skb, struct genl_info *i
>         if (nla_put_u16(msg, VDPA_ATTR_DEV_MIN_VQ_SIZE, min_vq_size))
>                 goto msg_err;
>
> +       err = vdpa_dev_cfgattrs_fill(vdev, msg, device_id);
> +       if (err)
> +               goto msg_err;
> +
>         genlmsg_end(msg, hdr);
>         return 0;
>
> --
> 1.8.3.1
>