netdev - Re: [PATCH V2 RESEND 2/6] vDPA: only report driver features if FEATURES

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Date:   Tue, 27 Sep 2022 12:37:32 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...el.com>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH V2 RESEND 2/6] vDPA: only report driver features if
 FEATURES_OK is set

On Tue, Sep 27, 2022 at 11:09 AM Zhu Lingshan <lingshan.zhu@...el.com> wrote:
>
> This commit reports driver features to user space
> only after FEATURES_OK is features negotiation is done.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
> ---
>  drivers/vdpa/vdpa.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 2035700d6fc8..e7765953307f 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -816,7 +816,7 @@ static int vdpa_dev_net_mq_config_fill(struct vdpa_device *vdev,
>  static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *msg)
>  {
>         struct virtio_net_config config = {};
> -       u64 features_device, features_driver;
> +       u64 features_device;
>         u16 val_u16;
>
>         vdev->config->get_config(vdev, 0, &config, sizeof(config));
> @@ -833,11 +833,6 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
>         if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16))
>                 return -EMSGSIZE;
>
> -       features_driver = vdev->config->get_driver_features(vdev);
> -       if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
> -                             VDPA_ATTR_PAD))
> -               return -EMSGSIZE;
> -
>         features_device = vdev->config->get_device_features(vdev);
>
>         if (nla_put_u64_64bit(msg, VDPA_ATTR_VDPA_DEV_SUPPORTED_FEATURES, features_device,
> @@ -851,6 +846,8 @@ static int
>  vdpa_dev_config_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq,
>                      int flags, struct netlink_ext_ack *extack)
>  {
> +       u64 features_driver;
> +       u8 status = 0;
>         u32 device_id;
>         void *hdr;
>         int err;
> @@ -874,6 +871,19 @@ vdpa_dev_config_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid,
>                 goto msg_err;
>         }
>
> +       /* only read driver features after the feature negotiation is done */
> +       if (vdev->config->get_status)
> +               status = vdev->config->get_status(vdev);

get_status is mandatory, so I think we can remove this check.

Or if you want a strict check on the config operations, we need to do
that in __vdpa_alloc_device().

Thanks

> +
> +       if (status & VIRTIO_CONFIG_S_FEATURES_OK) {
> +               features_driver = vdev->config->get_driver_features(vdev);
> +               if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features_driver,
> +                                     VDPA_ATTR_PAD)) {
> +                       err = -EMSGSIZE;
> +                       goto msg_err;
> +               }
> +       }
> +
>         switch (device_id) {
>         case VIRTIO_ID_NET:
>                 err = vdpa_dev_net_config_fill(vdev, msg);
> --
> 2.31.1
>