netdev - Re: [PATCH net-next v2] virtio-net: ethtool configurable RXCSUM

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Date:   Wed, 30 Sep 2020 12:05:12 +0200
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Tonghao Zhang <xiangxia.m.yue@...il.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2] virtio-net: ethtool configurable RXCSUM

On Wed, Sep 30, 2020 at 4:05 AM <xiangxia.m.yue@...il.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@...il.com>
>
> Allow user configuring RXCSUM separately with ethtool -K,
> reusing the existing virtnet_set_guest_offloads helper
> that configures RXCSUM for XDP. This is conditional on
> VIRTIO_NET_F_CTRL_GUEST_OFFLOADS.
>
> If Rx checksum is disabled, LRO should also be disabled.
>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>

The first patch was merged into net.

Please wait until that is merged into net-next, as this depends on the
other patch.

> ---
> v2:
> * LRO depends the rx csum
> * remove the unnecessary check
> ---
>  drivers/net/virtio_net.c | 49 ++++++++++++++++++++++++++++++----------
>  1 file changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 21b71148c532..5407a0106771 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -68,6 +68,8 @@ static const unsigned long guest_offloads[] = {
>                                 (1ULL << VIRTIO_NET_F_GUEST_ECN)  | \
>                                 (1ULL << VIRTIO_NET_F_GUEST_UFO))
>
> +#define GUEST_OFFLOAD_CSUM_MASK (1ULL << VIRTIO_NET_F_GUEST_CSUM)
> +
>  struct virtnet_stat_desc {
>         char desc[ETH_GSTRING_LEN];
>         size_t offset;
> @@ -2522,29 +2524,49 @@ static int virtnet_get_phys_port_name(struct net_device *dev, char *buf,
>         return 0;
>  }
>
> +static netdev_features_t virtnet_fix_features(struct net_device *netdev,
> +                                             netdev_features_t features)
> +{
> +       /* If Rx checksum is disabled, LRO should also be disabled.
> +        * That is life. :)

Please remove this second line.

> +        */
> +       if (!(features & NETIF_F_RXCSUM))
> +               features &= ~NETIF_F_LRO;
> +
> +       return features;
> +}
> +
>  static int virtnet_set_features(struct net_device *dev,
>                                 netdev_features_t features)
>  {
>         struct virtnet_info *vi = netdev_priv(dev);
> -       u64 offloads;
> +       u64 offloads = vi->guest_offloads &
> +                      vi->guest_offloads_capable;

When can vi->guest_offloads have bits set outside the mask of
vi->guest_offloads_capable?