netdev - Re: [PATCH 2/2] virtio-net: ethtool configurable RXCSUM

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Date:   Mon, 28 Sep 2020 17:22:53 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...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 2/2] virtio-net: ethtool configurable RXCSUM

On Mon, Sep 28, 2020 at 4:39 PM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> On Mon, Sep 28, 2020 at 5:42 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.
> >
> > Cc: Michael S. Tsirkin <mst@...hat.com>
> > Cc: Jason Wang <jasowang@...hat.com>
> > Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
> > ---
> >  drivers/net/virtio_net.c | 40 ++++++++++++++++++++++++++++------------
> >  1 file changed, 28 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 21b71148c532..2e3af0b2c281 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;
> > @@ -2526,25 +2528,37 @@ 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;
> >         int err;
> >
> > -       if ((dev->features ^ features) & NETIF_F_LRO) {
> > -               if (vi->xdp_queue_pairs)
> > -                       return -EBUSY;
> > +       /* Don't allow configuration while XDP is active. */
> > +       if (vi->xdp_queue_pairs)
> > +               return -EBUSY;
> >
> > +       if ((dev->features ^ features) & NETIF_F_LRO) {
> >                 if (features & NETIF_F_LRO)
> > -                       offloads = vi->guest_offloads_capable;
> > +                       offloads |= GUEST_OFFLOAD_LRO_MASK;
> >                 else
> > -                       offloads = vi->guest_offloads_capable &
> > -                                  ~GUEST_OFFLOAD_LRO_MASK;
> > +                       offloads &= ~GUEST_OFFLOAD_LRO_MASK;
> > +       }
> >
> > -               err = virtnet_set_guest_offloads(vi, offloads);
> > -               if (err)
> > -                       return err;
> > -               vi->guest_offloads = offloads;
> > +       if ((dev->features ^ features) & NETIF_F_RXCSUM) {
> > +               if (features & NETIF_F_RXCSUM)
> > +                       offloads |= GUEST_OFFLOAD_CSUM_MASK;
> > +               else
> > +                       offloads &= ~GUEST_OFFLOAD_CSUM_MASK;
> >         }
>
> LRO requires receive checksum offload: packets must have their
> checksum verified prior to coalescing.
Oh, sorry for that, I will change that patch. thanks!
> The two features can thus not be configured fully independently.



-- 
Best regards, Tonghao