Subject: Re: [PATCH 1/2] virtio-net: don't disable guest csum when disable LRO

From: "Michael S. Tsirkin" <[email-masked]>
Date: Tue, 29 Sep 2020 01:56:54 -0400

On Tue, Sep 29, 2020 at 09:40:22AM +0800, Tonghao Zhang wrote:
> On Tue, Sep 29, 2020 at 3:21 AM Michael S. Tsirkin <[email-masked]> wrote:
> >
> > On Mon, Sep 28, 2020 at 11:39:14AM +0800, [email-masked] wrote:
> > > From: Tonghao Zhang <[email-masked]>
> > >
> > > Open vSwitch and Linux bridge will disable LRO of the interface
> > > when this interface added to them. Now when disable the LRO, the
> > > virtio-net csum is disable too. That drops the forwarding performance.
> > >
> > > Fixes: e59ff2c49ae1 ("virtio-net: disable guest csum during XDP set")
> >
> > I am a bit confused by this tag. Did this change bring about
> > disabling checksum when LRO is disabled? I am not sure
> > I follow how ...
> Hi Michael
> It's not right fix tag.
> The commit a02e8964eaf9 ("virtio-net: ethtool configurable LRO"),
> disable the csum, when we disable the LRO

OK then, pls send a correct Fixes tag when you repost this ...

> > > Cc: Michael S. Tsirkin <[email-masked]>
> > > Cc: Jason Wang <[email-masked]>
> > > Cc: Willem de Bruijn <[email-masked]>
> > > Signed-off-by: Tonghao Zhang <[email-masked]>
> > > ---
> > >  drivers/net/virtio_net.c | 8 +++++++-
> > >  1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 7145c83c6c8c..21b71148c532 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -63,6 +63,11 @@ static const unsigned long guest_offloads[] = {
> > >       VIRTIO_NET_F_GUEST_CSUM
> > >  };
> > >
> > > +#define GUEST_OFFLOAD_LRO_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
> > > +                             (1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
> > > +                             (1ULL << VIRTIO_NET_F_GUEST_ECN)  | \
> > > +                             (1ULL << VIRTIO_NET_F_GUEST_UFO))
> > > +
> > >  struct virtnet_stat_desc {
> > >       char desc[ETH_GSTRING_LEN];
> > >       size_t offset;
> > > @@ -2531,7 +2536,8 @@ static int virtnet_set_features(struct net_device *dev,
> > >               if (features & NETIF_F_LRO)
> > >                       offloads = vi->guest_offloads_capable;
> > >               else
> > > -                     offloads = 0;
> > > +                     offloads = vi->guest_offloads_capable &
> > > +                                ~GUEST_OFFLOAD_LRO_MASK;
> > >
> > >               err = virtnet_set_guest_offloads(vi, offloads);
> > >               if (err)
> > > --
> > > 2.23.0
> >
> 
> 
> -- 
> Best regards, Tonghao