Re: [PATCH net v2] virtio-net: don't disable guest csum when disable LRO

[Tonghao Zhang <xiangxia.m.yue@gmail.com>]

On Tue, Sep 29, 2020 at 2:23 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Tue, Sep 29, 2020 at 09:58:06AM +0800, xiangxia.m.yue@gmail.com wrote:
> > From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> >
> > 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: a02e8964eaf9 ("virtio-net: ethtool configurable LRO")
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Jason Wang <jasowang@redhat.com>
> > Cc: Willem de Bruijn <willemb@google.com>
> > Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> > ---
> > v2:
> > * change the fix-tag
> > ---
> >  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))
> > +
>
> I think I'd rather we open-coded this, the macro is only
> used in one place ...
Yes, in this patch, it is used only in one place. But in next patch
[1], we use it twice and that make the code look a bit nicer.
Would we open-coded this in this patch ?

[1] - http://patchwork.ozlabs.org/project/netdev/patch/20200928033915.82810-2-xiangxia.m.yue@gmail.com/

> >  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