linux-kernel - Re: [PATCH v2 2/3] virtio_net: Add missing virtio header in skb for XDP

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Date: Thu, 25 Jan 2024 14:41:03 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: Liang Chen <liangchen.linux@...il.com>,
 virtualization@...ts.linux-foundation.org,
 linux-kernel@...r.kernel.org,
 mst@...hat.com,
 hengqi@...ux.alibaba.com
Subject: Re: [PATCH v2 2/3] virtio_net: Add missing virtio header in skb for XDP_PASS

On Thu, 25 Jan 2024 11:48:18 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Wed, Jan 24, 2024 at 5:16 PM Xuan Zhuo <xuanzhuo@...ux.alibabacom> wrote:
> >
> > On Wed, 24 Jan 2024 16:57:20 +0800, Liang Chen <liangchen.linux@...il.com> wrote:
> > > For the XDP_PASS scenario of the XDP path, the skb constructed with
> > > xdp_buff does not include the virtio header. Adding the virtio header
> > > information back when creating the skb.
> > >
> > > Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> > > ---
> > >  drivers/net/virtio_net.c | 6 ++++++
> > >  1 file changed, 6 insertions(+)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index b56828804e5f..2de46eb4c661 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -1270,6 +1270,9 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
> > >       if (unlikely(!skb))
> > >               goto err;
> > >
> > > +     /* Store the original virtio header for subsequent use by the driver. */
> > > +     memcpy(skb_vnet_common_hdr(skb), &virtnet_xdp.hdr, vi->hdr_len);
> >
> > About this, a spec is waiting for voting.
> >
>
> A pointer?

Sorry.

http://lore.kernel.org/all/1704263702-50528-1-git-send-email-hengqi@linux.alibaba.com


>
> > This may change the logic of the csum offset and so on.
>
>  Btw, doesn't it need a new feature bit?

Yes.

But this patch set should not include this.
We may do the similar thing, but the commit log will
include more info about the spec.

Thanks.


>
> Thanks
>
> >
> > Please not do this.
> >
> > Thanks.
> >
> >
> > > +
> > >       if (metasize)
> > >               skb_metadata_set(skb, metasize);
> > >
> > > @@ -1635,6 +1638,9 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
> > >               head_skb = build_skb_from_xdp_buff(dev, vi, xdp, xdp_frags_truesz);
> > >               if (unlikely(!head_skb))
> > >                       break;
> > > +             /* Store the original virtio header for subsequent use by the driver. */
> > > +             memcpy(skb_vnet_common_hdr(head_skb), &virtnet_xdp.hdr, vi->hdr_len);
> > > +
> > >               return head_skb;
> > >
> > >       case XDP_TX:
> > > --
> > > 2.40.1
> > >
> >
>