On Tue, Jun 20, 2023 at 11:24:30AM +0800, Heng Qi wrote:
> On Mon, Jun 19, 2023 at 07:26:44AM -0400, Michael S. Tsirkin wrote:
> > On Mon, Jun 19, 2023 at 06:57:37PM +0800, Heng Qi wrote:
> > > We are now re-probing the csum related fields and trying
> > > to have XDP and RX hw checksum capabilities coexist on the
> > > XDP path. For the benefit of:
> > > 1. RX hw checksum capability can be used if XDP is loaded.
> > > 2. Avoid packet loss when loading XDP in the vm-vm scenario.
> > >
> > > Signed-off-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
> > > Reviewed-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > > ---
> > > drivers/net/virtio_net.c | 36 ++++++++++++++++++++++++------------
> > > 1 file changed, 24 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 07b4801d689c..25b486ab74db 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -1709,6 +1709,7 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
> > > struct net_device *dev = vi->dev;
> > > struct sk_buff *skb;
> > > struct virtio_net_hdr_mrg_rxbuf *hdr;
> > > + __u8 flags;
> > >
> > > if (unlikely(len < vi->hdr_len + ETH_HLEN)) {
> > > pr_debug("%s: short packet %i\n", dev->name, len);
> > > @@ -1717,6 +1718,8 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
> > > return;
> > > }
> > >
> > > + flags = ((struct virtio_net_hdr_mrg_rxbuf *)buf)->hdr.flags;
> > > +
> > > if (vi->mergeable_rx_bufs)
> > > skb = receive_mergeable(dev, vi, rq, buf, ctx, len, xdp_xmit,
> > > stats);
> >
> > what's going on here?
>
> Hi, Michael.
>
> Is your question about the function of this code?
> 1. If yes,
> this sentence saves the flags value in virtio-net-hdr in advance
> before entering the XDP processing logic, so that it can be used to
> judge further logic after XDP processing.
>
> If _NEEDS_CSUM is included in flags before XDP processing, then after
> XDP processing we need to re-probe the csum fields and calculate the
> pseudo-header checksum.
Yes but we previously used this:
- hdr = skb_vnet_hdr(skb);
which pokes at the copy in skb cb.
Is anything wrong with this?
It seems preferable not to poke at the header an extra time.
--
MST
