From: "Michael S. Tsirkin" <mst@redhat.com>
To: Heng Qi <hengqi@linux.alibaba.com>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
Jason Wang <jasowang@redhat.com>,
Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>
Subject: Re: [PATCH net-next 3/4] virtio-net: support coexistence of XDP and _F_GUEST_CSUM
Date: Tue, 20 Jun 2023 06:50:34 -0400 [thread overview]
Message-ID: <20230620064711-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20230620032430.GE74977@h68b04307.sqa.eu95>
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@linux.alibaba.com>
> > > Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > ---
> > > 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
next prev parent reply other threads:[~2023-06-20 10:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-19 10:57 [PATCH net-next 0/4] virtio-net: avoid XDP and _F_GUEST_CSUM Heng Qi
2023-06-19 10:57 ` [PATCH net-next 1/4] virtio-net: a helper for probing the pseudo-header checksum Heng Qi
2023-06-19 12:30 ` kernel test robot
2023-06-19 12:30 ` kernel test robot
2023-06-19 10:57 ` [PATCH net-next 2/4] virtio-net: reprobe csum related fields for skb passed by XDP Heng Qi
2023-06-19 11:27 ` Michael S. Tsirkin
2023-06-19 12:29 ` Heng Qi
2023-06-19 13:32 ` kernel test robot
2023-06-19 10:57 ` [PATCH net-next 3/4] virtio-net: support coexistence of XDP and _F_GUEST_CSUM Heng Qi
2023-06-19 11:26 ` Michael S. Tsirkin
2023-06-19 12:31 ` Heng Qi
2023-06-20 3:24 ` Heng Qi
2023-06-20 10:50 ` Michael S. Tsirkin [this message]
2023-06-20 11:01 ` Heng Qi
2023-06-20 12:10 ` Michael S. Tsirkin
2023-06-20 14:15 ` Heng Qi
2023-06-19 10:57 ` [PATCH net-next 4/4] virtio-net: remove F_GUEST_CSUM check for XDP loading Heng Qi
2023-06-19 11:16 ` Michael S. Tsirkin
2023-06-19 12:41 ` Heng Qi
2023-06-19 14:33 ` Michael S. Tsirkin
2023-06-19 15:43 ` Heng Qi
2023-06-19 18:36 ` Michael S. Tsirkin
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