netdev - Re: [PATCH v2 0/9] virtio_net: support multi buffer xdp

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Date:   Mon, 26 Dec 2022 12:14:33 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Heng Qi <hengqi@...ux.alibaba.com>
Cc:     "Michael S . Tsirkin" <mst@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 0/9] virtio_net: support multi buffer xdp

On Mon, Dec 26, 2022 at 10:33 AM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>
>
> Hi Jason, do you have any comments on this?

I will review this no later than the end of this week.

Thanks

>
> Thanks.
>
> 在 2022/12/20 下午10:14, Heng Qi 写道:
> > Changes since RFC:
> > - Using headroom instead of vi->xdp_enabled to avoid re-reading
> >    in add_recvbuf_mergeable();
> > - Disable GRO_HW and keep linearization for single buffer xdp;
> > - Renamed to virtnet_build_xdp_buff_mrg();
> > - pr_debug() to netdev_dbg();
> > - Adjusted the order of the patch series.
> >
> > Currently, virtio net only supports xdp for single-buffer packets
> > or linearized multi-buffer packets. This patchset supports xdp for
> > multi-buffer packets, then larger MTU can be used if xdp sets the
> > xdp.frags. This does not affect single buffer handling.
> >
> > In order to build multi-buffer xdp neatly, we integrated the code
> > into virtnet_build_xdp_buff_mrg() for xdp. The first buffer is used
> > for prepared xdp buff, and the rest of the buffers are added to
> > its skb_shared_info structure. This structure can also be
> > conveniently converted during XDP_PASS to get the corresponding skb.
> >
> > Since virtio net uses comp pages, and bpf_xdp_frags_increase_tail()
> > is based on the assumption of the page pool,
> > (rxq->frag_size - skb_frag_size(frag) - skb_frag_off(frag))
> > is negative in most cases. So we didn't set xdp_rxq->frag_size in
> > virtnet_open() to disable the tail increase.
> >
> > Heng Qi (9):
> >    virtio_net: disable the hole mechanism for xdp
> >    virtio_net: set up xdp for multi buffer packets
> >    virtio_net: update bytes calculation for xdp_frame
> >    virtio_net: build xdp_buff with multi buffers
> >    virtio_net: construct multi-buffer xdp in mergeable
> >    virtio_net: transmit the multi-buffer xdp
> >    virtio_net: build skb from multi-buffer xdp
> >    virtio_net: remove xdp related info from page_to_skb()
> >    virtio_net: support multi-buffer xdp
> >
> >   drivers/net/virtio_net.c | 332 ++++++++++++++++++++++++++-------------
> >   1 file changed, 219 insertions(+), 113 deletions(-)
> >
>