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

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Date:   Fri, 2 Dec 2022 12:50:30 +0800
From:   Heng Qi <hengqi@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.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>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [RFC PATCH 0/9] virtio_net: support multi buffer xdp

Hi, Jason.

Do you have any comments on this series?

Thanks.

在 2022/11/22 下午3:43, Heng Qi 写道:
> Currently, virtio net only supports xdp for single-buffer packets
> or linearized multi-buffer packets. This patchset supports xdp for
> multi-buffer packets, then GRO_HW related features can be
> negotiated, and do not affect the processing of single-buffer xdp.
>
> In order to build multi-buffer xdp neatly, we integrated the code
> into virtnet_build_xdp_buff() 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: remove xdp related info from page_to_skb()
>    virtio_net: build xdp_buff with multi buffers
>    virtio_net: construct multi-buffer xdp in mergeable
>    virtio_net: build skb from multi-buffer xdp
>    virtio_net: transmit the multi-buffer xdp
>    virtio_net: support multi-buffer xdp
>
>   drivers/net/virtio_net.c | 356 ++++++++++++++++++++++++---------------
>   1 file changed, 219 insertions(+), 137 deletions(-)
>