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

Heng Qi
2022-12-20T14:14:58Z

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(-)

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2.19.1.6.gb485710b