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Message-ID: <3155cdb517e0db77d8664e5623c9d39e437fd796.camel@redhat.com>
Date: Thu, 30 Mar 2023 12:18:15 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next 7/8] virtio_net: introduce
receive_mergeable_xdp()
Hi,
On Tue, 2023-03-28 at 20:04 +0800, Xuan Zhuo wrote:
> The purpose of this patch is to simplify the receive_mergeable().
> Separate all the logic of XDP into a function.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
> drivers/net/virtio_net.c | 128 +++++++++++++++++++++++----------------
> 1 file changed, 76 insertions(+), 52 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 136131a7868a..c8978d8d8adb 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1316,6 +1316,63 @@ static void *mergeable_xdp_prepare(struct virtnet_info *vi,
> return page_address(xdp_page) + VIRTIO_XDP_HEADROOM;
> }
>
> +static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
> + struct virtnet_info *vi,
> + struct receive_queue *rq,
> + struct bpf_prog *xdp_prog,
> + void *buf,
> + void *ctx,
> + unsigned int len,
> + unsigned int *xdp_xmit,
> + struct virtnet_rq_stats *stats)
> +{
> + struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
> + int num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
> + struct page *page = virt_to_head_page(buf);
> + int offset = buf - page_address(page);
> + unsigned int xdp_frags_truesz = 0;
> + struct sk_buff *head_skb;
> + unsigned int frame_sz;
> + struct xdp_buff xdp;
> + void *data;
> + u32 act;
> + int err;
> +
> + data = mergeable_xdp_prepare(vi, rq, xdp_prog, ctx, &frame_sz, &num_buf, &page,
> + offset, &len, hdr);
> + if (!data)
> + goto err_xdp;
> +
> + err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
> + &num_buf, &xdp_frags_truesz, stats);
> + if (unlikely(err))
> + goto err_xdp;
> +
> + act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> +
> + switch (act) {
> + case VIRTNET_XDP_RES_PASS:
> + head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
> + if (unlikely(!head_skb))
> + goto err_xdp;
> + return head_skb;
> +
> + case VIRTNET_XDP_RES_CONSUMED:
> + return NULL;
> +
> + case VIRTNET_XDP_RES_DROP:
> + break;
> + }
> +
> +err_xdp:
> + put_page(page);
> + mergeable_buf_free(rq, num_buf, dev, stats);
> +
> + stats->xdp_drops++;
> + stats->drops++;
> + return NULL;
> +}
> +
> static struct sk_buff *receive_mergeable(struct net_device *dev,
> struct virtnet_info *vi,
> struct receive_queue *rq,
> @@ -1325,21 +1382,22 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> unsigned int *xdp_xmit,
> struct virtnet_rq_stats *stats)
> {
> - struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
> - int num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
> - struct page *page = virt_to_head_page(buf);
> - int offset = buf - page_address(page);
> - struct sk_buff *head_skb, *curr_skb;
> - struct bpf_prog *xdp_prog;
> unsigned int truesize = mergeable_ctx_to_truesize(ctx);
> unsigned int headroom = mergeable_ctx_to_headroom(ctx);
> unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
> unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
> - unsigned int frame_sz;
> - int err;
> + struct virtio_net_hdr_mrg_rxbuf *hdr;
> + struct sk_buff *head_skb, *curr_skb;
> + struct bpf_prog *xdp_prog;
> + struct page *page;
> + int num_buf;
> + int offset;
>
> head_skb = NULL;
> stats->bytes += len - vi->hdr_len;
> + hdr = buf;
> + num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
> + page = virt_to_head_page(buf);
>
> if (unlikely(len > truesize - room)) {
> pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
> @@ -1348,51 +1406,21 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> goto err_skb;
> }
>
> - if (likely(!vi->xdp_enabled)) {
> - xdp_prog = NULL;
> - goto skip_xdp;
> - }
> -
> - rcu_read_lock();
> - xdp_prog = rcu_dereference(rq->xdp_prog);
> - if (xdp_prog) {
> - unsigned int xdp_frags_truesz = 0;
> - struct xdp_buff xdp;
> - void *data;
> - u32 act;
> -
> - data = mergeable_xdp_prepare(vi, rq, xdp_prog, ctx, &frame_sz, &num_buf, &page,
> - offset, &len, hdr);
> - if (!data)
> - goto err_xdp;
> -
> - err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
> - &num_buf, &xdp_frags_truesz, stats);
> - if (unlikely(err))
> - goto err_xdp;
> -
> - act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> -
> - switch (act) {
> - case VIRTNET_XDP_RES_PASS:
> - head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
> - if (unlikely(!head_skb))
> - goto err_xdp;
> -
> + if (likely(vi->xdp_enabled)) {
This changes the branch prediction hint compared to the existing code;
as we currently have:
if (likely(!vi->xdp_enabled)) {
and I think it would be better avoid such change.
Thanks,
Paolo
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