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Message-ID: <CACGkMEsdwApvHFTWc4biY-AvwQf9sPuonYFU_Zdn2=wa3cHBjg@mail.gmail.com>
Date: Thu, 20 Apr 2023 14:23:48 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
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 v2 11/14] virtio_net: introduce receive_small_xdp()
On Tue, Apr 18, 2023 at 2:53 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> The purpose of this patch is to simplify the receive_small().
> Separate all the logic of XDP of small into a function.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
> drivers/net/virtio_net.c | 165 +++++++++++++++++++++++----------------
> 1 file changed, 99 insertions(+), 66 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index a4bb25f39f12..34220f5f27d1 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -941,6 +941,98 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
> return NULL;
> }
>
> +static struct sk_buff *receive_small_xdp(struct net_device *dev,
> + struct virtnet_info *vi,
> + struct receive_queue *rq,
> + struct bpf_prog *xdp_prog,
> + void *buf,
> + unsigned int xdp_headroom,
> + unsigned int len,
> + unsigned int *xdp_xmit,
> + struct virtnet_rq_stats *stats)
> +{
> + unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
> + unsigned int headroom = vi->hdr_len + header_offset;
> + struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
> + struct page *page = virt_to_head_page(buf);
> + struct page *xdp_page;
> + unsigned int buflen;
> + struct xdp_buff xdp;
> + struct sk_buff *skb;
> + unsigned int delta = 0;
> + unsigned int metasize = 0;
> + void *orig_data;
> + u32 act;
> +
> + if (unlikely(hdr->hdr.gso_type))
> + goto err_xdp;
> +
> + buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> + SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> +
> + if (unlikely(xdp_headroom < virtnet_get_headroom(vi))) {
> + int offset = buf - page_address(page) + header_offset;
> + unsigned int tlen = len + vi->hdr_len;
> + int num_buf = 1;
> +
> + xdp_headroom = virtnet_get_headroom(vi);
> + header_offset = VIRTNET_RX_PAD + xdp_headroom;
> + headroom = vi->hdr_len + header_offset;
> + buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> + SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> + xdp_page = xdp_linearize_page(rq, &num_buf, page,
> + offset, header_offset,
> + &tlen);
> + if (!xdp_page)
> + goto err_xdp;
> +
> + buf = page_address(xdp_page);
> + put_page(page);
> + page = xdp_page;
> + }
> +
> + xdp_init_buff(&xdp, buflen, &rq->xdp_rxq);
> + xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
> + xdp_headroom, len, true);
> + orig_data = xdp.data;
> +
> + act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> +
> + switch (act) {
> + case VIRTNET_XDP_RES_PASS:
> + /* Recalculate length in case bpf program changed it */
> + delta = orig_data - xdp.data;
> + len = xdp.data_end - xdp.data;
> + metasize = xdp.data - xdp.data_meta;
> + break;
> +
> + case VIRTNET_XDP_RES_CONSUMED:
> + goto xdp_xmit;
> +
> + case VIRTNET_XDP_RES_DROP:
> + goto err_xdp;
> + }
> +
> + skb = build_skb(buf, buflen);
> + if (!skb)
> + goto err;
> +
> + skb_reserve(skb, headroom - delta);
> + skb_put(skb, len);
> + if (metasize)
> + skb_metadata_set(skb, metasize);
> +
> + return skb;
> +
> +err_xdp:
> + stats->xdp_drops++;
> +err:
> + stats->drops++;
> + put_page(page);
> +xdp_xmit:
> + return NULL;
> +}
> +
> static struct sk_buff *receive_small(struct net_device *dev,
> struct virtnet_info *vi,
> struct receive_queue *rq,
> @@ -957,9 +1049,6 @@ static struct sk_buff *receive_small(struct net_device *dev,
> unsigned int buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> struct page *page = virt_to_head_page(buf);
> - unsigned int delta = 0;
> - struct page *xdp_page;
> - unsigned int metasize = 0;
>
> len -= vi->hdr_len;
> stats->bytes += len;
> @@ -979,57 +1068,10 @@ static struct sk_buff *receive_small(struct net_device *dev,
> rcu_read_lock();
> xdp_prog = rcu_dereference(rq->xdp_prog);
> if (xdp_prog) {
> - struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
> - struct xdp_buff xdp;
> - void *orig_data;
> - u32 act;
> -
> - if (unlikely(hdr->hdr.gso_type))
> - goto err_xdp;
> -
> - if (unlikely(xdp_headroom < virtnet_get_headroom(vi))) {
> - int offset = buf - page_address(page) + header_offset;
> - unsigned int tlen = len + vi->hdr_len;
> - int num_buf = 1;
> -
> - xdp_headroom = virtnet_get_headroom(vi);
> - header_offset = VIRTNET_RX_PAD + xdp_headroom;
> - headroom = vi->hdr_len + header_offset;
> - buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> - SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> - xdp_page = xdp_linearize_page(rq, &num_buf, page,
> - offset, header_offset,
> - &tlen);
> - if (!xdp_page)
> - goto err_xdp;
> -
> - buf = page_address(xdp_page);
> - put_page(page);
> - page = xdp_page;
> - }
> -
> - xdp_init_buff(&xdp, buflen, &rq->xdp_rxq);
> - xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
> - xdp_headroom, len, true);
> - orig_data = xdp.data;
> -
> - act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> -
> - switch (act) {
> - case VIRTNET_XDP_RES_PASS:
> - /* Recalculate length in case bpf program changed it */
> - delta = orig_data - xdp.data;
> - len = xdp.data_end - xdp.data;
> - metasize = xdp.data - xdp.data_meta;
> - break;
> -
> - case VIRTNET_XDP_RES_CONSUMED:
> - rcu_read_unlock();
> - goto xdp_xmit;
> -
> - case VIRTNET_XDP_RES_DROP:
> - goto err_xdp;
> - }
> + skb = receive_small_xdp(dev, vi, rq, xdp_prog, buf, xdp_headroom,
> + len, xdp_xmit, stats);
> + rcu_read_unlock();
> + return skb;
> }
> rcu_read_unlock();
>
> @@ -1037,25 +1079,16 @@ static struct sk_buff *receive_small(struct net_device *dev,
> skb = build_skb(buf, buflen);
> if (!skb)
> goto err;
> - skb_reserve(skb, headroom - delta);
> + skb_reserve(skb, headroom);
> skb_put(skb, len);
> - if (!xdp_prog) {
> - buf += header_offset;
> - memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
> - } /* keep zeroed vnet hdr since XDP is loaded */
> -
> - if (metasize)
> - skb_metadata_set(skb, metasize);
>
> + buf += header_offset;
> + memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
So we end up with some code duplication between receive_small() and
receive_small_xdp() on building skbs. Is this intended?
For mergeable, we're probably fine since XDP_PASS doesn't need to
get_buf(). But for the path of small, I wonder if it's better to keep
the original code for building skb.
Thanks
> return skb;
>
> -err_xdp:
> - rcu_read_unlock();
> - stats->xdp_drops++;
> err:
> stats->drops++;
> put_page(page);
> -xdp_xmit:
> return NULL;
> }
>
> --
> 2.32.0.3.g01195cf9f
>
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