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Message-ID: <CACGkMEsvKFBCfwsv1J5gXW6anQOZGuJfWPm9ku6v8i_BbWjLCw@mail.gmail.com>
Date: Tue, 6 Dec 2022 13:36:44 +0800
From: Jason Wang <jasowang@...hat.com>
To: Heng Qi <hengqi@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
"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>
Subject: Re: [RFC PATCH 4/9] virtio_net: remove xdp related info from page_to_skb()
On Tue, Nov 22, 2022 at 3:44 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>
> For the clear construction of multi-buffer xdp_buff, we now remove the xdp
> processing interleaved with page_to_skb() before, and the logic of xdp and
> building skb from xdp will be separate and independent.
>
> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
> Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
So I think the organization of this series needs some tweak.
If I was not not and if we do things like this, XDP support is
actually broken and it breaks bisection and a lot of other things.
We need make sure each patch does not break anything, it probably requires
1) squash the following patches or
2) having a new helper to do XDP stuffs after/before page_to_skb()
Thanks
> ---
> drivers/net/virtio_net.c | 41 +++++++++-------------------------------
> 1 file changed, 9 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d3e8c63b9c4b..cd65f85d5075 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -439,9 +439,7 @@ static unsigned int mergeable_ctx_to_truesize(void *mrg_ctx)
> static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> struct receive_queue *rq,
> struct page *page, unsigned int offset,
> - unsigned int len, unsigned int truesize,
> - bool hdr_valid, unsigned int metasize,
> - unsigned int headroom)
> + unsigned int len, unsigned int truesize)
> {
> struct sk_buff *skb;
> struct virtio_net_hdr_mrg_rxbuf *hdr;
> @@ -459,21 +457,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> else
> hdr_padded_len = sizeof(struct padded_vnet_hdr);
>
> - /* If headroom is not 0, there is an offset between the beginning of the
> - * data and the allocated space, otherwise the data and the allocated
> - * space are aligned.
> - *
> - * Buffers with headroom use PAGE_SIZE as alloc size, see
> - * add_recvbuf_mergeable() + get_mergeable_buf_len()
> - */
> - truesize = headroom ? PAGE_SIZE : truesize;
> - tailroom = truesize - headroom;
> - buf = p - headroom;
> -
> + buf = p;
> len -= hdr_len;
> offset += hdr_padded_len;
> p += hdr_padded_len;
> - tailroom -= hdr_padded_len + len;
> + tailroom = truesize - hdr_padded_len - len;
>
> shinfo_size = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
>
> @@ -503,7 +491,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> if (len <= skb_tailroom(skb))
> copy = len;
> else
> - copy = ETH_HLEN + metasize;
> + copy = ETH_HLEN;
> skb_put_data(skb, p, copy);
>
> len -= copy;
> @@ -542,19 +530,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> give_pages(rq, page);
>
> ok:
> - /* hdr_valid means no XDP, so we can copy the vnet header */
> - if (hdr_valid) {
> - hdr = skb_vnet_hdr(skb);
> - memcpy(hdr, hdr_p, hdr_len);
> - }
> + hdr = skb_vnet_hdr(skb);
> + memcpy(hdr, hdr_p, hdr_len);
> if (page_to_free)
> put_page(page_to_free);
>
> - if (metasize) {
> - __skb_pull(skb, metasize);
> - skb_metadata_set(skb, metasize);
> - }
> -
> return skb;
> }
>
> @@ -917,7 +897,7 @@ static struct sk_buff *receive_big(struct net_device *dev,
> {
> struct page *page = buf;
> struct sk_buff *skb =
> - page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, true, 0, 0);
> + page_to_skb(vi, rq, page, 0, len, PAGE_SIZE);
>
> stats->bytes += len - vi->hdr_len;
> if (unlikely(!skb))
> @@ -1060,9 +1040,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> rcu_read_unlock();
> put_page(page);
> head_skb = page_to_skb(vi, rq, xdp_page, offset,
> - len, PAGE_SIZE, false,
> - metasize,
> - headroom);
> + len, PAGE_SIZE);
> return head_skb;
> }
> break;
> @@ -1116,8 +1094,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> rcu_read_unlock();
>
> skip_xdp:
> - head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
> - metasize, headroom);
> + head_skb = page_to_skb(vi, rq, page, offset, len, truesize);
> curr_skb = head_skb;
>
> if (unlikely(!curr_skb))
> --
> 2.19.1.6.gb485710b
>
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