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Date: Mon, 1 Jul 2019 17:30:29 +0800
From: Jason Wang <jasowang@...hat.com>
To: Yuya Kusakabe <yuya.kusakabe@...il.com>, davem@...emloft.net
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next] virtio_net: add XDP meta data support
On 2019/6/27 下午4:06, Yuya Kusakabe wrote:
> This adds XDP meta data support to both receive_small() and
> receive_mergeable().
>
> Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")
> Signed-off-by: Yuya Kusakabe <yuya.kusakabe@...il.com>
> ---
> drivers/net/virtio_net.c | 40 +++++++++++++++++++++++++++++-----------
> 1 file changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4f3de0ac8b0b..e787657fc568 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -371,7 +371,7 @@ 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)
> + bool hdr_valid, unsigned int metasize)
> {
> struct sk_buff *skb;
> struct virtio_net_hdr_mrg_rxbuf *hdr;
> @@ -393,17 +393,25 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> else
> hdr_padded_len = sizeof(struct padded_vnet_hdr);
>
> - if (hdr_valid)
> + if (hdr_valid && !metasize)
> memcpy(hdr, p, hdr_len);
>
> len -= hdr_len;
> offset += hdr_padded_len;
> p += hdr_padded_len;
>
> - copy = len;
> + copy = len + metasize;
> if (copy > skb_tailroom(skb))
> copy = skb_tailroom(skb);
> - skb_put_data(skb, p, copy);
> +
> + if (metasize) {
> + skb_put_data(skb, p - metasize, copy);
I would rather keep copy untouched above, and use copy + metasize here,
then you can save the following decrement as well. Or tweak the caller
the count the meta in to offset, then we need only deal with skb_pull()
and skb_metadata_set() here.
> + __skb_pull(skb, metasize);
> + skb_metadata_set(skb, metasize);
> + copy -= metasize;
> + } else {
> + skb_put_data(skb, p, copy);
> + }
>
> len -= copy;
> offset += copy;
> @@ -644,6 +652,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
> unsigned int delta = 0;
> struct page *xdp_page;
> int err;
> + unsigned int metasize = 0;
>
> len -= vi->hdr_len;
> stats->bytes += len;
> @@ -683,8 +692,8 @@ static struct sk_buff *receive_small(struct net_device *dev,
>
> xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len;
> xdp.data = xdp.data_hard_start + xdp_headroom;
> - xdp_set_data_meta_invalid(&xdp);
> xdp.data_end = xdp.data + len;
> + xdp.data_meta = xdp.data;
> xdp.rxq = &rq->xdp_rxq;
> orig_data = xdp.data;
> act = bpf_prog_run_xdp(xdp_prog, &xdp);
> @@ -695,9 +704,11 @@ static struct sk_buff *receive_small(struct net_device *dev,
> /* 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 XDP_TX:
> stats->xdp_tx++;
> + xdp.data_meta = xdp.data;
Why need this?
> xdpf = convert_to_xdp_frame(&xdp);
> if (unlikely(!xdpf))
> goto err_xdp;
> @@ -735,11 +746,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
> }
> skb_reserve(skb, headroom - delta);
> skb_put(skb, len);
> - if (!delta) {
> + if (!delta && !metasize) {
> buf += header_offset;
> memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
> } /* keep zeroed vnet hdr since packet was changed by bpf */
Is there any method to preserve the vnet header here? We probably don't
want to lose it for XDP_PASS when packet is not modified.
>
> + if (metasize)
> + skb_metadata_set(skb, metasize);
> +
> err:
> return skb;
>
> @@ -761,7 +775,7 @@ 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);
> + PAGE_SIZE, true, 0);
>
> stats->bytes += len - vi->hdr_len;
> if (unlikely(!skb))
> @@ -793,6 +807,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> unsigned int truesize;
> unsigned int headroom = mergeable_ctx_to_headroom(ctx);
> int err;
> + unsigned int metasize = 0;
>
> head_skb = NULL;
> stats->bytes += len - vi->hdr_len;
> @@ -839,8 +854,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> data = page_address(xdp_page) + offset;
> xdp.data_hard_start = data - VIRTIO_XDP_HEADROOM + vi->hdr_len;
> xdp.data = data + vi->hdr_len;
> - xdp_set_data_meta_invalid(&xdp);
> xdp.data_end = xdp.data + (len - vi->hdr_len);
> + xdp.data_meta = xdp.data;
> xdp.rxq = &rq->xdp_rxq;
>
> act = bpf_prog_run_xdp(xdp_prog, &xdp);
> @@ -859,18 +874,20 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> * adjusted
> */
> len = xdp.data_end - xdp.data + vi->hdr_len;
> + metasize = xdp.data - xdp.data_meta;
> /* We can only create skb based on xdp_page. */
> if (unlikely(xdp_page != page)) {
> rcu_read_unlock();
> put_page(page);
> head_skb = page_to_skb(vi, rq, xdp_page,
> - offset, len,
> - PAGE_SIZE, false);
> + offset, len,
> + PAGE_SIZE, false, metasize);
Indentation is wired.
Thanks
> return head_skb;
> }
> break;
> case XDP_TX:
> stats->xdp_tx++;
> + xdp.data_meta = xdp.data;
> xdpf = convert_to_xdp_frame(&xdp);
> if (unlikely(!xdpf))
> goto err_xdp;
> @@ -921,7 +938,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> goto err_skb;
> }
>
> - head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog);
> + head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
> + metasize);
> curr_skb = head_skb;
>
> if (unlikely(!curr_skb))
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