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Date: Tue, 2 Jul 2019 16:33:28 +0800
From: Jason Wang <jasowang@...hat.com>
To: Yuya Kusakabe <yuya.kusakabe@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, davem@...emloft.net,
hawk@...nel.org, jakub.kicinski@...ronome.com,
john.fastabend@...il.com, kafai@...com, mst@...hat.com,
netdev@...r.kernel.org, songliubraving@...com, yhs@...com
Subject: Re: [PATCH bpf-next v3] virtio_net: add XDP meta data support
On 2019/7/2 下午4:16, 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>
> ---
> v3:
> - fix preserve the vnet header in receive_small().
> v2:
> - keep copy untouched in page_to_skb().
> - preserve the vnet header in receive_small().
> - fix indentation.
> ---
> drivers/net/virtio_net.c | 45 +++++++++++++++++++++++++++-------------
> 1 file changed, 31 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4f3de0ac8b0b..03a1ae6fe267 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;
> @@ -393,7 +393,7 @@ 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;
> @@ -405,6 +405,11 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> copy = skb_tailroom(skb);
> skb_put_data(skb, p, copy);
>
> + if (metasize) {
> + __skb_pull(skb, metasize);
> + skb_metadata_set(skb, metasize);
> + }
> +
> len -= copy;
> offset += copy;
>
> @@ -644,6 +649,7 @@ 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;
> @@ -683,10 +689,13 @@ 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;
> + /* Copy the vnet header to the front of data_hard_start to avoid
> + * overwriting by XDP meta data */
> + memcpy(xdp.data_hard_start - vi->hdr_len, xdp.data - vi->hdr_len, vi->hdr_len);
What happens if we have a large metadata that occupies all headroom here?
Thanks
> act = bpf_prog_run_xdp(xdp_prog, &xdp);
> stats->xdp_packets++;
>
> @@ -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;
> xdpf = convert_to_xdp_frame(&xdp);
> if (unlikely(!xdpf))
> goto err_xdp;
> @@ -736,10 +747,12 @@ static struct sk_buff *receive_small(struct net_device *dev,
> skb_reserve(skb, headroom - delta);
> skb_put(skb, len);
> if (!delta) {
> - buf += header_offset;
> - memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
> + memcpy(skb_vnet_hdr(skb), buf + VIRTNET_RX_PAD, vi->hdr_len);
> } /* keep zeroed vnet hdr since packet was changed by bpf */
>
> + if (metasize)
> + skb_metadata_set(skb, metasize);
> +
> err:
> return skb;
>
> @@ -760,8 +773,8 @@ static struct sk_buff *receive_big(struct net_device *dev,
> struct virtnet_rq_stats *stats)
> {
> struct page *page = buf;
> - struct sk_buff *skb = page_to_skb(vi, rq, page, 0, len,
> - PAGE_SIZE, true);
> + struct sk_buff *skb =
> + page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, true, 0);
>
> stats->bytes += len - vi->hdr_len;
> if (unlikely(!skb))
> @@ -793,6 +806,7 @@ 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 +853,8 @@ 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);
> @@ -852,8 +866,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> * adjustments. Note other cases do not build an
> * skb and avoid using offset
> */
> - offset = xdp.data -
> - page_address(xdp_page) - vi->hdr_len;
> + metasize = xdp.data - xdp.data_meta;
> + offset = xdp.data - page_address(xdp_page) -
> + vi->hdr_len - metasize;
>
> /* recalculate len if xdp.data or xdp.data_end were
> * adjusted
> @@ -863,14 +878,15 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> 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);
> + head_skb = page_to_skb(vi, rq, xdp_page, offset,
> + len, PAGE_SIZE, false,
> + metasize);
> 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 +937,8 @@ 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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