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Message-ID: <5bf11065-6b85-8253-8548-683c01c98ac1@redhat.com>
Date: Fri, 21 Feb 2020 12:23:31 +0800
From: Jason Wang <jasowang@...hat.com>
To: Yuya Kusakabe <yuya.kusakabe@...il.com>
Cc: andriin@...com, ast@...nel.org, bpf@...r.kernel.org,
daniel@...earbox.net, davem@...emloft.net, hawk@...nel.org,
john.fastabend@...il.com, kafai@...com, kuba@...nel.org,
linux-kernel@...r.kernel.org, mst@...hat.com,
netdev@...r.kernel.org, songliubraving@...com, yhs@...com
Subject: Re: [PATCH bpf-next v5] virtio_net: add XDP meta data support
On 2020/2/20 下午4:55, Yuya Kusakabe wrote:
> Implement support for transferring XDP meta data into skb for
> virtio_net driver; before calling into the program, xdp.data_meta points
> to xdp.data, where on program return with pass verdict, we call
> into skb_metadata_set().
>
> Tested with the script at
> https://github.com/higebu/virtio_net-xdp-metadata-test.
>
> Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")
I'm not sure this is correct since virtio-net claims to not support
metadata by calling xdp_set_data_meta_invalid()?
> Signed-off-by: Yuya Kusakabe <yuya.kusakabe@...il.com>
> ---
> v5:
> - page_to_skb(): copy vnet header if hdr_valid without checking metasize.
> - receive_small(): do not copy vnet header if xdp_prog is availavle.
> - __virtnet_xdp_xmit_one(): remove the xdp_set_data_meta_invalid().
> - improve comments.
> v4:
> - improve commit message
> 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 | 54 ++++++++++++++++++++++++----------------
> 1 file changed, 33 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 2fe7a3188282..4ea0ae60c000 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;
> @@ -393,6 +393,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> else
> hdr_padded_len = sizeof(struct padded_vnet_hdr);
>
> + /* hdr_valid means no XDP, so we can copy the vnet header */
> if (hdr_valid)
> memcpy(hdr, p, hdr_len);
>
> @@ -405,6 +406,11 @@ 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;
>
> @@ -450,10 +456,6 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
> struct virtio_net_hdr_mrg_rxbuf *hdr;
> int err;
>
> - /* virtqueue want to use data area in-front of packet */
> - if (unlikely(xdpf->metasize > 0))
> - return -EOPNOTSUPP;
> -
> if (unlikely(xdpf->headroom < vi->hdr_len))
> return -EOVERFLOW;
>
> @@ -644,6 +646,7 @@ 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 +686,8 @@ 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);
> @@ -695,6 +698,7 @@ 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++;
> @@ -735,11 +739,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
> }
> skb_reserve(skb, headroom - delta);
> skb_put(skb, len);
> - if (!delta) {
> + if (!xdp_prog) {
> buf += header_offset;
> memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
> } /* keep zeroed vnet hdr since packet was changed by bpf */
I prefer to make this an independent patch and cc stable.
Other looks good.
Thanks
>
> + if (metasize)
> + skb_metadata_set(skb, metasize);
> +
> err:
> return skb;
>
> @@ -760,8 +767,8 @@ 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 +800,7 @@ 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 +847,8 @@ 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);
> @@ -848,24 +856,27 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>
> switch (act) {
> case XDP_PASS:
> + metasize = xdp.data - xdp.data_meta;
> +
> /* recalculate offset to account for any header
> - * adjustments. Note other cases do not build an
> - * skb and avoid using offset
> + * adjustments and minus the metasize to copy the
> + * metadata in page_to_skb(). Note other cases do not
> + * build an skb and avoid using offset
> */
> - offset = xdp.data -
> - page_address(xdp_page) - vi->hdr_len;
> + offset = xdp.data - page_address(xdp_page) -
> + vi->hdr_len - metasize;
>
> - /* recalculate len if xdp.data or xdp.data_end were
> - * adjusted
> + /* recalculate len if xdp.data, xdp.data_end or
> + * xdp.data_meta were adjusted
> */
> - len = xdp.data_end - xdp.data + vi->hdr_len;
> + len = xdp.data_end - xdp.data + vi->hdr_len + metasize;
> /* 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);
> + head_skb = page_to_skb(vi, rq, xdp_page, offset,
> + len, PAGE_SIZE, false,
> + metasize);
> return head_skb;
> }
> break;
> @@ -921,7 +932,8 @@ 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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