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Message-ID: <8fafd23d-4c80-539d-9f74-bc5cda0d5575@gmail.com>
Date: Fri, 21 Feb 2020 17:36:08 +0900
From: Yuya Kusakabe <yuya.kusakabe@...il.com>
To: Jason Wang <jasowang@...hat.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 2/21/20 1:23 PM, Jason Wang wrote:
>
> 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()?
virtio_net doesn't support by calling xdp_set_data_meta_invalid() for now.
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/drivers/net/virtio_net.c?id=e42da4c62abb547d9c9138e0e7fcd1f36057b5e8#n686
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/drivers/net/virtio_net.c?id=e42da4c62abb547d9c9138e0e7fcd1f36057b5e8#n842
And xdp_set_data_meta_invalid() are added by de8f3a83b0a0.
$ git blame ./drivers/net/virtio_net.c | grep xdp_set_data_meta_invalid
de8f3a83b0a0f (Daniel Borkmann 2017-09-25 02:25:51 +0200 686) xdp_set_data_meta_invalid(&xdp);
de8f3a83b0a0f (Daniel Borkmann 2017-09-25 02:25:51 +0200 842) xdp_set_data_meta_invalid(&xdp);
So I added `Fixes: de8f3a83b0a0 ("bpf: add meta pointer for direct access")` to the comment.
>
>
>> 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
I see. So I need to revert to delta from xdp_prog?
Thank you.
>
>> + 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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