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SubjectRe: [PATCH bpf-next v5] virtio_net: add XDP meta data support
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On 2020/2/23 下午4:14, Michael S. Tsirkin wrote:
> On Fri, Feb 21, 2020 at 05:36:08PM +0900, Yuya Kusakabe wrote:
>> 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@gmail.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.
> So maybe send a 2 patch series: 1/2 is this chunk with the appropriate
> description. Actually for netdev David prefers that people do not
> cc stable directly, just include Fixes tag and mention in the
> commit log it's also needed for stable. Patch 2/2 is the rest
> handling metadata.


+1

Thanks


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