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Date: Mon, 24 Feb 2020 12:05:17 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>,
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, netdev@...r.kernel.org,
songliubraving@...com, yhs@...com
Subject: Re: [PATCH bpf-next v5] virtio_net: add XDP meta data support
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@...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.
> 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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