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Message-ID: <455941f9-aadb-ab70-2745-34f8fd893e89@gmail.com>
Date: Tue, 2 Jul 2019 10:00:27 +0900
From: Yuya Kusakabe <yuya.kusakabe@...il.com>
To: Jason Wang <jasowang@...hat.com>, davem@...emloft.net
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next] virtio_net: add XDP meta data support
On 7/1/19 6:30 PM, Jason Wang wrote:
>
> On 2019/6/27 下午4:06, 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>
>> ---
>> drivers/net/virtio_net.c | 40 +++++++++++++++++++++++++++++-----------
>> 1 file changed, 29 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 4f3de0ac8b0b..e787657fc568 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;
>> @@ -393,17 +393,25 @@ 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;
>> offset += hdr_padded_len;
>> p += hdr_padded_len;
>> - copy = len;
>> + copy = len + metasize;
>> if (copy > skb_tailroom(skb))
>> copy = skb_tailroom(skb);
>> - skb_put_data(skb, p, copy);
>> +
>> + if (metasize) {
>> + skb_put_data(skb, p - metasize, copy);
>
>
> I would rather keep copy untouched above, and use copy + metasize here, then you can save the following decrement as well. Or tweak the caller the count the meta in to offset, then we need only deal with skb_pull() and skb_metadata_set() here.
I think the latter is better, because copy + metasize must be smaller than skb tailroom size.
>
>> + __skb_pull(skb, metasize);
>> + skb_metadata_set(skb, metasize);
>> + copy -= metasize;
>> + } else {
>> + skb_put_data(skb, p, copy);
>> + }
>> len -= copy;
>> offset += copy;
>> @@ -644,6 +652,7 @@ 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 +692,8 @@ 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);
>> @@ -695,9 +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;
>
>
> Why need this?
Because virtnet_xdp_xmit() doesn't support XDP meta data as below. And I suppose that we don't need to support XDP metadata for XDP_TX.
static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
struct send_queue *sq,
struct xdp_frame *xdpf)
{
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;
>
>> xdpf = convert_to_xdp_frame(&xdp);
>> if (unlikely(!xdpf))
>> goto err_xdp;
>> @@ -735,11 +746,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
>> }
>> skb_reserve(skb, headroom - delta);
>> skb_put(skb, len);
>> - if (!delta) {
>> + if (!delta && !metasize) {
>> buf += header_offset;
>> memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
>> } /* keep zeroed vnet hdr since packet was changed by bpf */
>
>
> Is there any method to preserve the vnet header here? We probably don't want to lose it for XDP_PASS when packet is not modified.
I'll try to keep the vnet header with moving the meta data to the front of the vnet header.
>
>> + if (metasize)
>> + skb_metadata_set(skb, metasize);
>> +
>> err:
>> return skb;
>> @@ -761,7 +775,7 @@ static struct sk_buff *receive_big(struct net_device *dev,
>> {
>> struct page *page = buf;
>> struct sk_buff *skb = page_to_skb(vi, rq, page, 0, len,
>> - PAGE_SIZE, true);
>> + PAGE_SIZE, true, 0);
>> stats->bytes += len - vi->hdr_len;
>> if (unlikely(!skb))
>> @@ -793,6 +807,7 @@ 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 +854,8 @@ 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);
>> @@ -859,18 +874,20 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>> * adjusted
>> */
>> len = xdp.data_end - xdp.data + vi->hdr_len;
>> + metasize = xdp.data - xdp.data_meta;
>> /* 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);
>> + offset, len,
>> + PAGE_SIZE, false, metasize);
>
>
> Indentation is wired.
Sorry. I'll fix it.
>
> Thanks
>
>
>> 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 +938,8 @@ 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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