| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <8aa5b8fb-d766-ac84-dfc1-4f9947e86e27@linux.alibaba.com>
Date: Tue, 27 Dec 2022 17:10:31 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
bpf@...r.kernel.org
Cc: "Michael S . Tsirkin" <mst@...hat.com>,
Paolo Abeni <pabeni@...hat.com>,
Jakub Kicinski <kuba@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
"David S . Miller" <davem@...emloft.net>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH v2 4/9] virtio_net: build xdp_buff with multi buffers
在 2022/12/27 下午2:46, Jason Wang 写道:
>
> 在 2022/12/20 22:14, Heng Qi 写道:
>> Support xdp for multi buffer packets in mergeable mode.
>>
>> Putting the first buffer as the linear part for xdp_buff,
>> and the rest of the buffers as non-linear fragments to struct
>> skb_shared_info in the tailroom belonging to xdp_buff.
>>
>> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
>> Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
>> ---
>> drivers/net/virtio_net.c | 78 ++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 78 insertions(+)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 08f209d7b0bf..8fc3b1841d92 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -931,6 +931,84 @@ static struct sk_buff *receive_big(struct
>> net_device *dev,
>> return NULL;
>> }
>> +/* TODO: build xdp in big mode */
>> +static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
>> + struct virtnet_info *vi,
>> + struct receive_queue *rq,
>> + struct xdp_buff *xdp,
>> + void *buf,
>> + unsigned int len,
>> + unsigned int frame_sz,
>> + u16 *num_buf,
>> + unsigned int *xdp_frags_truesize,
>> + struct virtnet_rq_stats *stats)
>> +{
>> + unsigned int tailroom = SKB_DATA_ALIGN(sizeof(struct
>> skb_shared_info));
>> + struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
>> + unsigned int truesize, headroom;
>> + struct skb_shared_info *shinfo;
>> + unsigned int xdp_frags_truesz = 0;
>> + unsigned int cur_frag_size;
>> + struct page *page;
>> + skb_frag_t *frag;
>> + int offset;
>> + void *ctx;
>> +
>> + xdp_init_buff(xdp, frame_sz, &rq->xdp_rxq);
>> + xdp_prepare_buff(xdp, buf - VIRTIO_XDP_HEADROOM,
>> + VIRTIO_XDP_HEADROOM + vi->hdr_len, len - vi->hdr_len,
>> true);
>> +
>> + if (*num_buf > 1) {
>> + shinfo = xdp_get_shared_info_from_buff(xdp);
>> + shinfo->nr_frags = 0;
>> + shinfo->xdp_frags_size = 0;
>> + }
>> +
>> + if ((*num_buf - 1) > MAX_SKB_FRAGS)
>> + return -EINVAL;
>> +
>> + while ((--*num_buf) >= 1) {
>> + buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
>> + if (unlikely(!buf)) {
>> + pr_debug("%s: rx error: %d buffers out of %d missing\n",
>> + dev->name, *num_buf,
>> + virtio16_to_cpu(vi->vdev, hdr->num_buffers));
>> + dev->stats.rx_length_errors++;
>> + return -EINVAL;
>> + }
>> +
>> + if (!xdp_buff_has_frags(xdp))
>> + xdp_buff_set_frags_flag(xdp);
>
>
> Any reason to put this inside the loop?
I'll move it outside the loop in the next version.
>
>
>> +
>> + stats->bytes += len;
>> + page = virt_to_head_page(buf);
>> + offset = buf - page_address(page);
>> + truesize = mergeable_ctx_to_truesize(ctx);
>> + headroom = mergeable_ctx_to_headroom(ctx);
>> +
>> + cur_frag_size = truesize + (headroom ? (headroom + tailroom)
>> : 0);
>> + xdp_frags_truesz += cur_frag_size;
>
>
> Not related to this patch, but it would easily confuse the future
> readers that the we need another math for truesize. I think at least
> we need some comments for this or
Yes it might, I'll add more comments on this.
>
> I guess the root cause is in get_mergeable_buf_len:
>
> static unsigned int get_mergeable_buf_len(struct receive_queue *rq,
> struct ewma_pkt_len *avg_pkt_len,
> unsigned int room)
> {
> struct virtnet_info *vi = rq->vq->vdev->priv;
> const size_t hdr_len = vi->hdr_len;
> unsigned int len;
>
> if (room)
> return PAGE_SIZE - room;
>
> And we do
>
> len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
>
> ...
>
> ctx = mergeable_len_to_ctx(len, headroom);
>
>
> I wonder if it's better to pack the real truesize (PAGE_SIZE) here.
> This may ease a lot of things.
I don't know the historical reason for not packing, but I guess this is
for the convenience of
comparing the actual length len given by the device with truesize.
Therefore, I think it would
be better to keep the above practice for now? Perhaps, I can add more
explanation to the
above code to help future readers try not to get confused.
Thanks.
>
> Thanks
>
>
>> + if (unlikely(len > truesize || cur_frag_size > PAGE_SIZE)) {
>> + pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
>> + dev->name, len, (unsigned long)ctx);
>> + dev->stats.rx_length_errors++;
>> + return -EINVAL;
>> + }
>> +
>> + frag = &shinfo->frags[shinfo->nr_frags++];
>> + __skb_frag_set_page(frag, page);
>> + skb_frag_off_set(frag, offset);
>> + skb_frag_size_set(frag, len);
>> + if (page_is_pfmemalloc(page))
>> + xdp_buff_set_frag_pfmemalloc(xdp);
>> +
>> + shinfo->xdp_frags_size += len;
>> + }
>> +
>> + *xdp_frags_truesize = xdp_frags_truesz;
>> + return 0;
>> +}
>> +
>> static struct sk_buff *receive_mergeable(struct net_device *dev,
>> struct virtnet_info *vi,
>> struct receive_queue *rq,
Powered by blists - more mailing lists