| 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
| ||
|
Date: Tue, 27 Dec 2022 17:31:28 +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 5/9] virtio_net: construct multi-buffer xdp in
mergeable
在 2022/12/27 下午3:01, Jason Wang 写道:
>
> 在 2022/12/20 22:14, Heng Qi 写道:
>> Build multi-buffer xdp using virtnet_build_xdp_buff_mrg().
>>
>> For the prefilled buffer before xdp is set, we will probably use
>> vq reset in the future. At the same time, virtio net currently
>> uses comp pages, and bpf_xdp_frags_increase_tail() needs to calculate
>> the tailroom of the last frag, which will involve the offset of the
>> corresponding page and cause a negative value, so we disable tail
>> increase by not setting xdp_rxq->frag_size.
>>
>> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
>> Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
>> ---
>> drivers/net/virtio_net.c | 60 +++++++++++++++++++++++++++++-----------
>> 1 file changed, 44 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 8fc3b1841d92..40bc58fa57f5 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1018,6 +1018,7 @@ static struct sk_buff *receive_mergeable(struct
>> net_device *dev,
>> unsigned int *xdp_xmit,
>> struct virtnet_rq_stats *stats)
>> {
>> + unsigned int tailroom = SKB_DATA_ALIGN(sizeof(struct
>> skb_shared_info));
>> struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
>> u16 num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
>> struct page *page = virt_to_head_page(buf);
>> @@ -1048,11 +1049,14 @@ static struct sk_buff
>> *receive_mergeable(struct net_device *dev,
>> rcu_read_lock();
>> xdp_prog = rcu_dereference(rq->xdp_prog);
>> if (xdp_prog) {
>> + unsigned int xdp_frags_truesz = 0;
>> + struct skb_shared_info *shinfo;
>> struct xdp_frame *xdpf;
>> struct page *xdp_page;
>> struct xdp_buff xdp;
>> void *data;
>> u32 act;
>> + int i;
>> /* Transient failure which in theory could occur if
>> * in-flight packets from before XDP was enabled reach
>> @@ -1061,19 +1065,23 @@ static struct sk_buff
>> *receive_mergeable(struct net_device *dev,
>> if (unlikely(hdr->hdr.gso_type))
>> goto err_xdp;
>> - /* Buffers with headroom use PAGE_SIZE as alloc size,
>> - * see add_recvbuf_mergeable() + get_mergeable_buf_len()
>> + /* Now XDP core assumes frag size is PAGE_SIZE, but buffers
>> + * with headroom may add hole in truesize, which
>> + * make their length exceed PAGE_SIZE. So we disabled the
>> + * hole mechanism for xdp. See add_recvbuf_mergeable().
>> */
>> frame_sz = headroom ? PAGE_SIZE : truesize;
>> - /* This happens when rx buffer size is underestimated
>> - * or headroom is not enough because of the buffer
>> - * was refilled before XDP is set. This should only
>> - * happen for the first several packets, so we don't
>> - * care much about its performance.
>> + /* This happens when headroom is not enough because
>> + * of the buffer was prefilled before XDP is set.
>> + * This should only happen for the first several packets.
>> + * In fact, vq reset can be used here to help us clean up
>> + * the prefilled buffers, but many existing devices do not
>> + * support it, and we don't want to bother users who are
>> + * using xdp normally.
>> */
>> - if (unlikely(num_buf > 1 ||
>> - headroom < virtnet_get_headroom(vi))) {
>> + if (!xdp_prog->aux->xdp_has_frags &&
>> + (num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
>> /* linearize data for XDP */
>> xdp_page = xdp_linearize_page(rq, &num_buf,
>> page, offset,
>> @@ -1084,17 +1092,26 @@ static struct sk_buff
>> *receive_mergeable(struct net_device *dev,
>> if (!xdp_page)
>> goto err_xdp;
>> offset = VIRTIO_XDP_HEADROOM;
>> + } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
>
>
> I believe we need to check xdp_prog->aux->xdp_has_frags at least since
> this may not work if it needs more than one frags?
Sorry Jason, I didn't understand you, I'll try to answer. For
multi-buffer xdp programs, if the first buffer is a pre-filled buffer
(no headroom),
we need to copy it out and use the subsequent buffers of this packet as
its frags (this is done in virtnet_build_xdp_buff_mrg()), therefore,
it seems that there is no need to check 'xdp_prog->aux->xdp_has_frags'
to mark multi-buffer xdp (of course I can add it),
+ } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
Because the linearization of single-buffer xdp has all been done before,
the subsequent situation can only be applied to multi-buffer xdp:
+ if (!xdp_prog->aux->xdp_has_frags &&
+ (num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
>
> Btw, I don't see a reason why we can't reuse xdp_linearize_page(), (we
> probably don't need error is the buffer exceeds PAGE_SIZE).
For multi-buffer xdp, we only need to copy out the pre-filled first
buffer, and use the remaining buffers of this packet as frags in
virtnet_build_xdp_buff_mrg().
Thanks.
>
> Other looks good.
>
> Thanks
>
>
>> + if ((VIRTIO_XDP_HEADROOM + len + tailroom) > PAGE_SIZE)
>> + goto err_xdp;
>> +
>> + xdp_page = alloc_page(GFP_ATOMIC);
>> + if (!xdp_page)
>> + goto err_xdp;
>> +
>> + memcpy(page_address(xdp_page) + VIRTIO_XDP_HEADROOM,
>> + page_address(page) + offset, len);
>> + frame_sz = PAGE_SIZE;
>> + offset = VIRTIO_XDP_HEADROOM;
>> } else {
>> xdp_page = page;
>> }
>> -
>> - /* Allow consuming headroom but reserve enough space to push
>> - * the descriptor on if we get an XDP_TX return code.
>> - */
>> data = page_address(xdp_page) + offset;
>> - xdp_init_buff(&xdp, frame_sz - vi->hdr_len, &rq->xdp_rxq);
>> - xdp_prepare_buff(&xdp, data - VIRTIO_XDP_HEADROOM +
>> vi->hdr_len,
>> - VIRTIO_XDP_HEADROOM, len - vi->hdr_len, true);
>> + err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data,
>> len, frame_sz,
>> + &num_buf, &xdp_frags_truesz, stats);
>> + if (unlikely(err))
>> + goto err_xdp_frags;
>> act = bpf_prog_run_xdp(xdp_prog, &xdp);
>> stats->xdp_packets++;
>> @@ -1190,6 +1207,17 @@ static struct sk_buff
>> *receive_mergeable(struct net_device *dev,
>> __free_pages(xdp_page, 0);
>> goto err_xdp;
>> }
>> +err_xdp_frags:
>> + shinfo = xdp_get_shared_info_from_buff(&xdp);
>> +
>> + if (unlikely(xdp_page != page))
>> + __free_pages(xdp_page, 0);
>> +
>> + for (i = 0; i < shinfo->nr_frags; i++) {
>> + xdp_page = skb_frag_page(&shinfo->frags[i]);
>> + put_page(xdp_page);
>> + }
>> + goto err_xdp;
>> }
>> rcu_read_unlock();
Powered by blists - more mailing lists