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Message-ID: <CAKhg4tKGuA=ZC1agLGsqzNSKnzWvVewZj2gTEHFmX7HAK1Xfwg@mail.gmail.com>
Date: Thu, 25 Jan 2024 18:17:40 +0800
From: Liang Chen <liangchen.linux@...il.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
mst@...hat.com, jasowang@...hat.com, hengqi@...ux.alibaba.com
Subject: Re: [PATCH v2 1/3] virtio_net: Preserve virtio header before XDP
program execution
On Wed, Jan 24, 2024 at 5:08 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> On Wed, 24 Jan 2024 16:57:19 +0800, Liang Chen <liangchen.linux@...il.com> wrote:
> > The xdp program may overwrite the inline virtio header. To ensure the
> > integrity of the virtio header, it is saved in a data structure that
> > wraps both the xdp_buff and the header before running the xdp program.
> >
> > Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> > ---
> > drivers/net/virtio_net.c | 43 +++++++++++++++++++++++++++++-----------
> > 1 file changed, 31 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index d7ce4a1011ea..b56828804e5f 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -349,6 +349,11 @@ struct virtio_net_common_hdr {
> > };
> > };
> >
> > +struct virtnet_xdp_buff {
> > + struct xdp_buff xdp;
> > + struct virtio_net_common_hdr hdr;
>
> Not all items of the hdr are useful, we can just save the useful items.
>
Sure. Will do in v3. Thanks.
> > +};
> > +
> > static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
> >
> > static bool is_xdp_frame(void *ptr)
> > @@ -1199,9 +1204,10 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
> > unsigned int headroom = vi->hdr_len + header_offset;
> > struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
> > struct page *page = virt_to_head_page(buf);
> > + struct virtnet_xdp_buff virtnet_xdp;
> > struct page *xdp_page;
> > + struct xdp_buff *xdp;
> > unsigned int buflen;
> > - struct xdp_buff xdp;
> > struct sk_buff *skb;
> > unsigned int metasize = 0;
> > u32 act;
> > @@ -1233,17 +1239,23 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
> > page = xdp_page;
> > }
> >
> > - xdp_init_buff(&xdp, buflen, &rq->xdp_rxq);
> > - xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
> > + xdp = &virtnet_xdp.xdp;
> > + xdp_init_buff(xdp, buflen, &rq->xdp_rxq);
> > + xdp_prepare_buff(xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
> > xdp_headroom, len, true);
> >
> > - act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> > + /* Copy out the virtio header, as it may be overwritten by the
> > + * xdp program.
> > + */
> > + memcpy(&virtnet_xdp.hdr, hdr, vi->hdr_len);
>
> Can we put this into virtnet_xdp_handler?
>
> And just do that when the hash is negotiated.
>
> > +
> > + act = virtnet_xdp_handler(xdp_prog, xdp, dev, xdp_xmit, stats);
> >
> > switch (act) {
> > case XDP_PASS:
> > /* Recalculate length in case bpf program changed it */
> > - len = xdp.data_end - xdp.data;
> > - metasize = xdp.data - xdp.data_meta;
> > + len = xdp->data_end - xdp->data;
> > + metasize = xdp->data - xdp->data_meta;
> > break;
> >
> > case XDP_TX:
> > @@ -1254,7 +1266,7 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
> > goto err_xdp;
> > }
> >
> > - skb = virtnet_build_skb(buf, buflen, xdp.data - buf, len);
> > + skb = virtnet_build_skb(buf, buflen, xdp->data - buf, len);
> > if (unlikely(!skb))
> > goto err;
> >
> > @@ -1591,10 +1603,11 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
> > int num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
> > struct page *page = virt_to_head_page(buf);
> > int offset = buf - page_address(page);
> > + struct virtnet_xdp_buff virtnet_xdp;
> > unsigned int xdp_frags_truesz = 0;
> > struct sk_buff *head_skb;
> > unsigned int frame_sz;
> > - struct xdp_buff xdp;
> > + struct xdp_buff *xdp;
> > void *data;
> > u32 act;
> > int err;
> > @@ -1604,16 +1617,22 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
> > if (unlikely(!data))
> > goto err_xdp;
> >
> > - err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
> > + xdp = &virtnet_xdp.xdp;
> > + 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;
> >
> > - act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> > + /* Copy out the virtio header, as it may be overwritten by the
> > + * xdp program.
> > + */
> > + memcpy(&virtnet_xdp.hdr, hdr, vi->hdr_len);
> > +
> > + act = virtnet_xdp_handler(xdp_prog, xdp, dev, xdp_xmit, stats);
> >
> > switch (act) {
> > case XDP_PASS:
> > - head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
> > + head_skb = build_skb_from_xdp_buff(dev, vi, xdp, xdp_frags_truesz);
> > if (unlikely(!head_skb))
> > break;
> > return head_skb;
> > @@ -1626,7 +1645,7 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
> > break;
> > }
> >
> > - put_xdp_frags(&xdp);
> > + put_xdp_frags(xdp);
> >
> > err_xdp:
> > put_page(page);
> > --
> > 2.40.1
> >
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