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Date: Sun, 23 Apr 2023 09:57:48 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: netdev@...r.kernel.org, Jason Wang <jasowang@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next v2 05/14] virtio_net: introduce xdp res enums
On Fri, 21 Apr 2023 07:54:11 -0400, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Fri, Apr 21, 2023 at 03:24:00PM +0800, Xuan Zhuo wrote:
> > On Fri, 21 Apr 2023 03:00:15 -0400, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> > > On Tue, Apr 18, 2023 at 02:53:18PM +0800, Xuan Zhuo wrote:
> > > > virtnet_xdp_handler() is to process all the logic related to XDP. The
> > > > caller only needs to care about how to deal with the buf. So this commit
> > > > introduces new enums:
> > > >
> > > > 1. VIRTNET_XDP_RES_PASS: make skb by the buf
> > > > 2. VIRTNET_XDP_RES_DROP: xdp return drop action or some error, caller
> > > > should release the buf
> > > > 3. VIRTNET_XDP_RES_CONSUMED: xdp consumed the buf, the caller doesnot to
> > > > do anything
> > > >
> > > > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > >
> > >
> > > I am not excited about using virtio specific enums then translating
> > > to standard ones.
> >
> >
> > My fault, my expression is not very complete.
> >
> > This is not a replacement, but just want to say, there are only three cases of
> > virtnet_xdp_handler. Caller only needs to handle this three cases. Instead
> > of paying attention to the detailed return results of XDP.
> >
> > In addition, virtnet_xdp_handler returns XDP_TX, but in fact, the work of XDP_TX
> > is already done in Virtnet_xdp_handler. Caller does not need to do anything for
> > XDP_TX, giving people a feeling, XDP_TX does not need to be processed. I think
> > it is not good.
> >
> > Thanks.
>
> I don't really get it, sorry. If it's possible to stick to
> XDP return codes, that is preferable.
Although, I still think that it would be better to use VIRTNET_XDP_RES_*, and
other drivers did the same thing. If you still insist, I can remove this commit.
In addition, I think squashing this patch to the previous patch may be more
suitable. Just like I done in last patchset. @Jason
Because what I want to express is that virtnet_xdp_handler() has only three
kinds of returns, caller does not need to pay attention to the details of XDP
returns.
Thanks.
>
> >
> >
> > >
> > > > ---
> > > > drivers/net/virtio_net.c | 42 ++++++++++++++++++++++++++--------------
> > > > 1 file changed, 27 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index 0fa64c314ea7..4dfdc211d355 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -301,6 +301,15 @@ struct padded_vnet_hdr {
> > > > char padding[12];
> > > > };
> > > >
> > > > +enum {
> > > > + /* xdp pass */
> > > > + VIRTNET_XDP_RES_PASS,
> > > > + /* drop packet. the caller needs to release the page. */
> > > > + VIRTNET_XDP_RES_DROP,
> > > > + /* packet is consumed by xdp. the caller needs to do nothing. */
> > > > + VIRTNET_XDP_RES_CONSUMED,
> > > > +};
> > > > +
> > > > static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
> > > > static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
> > > >
> > > > @@ -803,14 +812,14 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> > > >
> > > > switch (act) {
> > > > case XDP_PASS:
> > > > - return act;
> > > > + return VIRTNET_XDP_RES_PASS;
> > > >
> > > > case XDP_TX:
> > > > stats->xdp_tx++;
> > > > xdpf = xdp_convert_buff_to_frame(xdp);
> > > > if (unlikely(!xdpf)) {
> > > > netdev_dbg(dev, "convert buff to frame failed for xdp\n");
> > > > - return XDP_DROP;
> > > > + return VIRTNET_XDP_RES_DROP;
> > > > }
> > > >
> > > > err = virtnet_xdp_xmit(dev, 1, &xdpf, 0);
> > > > @@ -818,19 +827,20 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> > > > xdp_return_frame_rx_napi(xdpf);
> > > > } else if (unlikely(err < 0)) {
> > > > trace_xdp_exception(dev, xdp_prog, act);
> > > > - return XDP_DROP;
> > > > + return VIRTNET_XDP_RES_DROP;
> > > > }
> > > > +
> > > > *xdp_xmit |= VIRTIO_XDP_TX;
> > > > - return act;
> > > > + return VIRTNET_XDP_RES_CONSUMED;
> > > >
> > > > case XDP_REDIRECT:
> > > > stats->xdp_redirects++;
> > > > err = xdp_do_redirect(dev, xdp, xdp_prog);
> > > > if (err)
> > > > - return XDP_DROP;
> > > > + return VIRTNET_XDP_RES_DROP;
> > > >
> > > > *xdp_xmit |= VIRTIO_XDP_REDIR;
> > > > - return act;
> > > > + return VIRTNET_XDP_RES_CONSUMED;
> > > >
> > > > default:
> > > > bpf_warn_invalid_xdp_action(dev, xdp_prog, act);
> > > > @@ -839,7 +849,7 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> > > > trace_xdp_exception(dev, xdp_prog, act);
> > > > fallthrough;
> > > > case XDP_DROP:
> > > > - return XDP_DROP;
> > > > + return VIRTNET_XDP_RES_DROP;
> > > > }
> > > > }
> > > >
> > > > @@ -987,17 +997,18 @@ static struct sk_buff *receive_small(struct net_device *dev,
> > > > act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> > > >
> > > > switch (act) {
> > > > - case XDP_PASS:
> > > > + case VIRTNET_XDP_RES_PASS:
> > > > /* 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:
> > > > - case XDP_REDIRECT:
> > > > +
> > > > + case VIRTNET_XDP_RES_CONSUMED:
> > > > rcu_read_unlock();
> > > > goto xdp_xmit;
> > > > - default:
> > > > +
> > > > + case VIRTNET_XDP_RES_DROP:
> > > > goto err_xdp;
> > > > }
> > > > }
> > > > @@ -1324,18 +1335,19 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> > > > act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> > > >
> > > > switch (act) {
> > > > - case XDP_PASS:
> > > > + case VIRTNET_XDP_RES_PASS:
> > > > head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
> > > > if (unlikely(!head_skb))
> > > > goto err_xdp_frags;
> > > >
> > > > rcu_read_unlock();
> > > > return head_skb;
> > > > - case XDP_TX:
> > > > - case XDP_REDIRECT:
> > > > +
> > > > + case VIRTNET_XDP_RES_CONSUMED:
> > > > rcu_read_unlock();
> > > > goto xdp_xmit;
> > > > - default:
> > > > +
> > > > + case VIRTNET_XDP_RES_DROP:
> > > > break;
> > > > }
> > > > err_xdp_frags:
> > > > --
> > > > 2.32.0.3.g01195cf9f
> > >
>
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