netdev - Re: [PATCH net 2/2] virtio_net: add checking sq is full inside xdp xmit

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Message-ID: <1678153623.7521684-1-xuanzhuo@linux.alibaba.com>
Date:   Tue, 7 Mar 2023 09:47:03 +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,
        Yichun Zhang <yichun@...nresty.com>
Subject: Re: [PATCH net 2/2] virtio_net: add checking sq is full inside xdp xmit

On Mon, 6 Mar 2023 12:57:34 -0500, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Mon, Mar 06, 2023 at 12:15:35PM +0800, Xuan Zhuo wrote:
> > If the queue of xdp xmit is not an independent queue, then when the xdp
> > xmit used all the desc, the xmit from the __dev_queue_xmit() may encounter
> > the following error.
> >
> > net ens4: Unexpected TXQ (0) queue failure: -28
> >
> > This patch adds a check whether sq is full in XDP Xmit.
> >
> > Reported-by: Yichun Zhang <yichun@...nresty.com>
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >  drivers/net/virtio_net.c | 25 +++++++++++++++----------
> >  1 file changed, 15 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 777de0ec0b1b..3001b9a548e5 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -302,6 +302,8 @@ struct padded_vnet_hdr {
> >
> >  static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
> >  static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
> > +static void check_sq_full(struct virtnet_info *vi, struct net_device *dev,
> > +			  struct send_queue *sq);
> >
> >  static bool is_xdp_frame(void *ptr)
> >  {
> > @@ -341,6 +343,16 @@ static int rxq2vq(int rxq)
> >  	return rxq * 2;
> >  }
> >
>
> I'd really rather we ordered functions reasonably so declarations
> are not needed.

Yes, but this function depends on some other functions. If we put this function
above, then these dependent functions must be processed. The current method
should be a relatively simple way.

Thanks.


>
> > +static bool is_xdp_raw_buffer_queue(struct virtnet_info *vi, int q)
> > +{
> > +	if (q < (vi->curr_queue_pairs - vi->xdp_queue_pairs))
> > +		return false;
> > +	else if (q < vi->curr_queue_pairs)
> > +		return true;
> > +	else
> > +		return false;
> > +}
> > +
> >  static inline struct virtio_net_hdr_mrg_rxbuf *skb_vnet_hdr(struct sk_buff *skb)
> >  {
> >  	return (struct virtio_net_hdr_mrg_rxbuf *)skb->cb;
> > @@ -686,6 +698,9 @@ static int virtnet_xdp_xmit(struct net_device *dev,
> >  	}
> >  	ret = nxmit;
> >
> > +	if (!is_xdp_raw_buffer_queue(vi, sq - vi->sq))
> > +		check_sq_full(vi, dev, sq);
> > +
> >  	if (flags & XDP_XMIT_FLUSH) {
> >  		if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
> >  			kicks = 1;
> > @@ -1784,16 +1799,6 @@ static void check_sq_full(struct virtnet_info *vi, struct net_device *dev,
> >  	}
> >  }
> >
> > -static bool is_xdp_raw_buffer_queue(struct virtnet_info *vi, int q)
> > -{
> > -	if (q < (vi->curr_queue_pairs - vi->xdp_queue_pairs))
> > -		return false;
> > -	else if (q < vi->curr_queue_pairs)
> > -		return true;
> > -	else
> > -		return false;
> > -}
> > -
> >  static void virtnet_poll_cleantx(struct receive_queue *rq)
> >  {
> >  	struct virtnet_info *vi = rq->vq->vdev->priv;
> > --
> > 2.32.0.3.g01195cf9f
>