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([2601:282:800:fd80:f02b:2058:cbd0:634d]) by smtp.googlemail.com with ESMTPSA id j67sm40988977pfc.72.2019.04.24.10.40.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Apr 2019 10:40:41 -0700 (PDT) Subject: Re: virtio_net: suspicious RCU usage with xdp To: "Michael S. Tsirkin" Cc: makita.toshiaki@lab.ntt.co.jp, Jesper Dangaard Brouer , =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , "netdev@vger.kernel.org" , Jason Wang References: <20190424132533-mutt-send-email-mst@kernel.org> From: David Ahern Message-ID: <8dcadb7a-b1d3-1739-9a8d-2bb09b38969c@gmail.com> Date: Wed, 24 Apr 2019 11:40:40 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190424132533-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/24/19 11:37 AM, Michael S. Tsirkin wrote: > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 9010938e2d71..ccc1bdd1bb1f 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -495,8 +495,8 @@ static struct send_queue *virtnet_xdp_sq(struct virtnet_info *vi) > return &vi->sq[qp]; > } > > -static int virtnet_xdp_xmit(struct net_device *dev, > - int n, struct xdp_frame **frames, u32 flags) > +static int __virtnet_xdp_xmit(struct net_device *dev, > + int n, struct xdp_frame **frames, u32 flags) > { > struct virtnet_info *vi = netdev_priv(dev); > struct receive_queue *rq = vi->rq; > @@ -569,6 +569,17 @@ static int virtnet_xdp_xmit(struct net_device *dev, > return ret; > } > > +static int virtnet_xdp_xmit(struct net_device *dev, > + int n, struct xdp_frame **frames, u32 flags) > +{ > + int r; > + > + rcu_read_lock_bh(); > + r = __virtnet_xdp_xmit(dev, n, frames, flags); > + rcu_read_unlock_bh(); > + return r; > +} > + > static unsigned int virtnet_get_headroom(struct virtnet_info *vi) > { > return vi->xdp_queue_pairs ? VIRTIO_XDP_HEADROOM : 0; > @@ -714,7 +725,7 @@ static struct sk_buff *receive_small(struct net_device *dev, receive_small takes the rcu lock at the beginning. > xdpf = convert_to_xdp_frame(&xdp); > if (unlikely(!xdpf)) > goto err_xdp; > - err = virtnet_xdp_xmit(dev, 1, &xdpf, 0); > + err = __virtnet_xdp_xmit(dev, 1, &xdpf, 0); > if (unlikely(err < 0)) { > trace_xdp_exception(vi->dev, xdp_prog, act); > goto err_xdp; > @@ -887,7 +898,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, same here. > xdpf = convert_to_xdp_frame(&xdp); > if (unlikely(!xdpf)) > goto err_xdp; > - err = virtnet_xdp_xmit(dev, 1, &xdpf, 0); > + err = __virtnet_xdp_xmit(dev, 1, &xdpf, 0); > if (unlikely(err < 0)) { > trace_xdp_exception(vi->dev, xdp_prog, act); > if (unlikely(xdp_page != page)) > > bq_xmit_all is invoking the xdp_xmit callback without taking the rcu lock, but from the git history does not appear to have any recent changes.