From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net] virtio-net: disable NAPI only when enabled during XDP set Date: Wed, 28 Feb 2018 17:27:44 +0200 Message-ID: <20180228172739-mutt-send-email-mst@kernel.org> References: <1519813204-10002-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <1519813204-10002-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, Feb 28, 2018 at 06:20:04PM +0800, Jason Wang wrote: > We try to disable NAPI to prevent a single XDP TX queue being used by > multiple cpus. But we don't check if device is up (NAPI is enabled), > this could result stall because of infinite wait in > napi_disable(). Fixing this by checking device state through > netif_running() before. > > Fixes: 4941d472bf95b ("virtio-net: do not reset during XDP set") > Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin > --- > drivers/net/virtio_net.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 9bb9e56..2d54123 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -2185,8 +2185,9 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > } > > /* Make sure NAPI is not using any XDP TX queues for RX. */ > - for (i = 0; i < vi->max_queue_pairs; i++) > - napi_disable(&vi->rq[i].napi); > + if (netif_running(dev)) > + for (i = 0; i < vi->max_queue_pairs; i++) > + napi_disable(&vi->rq[i].napi); > > netif_set_real_num_rx_queues(dev, curr_qp + xdp_qp); > err = _virtnet_set_queues(vi, curr_qp + xdp_qp); > @@ -2205,7 +2206,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > } > if (old_prog) > bpf_prog_put(old_prog); > - virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi); > + if (netif_running(dev)) > + virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi); > } > > return 0; > -- > 2.7.4