This is a note to let you know that I've just added the patch titled

virtio-net: disable NAPI only when enabled during XDP set

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: virtio-net-disable-napi-only-when-enabled-during-xdp-set.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Tue Mar 6 19:02:12 PST 2018

From: Jason Wang jasowang@redhat.com Date: Wed, 28 Feb 2018 18:20:04 +0800 Subject: virtio-net: disable NAPI only when enabled during XDP set

From: Jason Wang jasowang@redhat.com

[ Upstream commit 4e09ff5362843dff3accfa84c805c7f3a99de9cd ]

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 jasowang@redhat.com Acked-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/virtio_net.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1995,8 +1995,9 @@ static int virtnet_xdp_set(struct net_de }

/* 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); @@ -2015,7 +2016,8 @@ static int virtnet_xdp_set(struct net_de } 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;

Patches currently in stable-queue which might be from jasowang@redhat.com are

queue-4.14/tuntap-correctly-add-the-missing-xdp-flush.patch queue-4.14/virtio-net-disable-napi-only-when-enabled-during-xdp-set.patch queue-4.14/tuntap-disable-preemption-during-xdp-processing.patch