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

BugLink: http://bugs.launchpad.net/bugs/1755179
[ 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>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 559b215c016967f2b6525e7f3bc4fca2a2ee9e90..5907a8d0e92121840893bc081dd816093aab0d9d 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2040,8 +2040,9 @@ 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);
@@ -2060,7 +2061,8 @@ 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;