4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasow...@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 <jasow...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@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;


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