Patch "virtio-net: disable NAPI only when enabled during XDP set" has been added to the 4.14-stable tree

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;a=summary

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 <[email protected]> know about it.

From: Jason Wang <[email protected]>
Date: Wed, 28 Feb 2018 18:20:04 +0800
Subject: virtio-net: disable NAPI only when enabled during XDP set

From: Jason Wang <[email protected]>

[ 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.

---
 drivers/net/virtio_net.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

@@ -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 [email protected] 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