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

jasowang · davem330 · commit 4e09ff536284 · 2018-02-28T12:21:28.000-05:00
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: 4941d47 ("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>
diff --git 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;

Original file line number	Diff line number	Diff line change
`@@ -2185,8 +2185,9 @@ static int virtnet_xdp_set(struct net_device dev, struct bpf_prog prog,`
`2185`	`2185`	`}`
`2186`	`2186`
`2187`	`2187`	`/* Make sure NAPI is not using any XDP TX queues for RX. */`
`2188`		`- for (i = 0; i < vi->max_queue_pairs; i++)`
`2189`		`- napi_disable(&vi->rq[i].napi);`
	`2188`	`+ if (netif_running(dev))`
	`2189`	`+ for (i = 0; i < vi->max_queue_pairs; i++)`
	`2190`	`+ napi_disable(&vi->rq[i].napi);`
`2190`	`2191`
`2191`	`2192`	`netif_set_real_num_rx_queues(dev, curr_qp + xdp_qp);`
`2192`	`2193`	`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,`
`2205`	`2206`	`}`
`2206`	`2207`	`if (old_prog)`
`2207`	`2208`	`bpf_prog_put(old_prog);`
`2208`		`- virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);`
	`2209`	`+ if (netif_running(dev))`
	`2210`	`+ virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);`
`2209`	`2211`	`}`
`2210`	`2212`
`2211`	`2213`	`return 0;`