netvsc: Initialize all channel related state prior to opening the channel

Prior to opening the channel we should have all the state setup to handle
interrupts. The current code does not do that; fix the bug. This bug
can result in faults in the interrupt path.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc.c

@@ -1289,6 +1289,21 @@ int netvsc_device_add(struct hv_device *device,
 	 */
 	set_channel_read_mode(device->channel, HV_CALL_ISR);
 
+	/* If we're reopening the device we may have multiple queues, fill the
+	 * chn_table with the default channel to use it before subchannels are
+	 * opened.
+	 * Initialize the channel state before we open;
+	 * we can be interrupted as soon as we open the channel.
+	 */
+
+	for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
+		struct netvsc_channel *nvchan = &net_device->chan_table[i];
+
+		nvchan->channel = device->channel;
+		netif_napi_add(ndev, &nvchan->napi,
+			       netvsc_poll, NAPI_POLL_WEIGHT);
+	}
+
 	/* Open the channel */
 	ret = vmbus_open(device->channel, ring_size * PAGE_SIZE,
 			 ring_size * PAGE_SIZE, NULL, 0,
@@ -1303,18 +1318,6 @@ int netvsc_device_add(struct hv_device *device,
 	/* Channel is opened */
 	netdev_dbg(ndev, "hv_netvsc channel opened successfully\n");
 
-	/* If we're reopening the device we may have multiple queues, fill the
-	 * chn_table with the default channel to use it before subchannels are
-	 * opened.
-	 */
-	for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
-		struct netvsc_channel *nvchan = &net_device->chan_table[i];
-
-		nvchan->channel = device->channel;
-		netif_napi_add(ndev, &nvchan->napi,
-			       netvsc_poll, NAPI_POLL_WEIGHT);
-	}
-
 	/* Enable NAPI handler for init callbacks */
 	napi_enable(&net_device->chan_table[0].napi);
 

drivers/net/hyperv/rndis_filter.c

@@ -1007,12 +1007,13 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
 	 */
 	set_channel_read_mode(new_sc, HV_CALL_ISR);
 
+	/* Set the channel before opening.*/
+	nvchan->channel = new_sc;
+
 	ret = vmbus_open(new_sc, nvscdev->ring_size * PAGE_SIZE,
 			 nvscdev->ring_size * PAGE_SIZE, NULL, 0,
 			 netvsc_channel_cb, nvchan);
 
-	if (ret == 0)
-		nvchan->channel = new_sc;
 
 	napi_enable(&nvchan->napi);