ibmveth: lost IRQ while closing/opening device leads to service loss

The order of freeing the IRQ and freeing the device in firmware
in ibmveth_close can cause the adapter to become unusable after a
subsequent ibmveth_open.  Only a reboot of the OS will make the
network device usable again. This is seen when cycling the adapter
up and down while there is network activity.

There is a window where an IRQ will be left unserviced (H_EOI will not
be called).  The solution is to make a VIO_IRQ_DISABLE h_call, free the
device with firmware, and then call free_irq.

Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ibmveth.c

@@ -677,7 +677,7 @@ static int ibmveth_close(struct net_device *netdev)
 	if (!adapter->pool_config)
 		netif_stop_queue(netdev);
 
-	free_irq(netdev->irq, netdev);
+	h_vio_signal(adapter->vdev->unit_address, VIO_IRQ_DISABLE);
 
 	do {
 		lpar_rc = h_free_logical_lan(adapter->vdev->unit_address);
@@ -689,6 +689,8 @@ static int ibmveth_close(struct net_device *netdev)
 				     lpar_rc);
 	}
 
+	free_irq(netdev->irq, netdev);
+
 	adapter->rx_no_buffer = *(u64*)(((char*)adapter->buffer_list_addr) + 4096 - 8);
 
 	ibmveth_cleanup(adapter);