net: ena: fix bug that might cause hang after consecutive open/close interface.

Fixing a bug that the driver does not unmask the IO interrupts
in ndo_open():
occasionally, the MSI-X interrupt (for one or more IO queues)
can be masked when ndo_close() was called.
If that is followed by ndo open(),
then the MSI-X will be still masked so no interrupt
will be received by the driver.

Fixes: 1738cd3e ("Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Netanel Belgazal <netanel@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -1078,6 +1078,26 @@ inline void ena_adjust_intr_moderation(struct ena_ring *rx_ring,
 	rx_ring->per_napi_bytes = 0;
 }
 
+static inline void ena_unmask_interrupt(struct ena_ring *tx_ring,
+					struct ena_ring *rx_ring)
+{
+	struct ena_eth_io_intr_reg intr_reg;
+
+	/* Update intr register: rx intr delay,
+	 * tx intr delay and interrupt unmask
+	 */
+	ena_com_update_intr_reg(&intr_reg,
+				rx_ring->smoothed_interval,
+				tx_ring->smoothed_interval,
+				true);
+
+	/* It is a shared MSI-X.
+	 * Tx and Rx CQ have pointer to it.
+	 * So we use one of them to reach the intr reg
+	 */
+	ena_com_unmask_intr(rx_ring->ena_com_io_cq, &intr_reg);
+}
+
 static inline void ena_update_ring_numa_node(struct ena_ring *tx_ring,
 					     struct ena_ring *rx_ring)
 {
@@ -1108,7 +1128,6 @@ static int ena_io_poll(struct napi_struct *napi, int budget)
 {
 	struct ena_napi *ena_napi = container_of(napi, struct ena_napi, napi);
 	struct ena_ring *tx_ring, *rx_ring;
-	struct ena_eth_io_intr_reg intr_reg;
 
 	u32 tx_work_done;
 	u32 rx_work_done;
@@ -1149,22 +1168,9 @@ static int ena_io_poll(struct napi_struct *napi, int budget)
 			if (ena_com_get_adaptive_moderation_enabled(rx_ring->ena_dev))
 				ena_adjust_intr_moderation(rx_ring, tx_ring);
 
-			/* Update intr register: rx intr delay,
-			 * tx intr delay and interrupt unmask
-			 */
-			ena_com_update_intr_reg(&intr_reg,
-						rx_ring->smoothed_interval,
-						tx_ring->smoothed_interval,
-						true);
-
-			/* It is a shared MSI-X.
-			 * Tx and Rx CQ have pointer to it.
-			 * So we use one of them to reach the intr reg
-			 */
-			ena_com_unmask_intr(rx_ring->ena_com_io_cq, &intr_reg);
+			ena_unmask_interrupt(tx_ring, rx_ring);
 		}
 
-
 		ena_update_ring_numa_node(tx_ring, rx_ring);
 
 		ret = rx_work_done;
@@ -1485,6 +1491,11 @@ static int ena_up_complete(struct ena_adapter *adapter)
 
 	ena_napi_enable_all(adapter);
 
+	/* Enable completion queues interrupt */
+	for (i = 0; i < adapter->num_queues; i++)
+		ena_unmask_interrupt(&adapter->tx_ring[i],
+				     &adapter->rx_ring[i]);
+
 	/* schedule napi in case we had pending packets
 	 * from the last time we disable napi
 	 */