iavf: Prevent changing static ITR values if adaptive moderation is on

Resolve being able to change static values on VF when adaptive interrupt
moderation is enabled.

This problem is fixed by checking the interrupt settings is not
a combination of change of static value while adaptive interrupt
moderation is turned on.

Without this fix, the user would be able to change static values
on VF with adaptive moderation enabled.

Fixes: 65e87c0 ("i40evf: support queue-specific settings for interrupt moderation")
Signed-off-by: Nitesh B Venkatesh <nitesh.b.venkatesh@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/iavf/iavf_ethtool.c

@@ -723,12 +723,31 @@ static int iavf_get_per_queue_coalesce(struct net_device *netdev, u32 queue,
  *
  * Change the ITR settings for a specific queue.
  **/
-static void iavf_set_itr_per_queue(struct iavf_adapter *adapter,
-				   struct ethtool_coalesce *ec, int queue)
+static int iavf_set_itr_per_queue(struct iavf_adapter *adapter,
+				  struct ethtool_coalesce *ec, int queue)
 {
 	struct iavf_ring *rx_ring = &adapter->rx_rings[queue];
 	struct iavf_ring *tx_ring = &adapter->tx_rings[queue];
 	struct iavf_q_vector *q_vector;
+	u16 itr_setting;
+
+	itr_setting = rx_ring->itr_setting & ~IAVF_ITR_DYNAMIC;
+
+	if (ec->rx_coalesce_usecs != itr_setting &&
+	    ec->use_adaptive_rx_coalesce) {
+		netif_info(adapter, drv, adapter->netdev,
+			   "Rx interrupt throttling cannot be changed if adaptive-rx is enabled\n");
+		return -EINVAL;
+	}
+
+	itr_setting = tx_ring->itr_setting & ~IAVF_ITR_DYNAMIC;
+
+	if (ec->tx_coalesce_usecs != itr_setting &&
+	    ec->use_adaptive_tx_coalesce) {
+		netif_info(adapter, drv, adapter->netdev,
+			   "Tx interrupt throttling cannot be changed if adaptive-tx is enabled\n");
+		return -EINVAL;
+	}
 
 	rx_ring->itr_setting = ITR_REG_ALIGN(ec->rx_coalesce_usecs);
 	tx_ring->itr_setting = ITR_REG_ALIGN(ec->tx_coalesce_usecs);
@@ -751,6 +770,7 @@ static void iavf_set_itr_per_queue(struct iavf_adapter *adapter,
 	 * the Tx and Rx ITR values based on the values we have entered
 	 * into the q_vector, no need to write the values now.
 	 */
+	return 0;
 }
 
 /**
@@ -792,9 +812,11 @@ static int __iavf_set_coalesce(struct net_device *netdev,
 	 */
 	if (queue < 0) {
 		for (i = 0; i < adapter->num_active_queues; i++)
-			iavf_set_itr_per_queue(adapter, ec, i);
+			if (iavf_set_itr_per_queue(adapter, ec, i))
+				return -EINVAL;
 	} else if (queue < adapter->num_active_queues) {
-		iavf_set_itr_per_queue(adapter, ec, queue);
+		if (iavf_set_itr_per_queue(adapter, ec, queue))
+			return -EINVAL;
 	} else {
 		netif_info(adapter, drv, netdev, "Invalid queue value, queue range is 0 - %d\n",
 			   adapter->num_active_queues - 1);