net: ena: return 0 in ena_get_rxfh_key_size() when RSS hash key is not configurable

In EC2 instances where the RSS hash key is not configurable, ethtool
shows bogus RSS hash key since ena_get_rxfh_key_size() unconditionally
returns ENA_HASH_KEY_SIZE.

Commit 6a4f7dc82d1e ("net: ena: rss: do not allocate key when not
supported") added proper handling for devices that don't support RSS
hash key configuration, but ena_get_rxfh_key_size() has been unchanged.

When the RSS hash key is not configurable, return 0 instead of
ENA_HASH_KEY_SIZE to clarify getting the value is not supported.

Tested on m5 instance families.

Without patch:
 # ethtool -x ens5 | grep -A 1 "RSS hash key"
 RSS hash key:
 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00

With patch:
 # ethtool -x ens5 | grep -A 1 "RSS hash key"
 RSS hash key:
 Operation not supported

Fixes: 6a4f7dc82d1e ("net: ena: rss: do not allocate key when not supported")
Signed-off-by: Kohei Enju <enjuk@amazon.com>
Link: https://patch.msgid.link/20250929050247.51680-1-enjuk@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/amazon/ena/ena_ethtool.c b/drivers/net/ethernet/amazon/ena/ena_ethtool.c
index a81d3a7a3bb9ae6aef878821363a887558f349cb..fe3479b84a1f317aa2b58b654d08e3eb223a625d 100644 (file)
--- a/drivers/net/ethernet/amazon/ena/ena_ethtool.c
+++ b/drivers/net/ethernet/amazon/ena/ena_ethtool.c
@@ -865,7 +865,10 @@ static u32 ena_get_rxfh_indir_size(struct net_device *netdev)
 
 static u32 ena_get_rxfh_key_size(struct net_device *netdev)
 {
-       return ENA_HASH_KEY_SIZE;
+       struct ena_adapter *adapter = netdev_priv(netdev);
+       struct ena_rss *rss = &adapter->ena_dev->rss;
+
+       return rss->hash_key ? ENA_HASH_KEY_SIZE : 0;
 }
 
 static int ena_indirection_table_set(struct ena_adapter *adapter,