[PATCH net-next] ethtool: Fix set RXFH for drivers without RXFH fields support

[Gal Pressman <gal@nvidia.com>]

Some drivers (e.g., mlx4_en) support ->set_rxfh() functionality (such as
setting hash function), but not setting the RXFH fields.

The requirement of ->get_rxfh_fields() in ethtool_set_rxfh() is there to
verify that we have no conflict with the RSS fields options, if it
doesn't exist then there is no point in doing the check.
Soften the check in ethtool_set_rxfh() so it doesn't fail when
->get_rxfh_fields() doesn't exist.

This fixes the following error:
$ ethtool --set-rxfh-indir eth2 hfunc xor
Cannot set RX flow hash configuration: Operation not supported

Fixes: 72792461c8e8 ("net: ethtool: don't mux RXFH via rxnfc callbacks")
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Gal Pressman <gal@nvidia.com>
---
 net/ethtool/ioctl.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index b6d96e562c9a..4bb8bf20a0eb 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1519,7 +1519,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	u8 *rss_config;
 	int ret;
 
-	if (!ops->get_rxnfc || !ops->get_rxfh_fields || !ops->set_rxfh)
+	if (!ops->get_rxnfc || !ops->set_rxfh)
 		return -EOPNOTSUPP;
 
 	if (ops->get_rxfh_indir_size)
@@ -1623,9 +1623,11 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 
 	mutex_lock(&dev->ethtool->rss_lock);
 
-	ret = ethtool_check_flow_types(dev, rxfh.input_xfrm);
-	if (ret)
-		goto out_unlock;
+	if (ops->get_rxfh_fields) {
+		ret = ethtool_check_flow_types(dev, rxfh.input_xfrm);
+		if (ret)
+			goto out_unlock;
+	}
 
 	if (rxfh.rss_context && rxfh_dev.rss_delete) {
 		ret = ethtool_check_rss_ctx_busy(dev, rxfh.rss_context);
-- 
2.40.1