Re: [PATCH iwl-next v5 2/2] ice: implement symmetric RSS hash configuration

[Jakub Kicinski <kuba@kernel.org>]

On Fri, 26 Jun 2026 07:47:30 +0200 Aleksandr Loktionov wrote:
> -	/* Update the VSI's hash function */
> -	if (rxfh->input_xfrm & RXH_XFRM_SYM_XOR)
> -		hfunc = ICE_AQ_VSI_Q_OPT_RSS_HASH_SYM_TPLZ;
> +	/* Handle RSS symmetric hash transformation */
> +	if (rxfh->input_xfrm != RXH_XFRM_NO_CHANGE) {
> +		u8 new_hfunc;

I think this is the very bad part. Please extract it out and send it as
a fix to net. Looks like any changes to RSS confing on ice randomly
enable xfrm sym. I isolated it to the ntuple.py test which just changes
the indir table, and the driver says:

  ice 0000:e1:00.0 ens1f0np0: Hash function set to: Symmetric Toeplitz

Which we never asked for. I drafted this before seeing your reply:

--- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
+++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
@@ -3692,10 +3692,10 @@ ice_set_rxfh(struct net_device *netdev, struct ethtool_rxfh_param *rxfh,
             struct netlink_ext_ack *extack)
 {
        struct ice_netdev_priv *np = netdev_priv(netdev);
-       u8 hfunc = ICE_AQ_VSI_Q_OPT_RSS_HASH_TPLZ;
        struct ice_vsi *vsi = np->vsi;
        struct ice_pf *pf = vsi->back;
        struct device *dev;
+       u8 hfunc;
        int err;
 
        dev = ice_pf_to_dev(pf);
@@ -3714,9 +3714,12 @@ ice_set_rxfh(struct net_device *netdev, struct ethtool_rxfh_param *rxfh,
                return -EOPNOTSUPP;
        }
 
-       /* Update the VSI's hash function */
-       if (rxfh->input_xfrm & RXH_XFRM_SYM_XOR)
+       if (rxfh->input_xfrm == RXH_XFRM_NO_CHANGE)
+               hfunc = vsi->rss_hfunc;
+       else if (rxfh->input_xfrm & RXH_XFRM_SYM_XOR)
                hfunc = ICE_AQ_VSI_Q_OPT_RSS_HASH_SYM_TPLZ;
+       else /* input_xfrm == 0; core rejects any other value */
+               hfunc = ICE_AQ_VSI_Q_OPT_RSS_HASH_TPLZ;
 
        err = ice_set_rss_hfunc(vsi, hfunc);