netdev - RE: [PATCH iwl-net v2 2/3] idpf: Fix RSS LUT configuration on down interfaces

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Message-ID: <IA1PR11MB62896483A29729204B33F12989DCA@IA1PR11MB6289.namprd11.prod.outlook.com>
Date: Fri, 28 Nov 2025 23:30:47 +0000
From: "Joshi, Sreedevi" <sreedevi.joshi@...el.com>
To: Simon Horman <horms@...nel.org>
CC: "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "Loktionov, Aleksandr"
	<aleksandr.loktionov@...el.com>, "Samudrala, Sridhar"
	<sridhar.samudrala@...el.com>, "Tantilov, Emil S" <emil.s.tantilov@...el.com>
Subject: RE: [PATCH iwl-net v2 2/3] idpf: Fix RSS LUT configuration on down
 interfaces

> -----Original Message-----
> From: Simon Horman <horms@...nel.org>
> Sent: Thursday, November 27, 2025 6:45 AM
> To: Joshi, Sreedevi <sreedevi.joshi@...el.com>
> Cc: intel-wired-lan@...ts.osuosl.org; netdev@...r.kernel.org; Loktionov, Aleksandr <aleksandr.loktionov@...el.com>; Samudrala,
> Sridhar <sridhar.samudrala@...el.com>; Tantilov, Emil S <emil.s.tantilov@...el.com>
> Subject: Re: [PATCH iwl-net v2 2/3] idpf: Fix RSS LUT configuration on down interfaces
> 
> On Mon, Nov 24, 2025 at 12:47:49PM -0600, Sreedevi Joshi wrote:
> > RSS LUT provisioning and queries on a down interface currently return
> > silently without effect. Users should be able to configure RSS settings
> > even when the interface is down.
> >
> > Fix by maintaining RSS configuration changes in the driver's soft copy and
> > deferring HW programming until the interface comes up.
> >
> > Fixes: 02cbfba1add5 ("idpf: add ethtool callbacks")
> > Signed-off-by: Sreedevi Joshi <sreedevi.joshi@...el.com>
> > Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@...el.com>
> > Reviewed-by: Sridhar Samudrala <sridhar.samudrala@...el.com>
> > Reviewed-by: Emil Tantilov <emil.s.tantilov@...el.com>
> > ---
> >  drivers/net/ethernet/intel/idpf/idpf_ethtool.c | 17 +++++++++++------
> >  1 file changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/idpf/idpf_ethtool.c b/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
> 
> ...
> 
> > @@ -424,7 +429,7 @@ static int idpf_get_rxfh(struct net_device *netdev,
> >
> >  	if (rxfh->indir) {
> >  		for (i = 0; i < rss_data->rss_lut_size; i++)
> > -			rxfh->indir[i] = rss_data->rss_lut[i];
> > +			rxfh->indir[i] = rxhash_ena ? rss_data->rss_lut[i] : 0;
> 
> Hi,
> 
> I feel that I am missing something here.
> But I would have expected rxfh->indir to be populated by rss_data->rss_lut
> regardless of the port is up or down. IOW, I'm unclear on why
> 0 is reported for the indirection table if the interface is down.
> 
Interface being up/down does not affect filling out the rxfh->indir[]. User will be able to setup the indirection
table even when interface is down and query the table as well (changes are cached in driver's copy and setup in HW
when interface is brought up).  However, when the rxhash is disabled on the interface, the indirection table has no
effect, and it is programmed with zeros in the HW and returning all zeros in rxfh->indir[] here reflects that state.
Thanks for your review, Simon!
Regards,
Sreedevi
> >  	}
> >
> >  unlock_mutex:
> 
> ...