netdev - Re: [PATCH net-next v4 1/6] net: ethtool: allow symmetric-xor RSS hash for any flow type

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Message-ID: <CAKgT0UeP8mbpakyjEqkDNZPArZpM59mxb5ExMCQ2qV2qSf-jMg@mail.gmail.com>
Date: Tue, 17 Oct 2023 13:28:53 -0700
From: Alexander Duyck <alexander.duyck@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Ahmed Zaki <ahmed.zaki@...el.com>, netdev@...r.kernel.org, 
	intel-wired-lan@...ts.osuosl.org, corbet@....net, jesse.brandeburg@...el.com, 
	anthony.l.nguyen@...el.com, davem@...emloft.net, edumazet@...gle.com, 
	pabeni@...hat.com, vladimir.oltean@....com, andrew@...n.ch, horms@...nel.org, 
	mkubecek@...e.cz, willemdebruijn.kernel@...il.com, linux-doc@...r.kernel.org, 
	Wojciech Drewek <wojciech.drewek@...el.com>
Subject: Re: [PATCH net-next v4 1/6] net: ethtool: allow symmetric-xor RSS
 hash for any flow type

On Tue, Oct 17, 2023 at 1:20 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 17 Oct 2023 13:03:39 -0700 Alexander Duyck wrote:
> > > > My thought would be to possibly just look at reducing your messaging
> > > > to a warning from the driver if the inputs are not symmetric, but you
> > > > have your symmetric xor hash function enabled.
> > >
> > > With the restrictions (to be moved into ice_ethtool), the user is unable
> > > to use non-symmetric inputs.
> >
> > I think a warning would make more sense than an outright restriction.
> > You could warn on both the enabling if the mask is already unbalanced,
> > or you could warn if the mask is set to be unbalanced after enabling
> > your hashing.
>
> Either it's a valid configuration or we should error out in the core.
> Keep in mind that we can always _loosen_ the restriction, like you
> asked for VLAN ID, but we can never _tighten_ it without breaking uAPI.
> So error.

I would say it is a valid configuration then. If the user opts to
shoot themselves in the foot then so be it. It doesn't actually break
anything and is just there to make sure the hashing conforms to the
marketing use case.