linux-kernel - Re: [RFC PATCH 03/56] cpu: Reset global mitigations

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Message-ID: <lrwbwfedilu4x3rizxn4i7pg3nuvoolbsnpfyb3ijbtf4ttjet@amyxglszq2fi>
Date: Fri, 17 Oct 2025 09:03:08 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: "Kaplan, David" <David.Kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, 
	Peter Zijlstra <peterz@...radead.org>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, 
	Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	"x86@...nel.org" <x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, 
	Alexander Graf <graf@...zon.com>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 03/56] cpu: Reset global mitigations

On Fri, Oct 17, 2025 at 02:19:43PM +0000, Kaplan, David wrote:
> > > Considering this will have no effect on other arches (or even on x86 at
> > > this point in the series), should CONFIG_DYNAMIC_MITIGATIONS depend on
> > > an arch-specific CONFIG_HAVE_DYNAMIC_MITIGATIONS?
> > >
> > > Then the weak function can be removed (and weak functions should be
> > > avoided anyway, IMO).
> > >
> >
> > Ok.  I agree, the feature doesn't make sense without arch-specific support anyway,
> > so that seems reasonable.
> 
> Well, so right now CONFIG_DYNAMIC_MITIGATIONS is only defined in
> arch/x86/Kconfig so it's already arch-specific.  It's part of the CPU
> mitigations menu there.
> 
> So I guess these weak functions aren't actually needed in the first
> place.
> 
> Alternatively I suppose I could make CONFIG_DYNAMIC_MITIGATIONS a
> generic feature (which requires an arch to support it).

I'd say generic is probably the way to go, as the sysfs files and
mitigations= interfaces are already generic, and users might want this
on other arches eventually.

-- 
Josh