linux-kernel - Re: [PATCH 2/2] cpu: Ignore "mitigations" kernel parameter if CPU

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Message-ID: <ZiKVPoK6qrGRos6M@google.com>
Date: Fri, 19 Apr 2024 09:01:02 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Jonathan Corbet <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Peter Zijlstra <peterz@...radead.org>, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Stephen Rothwell <sfr@...b.auug.org.au>, Michael Ellerman <mpe@...erman.id.au>, 
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH 2/2] cpu: Ignore "mitigations" kernel parameter if CPU_MITIGATIONS=n

On Fri, Apr 19, 2024, Borislav Petkov wrote:
> On Tue, Apr 16, 2024 at 05:15:07PM -0700, Sean Christopherson wrote:
> > Explicitly disallow enabling mitigations at runtime for kernels that were
> > built with CONFIG_CPU_MITIGATIONS=n, which currently is possible only on
> > x86 (via x86's SPECULATION_MITIGATIONS menuconfig).
> 
> Hm, so the umbrella term is CPU_MITIGATIONS, the x86-one is
> SPECULATION_MITIGATIONS.
> 
> I wanna streamline our namespacing and say, the arch agnostic term
> should be CPU_MITIGATIONS and the x86 one should be then
> X86_CPU_MITIGATIONS, the Arm one would be ARM_CPU_MITIGATIONS and so on.

+1.  That would help avoid goofs like mine.  Maybe.  :-)

> This way we can stick all kinds of special mitigations code - not only
> speculative execution ones - under those config items and have it all
> straight from the get-go.
> 
> And I think we should do it now, before it all propagates down the tree
> and becomes a lot harder to rename.
> 
> Thoughts?
> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette