linux-kernel - Re: [PATCH 1/2] cpu: Re-enable CPU mitigations by default for !X86 architectures

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Message-ID: <20240419173429.dj6nzgg3t23f52ol@treble>
Date: Fri, 19 Apr 2024 10:34:29 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Jonathan Corbet <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	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 1/2] cpu: Re-enable CPU mitigations by default for !X86
 architectures

On Fri, Apr 19, 2024 at 09:46:58AM -0700, Sean Christopherson wrote:
> > It seems confusing to have two config options which have very similar
> > names and similar purposes (with subtle differences depending on the
> > arch).
> > 
> > How about we instead just get rid of the x86-specific
> > SPECULATION_MITIGATIONS and replace it with a menu which depends on
> > CPU_MITIGATIONS:
> 
> Huh, didn't realize that was possible.
> 
> I agree that having two things for the same thing is confusing, though Boris'
> idea to do s/SPECULATION_MITIGATIONS/X86_CPU_MITIGATIONS would help a fair bit
> on that front.
> 
> My only hesitation is that x86's menu and the common config knob end up in
> completely different locations.

I'm thinking this is a minor issue because CPU_MITIGATIONS is enabled by
default, so it should almost always be enabled unless the user disables
it, in which case they wouldn't be looking for the x86-specific
mitigations anyway.

Regardless it seems very common for a menu "depends on" to be in a
different file.  We could put CPU_MITIGATIONS in arch/Kconfig which is a
fairly logical place for the dependency.

-- 
Josh