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Message-ID: <20240420133630.GCZiPE3lZ3m-M1CqG_@fat_crate.local>
Date: Sat, 20 Apr 2024 15:36:30 +0200
From: Borislav Petkov <bp@...en8.de>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
Peter Zijlstra <peterz@...radead.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>,
Josh Poimboeuf <jpoimboe@...nel.org>, Will Deacon <will@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2 2/2] cpu: Ignore "mitigations" kernel parameter if
CPU_MITIGATIONS=n
On Fri, Apr 19, 2024 at 05:05:55PM -0700, Sean Christopherson wrote:
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 619a04d5c131..928820e61cb5 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2495,9 +2495,13 @@ menuconfig CPU_MITIGATIONS
> help
> Say Y here to enable options which enable mitigations for hardware
> vulnerabilities (usually related to speculative execution).
> + Mitigations can be disabled or restricted to SMT systems at runtime
> + via the "mitigations" kernel parameter.
>
> - If you say N, all mitigations will be disabled. You really
> - should know what you are doing to say so.
> + If you say N, all mitigations will be disabled. This CANNOT be
> + overridden at runtime.
You probably wanna highlight the fact here that saying N means it'll
simply not even build in the mitigations code, leading to the physical
inability :) to enable them later, at run time.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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