linux-kernel - Re: [RFC PATCH 05/56] x86/bugs: Reset spectre

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Message-ID: <20251103202811.GMaQkQW54Gml6i1jQy@fat_crate.local>
Date: Mon, 3 Nov 2025 21:28:11 +0100
From: Borislav Petkov <bp@...en8.de>
To: "Kaplan, David" <David.Kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.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 05/56] x86/bugs: Reset spectre_v2 mitigations

On Mon, Nov 03, 2025 at 08:10:39PM +0000, Kaplan, David wrote:
> Do you really want it all in one big function?  Or just to relocate all the
> *_reset_mitigation() functions to a single place so they can all go under
> one ifdef?
> 
> I can do it in one big function, but it'd probably look something like:
> 
> /* Reset spectre_v1 */
> setup_clear_cpu_cap(X86_FEATURE_FENCE_SWAPGS_USER);
> setup_clear_cpu_cap(X86_FEATURE_FENCE_SWAPGS_KERNEL);
> spectre_v1_mitigation = SPECTRE_V1_MITIGATION_AUTO;
> /* Reset mds */
> setup_clear_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
> static_branch_disable(&cpu_buf_idle_clear);
> mds_mitigation = IS_ENABLED(CONFIG_MITIGATION_MDS) ?
>                 MDS_MITIGATION_AUTO : MDS_MITIGATION_OFF;
> /* Reset spectre_v2 */
> Etc.

Yap, that's what I thought too.

Since there's no point to have separate functions, the comment separation is
perfectly sufficient, I'd say.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette