linux-kernel - RE: [PATCH v3 06/35] x86/bugs: Restructure mmio mitigation

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Message-ID:
 <LV3PR12MB92652B0B616A192A117976B194C72@LV3PR12MB9265.namprd12.prod.outlook.com>
Date: Fri, 21 Feb 2025 21:48:44 +0000
From: "Kaplan, David" <David.Kaplan@....com>
To: Borislav Petkov <bp@...en8.de>, Josh Poimboeuf <jpoimboe@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 06/35] x86/bugs: Restructure mmio mitigation

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Borislav Petkov <bp@...en8.de>
> Sent: Wednesday, February 19, 2025 12:21 PM
> To: Josh Poimboeuf <jpoimboe@...nel.org>
> Cc: Kaplan, David <David.Kaplan@....com>; Thomas Gleixner
> <tglx@...utronix.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; H . Peter Anvin
> <hpa@...or.com>; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v3 06/35] x86/bugs: Restructure mmio mitigation
>
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
>
>
> On Wed, Feb 12, 2025 at 03:16:46PM -0800, Josh Poimboeuf wrote:
> > static bool __init verw_mitigation_enabled(void) {
> >       return mds_mitigation != MDS_MITIGATION_OFF ||
> >               (taa_mitigation != TAA_MITIGATION_OFF && taa_vulnerable()) ||
> >               (mmio_mitigation != MMIO_MITIGATION_OFF && mmio_needs_verw());
> >               (rfds_mitigation != RFDS_MITIGATION_OFF &&
> > !rfds_needs_ucode()); }
>
> Instead of turning it into a head-scratching madness, it might be a lot easier if all the
> places which enable VERW mitigation, would do
>
>         verw_mitigation_enabled = true;
>
> and then the code can simply check that static var...
>

Yeah, just implemented this and it does keep it pretty clean.

Thanks! --David Kaplan