linux-kernel - RE: [PATCH v3 15/35] x86/bugs: Restructure spectre

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Message-ID:
 <LV3PR12MB9265DD4D99D05F4F64D7FBC894FC2@LV3PR12MB9265.namprd12.prod.outlook.com>
Date: Wed, 12 Feb 2025 16:40:49 +0000
From: "Kaplan, David" <David.Kaplan@....com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.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 15/35] x86/bugs: Restructure spectre_v2 mitigation

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Josh Poimboeuf <jpoimboe@...nel.org>
> Sent: Monday, February 10, 2025 7:08 PM
> To: Kaplan, David <David.Kaplan@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>; Borislav Petkov <bp@...en8.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 15/35] x86/bugs: Restructure spectre_v2 mitigation
>
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
>
>
> On Wed, Jan 08, 2025 at 02:24:55PM -0600, David Kaplan wrote:
> > +static void __init spectre_v2_update_mitigation(void)
> > +{
> > +     if (spectre_v2_cmd == SPECTRE_V2_CMD_AUTO) {
> > +             if (IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY) &&
> > +                 boot_cpu_has_bug(X86_BUG_RETBLEED) &&
> > +                 retbleed_mitigation != RETBLEED_MITIGATION_NONE &&
> > +                 retbleed_mitigation != RETBLEED_MITIGATION_STUFF &&
> > +                 boot_cpu_has(X86_FEATURE_IBRS) &&
> > +                 boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
> > +                     spectre_v2_enabled = SPECTRE_V2_IBRS;
> > +             }
> > +     }
>
> This has a dependency on retbleed_update_mitigation() which hasn't run yet?
>

It's actually the reverse, retbleed_update_mitigation() needs to run after this.  That hasn't changed vs upstream, although I do need to document that.

--David Kaplan