linux-kernel - Re: [PATCH v5 02/16] x86/bugs: Restructure TAA mitigation

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Message-ID: <20250422085646.GBaAdZzlRuyJmo4Tct@renoirsky.local>
Date: Tue, 22 Apr 2025 10:56:46 +0200
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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 02/16] x86/bugs: Restructure TAA mitigation

On Sun, Apr 20, 2025 at 09:03:25PM +0000, Kaplan, David wrote:
> No, because taa_vulnerable() requires both X86_BUG_TAA and X86_FEATURE_RTM.
> 
> In taa_select_mitigation() there is a difference depending on which of these doesn't exist which sets the mitigation to either OFF (if unaffected) or TSX_DISABLED (if no RTM).
> 

Yah, another mis-designed thing from back then. If RTM is disabled, then
TAA is mitigated. Period.

And us making how a vuln is mitigated into a separate thing is
unnecessary complication IMO. IOW, TAA_MITIGATION_TSX_DISABLED shouldn've
been done, in hindsight.

But whatever, another topic.

Thx.

-- 
Regards/Gruss,
    Boris.

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