linux-kernel - Re: [PATCH v3 12/35] x86/bugs: Restructure retbleed mitigation

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Message-ID: <CA+i-1C0KpYA3BaPQb--AjRcZU5mi-Mk=kxpG3jy_TKufn+rk7A@mail.gmail.com>
Date: Mon, 10 Feb 2025 19:35:06 +0100
From: Brendan Jackman <jackmanb@...gle.com>
To: David Kaplan <david.kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.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, 
	"H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 12/35] x86/bugs: Restructure retbleed mitigation

On Wed, 8 Jan 2025 at 21:29, David Kaplan <david.kaplan@....com> wrote:
> @@ -1827,16 +1821,6 @@ static void __init spectre_v2_select_mitigation(void)
>                         break;
>                 }
>
> -               if (IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY) &&
> -                   boot_cpu_has_bug(X86_BUG_RETBLEED) &&
> -                   retbleed_cmd != RETBLEED_CMD_OFF &&
> -                   retbleed_cmd != RETBLEED_CMD_STUFF &&
> -                   boot_cpu_has(X86_FEATURE_IBRS) &&
> -                   boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
> -                       mode = SPECTRE_V2_IBRS;
> -                       break;
> -               }
> -
>                 mode = spectre_v2_select_retpoline();
>                 break;

It isn't quite clear why this gets removed here. Doesn't
retbleed_update_mitigation() still depend on this?

It gets added back in 15/35 so this would be at most a problem of git history.