linux-kernel - Re: [PATCH v3 30/35] x86/bugs: Add attack vector controls for spectre_v2

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Message-ID: <20250211190307.g36lotfyi6dmc3cx@jpoimboe>
Date: Tue, 11 Feb 2025 11:03:07 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: David Kaplan <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 30/35] x86/bugs: Add attack vector controls for
 spectre_v2_user

On Wed, Jan 08, 2025 at 02:25:10PM -0600, David Kaplan wrote:
> @@ -1614,6 +1614,13 @@ spectre_v2_user_select_mitigation(void)
>  		spectre_v2_user_stibp = SPECTRE_V2_USER_STRICT;
>  		break;
>  	case SPECTRE_V2_USER_CMD_AUTO:
> +		if (should_mitigate_vuln(X86_BUG_SPECTRE_V2_USER)) {
> +			spectre_v2_user_ibpb = SPECTRE_V2_USER_PRCTL;
> +			spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;
> +		} else {
> +			return;
> +		}
> +		break;

Can just fallthrough in the should_mitigate_vuln() case?

>  	case SPECTRE_V2_USER_CMD_PRCTL:
>  		spectre_v2_user_ibpb = SPECTRE_V2_USER_PRCTL;
>  		spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;

-- 
Josh