linux-kernel - Re: [PATCH] x86/bugs: Restructure ITS mitigation

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Message-ID: <20250515151601.GHaCYFMdcyIUmFgCNx@fat_crate.local>
Date: Thu, 15 May 2025 17:16:01 +0200
From: Borislav Petkov <bp@...en8.de>
To: David Kaplan <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,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/bugs: Restructure ITS mitigation

On Thu, May 15, 2025 at 08:47:56AM -0500, David Kaplan wrote:
> @@ -1242,11 +1261,19 @@ static void __init retbleed_update_mitigation(void)
>  	/*
>  	 * retbleed=stuff is only allowed on Intel.  If stuffing can't be used
>  	 * then a different mitigation will be selected below.
> +	 *
> +	 * its=stuff will also attempt to enable stuffing.
>  	 */
> -	if (retbleed_mitigation == RETBLEED_MITIGATION_STUFF) {
> +	if (retbleed_mitigation == RETBLEED_MITIGATION_STUFF ||
> +	    its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF) {
>  		if (spectre_v2_enabled != SPECTRE_V2_RETPOLINE) {
>  			pr_err("WARNING: retbleed=stuff depends on spectre_v2=retpoline\n");
>  			retbleed_mitigation = RETBLEED_MITIGATION_AUTO;
> +		} else {
> +			if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF)
> +				pr_info("Retbleed mitigation updated to stuffing\n");

I've seen this patch offlist already so only one thing about this here above
which is already there in the current tree.

Let's zap it. One can see to what the retbleed mitigation was updated by other
means. No need to add more spaghetti to the code.

-- 
Regards/Gruss,
    Boris.

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