linux-kernel - Re: [PATCH] x86/bugs: Don't warn when overwriting retbleed_return_thunk with srso_return

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Message-ID: <20250514222507.GKaCUYQ9TVadHl7zMv@fat_crate.local>
Date: Thu, 15 May 2025 00:25:07 +0200
From: Borislav Petkov <bp@...en8.de>
To: Suraj Jitindar Singh <surajjs@...zon.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
	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>, stable@...r.kernel.org
Subject: Re: [PATCH] x86/bugs: Don't warn when overwriting
 retbleed_return_thunk with srso_return_thunk

On Wed, May 14, 2025 at 03:08:35PM -0700, Suraj Jitindar Singh wrote:
> -	if (x86_return_thunk != __x86_return_thunk)
> +	/*
> +	 * There can only be one return thunk enabled at a time, so issue a
> +	 * warning when overwriting it. retbleed_return_thunk is a special case
> +	 * which is safe to be overwritten with srso_return_thunk since it
> +	 * provides a superset of the functionality and is handled correctly in
> +	 * entry_untrain_ret().
> +	 */
> +	if ((x86_return_thunk != __x86_return_thunk) &&
> +	    (thunk != srso_return_thunk ||
> +	     x86_return_thunk != retbleed_return_thunk))

Instead of making this an unreadable conditional, why don't we ...

>  		pr_warn("x86/bugs: return thunk changed\n");

... turn this into a

	pr_info("set return thunk to: %ps\n", ...)

and simply say which thunk was set?

-- 
Regards/Gruss,
    Boris.

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