linux-kernel - Re: [PATCH v8 04/12] x86/spectre: Add boot time option to select Spectre v2 mitigation

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Date:   Wed, 24 Jan 2018 10:56:49 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...ux-foundation.org>
cc:     Andi Kleen <ak@...ux.intel.com>, Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Paul Turner <pjt@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        gnomes@...rguk.ukuu.org.uk, x86@...nel.org,
        thomas.lendacky@....com, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v8 04/12] x86/spectre: Add boot time option to select
 Spectre v2 mitigation

On Wed, 24 Jan 2018, Greg Kroah-Hartman wrote:

> But will Andi's patch work well for you?  Adding a MODULE_INFO() tag to 
> every module?  

Yes, that would work -- all the modules that get built in tree, or out of 
tree but with retpolined compiler, would have that marker that could be 
optionally checked for by the kernel.

> I just thought since you were already using modversions in enterprise 
> distros already, that adding it there would be the simplest.

The patch as-is introduces immediate modversion mismatch between 
retpolined kernel and non-retpolined module, making each and every one 
fail to load.

Thanks,

-- 
Jiri Kosina
SUSE Labs