linux-kernel - Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes

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Date:   Mon, 19 Nov 2018 16:00:56 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     Jiri Kosina <jikos@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app
 protection modes

On Fri, 16 Nov 2018, Tim Chen wrote:
> +DEFINE_STATIC_KEY_FALSE(spectre_v2_app_lite);
> +EXPORT_SYMBOL_GPL(spectre_v2_app_lite);

Why would this be exported? The only usage site outside of this code is in
tlb.c which is hardly modular.

> @@ -328,14 +411,19 @@ static bool stibp_needed(void)
>  	/*
>  	 * Determine if STIBP should be always on.
>  	 * Using enhanced IBRS makes using STIBP unnecessary.
> +	 * For lite option, STIBP is used only for task with
> +	 * TIF_STIBP flag. STIBP is not always on for that case.

Having the comment detached from the code is really not helpful.

Thanks,

	tglx