linux-kernel - Re: [PATCH v2 1/2] retpolines: Only enable retpoline support when compiler support it

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Message-ID: <20181101095002.GA118944@gmail.com>
Date:   Thu, 1 Nov 2018 10:50:02 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Zhenzhong Duan <zhenzhong.duan@...cle.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        konrad.wilk@...cle.com, luto@...nel.org, tglx@...utronix.de,
        dwmw@...zon.co.uk, bp@...e.de, srinivas.eeda@...cle.com,
        daniel@...earbox.net, yamada.masahiro@...ionext.com,
        michal.lkml@...kovi.net, peterz@...radead.org, hpa@...or.com
Subject: Re: [PATCH v2 1/2] retpolines: Only enable retpoline support when
 compiler support it


* Zhenzhong Duan <zhenzhong.duan@...cle.com> wrote:

> Since retpoline capable compilers are widely available, make
> CONFIG_RETPOLINE hard depend on it.
> 
> The check of RETPOLINE is changed to CONFIG_RETPOLINE.
> 
> This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Peter Zijlstra <peterz@...radead.org>

Please turn such 'based on suggestions' into proper tags as well, i.e. 
something like:

  Suggested-by: David Woodhouse <dwmw2@...radead.org>

>  config RETPOLINE
>  	bool "Avoid speculative indirect branches in kernel"
> +	depends on $(cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register) || \
> +                    $(cc-option,-mretpoline-external-thunk)

At least a comment should be added that this is the retpoline feature 
check for GCC and Clang.

Also, whitespace damage plus the two options should align vertically.

Thanks,

	Ingo