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Date:   Tue, 30 Oct 2018 09:32:10 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc:     Linux-Kernel <linux-kernel@vger.kernel.org>, mingo@redhat.com,
        luto@kernel.org, konrad.wilk@oracle.com, dwmw@amazon.co.uk,
        tglx@linutronix.de, Srinivas REDDY Eeda <srinivas.eeda@oracle.com>,
        bp@suse.de, daniel@iogearbox.net, yamada.masahiro@socionext.com,
        michal.lkml@markovi.net, hpa@zytor.com
Subject: Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler
 support it
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On Mon, Oct 29, 2018 at 11:55:04PM -0700, Zhenzhong Duan wrote:
> Since retpoline capable compilers are widely available, make
> CONFIG_RETPOLINE hard depend on it.
> 
> Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
> CONFIG_RETPOLINE which is used by kernel.
> 
> With all that stuff, the check of RETPOLINE is changed to
> CONFIG_RETPOLINE.

So what happens when we select CONFIG_RETPOLINE but do not have
RETPOLINE_SUPPORT ? From a quick reading we'll silently build a
!retpoline kernel. I would expect a build failure.