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Message-ID: <1516983879.30244.236.camel@infradead.org>
Subject: Re: [PATCH 3/4] x86/retpoline: Simplify vmexit_fill_RSB()
From:   David Woodhouse <dwmw2@infradead.org>
To:     Borislav Petkov <bp@alien8.de>
Cc:     X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        tim.c.chen@linux.intel.com, pjt@google.com, jikos@kernel.org,
        gregkh@linux-foundation.org, dave.hansen@intel.com,
        riel@redhat.com, luto@amacapital.net,
        torvalds@linux-foundation.org, ak@linux.intel.com,
        keescook@google.com, peterz@infradead.org
In-Reply-To: <20180126132431.fsbd3c3g2yreazy6@pd.tnic>
References: <20180126121139.31959-1-bp@alien8.de>
         <20180126121139.31959-4-bp@alien8.de>
         <1516970011.30244.223.camel@infradead.org>
         <20180126132431.fsbd3c3g2yreazy6@pd.tnic>
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Date:   Fri, 26 Jan 2018 16:24:39 +0000
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On Fri, 2018-01-26 at 14:24 +0100, Borislav Petkov wrote:
> diff --git a/arch/x86/include/asm/asm-prototypes.h b/arch/x86/include/asm=
/asm-prototypes.h
> index 1908214b9125..b889705f995a 100644
> --- a/arch/x86/include/asm/asm-prototypes.h
> +++ b/arch/x86/include/asm/asm-prototypes.h
> @@ -38,4 +38,7 @@ INDIRECT_THUNK(dx)
> =C2=A0INDIRECT_THUNK(si)
> =C2=A0INDIRECT_THUNK(di)
> =C2=A0INDIRECT_THUNK(bp)
> +asmlinkage void __fill_rsb_clobber_ax(void);
> +asmlinkage void __clr_rsb_clobber_ax(void);
> =C2=A0#endif /* CONFIG_RETPOLINE */
>=20

Dammit, have the IBM vowel-stealers escaped again? What was wrong with
'__clear_rsb_clobber_ax'?

>=20
> -/*
> - * Google experimented with loop-unrolling and this turned out to be
> - * the optimal version =E2=80=94 two calls, each with their own speculat=
ion
> - * trap should their return address end up getting used, in a loop.
> - */

Let's not lose that comment?

Other than that, I think it'll look OK when it's a sane patch on top of
my existing tree instead of incremental on your last one. Thanks.
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