linux-kernel - Re: [PATCH v2 05/10] x86: Annotate static_cpu

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Message-ID: <20180118131513.jzhqyd2ucrwwnwez@pd.tnic>
Date:   Thu, 18 Jan 2018 14:15:13 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>
Subject: Re: [PATCH v2 05/10] x86: Annotate static_cpu_has alternative

On Tue, Jan 16, 2018 at 03:28:30PM +0100, Peter Zijlstra wrote:
> In order to recognise static_cpu_has() alternatives from any other
> alternative without dodgy heuristics, we need to explicitly mark them.
> Use the new type field for this.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/include/asm/alternative.h |    1 +
>  arch/x86/include/asm/cpufeature.h  |    5 +++--
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -46,6 +46,7 @@
>  #endif
>  
>  #define ALT_TYPE_DEFAULT	0
> +#define ALT_TYPE_STATIC_CPU_HAS	1 /* objtool, static_cpu_has */

Just a nitpick: let's be more verbose in that comment:

/*
 * This alt_instr descriptor is part of a static_cpu_has() construct. Use it to
 * detect its type when processing with other tools, like objtool, for example.
 */
#define ALT_TYPE_STATIC_CPU_HAS	1

With that:

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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