linux-kernel - Re: [PATCH 2/2] x86/cpufeature: Add CLZERO feature

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Date:	Sun, 25 Oct 2015 11:37:03 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	tony.luck@...el.com, x86@...nel.org, ashok.raj@...el.com,
	linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
	peterz@...radead.org, luto@...nel.org, dvlasenk@...hat.com,
	ross.zwisler@...ux.intel.com, peter.p.waskiewicz.jr@...el.com,
	dirk.j.brandewie@...el.com, Wan Zongshun <Vincent.Wan@....com>
Subject: Re: [PATCH 2/2] x86/cpufeature: Add CLZERO feature

On Fri, Oct 23, 2015 at 06:18:33AM -0500, Aravind Gopalakrishnan wrote:
> CLZERO instruction introduced in AMD Fam17h processors
> zero's out a 64 byte cache line specified in RAX.
> 
> Add the bit here to allow /proc/cpuinfo to list the feature
> 
> Signed-off-by: Wan Zongshun <Vincent.Wan@....com>
> Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>

This SOB chain looks wrong - if Vincent is the author and you're only
sending the patch, then his "From:" needs to appear before the commit
message. git send-email does that correctly, provided the authorship is
correctly set in the local branch you're sending the patch from.

> ---
>  arch/x86/include/asm/cpufeature.h | 5 ++++-
>  arch/x86/kernel/cpu/common.c      | 1 +
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> index 9727b3b..82d7c25 100644
> --- a/arch/x86/include/asm/cpufeature.h
> +++ b/arch/x86/include/asm/cpufeature.h
> @@ -12,7 +12,7 @@
>  #include <asm/disabled-features.h>
>  #endif
>  
> -#define NCAPINTS	13	/* N 32-bit words worth of info */
> +#define NCAPINTS	14	/* N 32-bit words worth of info */
>  #define NBUGINTS	1	/* N 32-bit bug flags */
>  
>  /*
> @@ -255,6 +255,9 @@
>  /* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:1 (edx), word 12 */
>  #define X86_FEATURE_CQM_OCCUP_LLC (12*32+ 0) /* LLC occupancy monitoring if 1 */
>  
> +/* AMD extended feature extension, CPUID level 0x80000008 (ebx), word 13 */

extended ... extension sounds like a tautology, please sanitize.

> +#define X86_FEATURE_CLZERO	(13*32+0) /* CLZERO instruction */

...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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