linux-kernel - Re: [PATCH 3/5] x86/mcheck/AMD: Reduce number of blocks scanned per bank

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Date:	Thu, 14 Jan 2016 23:37:39 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Cc:	tony.luck@...el.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] x86/mcheck/AMD: Reduce number of blocks scanned per
 bank

On Thu, Jan 14, 2016 at 04:05:38PM -0600, Aravind Gopalakrishnan wrote:
> From Fam17h onwards, the number of extended MISC register
> blocks is reduced to 4. It is an architectural change
> from what we had on earlier processors.
> 
> Changing the value of NRBLOCKS here to reflect that change.
> 
> Although theoritically the total number of extended MCx_MISC
> registers was 8 in earlier processor families, in practice
> we only had to use the extra registers for MC4. And only 2 of
> those were used. So this change does not affect older processors.
> Tested it on Fam10h, Fam15h systems and works fine.
> 
> Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
> ---
>  arch/x86/kernel/cpu/mcheck/mce_amd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> index da570a8..e650fdc 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> @@ -28,7 +28,7 @@
>  #include <asm/msr.h>
>  #include <asm/trace/irq_vectors.h>
>  
> -#define NR_BLOCKS         9
> +#define NR_BLOCKS         5

This doesn't look necessary to me. We do check MCi_MISC[BlkPtr] before
accessing that MSR.

-- 
Regards/Gruss,
    Boris.

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