linux-kernel - Re: [PATCH v2 10/11] arch/x86: Add AMD feature bit X86_FEATURE

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Date:   Fri, 5 Oct 2018 23:31:12 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Moger, Babu" <Babu.Moger@....com>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
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Subject: Re: [PATCH v2 10/11] arch/x86: Add AMD feature bit X86_FEATURE_MBA
 in cpuid bits array

On Fri, Oct 05, 2018 at 08:56:09PM +0000, Moger, Babu wrote:
> From: Sherry Hurwitz <sherry.hurwitz@....com>
> 
> The feature bit X86_FEATURE_MBA is detected via CPUID leaf 0x80000008
> EBX Bit 06. This bit indicates the support of AMD's MBA feature.
> 
> This feature is supported by both Intel and AMD. But they are detected
> different CPUID leaves.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> Signed-off-by: Sherry Hurwitz <sherry.hurwitz@....com>

This SOB chain should be the other way around - first Sherry, then you.

> ---
>  arch/x86/kernel/cpu/scattered.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
> index 772c219b6889..bd7853334b27 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -17,7 +17,11 @@ struct cpuid_bit {
>  	u32 sub_leaf;
>  };
>  
> -/* Please keep the leaf sorted by cpuid_bit.level for faster search. */
> +/*
> + * Please keep the leaf sorted by cpuid_bit.level for faster search.
> + * X86_FEATURE_MBA supported by both Intel and AMD. But the cpuid
> + * levels are different. Add a separate enty for each.
> + */
>  static const struct cpuid_bit cpuid_bits[] = {
>  	{ X86_FEATURE_APERFMPERF,       CPUID_ECX,  0, 0x00000006, 0 },
>  	{ X86_FEATURE_EPB,		CPUID_ECX,  3, 0x00000006, 0 },
> @@ -29,6 +33,7 @@ static const struct cpuid_bit cpuid_bits[] = {
>  	{ X86_FEATURE_HW_PSTATE,	CPUID_EDX,  7, 0x80000007, 0 },
>  	{ X86_FEATURE_CPB,		CPUID_EDX,  9, 0x80000007, 0 },
>  	{ X86_FEATURE_PROC_FEEDBACK,    CPUID_EDX, 11, 0x80000007, 0 },
> +	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
>  	{ X86_FEATURE_SME,		CPUID_EAX,  0, 0x8000001f, 0 },
>  	{ X86_FEATURE_SEV,		CPUID_EAX,  1, 0x8000001f, 0 },
>  	{ 0, 0, 0, 0, 0 }
> -- 

With that fixed:

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

-- 
Regards/Gruss,
    Boris.

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