[PATCH] x86: Correct index_cpu_LZCNT [BZ # 23456]

[Carlos O'Donell]

On 07/26/2018 12:46 PM, H.J. Lu wrote:
> cpu-features.h has
> 
>  #define bit_cpu_LZCNT		(1 << 5)
>  #define index_cpu_LZCNT	COMMON_CPUID_INDEX_1
>  #define reg_LZCNT
> 
> But the LZCNT feature bit is in COMMON_CPUID_INDEX_80000001:
> 
> Initial EAX Value: 80000001H
> ECX Extended Processor Signature and Feature Bits:
> Bit 05: LZCNT available
> 
> index_cpu_LZCNT should be COMMON_CPUID_INDEX_80000001, not
> COMMON_CPUID_INDEX_1.  The VMX feature bit is in COMMON_CPUID_INDEX_1:
> 
> Initial EAX Value: 01H
> Feature Information Returned in the ECX Register:
> 5 VMX
> 
> 	[BZ # 23456]
> 	* sysdeps/x86/cpu-features.h (index_cpu_LZCNT): Set to
> 	COMMON_CPUID_INDEX_80000001.

OK for 2.28.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  sysdeps/x86/cpu-features.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h
> index 624e681e96..3807a9d611 100644
> --- a/sysdeps/x86/cpu-features.h
> +++ b/sysdeps/x86/cpu-features.h
> @@ -204,7 +204,7 @@ extern const struct cpu_features *__get_cpu_features (void)
>  # define index_cpu_HTT		COMMON_CPUID_INDEX_1
>  # define index_cpu_BMI1		COMMON_CPUID_INDEX_7
>  # define index_cpu_BMI2		COMMON_CPUID_INDEX_7
> -# define index_cpu_LZCNT	COMMON_CPUID_INDEX_1
> +# define index_cpu_LZCNT	COMMON_CPUID_INDEX_80000001

Confirmed.

CPUID.EAX=80000001H:ECX.LZCNT[bit 5]: if 1 indicates the processor supports the LZCNT instruction.

>  # define index_cpu_MOVBE	COMMON_CPUID_INDEX_1
>  # define index_cpu_POPCNT	COMMON_CPUID_INDEX_1
>  # define index_cpu_IBT		COMMON_CPUID_INDEX_7
>