linux-kernel - Re: [PATCH v1 11/12] x86, alternative: Use alternative_2 in rdtsc

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Date:	Tue, 03 Feb 2015 11:55:11 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Richard Weinberger <richard@....at>
Subject: Re: [PATCH v1 11/12] x86, alternative: Use alternative_2 in rdtsc_barrier

On 02/03/2015 10:16 AM, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
>
> ... now that we have it.

Hallelujah!

Acked-by: Andy Lutomirski <luto@...capital.net>

>
> Cc: Richard Weinberger <richard@....at>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> ---
>   arch/x86/include/asm/barrier.h | 6 ++----
>   arch/x86/um/asm/barrier.h      | 4 ++--
>   2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
> index 2ab1eb33106e..959e45b81fe2 100644
> --- a/arch/x86/include/asm/barrier.h
> +++ b/arch/x86/include/asm/barrier.h
> @@ -95,13 +95,11 @@ do {									\
>    * Stop RDTSC speculation. This is needed when you need to use RDTSC
>    * (or get_cycles or vread that possibly accesses the TSC) in a defined
>    * code region.
> - *
> - * (Could use an alternative three way for this if there was one.)
>    */
>   static __always_inline void rdtsc_barrier(void)
>   {
> -	alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
> -	alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
> +	alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
> +			  "lfence", X86_FEATURE_LFENCE_RDTSC);
>   }
>
>   #endif /* _ASM_X86_BARRIER_H */
> diff --git a/arch/x86/um/asm/barrier.h b/arch/x86/um/asm/barrier.h
> index 2d7d9a1f5b53..8ffd2146fa6a 100644
> --- a/arch/x86/um/asm/barrier.h
> +++ b/arch/x86/um/asm/barrier.h
> @@ -64,8 +64,8 @@
>    */
>   static inline void rdtsc_barrier(void)
>   {
> -	alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
> -	alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
> +	alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
> +			  "lfence", X86_FEATURE_LFENCE_RDTSC);
>   }
>
>   #endif
>

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