Re: [PATCH v1 0/3] x86/cpu/AMD: Make LFENCE a serializing instruction on AMD

[Borislav Petkov]

On Fri, Jan 05, 2018 at 10:07:36AM -0600, Tom Lendacky wrote:
> To aid in speculation control, the LFENCE instruction will be turned into
> a serializing instruction. There is less performance impact using LFENCE
> in this way compared to MFENCE.
> 
> With LFENCE now being a serializing instruction, it can be used in
> rdtsc_ordered() in place of MFENCE_RDTSC.  The other two patches in this
> series make this change and remove the MFENCE_RDTSC feature.
> 
> The following patches are included in this series:
> - Make LFENCE a serializing instruction on AMD
> - Change over to LFENCE_RDTSC from MFENCE_RDTSC on AMD
> - Remove the MFENCE_RDTSC feature
> 
> This patch series is based on tip:x86/pti.
> 
> ---
> 
> Tom Lendacky (3):
>       x86/cpu/AMD: Make LFENCE a serializing instruction
>       x86/cpu/AMD: Use LFENCE_RDTSC instead of MFENCE_RDTSC
>       x86/msr: Remove now unused definition of MFENCE_RDTSC feature

All three:

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

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