Re: [Xen-devel] [PATCH v2] x86: improve MSR_SHADOW_GS accesses

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Thursday, March 8, 2018 7:16 PM
> 
> Instead of using RDMSR/WRMSR, on fsgsbase-capable systems use a
> double
> SWAPGS combined with RDGSBASE/WRGSBASE. This halves execution time
> for
> a shadow GS update alone on my Haswell (and we have indications of
> good performance improvements by this on Skylake too), while the win is
> even higher when e.g. updating more than one base (as may and
> commonly
> will happen in load_segments()).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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