Re: [Xen-devel] [PATCH v3] x86/VPMU: Support only versions 2 through 4 of architectural performance monitoring

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

> From: Boris Ostrovsky [mailto:boris.ostrovsky@xxxxxxxxxx]
> Sent: Friday, December 04, 2015 10:08 PM
> 
> We need to have at least version 2 since it's the first version to
> support various control and status registers (such as
> MSR_CORE_PERF_GLOBAL_CTRL) that VPMU relies on always having.
> 
> We don't fully emulate version 4 but since it's back compatible with
> earlier versions we can fall back to v3. At this point there is no
> compatibility statement for v5 so anything above 4 is not supported.
> 
> For guests querying PMU version via CPUID leaf 0xa clip it at v3.
> 
> With explicit testing for PMU version we can now remove CPUID model
> check.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

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


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