Re: Drop WARN on AMD lack of perfctrs

From: Borislav Petkov
Date: Fri May 17 2013 - 05:17:09 EST

On Fri, May 17, 2013 at 11:04:51AM +0200, Peter Zijlstra wrote:
> Mostly so that check_hw_exists() doesn't need to know about the vendor
> specifics like where the MSRs live, how many there are etc..

Yep, but there will still be issues with perf when booted on a guest and
kvm not supporting it. And AFAIU, they're signalling this by turning off
CPUID bits so that initializing perf doesn't happen.

So, I think init_hw_perf_events should as a first step look at CPUID
bits and then do anything else. And this is done on Intel with
X86_FEATURE_ARCH_PERFMON. But Robert is fixing this on AMD too so...



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