linux-kernel - Re: Drop WARN on AMD lack of perfctrs

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Message-ID: <20130517091651.GB23035@pd.tnic>
Date:	Fri, 17 May 2013 11:16:51 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Robert Richter <rric@...nel.org>, Josh Boyer <jwboyer@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	x86@...nel.org, linux-kernel@...r.kernel.org, gleb@...hat.com
Subject: Re: Drop WARN on AMD lack of perfctrs

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...

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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