linux-kernel - Re: [RFC,PATCH] VMWARE faults on accessing disabled counters

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Date:   Wed, 31 Aug 2016 15:41:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Ingo Molnar <mingo@...nel.org>, Andi Kleen <ak@...ux.intel.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: Re: [RFC,PATCH] VMWARE faults on accessing disabled counters

On Wed, Aug 31, 2016 at 03:19:24PM +0200, Jiri Olsa wrote:
> 
> I guess if real HW does not fault on this we dont need to bother,
> and treat it as the VMWARE issue.. but I couldn't find this info
> 

So I've once had a machine that backlisted one entry, but I've forgotten
what machine that was. But IIRC, you could program the thing just fine,
the results were crap though, which is why CPUID blacklisted the
counter.

/me pokes around some code...

Ah, see the AAJ80 code. That was some Nehalem part and the comment very
much implies programming the value 'works', you just get crap results.