From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Yan, Zheng" <zheng.z.yan@linux.intel.com>
Subject: Re: perf uncore & lkvm woes
Date: Fri, 17 Aug 2012 09:40:37 +0800
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Cc: Pekka Enberg <penberg@kernel.org>,
	Sasha Levin <levinsasha928@gmail.com>,
	Asias He <asias.hejun@gmail.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Ingo Molnar <mingo@elte.hu>, KVM General <kvm@vger.kernel.org>,
	Gleb Natapov <gleb@redhat.com>
To: Avi Kivity <avi@redhat.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
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On 08/16/2012 07:25 PM, Avi Kivity wrote:
> On 08/16/2012 02:17 PM, Peter Zijlstra wrote:
>> On Thu, 2012-08-16 at 14:06 +0300, Avi Kivity wrote:
>>
>>> Another option is to deal with them on the host side.  That has the
>>> benefit of working with non-Linux guests too.
>>
>> Right, its an insane amount of MSRs though, but it could be done if
>> someone takes the time to enumerate them all.
> 
> It's tedious but that's life.
> 
>>
>> If KVM then simply ignores all writes and returns all 0 on read we can
>> do the same we do for the regular PMU in check_hw_exists().
>>
>>> We can just ignore the MSR and print some warning.
>>
>> If you don't mind printing a warning every time a Linux guest boots ;-)
> 
> We can printk_once() it, or only under debug, now that we have dynamic
> debug.  We also need to print the warning only if the counter is
> enabled.  Will Linux configure uncore counters by default (why and which?)
> 

The uncore driver may write some global control MSRs during initialization.
I did it because of its simpleness.

Peter, do I need to submit a patch disables uncore on virtualized CPU?

Regards
Yan, Zheng