From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: KVM PMU virtualization
Date: Fri, 26 Feb 2010 15:49:02 +0100
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Cc: Ingo Molnar <mingo@elte.hu>,
	Jes Sorensen <Jes.Sorensen@redhat.com>,
	Joerg Roedel <joro@8bytes.org>,
	KVM General <kvm@vger.kernel.org>,
	Zachary Amsden <zamsden@redhat.com>,
	Gleb Natapov <gleb@redhat.com>, ming.m.lin@intel.com,
	"Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Arjan van de Ven <arjan@infradead.org>,
	Fr??d??ric Weisbecker <fweisbec@gmail.com>,
	Arnaldo Carvalho de Melo <acme@redhat.com>
To: Avi Kivity <avi@redhat.com>
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On Fri, 2010-02-26 at 15:30 +0200, Avi Kivity wrote:
> 
> Even if there were no security considerations, if the guest can observe 
> host data in the pmu, it means the pmu is inaccurate.  We should expose 
> guest data only in the guest pmu.  That's not difficult to do, you stop 
> the pmu on exit and swap the counters on context switches. 

That's not enough, memory node wide counters are impossible to isolate
like that, the same for core wide (ANY flag) counters.