From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: KVM PMU virtualization
Date: Fri, 26 Feb 2010 16:11:59 +0200
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References: <4B87987A.2020302@redhat.com> <20100226104437.GB7463@elte.hu> <4B87AF44.9090702@redhat.com> <20100226114217.GI7463@elte.hu> <4B87B5DE.30503@redhat.com> <20100226120750.GA11578@elte.hu> <4B87BC74.7050207@redhat.com> <20100226123850.GA19476@elte.hu> <4B87C6C4.3040407@redhat.com> <4B87C8EC.8080304@redhat.com> <20100226132751.GA20013@elte.hu> <4B87D59D.5050402@redhat.com>
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Cc: Ingo Molnar <mingo@elte.hu>, Joerg Roedel <joro@8bytes.org>,
	KVM General <kvm@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Zachary Amsden <zamsden@redhat.com>,
	Gleb Natapov <gleb@redhat.com>, ming.m.lin@intel.com,
	"Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	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: Jes Sorensen <Jes.Sorensen@redhat.com>
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On 02/26/2010 04:07 PM, Jes Sorensen wrote:
> On 02/26/10 14:27, Ingo Molnar wrote:
>>
>> * Jes Sorensen<Jes.Sorensen@redhat.com>  wrote:
>>> You certainly cannot emulate the Core2 on a P4. The Core2 is Perfmon 
>>> v2,
>>> whereas Nehalem and Atom are v3 if I remember correctly. [...]
>>
>> Of course you can emulate a good portion of it, as long as there's perf
>> support on the host side for P4.
>
> Actually P4 is pretty uninteresting in this discussion due to the lack
> of VMX support, it's the same issue for Nehalem vs Core2. The problem
> is the same though, we cannot tell the guest that yes P4 has this
> event, but no, we are going to feed you bogus data.

The Pentium D which is a P4 derivative has vmx support.  However it is 
so slow I'm fine with ignoring it for this feature.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.