From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jes Sorensen <Jes.Sorensen@redhat.com>
Subject: Re: KVM PMU virtualization
Date: Fri, 26 Feb 2010 14:32:44 +0100
Message-ID: <4B87CD7C.3050306@redhat.com>
References: <4B86917C.4070102@redhat.com> <20100225173423.GB4246@8bytes.org> <20100226084241.GF15885@elte.hu> <4B87987A.2020302@redhat.com> <20100226104437.GB7463@elte.hu> <4B87AF44.9090702@redhat.com> <20100226114217.GI7463@elte.hu> <4B87C354.9020209@redhat.com> <20100226130656.GA2518@elte.hu> <4B87CCF5.6000209@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: Avi Kivity <avi@redhat.com>
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On 02/26/10 14:30, Avi Kivity wrote:
> On 02/26/2010 03:06 PM, Ingo Molnar wrote:
>> That's precisely my point: the guest should obviously not get raw
>> access to
>> the PMU. (except where it might matter to performance, such as RDPMC)
>
> That's doable if all counters are steerable. IIRC some counters are
> fixed function, but I'm not certain about that.

I am not an expert, but from what I learned from Peter, there are
constraints on some of the counters. Ie. certain types of events can
only be counted on certain counters, which limits the already very
limited number of counters even further.

Cheers,
Jes