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Message-ID: <1277199060.1875.675.camel@laptop>
Date: Tue, 22 Jun 2010 11:31:00 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc: Jes Sorensen <Jes.Sorensen@...hat.com>,
Avi Kivity <avi@...hat.com>,
LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
Ingo Molnar <mingo@...e.hu>,
Fr??d??ric Weisbecker <fweisbec@...il.com>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Cyrill Gorcunov <gorcunov@...il.com>,
Lin Ming <ming.m.lin@...el.com>,
Sheng Yang <sheng@...ux.intel.com>,
Marcelo Tosatti <mtosatti@...hat.com>,
oerg Roedel <joro@...tes.org>, Gleb Natapov <gleb@...hat.com>,
Zachary Amsden <zamsden@...hat.com>, zhiteng.huang@...el.com,
tim.c.chen@...el.com
Subject: Re: [PATCH V2 1/5] ara virt interface of perf to support kvm guest
os statistics collection in guest os
On Tue, 2010-06-22 at 17:29 +0800, Zhang, Yanmin wrote:
> On Tue, 2010-06-22 at 10:00 +0200, Jes Sorensen wrote:
> > On 06/22/10 09:55, Peter Zijlstra wrote:
> > > On Tue, 2010-06-22 at 15:47 +0800, Zhang, Yanmin wrote:
> > >> Besides the para virt perf interface, I'm also considering the direct exposition
> > >> of PMU hardware to guest os.
> > >
> > > NAK NAK NAK NAK, we've been over that, its not going to happen, full
> > > stop!
> > >
> > > Use MSR read/write traps and host perf to emulate the hardware. In some
> > > cases we could allow the reads without trap but that's a later
> > > optimization.
> >
> > I believe whats meant here is a PMU compatible interface which is
> > partially emulated. Not a handover of the PMU.
> Right. We need capture all write to PMU MSR and allows guest os to read MSR directly.
That latter is not possible, only in a subset of cases can you allow
that read.
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