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Date: Tue, 22 Jun 2010 12:53:48 +0300
From: Avi Kivity <avi@redhat.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Jes Sorensen <Jes.Sorensen@redhat.com>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       LKML <linux-kernel@vger.kernel.org>, kvm@vger.kernel.org,
       Ingo Molnar <mingo@elte.hu>, Fr??d??ric Weisbecker <fweisbec@gmail.com>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Cyrill Gorcunov <gorcunov@gmail.com>, Lin Ming <ming.m.lin@intel.com>,
       Sheng Yang <sheng@linux.intel.com>,
       Marcelo Tosatti <mtosatti@redhat.com>, oerg Roedel <joro@8bytes.org>,
       Gleb Natapov <gleb@redhat.com>, Zachary Amsden <zamsden@redhat.com>,
       zhiteng.huang@intel.com, tim.c.chen@intel.com
Subject: Re: [PATCH V2 1/5] ara virt interface of perf to support kvm guest
 os statistics collection in guest os
References: <1277112680.2096.509.camel@ymzhang.sh.intel.com>	 <4C1F50D0.70205@redhat.com>	 <1277171344.2096.567.camel@ymzhang.sh.intel.com>	 <4C2062D8.20609@redhat.com>	 <1277192873.2096.690.camel@ymzhang.sh.intel.com>	 <1277193305.1875.537.camel@laptop>  <4C206D8B.4080105@redhat.com>	 <1277198943.2096.724.camel@ymzhang.sh.intel.com>	 <1277199060.1875.675.camel@laptop>  <4C2084BB.3040501@redhat.com> <1277200010.1875.692.camel@laptop>
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On 06/22/2010 12:46 PM, Peter Zijlstra wrote:
>
>> Avi's suggestion of using virtual MSRs makes a ton of sense for this
>> though, and it makes it possible to switch direct access on/off for the
>> cases where direct access is possible, and go emulated when it isn't.
>>      
> /me has no clue what virtual MSRs are,

MSRs that are not defined by the hardware, but instead by the hypervisor.

> but yeah, that sounds about
> right. Anyway, the generic case is full trap and emulate get that
> working first, then try and be smart and avoid some traps.
>    

I doubt we can avoid traps for the paravirt PMU since the counter 
indexes will not match.

When emulating the hardware PMU we can be clever at times and allow 
RDPMC not to trap.

-- 
error compiling committee.c: too many arguments to function