From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH 0/6 v2] Add support for RDTSCP in VMX
Date: Wed, 23 Dec 2009 11:37:40 -0200
Message-ID: <20091223133740.GA13991@amt.cnet>
References: <1261126127-9603-1-git-send-email-sheng@linux.intel.com> <4B2DEE98.4070702@redhat.com> <20091222172617.GA9541@amt.cnet> <4B310F51.9090909@redhat.com>
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Cc: Sheng Yang <sheng@linux.intel.com>, kvm@vger.kernel.org
To: Avi Kivity <avi@redhat.com>,
	Glauber de Oliveira Costa <gcosta@redhat.com>
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On Tue, Dec 22, 2009 at 08:26:25PM +0200, Avi Kivity wrote:
> On 12/22/2009 07:26 PM, Marcelo Tosatti wrote:
>> On Sun, Dec 20, 2009 at 11:30:00AM +0200, Avi Kivity wrote:
>>    
>>> On 12/18/2009 10:48 AM, Sheng Yang wrote:
>>>
>>> Applied all, thanks.
>>>      
>> Need to save/restore MSR_TSC_AUX in qemu-kvm.
>>    
>
> Should be automatic.  After all, we expose all the MSR list, so qemu can  
> read it and save everything there.

Hum, thinking a bit more about this (and reading Glauber's previous attempt) its not
entirely clear that using the list provided by KVM_GET_MSR_INDEX_LIST to automatically save/restore
is a good thing:

- The MSR must be saved in QEMU's CPUState representation, and its
  likely that it won't exist prior to the addition there.

- What about savevm/loadvm versioning? Currently the QEMU migration 
protocol is unable to deal with a new kernel that supports, for example, 
MSR_TSC_AUX vs a kernel that does not (in case MSRs were automatically
saved), with the same qemu-kvm version.