From mboxrd@z Thu Jan  1 00:00:00 1970
From: Huang Ying <ying.huang@intel.com>
Subject: Re: [PATCH 1/2] KVM: Expose MCE control MSRs to userspace
Date: Thu, 08 Jul 2010 16:03:48 +0800
Message-ID: <1278576228.2783.114.camel@yhuang-dev.sh.intel.com>
References: <1278500979-12725-1-git-send-email-avi@redhat.com>
	 <1278500979-12725-2-git-send-email-avi@redhat.com>
	 <1278554832.2783.2.camel@yhuang-dev.sh.intel.com>
	 <4C3581AB.8030404@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Cc: kvm@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>
To: Avi Kivity <avi@redhat.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mga02.intel.com ([134.134.136.20]:1593 "EHLO mga02.intel.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1753252Ab0GHIEC (ORCPT <rfc822;kvm@vger.kernel.org>);
	Thu, 8 Jul 2010 04:04:02 -0400
In-Reply-To: <4C3581AB.8030404@redhat.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Thu, 2010-07-08 at 15:43 +0800, Avi Kivity wrote:
> On 07/08/2010 05:07 AM, Huang Ying wrote:
> >
> >>   static u32 emulated_msrs[] = {
> >>   	MSR_IA32_MISC_ENABLE,
> >> +	MSR_IA32_MCG_STATUS,
> >> +	MSR_IA32_MCG_CTL,
> >>      
> > We need only clear MSR_IA32_MCG_STATUS during reset, but should not
> > clear MSR_IA32_MCG_CTL.
> >
> >    
> 
> Why not?

According to Intel 64 and IA32 Architectures Software Developer's Manual
(SDM) Vol 3A (Table 9-1), machine check MSRs should be sticky across
reset. Except we need some special processing for MSR_IA32_MCG_STATUS.

And if we clear MSR_IA32_MCG_CTL, the machine check reporting is
disabled according to SDM Vol 3A, section 15.3.1.3

Best Regards,
Huang Ying