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Subject: Re: [Qemu-devel] Re: [PATCH 11/11] kvm, x86: broadcast mce
	depending on the cpu version
From: Huang Ying <ying.huang@intel.com>
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	<20101015010649.GB32272@amt.cnet>  <4CB7B3C5.7070102@jp.fujitsu.com>
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Date: Fri, 15 Oct 2010 12:56:43 +0800
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To: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Dean@gnu.org, KVM list <kvm@vger.kernel.org>, Nelson <dnelson@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>, Jin Dongming <jin.dongming@np.css.fujitsu.com>

On Fri, 2010-10-15 at 09:52 +0800, Hidetoshi Seto wrote:
> (2010/10/15 10:06), Marcelo Tosatti wrote:
> > On Thu, Oct 14, 2010 at 05:55:28PM +0900, Jin Dongming wrote:
> >> There is no reason why SRAO event received by the main thread
> >> is the only one that being broadcasted.
> >>
> >> According to the x86 ASDM vol.3A 15.10.4.1,
> >> MCE signal is broadcast on processor version 06H_EH or later.
> >>
> >> This change is required to handle SRAR in the guest.
> >>
> >> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
> >> Tested-by: Jin Dongming <jin.dongming@np.css.fujitsu.com>
> >> ---
> >>  qemu-kvm.c |   63 +++++++++++++++++++++++++++++------------------------------
> >>  1 files changed, 31 insertions(+), 32 deletions(-)
> > 
> > Why is this necessary? _AO SIGBUS should be sent to all vcpu threads and
> > main thread.
> 
> Humm? If you are right, vcpu threads will receive same SRAO event twice,
> one is that received by itself and another is that received by main thread
> and forwarded by the broadcast.
> 
> My understanding is (Jin, please correct me if something wrong):
>  - _AO SIGBUS is sent to main thread only, and then SRAO event is
>    broadcasted to all vcpu threads.

Yes. It is.

>  - _AR SIGBUS is sent to a vcpu thread that tried to touch the
>    unmapped poisoned page, and SRAR event is posted to the vcpu.
> 
> One problem here is that SRAR is not broadcasted.
> The guest might observe the event differently, like "some cpus
> don't enter machine check."

Yes. SRAR "Broadcast" follows spec better.

Best Regards,
Huang Ying