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RE: [Xen-devel] [Patch] cpu synchronization while doing MTRR register up

To: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Subject: RE: [Xen-devel] [Patch] cpu synchronization while doing MTRR register update
From: "Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx>
Date: Wed, 5 Aug 2009 10:42:13 -0700
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Cc: "Mallick, Asit K" <asit.k.mallick@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>, "Siddha, Suresh B" <suresh.b.siddha@xxxxxxxxx>
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Thread-topic: [Xen-devel] [Patch] cpu synchronization while doing MTRR register update
>-----Original Message-----
>From: Tim Deegan [mailto:Tim.Deegan@xxxxxxxxxx]
>What's the observed failure here?  Hang/crash on resume from S3?  Or
>something more common?

  The issue is observed at the cpu hotplug time. At the time of cpu hot add, 
the MTRR registers are initialized on that cpu, and that involves disabling 
cache. If there is an HVM guest up at that time, who is consuming sibling of 
the hotplug-ed cpu, then that sibling cpu will not able to access it's vmcs and 
results in system crash.

Thanks & Regards,
Linux Open Source Technology Center, Intel Corporation
The Mind is like a parachute; it works much better when it's open.

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