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[Xen-devel] RE: cpuid information to hvm guest

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] RE: cpuid information to hvm guest
From: "Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx>
Date: Mon, 29 Sep 2008 10:48:00 -0700
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Thread-topic: cpuid information to hvm guest

From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]

Hiding those details by default is a good strategy we’d like to maintain.

[Nitin>] Why do you say it is a good strategy? What are the benefits associated with it?

Furthermore we cannot change CPU-to-LAPIC identifier mapping without breaking saved guest images, which is not acceptable.

[Nitin>]  I am not clear on this part, how saved guest images get broken? I think this change is like upgrading BIOS. It should not break guest images.

If our hiding of host information is broken, we’d like a patch to fix it; likewise any other CPUID inconsistency. What specific issues are you seeing?

[Nitin>] This is an issue with OS which have licensing restriction on CPUs. A customer reported to us that they were not seeing all cpus on windows server because Xen is exposing each vcpu as a socket on a multi-core host system.

 -- Keir

On 29/9/08 18:21, "Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx> wrote:

Currently guest is seeing broken thread/core siblings topology because some of cupid bits are getting blocked by default.
With the attached 2 patches hvm guest will see same topology as the host-os sees.
It is still possible to override these bits in the guest config file, so that migration across different topology system can work.
Please apply.
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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