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Re: [Xen-devel][PATCH][RFC] Supporting Enlightened Windows 2008 Server

To: Ky Srinivasan <ksrinivasan@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel][PATCH][RFC] Supporting Enlightened Windows 2008 Server
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 20 Feb 2008 09:44:35 +0000
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On 19/2/08 22:11, "Ky Srinivasan" <ksrinivasan@xxxxxxxxxx> wrote:

> B) Implement an adapter that implements the required Hyper-V functionality.
> We  have implemented only a subset of Hyper-V functionality that is required
> for enlightened windows 2008 guest today. However, we have the framework in
> place to implement any additional functionality that the windows guests may
> leverage going forward. The framework is extensible and one can easily
> implement OS specific enlightenments.

The appearance is that you hook on every significant emulation point in the
HVM code and implement a shadow hypervisor. Is that an accurate description?
What performance wins do you get from Hyper-V emulation, ignoring the
obvious wins you will get from installing PV I/O drivers? I think this is a
particularly interesting question since it was our impression that the PV
memory-management interfaces, which you appear to jump through hoops to
support, were not of much benefit with Xen's more sophisticated pagetable
algorithm (or with Intel EPT or AMD NPT).

 -- Keir

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