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

To: Ky Srinivasan <ksrinivasan@xxxxxxxxxx>
Subject: [Xen-devel] Re: Supporting Enlightened Windows 2008 Server
From: "Mike D. Day" <ncmike@xxxxxxxxxx>
Date: Wed, 20 Feb 2008 15:31:39 -0500
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On 19/02/08 15:11 -0700, Ky Srinivasan wrote:
> During the spring Xen Summit in New York, I presented our work on hosting 
> Enlightened windows 2008 server on  Xen based platforms. Now that Microsoft 
> has published their Hypervisor specification, we can release our code to the 
> community. The goal of this effort has been to host Enlightened windows 2008 
> server as a guest on a Xen based platform. We have addressed this requirement 
> by :
> A) Leveraging the I/O framework in the Xen based platform. Appropriate PV 
> drivers will be loaded up in the guest to improve the I/O performance.
> 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.
> I am enclosing three patches that implement our adapter for your 
> consideration:
> 1) ns_tools.patch: Modifications to xen tools to support the the adapter
> 2) ns_xen_base.patch: Modifications to the base Xen code to support the 
> adapter
> 3) ns_xen_extension.patch: New code implementing the adapter 
> These patches have been tested on a xen 3.2 based system (SLES10 SP2).
Right now there is not an implementation to support an enlightened
windows guest, just a shim.

First question: Do you plan on implementing the full enlightened guest
support as GPL source (as you have done with the elementary shim), or
are you planning on loading a blob and initializing the hypercall
vector, a la the vmware VMI? Has Microsoft agreed to a source-based
GPL implementation of the hypercall layer?

Second question: what do you believe the performance will be of an
enlightened guest running in the novell shim vs running on hyper-v?
Have you implemented enough to do any profiling? Have you done any
profiling of a standard hvm guest with and without the intercepts in
place? It looks like no measurable impact, just curious.

It doesn't seem as though you can batch page table updates, or did I
miss something? 


Mike D. Day
Cell: 919 412-3900
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