RE: [Xen-devel] XEN and windows licensing

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

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From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Stan Morey
Sent: 01 March 2006 00:31
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] XEN and windows licensing

To run windows under XEN running on windows, I'd have to pay an extra windows license... is there any way to get applications to run under Xen and pass the windows system calls through to windows so Xen isnt running an OS but rather a proxy OS? 

Microsoft allows you to run multiple copies of Windows under virtualization with a single license - although only for certain versions of the OS of course..

http://www.microsoft.com/presspass/features/2005/oct05/10-10virtualizationlicensing.mspx

However, what you describe isn't possible - well, at least it's not TRIVIALLY possible. You have to have a version of Windows installed on the machine when you want to run Windows application, unless you use some sort of Windows emulator, such as Wine under Linux.

Intercepting the system calls themselves isn't very difficult, but doing the work that the system call means has to be done isn't very easy - we'd have to write our own, compatible, version of Windows for Xen.

And by the way, if you're running Windows already (legally), you have a license. If you then convert that machine to run with Xen, you'd still own your legal license, so you could use that license to install Windows on top of Xen. Since Xen itself doesn't require a copy of Windows other than the one you're actually using to run your apps, you don't need another license - Xen uses a version of Linux to run the hardware emulation that you need to do to make Windows believe there's some real hardware there. Of course, running multiple copies of Windows would be under whatever rules apply to that version of Windows and virtualized systems.

--

Mats

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