It has finally happened
Microsoft Windows is a Linux app.
Hewlett-Packard is gunning for Amazon's corporate cloud business, with fully backed Windows Server on its cloud. HP is now running Windows Server 2008, Windows Server 2012, 2003 R2, 2008 and 2008 R2 on its Helion OpenStack cloud, with full support from Microsoft. Redmond will provide technical support for customers through …
"The irony for Microsoft is that its closed-source operating system is being floated on an open-source project once billed as a Linux for the cloud."
You can run Microsoft Hyper-V Server under Openstack. There has been a NOVA driver for 2 years now and it scales better than KVM does. Not to mention that security patches are free unlike certain KVM flavours, and Hyper-V Server has had far fewer of them. Also it's a proper Hypervisor layer unlike KVM, which is a bolt on to a full OS kernel...
The only gap at the moment is that you can't run the controller node on Windows Server, but hopefully that will be fixed eventually.