Microsoft Announces Hypercall API will be licensed Under Open Specification Promise

Microsoft today announced that it will extend the Open Specification Promise to the hypercall application programmer’s interface (API) within Windows Server virtualization (codename Viridian), and will be available when Windows Server virtualization is released to manufacturing (RTM). In the interim, today Microsoft posted an updated draft of the hypercall API to Microsoft’s website [] so that partners can continue to have early access to this important development interface. Microsoft first distributed hypercall API draft documentation to attendees of Windows Hardware Engineering Conference 2006.


The hypercall API enables partners to develop solutions with Windows Server virtualization allowing customers to achieve dynamic IT environments.   These APIs are available for use by any organization seeking to integrate or extend their software with Windows Server 2008 and Windows Server virtualization.


“The majority of our customers have mixed-source environments, and they want their platform vendors to make things work together,” said Roger Levy, senior vice president and general manager, Open Platform Solutions at Novell.  “That’s why we entered into a technical collaboration agreement with Microsoft.  As a result, Novell is the first vendor to develop and ship technology that will allow a paravirtualized Windows Server 2008 to be hosted as a guest on the Xen hypervisor.  Microsoft’s decision to put the hypercall API under their Open Specifications Promise will make it even easier for Novell, our customers and partners, and the entire open source community to develop high-quality virtualization solutions that deliver true interoperability between Windows and Linux.”


“Citrix is committed to the delivery of value-added virtualization solutions for  the Windows platform, so interoperability with Microsoft’s virtualization solutions is key to our success.  This is made possible by Microsoft’s  open and progressive approach to licensing key technologies such as its VHD image format and the Windows Server Virtualization hypercall API,” said Simon Crosby, CTO, Virtualization & Management Division, Citrix. “This will allow us to ensure that virtual machines created on XenServer will be compatible with Microsoft WSV when it is delivered as a component of Windows Server 2008.”


For more information on today’s announcements, please see the Windows Virtualization Team Blog and the feature press release titled Microsoft Collaborates with Customers, Competitors and Partners to Deliver Real-world Interoperability Solutions at Microsoft PressPass.


The hypercall API documentation download can be found here: