Microsoft to Open Access to Viridian Virtualization API

In a move to demonstrate its recent drive toward openness was not being done to appease the European Commission, Microsoft this afternoon announced it is adding the API for hypercalls - the ability for a host machine to communicate directly with a virtual machine - to the list of technologies covered by its Open Specification Promise.

The hypercall API will be one of the more intriguing additions to Windows Server 2008, which will be the vehicle in which the company's built-in virtualization technology, code-named Viridian, will premiere next year.

The interface enables a host operating system -- not necessarily Windows -- to place calls to a Windows environment being hosted within that system. As a result, the technology enables paravirtualization - the ability for the hosted VM to "know" it's hosted, and to behave specially in such circumstances.

Technologies covered by the Open Specification Promise - which also include Microsoft's implementation of SOAP, Remote Shell, and WS-* Web services - may be utilized, copied, and modified by developers without royalty or obligation, so long as they agree not to claim Microsoft has infringed upon their intellectual property. The promise is unilateral, and doesn't require developers to sign up or to agree.

Microsoft may have been prompted to make this move in the midst of speculation that, as a result of its first patent covenant with Novell, it enabled SUSE Enterprise Linux to have exclusive access to the hypercall API, giving it an automatic advantage over Red Hat and other distributions. The API was featured prominently in a Novell filing with the US Securities and Exchange Commission, explaining the terms of its covenant agreement with Microsoft and what technologies are being exchanged.

So perhaps it may not have been coincidence that the first quotation in this afternoon's statement was made not by a Microsoft executive or manager, but instead by Novell Senior Vice President for Open Platform Solutions, Roger Levy.

"The majority of our customers have mixed-source environments," Levy stated, "and they want their platform vendors to make things work together. 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."

For those of you keeping score at home, the Xen hypervisor is obviously not the same thing as the Viridian hypervisor. Citrix acquired XenSource -- which, with VMware and Microsoft, rounds out the big three virtualization technology producers -- making it a key competitor with Microsoft in a very hot market.

So the fact that Citrix CTO Simon Crosby was quoted next, is very interesting: "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," Crosby said.

The key "takeaway," to borrow a phrase from the world of PowerPoint presentations: There may be a market fight going on, but there's no conspiracy being played out with Viridian's hypercall API as a key factor. It seems Microsoft has been more than busy these past few weeks putting out fires.