Quoting from the Intel official annoucement:
Intel and Microsoft have also joined together to extend Intel Virtualization Technology (Intel VT) to include support for mapping I/O devices to virtual machines on servers with a new specification, published today, called Intel Virtualization for Directed I/O (Intel VT–d).
Part of the Intel VT family of technologies, Intel VT–d helps improve the reliability, flexibility and performance of I/O in a virtualized environment.
Microsoft has collaborated with Intel on development of the specification to help ensure it provides optimal functionality for users…