Desktop virtualization products such as Workstation, Fusion, Oracle VirtualBox and Microsoft Virtual PC have long had a place in many a test lab. However, these products have been unable to run some key workloads. For example, an attempt to install Hyper-V on a Windows virtual machine running under VirtualBox results in failure; the Hyper-V role requires that the host hardware have enabled VT or AMD-V extensions.
VT-x, an Intel technology, and AMD-V, from AMD, have the same goal in mind – provide hardware-based processor extensions that enable and improve the performance of virtual workloads. Obviously, there is more to these technologies, but the point here is that, in the past, although a host processor might support VT-x or AMD-V, these extensions have not been exposed or available for use by a guest operating system. For example, although you might be able to install Hyper-V on a host machine, if you were to install Windows/Hyper-V as a guest running on a host, those extensions would not be available.
With VMware Workstation 8, this is all changed. Guest virtual machines running under Workstation 8 can have a feature enabled that allows them to make use of VT-x or AMD-V extensions, making it possible to, for example, run a Windows/Hyper-V virtual machine inside of a Windows/Hyper-V virtual machine or run 64-bit guest operating systems inside a vSphere instance that is running inside Workstation.
For testers everywhere, this is a significant enhancement. However, when you enable this feature, you’re warned that doing so will make this virtual machine incompatible with other VMware products that do not support this capability.