Patent ID: 7478388

Claim:
A computer program embodied in a tangible medium, the computer program being executable in a computer system, the computer system comprising a new processor having a new operating mode and a legacy operating mode, the legacy operating mode being suitable for executing a legacy application and a legacy operating system (OS), the computer system further comprising a host OS that is executable on the new processor in the new operating mode, the computer program comprising: a virtualization software that is executable on the new processor in the legacy mode, the virtualization software supporting a virtual machine (VM) having a virtual legacy processor on which a legacy OS and a legacy application can run; a switch routine for switching between the host OS executing in the new operating mode and the virtualization software executing in the legacy operating mode, the new processor including a legacy instruction set for the legacy operating mode and a new instruction set for the new operation mode, the switching includes switching from the new instruction set to the legacy instruction set and switching paging tables, each of the new operating mode and the legacy operating mode having separate paging tables, wherein, the switch routine is incorporated in a switch page that is locked in physical memory, the switch page having a first section to store a part of switching instructions conforming to the new instruction set and a second section to store another part of the switching instructions conforming to the legacy instruction set; and a driver loaded in the host OS for initiating the switch routine from the host OS, wherein the switch routine is a part of the driver.