1. A method performed by a processor, comprising: executing an instruction to change address space for guest software running on a virtual machine, said executing including: without exiting said virtual machine's process, instruction execution logic circuitry of said processor replacing in private register space a first pointer that points to a first page table hierarchy with a second pointer that points to a second page table hierarchy, the first page table hierarchy for performing address translations for a first portion of said guest software that operates out of a first region of memory, the second page table hierarchy for performing address translations for a second portion of said guest software that operates out of a second region of memory.