Selective Hardware/Software Memory Virtualization
As virtualization becomes a key technique for supporting cloud computing, much effort has been made to reduce virtualization overhead, so a virtualized system can match its native performance. One major overhead is due to memory or page table virtualization. Conventional virtual machines rely on a shadow mechanism to manage page tables, where a shadow page table maintained by the VMM (Virtual Machine Monitor) maps virtual addresses to machine addresses while a guest maintains its own virtual to physical page table. This shadow mechanism will result in expensive VM exits whenever there is a page fault that requires synchronization between the two page tables.