A software monitor, interposed between the hardware layer of a computer system
and one or more guest operating systems, constructs and maintains a guest-physical-address-to-host-physical-address
map for each guest operating system, and maintains a virtual memory addressing
context for each guest operating system that may include a virtual-hash-page table
for each guest operating system, the contents of translation registers for each
guest operating system, CPU-specific virtual-memory translations for each guest
operating system, and the contents of various status registers. The monitor runs
at the highest privilege level provided by the hardware system, intercepting attempts
to execute privileged instructions by guest operating systems, and simulates or
enhances certain of the privileged instructions related to virtual-memory addressing
in order to construct and maintain the guest-physical-address-to-host-physical-address
map and to provide each guest operating system with the illusion that the guest
operating system is executing as the most privileged process on a virtual machine.
