In virtualization technology, hypervisor is a software
program that manages multiple operating systems
(or multiple instances of the same operating system) on a single
computer system. The hypervisor manages the
system's processor, memory,
and other resources to allocate what each operating system requires. Hypervisors
are designed for a particular processor architecture
and may also be called virtualization managers.
Coming Soon to VMware, Microsoft, and Xen: AMD Virtualization Technology Solves Virtualization Challenges All modern operating systems expect that their kernel and driver code is running in privileged mode, which of course is fine in a non-virtualized PC. However, in a virtual machine, you don't want that kernel and driver code, or the interrupt handlers, to really have full control over the hardware; you need the VMM to be able to be able to transparently manage the system.
