Hypervisor
2-2 Oracle VM Server User's Guide
2.2 Hypervisor
Oracle VM Server is designed so that the hypervisor (or monitor, or Virtual Machine
Manager) is the only fully privileged entity in the system, and has an extremely small
footprint. It controls only the most basic resources of the system, including CPU and
memory usage, privilege checks, and hardware interrupts.
2.3 Domains, Guests and Virtual Machines
The terms domain, guest and virtual machine are often used interchangeably, but they
have subtle differences. A domain is a configurable set of resources, including memory,
virtual CPUs, network devices and disk devices, in which virtual machines run. A
domain is granted virtual resources and can be started, stopped and restarted
independently. A guest is a virtualized operating system running within a domain. A
guest operating system may be paravirtualized or hardware virtualized. Multiple
guests can run on the same Oracle VM Server. A virtual machine is a guest operating
system and its associated application software.
Oracle VM Server guest operating systems may run in one of two modes,
paravirtualized or hardware virtualized. In paravirtualized mode, the kernel of the
guest operating system is recompiled to be made aware of the virtual environment.
This allows the paravirtualized guest to run at near native speed, since most memory,
disk and network accesses are optimized for maximum performance.
Figure 2–2 Virtual Machine Architecture
If support for hardware virtualization is available (either Intel VT or AMD-V), the
guest operating system may run completely unmodified. This hardware virtualized
guest is carefully monitored and trapped by Oracle VM Server when any instruction is
executed which would violate the isolation with other guests or dom0. In the current
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