Paravirtualization

paravirtualizedvirtualizationpara-virtualizedparavirtualisationparavirtualisedserver virtualization and partitioning technology
In computing, para-virtualization is a virtualization technique that presents a software interface to the virtual machines which is similar, yet not identical to the underlying hardware–software interface.wikipedia
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Virtualization

virtualizedvirtualvirtualisation
In computing, para-virtualization is a virtualization technique that presents a software interface to the virtual machines which is similar, yet not identical to the underlying hardware–software interface.

Xen

XenServerXenSourceXen Cloud Platform
For example, the Xen Windows GPLPV project provides a kit of paravirtualization-aware device drivers, licensed under the terms of the GPL, that are intended to be installed into a Microsoft Windows virtual guest running on the Xen hypervisor. The term is also used to describe the Xen, L4, TRANGO, VMware, Wind River and XtratuM hypervisors.
User domains may either be traditional operating systems, such as Microsoft Windows under which privileged instructions are provided by hardware virtualization instructions (if the host processor supports x86 virtualization, e.g., Intel VT-x and AMD-V), or paravirtualized operating systems whereby the operating system is aware that it is running inside a virtual machine, and so makes hypercalls directly, rather than issuing privileged instructions.

VM (operating system)

VM/CMSVMVM/370
IBM's VM operating system has offered such a facility since 1972 (and earlier as CP-67).

Denali (operating system)

Denali
The term "paravirtualization" was first used in the research literature in association with the Denali Virtual Machine Manager.
Denali makes use of paravirtualization to support high performance virtual machines, even on the notoriously uncooperative x86 architecture (see x86 virtualization).

Oracle VM Server for SPARC

Logical Domainshyperprivileged modeLDOM
Logical Domains (LDoms or LDOM) is the server virtualization and partitioning technology for SPARC V9 processors.

Hypervisor

hypervisorsvirtual machine monitorhost machine
A successful paravirtualized platform may allow the virtual machine monitor (VMM) to be simpler (by relocating execution of critical tasks from the virtual domain to the host domain), and/or reduce the overall performance degradation of machine execution inside the virtual guest. The term is also used to describe the Xen, L4, TRANGO, VMware, Wind River and XtratuM hypervisors.
This is called paravirtualization in Xen, a "hypercall" in Parallels Workstation, and a "DIAGNOSE code" in IBM's VM.

Kernel-based Virtual Machine

KVMLinux KVMVirtIO
Additionally, KVM provides paravirtualization support for Linux, OpenBSD, FreeBSD, NetBSD, Plan 9 and Windows guests using the VirtIO API.

OS-level virtualization

operating-system-level virtualizationcontainersoperating system-level virtualization
Operating-system-level virtualization usually imposes less overhead than full virtualization because programs in OS-level virtual partitions use the operating system's normal system call interface and do not need to be subjected to emulation or be run in an intermediate virtual machine, as is the case with full virtualization (such as VMware ESXi, QEMU or Hyper-V) and paravirtualization (such as Xen or User-mode Linux).

XtratuM

The term is also used to describe the Xen, L4, TRANGO, VMware, Wind River and XtratuM hypervisors.
para-virtualized operations are as close to the hardware as

VirtualBox

Oracle VirtualBoxVDIPortable-VirtualBox
VirtualBox also supports it from version 5.0.

Full virtualization

virtualization
In full virtualization, a guest operating system runs unmodified on a hypervisor.

Virtual machine

virtual machinesVMvirtual server
In computing, para-virtualization is a virtualization technique that presents a software interface to the virtual machines which is similar, yet not identical to the underlying hardware–software interface.

Operating system

operating systemsOScomputer operating system
Paravirtualization requires the guest operating system to be explicitly ported for the para-API – a conventional OS distribution that is not paravirtualization-aware cannot be run on top of a paravirtualizing VMM.

Porting

portedportports
Paravirtualization requires the guest operating system to be explicitly ported for the para-API – a conventional OS distribution that is not paravirtualization-aware cannot be run on top of a paravirtualizing VMM.

Application programming interface

APIAPIsapplication programming interfaces
Paravirtualization requires the guest operating system to be explicitly ported for the para-API – a conventional OS distribution that is not paravirtualization-aware cannot be run on top of a paravirtualizing VMM.

GNU General Public License

GPLGNU GPLGPLv2
For example, the Xen Windows GPLPV project provides a kit of paravirtualization-aware device drivers, licensed under the terms of the GPL, that are intended to be installed into a Microsoft Windows virtual guest running on the Xen hypervisor.

Microsoft Windows

WindowsPCMS Windows
For example, the Xen Windows GPLPV project provides a kit of paravirtualization-aware device drivers, licensed under the terms of the GPL, that are intended to be installed into a Microsoft Windows virtual guest running on the Xen hypervisor.

CP-67

IBM's VM operating system has offered such a facility since 1972 (and earlier as CP-67).

Parallels Workstation

Linux or MAC OS X virtualizationParallels
The Parallels Workstation operating system calls its equivalent a "hypercall".

L4 microkernel family

L4L4 microkernelseL4
The term is also used to describe the Xen, L4, TRANGO, VMware, Wind River and XtratuM hypervisors.

Trango Virtual Processors

TRANGOTrango's Virtual Processors
The term is also used to describe the Xen, L4, TRANGO, VMware, Wind River and XtratuM hypervisors.

VMware

VMware, Inc.HypericVMotion
The term is also used to describe the Xen, L4, TRANGO, VMware, Wind River and XtratuM hypervisors.

Wind River Systems

Wind RiverWind River LinuxWind River (Diab) Compiler
The term is also used to describe the Xen, L4, TRANGO, VMware, Wind River and XtratuM hypervisors.

X86

x86 architectureIntel x8680x86
All these projects use or can use paravirtualization techniques to support high performance virtual machines on x86 hardware by implementing a virtual machine that does not implement the hard-to-virtualize parts of the actual x86 instruction set.