Kernel-based Virtual Machine

KVM

Screenshot of QEMU/KVM running NetBSD, OpenSolaris and Kubuntu on an Arch Linux host.
Original author(s)	Qumranet
Developer(s)	Open Virtualization Alliance (OVA)
Stable release	1.2.0 / September 5, 2012 (2012-09-05)
Written in	C
Operating system	Unix-like
Type	Hypervisor
License	GNU General Public License or GNU Lesser General Public License
Website	www.linux-kvm.org (unofficial)

KVM (Kernel-based Virtual Machine) is a virtualization infrastructure for the Linux kernel which turns it into a hypervisor. KVM requires a processor with hardware virtualization extension.^[1] KVM has also been ported to FreeBSD^[2] and Illumos^[3] in the form of loadable kernel modules.

KVM originally supported x86 processors and has been ported to S/390,^[4] PowerPC,^[5] and IA-64. An ARM port was merged during the 3.9 kernel merge window.^[6]

A wide variety of guest operating systems work with KVM, including many flavours of Linux, BSD, Solaris, Windows, Haiku, ReactOS, Plan 9, and AROS Research Operating System.^[7] In addition Android 2.2, GNU/Hurd^[8] (Debian K16), Minix 3.1.2a, Solaris 10 U3, Darwin 8.0.1 and more OSs and some newer versions of these with limitations are known to work.^[9] A modified version of QEMU can use KVM to run Mac OS X.^[10]

Paravirtualization support for certain devices is available for Linux, OpenBSD,^[11] FreeBSD,^[12] NetBSD,^[13] Plan 9^[14] and Windows guests using the VirtIO framework. This supports a paravirtual Ethernet card, a paravirtual disk I/O controller,^[15] a balloon device for adjusting guest memory usage, and a VGA graphics interface using SPICE or VMware drivers.

KVM uses SeaBIOS.

Linux 2.6.20 (released February 2007) was the first to include KVM.^[16]

Design

By itself, KVM does not perform any emulation. Instead, it simply exposes the /dev/kvm interface, with which a user-space host can then:

• Set up the guest VM's address space. The host must also supply a firmware image (usually a custom BIOS when emulating PCs) with which the guest can bootstrap into its main OS.
• Feed it simulated I/O.
• Map its video display back onto the host.

On Linux, QEMU versions 0.10.1 and later is one such host. It will use KVM when available to virtualize guests at near-native speeds, but otherwise fall back to software-only emulation.

Licensing

KVM's parts are licensed under various GNU licenses:^[17]

• KVM kernel module: GPL v2
• KVM user module: LGPL v2
• QEMU virtual CPU core library (libqemu.a) and QEMU PC system emulator: LGPL
• Linux user mode QEMU emulator: GPL
• BIOS files (bios.bin, vgabios.bin and vgabios-cirrus.bin): LGPL v2 or later

History

Avi Kivity began the development of KVM at Qumranet, a technology startup company.^[18] Red Hat bought Qumranet in 2008.^[19] KVM is maintained by Paolo Bonzini and Gleb Natapov.

Graphical management tools

Kernel-based Virtual Machine is supported by libvirt.

• KIMCHI - web-based virtualization management tool for KVM
• UCS Virtual Machine Manager - web-based virtualization management tool for different virtualization technologies like KVM and Xen under Microsoft Windows and numerous Linux distributions; Integrated by default in the Enterprise Linux solution Univention Corporate Server.
• Archipel – An opensource libvirt-based Web UI, which uses XMPP to communicate with its "agents" installed on servers
• Witsbits – Simplified SaaS based centralized management with web UI.
• Virtual Machine Manager – Supports creating, editing, starting, and stopping KVM-based virtual machines, as well as live or cold drag-and-drop migration of VMs between hosts.
• ConVirt – Manages creating, editing, starting, and stopping KVM-based virtual machines, as well as live or cold drag-and-drop migration of VMs between hosts.
• Proxmox Virtual Environment – Free virtualization management package including KVM and OpenVZ. It has a bare-metal installer, a web-based remote management GUI, and optional commercial support.
• OpenNode – RHEL/CentOS-based open-source server virtualization and management solution with a simple bare-metal installer, providing KVM+OpenVZ host and standard libvirt, func management interfaces together with standard CLI tools like virsh and vzctl.
• OpenQRM - Management platform for managing heterogeneous data center infrastructures.
• SolusVM – Supports the management of KVM-based virtual machines as well as Xen and OpenVZ.
• Virtualizor – Supports the management of KVM-based virtual machines as well as Xen and OpenVZ.

Emulated hardware

Implementations

• Illumos based distributions
• OpenIndiana
• Red Hat Enterprise Linux (RHEL) 5.4 and above
• SmartOS
• SUSE Linux Enterprise Server (SLES) 11 SP1 and above
• Ubuntu 10.04 LTS and above
• Gentoo Linux
• Univention Corporate Server

See also

• Xen
• Comparison of platform virtual machines
• Open Virtualization Alliance
• Lguest
• oVirt
• libvirt
• libguestfs
• Vx32
• OpenNebula
• OpenStack
• CloudStack

References

External links

• Official website
• Wikibook QEMU & KVM
• First benchmarks of KVM
• "News, Blogs and Resources on the Linux (KVM) Kernel-Based Virtual Machine"
• Available KVM-Implementation from Collax
• UnifiedSessionsManager – An OpenSource based Service and Sessions Manager for QEMU/KVM