Kernel-based Virtual Machine

KVM
KVM
	Screenshot of QEMU/KVM running NetBSD and OpenIndiana guests on an Arch Linux host.
Original author	Qumranet
Developer	The Linux Kernel community
Written in	C
Operating system	Unix-like
Platform	ARM, PowerPC, z/Architecture, IA-32, x86-64, RISC-V, LoongArch
Type	Hypervisor
License	GNU GPL or LGPL
Website	www.linux-kvm.org
Repository	git.kernel.org/pub/scm/virt/kvm/kvm.git ;

Kernel-based Virtual Machine (KVM) is a free and open-source virtualization module in the Linux kernel that allows the kernel to function as a hypervisor. It was merged into the mainline Linux kernel in version 2.6.20, which was released on February 5, 2007. KVM requires a processor with hardware virtualization extensions, such as Intel VT or AMD-V. KVM has also been ported to other operating systems such as FreeBSD and illumos in the form of loadable kernel modules.

KVM was originally designed for x86 processors but has since been ported to z/Architecture, PowerPC, IA-64, and ARM. The IA-64 port was removed in 2014.

KVM supports hardware-assisted virtualization for a wide variety of guest operating systems including BSD, Solaris, Windows, Haiku, ReactOS, Plan 9, AROS, macOS, and even other Linux systems. In addition, Android 2.2, GNU/Hurd (Debian K16), Minix 3.1.2a, Solaris 10 U3 and Darwin 8.0.1, together with other operating systems and some newer versions of these listed, are known to work with certain limitations.

Additionally, KVM provides paravirtualization support for Linux, OpenBSD, FreeBSD, NetBSD, Plan 9 and Windows guests using the VirtIO API. This includes a paravirtual Ethernet card, disk I/O controller, balloon driver, and a VGA graphics interface using SPICE or VMware drivers.

History

Avi Kivity began the development of KVM in mid-2006 at Qumranet, a technology startup company that was acquired by Red Hat in 2008.

KVM surfaced in October 2006 and was merged into the Linux kernel mainline in version 2.6.20, released on 5 February 2007.

KVM is maintained by Paolo Bonzini.

Internals

KVM provides device abstraction but no processor emulation. It exposes the /dev/kvm interface, which a user mode host can then use to:

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

Originally, a forked version of QEMU was provided to launch guests and deal with hardware emulation that is not handled by the kernel. That support was eventually merged into the upstream project. There are now numerous Virtual Machine Monitors (VMMs) which can utilise the KVM interface including kvmtool, crosvm and Firecracker and numerous specialised VMMs built with frameworks such as rust-vmm.

Internally, KVM uses SeaBIOS as an open source implementation of a 16-bit x86 BIOS.

Features

KVM has had support for hot swappable vCPUs, dynamic memory management, and Live Migration since February 2007. It also reduces the impact that memory write-intensive workloads have on the migration process.

Emulated hardware

KVM itself emulates very little hardware, instead deferring to a higher level client application such as QEMU, crosvm, or Firecracker for device emulation.

KVM provides the following emulated devices:

Virtual CPU and memory
VirtIO

Graphical management tools

Kimchi – web-based virtualization management tool for KVM
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.
Proxmox Virtual Environment – an open-source virtualization management package including KVM and LXC. It has a bare-metal installer, a web-based remote management GUI, a HA cluster stack, unified storage, flexible network, and optional commercial support.
OpenQRM – management platform for managing heterogeneous data center infrastructures
GNOME Boxes – Gnome interface for managing libvirt guests on Linux
oVirt – open-source virtualization management tool for KVM built on top of libvirt
OpenNebula – is an open source cloud computing platform for managing heterogeneous data center, public cloud and edge computing infrastructure resources that are running on KVM, QEMU or LXC.

Licensing

The kernel-mode component of KVM is a part of the Linux kernel, itself licensed under GNU General Public License, version 2.

References

1 2 "Linux kernel 2.6.20, Section 2.2. Virtualization support through KVM". kernelnewbies.org. 2007-02-05. Retrieved 2014-06-16.
↑ "KVM FAQ: What do I need to use KVM?". www.linux-kvm.org. Retrieved 2026-04-24.
↑ "FreeBSD Quarterly Status Report: Porting Linux KVM to FreeBSD". freebsd.org. Retrieved 2026-04-24.
↑ "KVM on illumos". 15 August 2011.
1 2 3 "Linux_2_6_26". kernelnewbies.org. 2008-07-13. 1.2. KVM ported to IA64, PPC and S390. Retrieved 2025-08-23.
↑ "KVM: s390: arch backend for the kvm kernel module". git.kernel.org. 2008-04-27. Retrieved 2026-04-24.
↑ "KVM/ARM: An Open-Source ARM Virtualization System".
↑ "KVM/ARM Open Source Project". Archived from the original on 2013-03-10. Retrieved 2017-11-01.
↑ Christoffer Dall; Jason Nieh (2014). "KVM/ARM: The Design and Implementation of the Linux ARM Hypervisor". SIGARCH Comput. Archit. News. 42 (1). ACM International Conference on Architectural Support for Programming Languages and Operating Systems: 333–348. doi:10.1145/2654822.2541946.
↑ "kernel/git/torvalds/linux.git: KVM: ia64: remove". git.kernel.org. 2014-11-19. Retrieved 2026-04-24.
1 2 "KVM wiki: Guest support status". Retrieved 2007-05-27.
↑ "Running Mac OS X as a QEMU/KVM Guest". Retrieved 2014-08-20.
↑ "status". Gnu.org. Retrieved 2014-02-12.
↑ "OpenBSD man page virtio(4)". Retrieved 2018-02-04.
↑ "virtio binary packages for FreeBSD". Retrieved 2012-10-29.
↑ "NetBSD man page virtio(4)". Archived from the original on 2019-11-13. Retrieved 2013-07-15.
↑ "plan9front". Archived from the original on 2011-07-22. Retrieved 2013-02-11.
↑ "An API for virtual I/O: virtio". LWN.net. 2007-07-11. Retrieved 2014-04-16.
↑ "SCSI target for KVM wiki". linux-iscsi.org. 2012-08-07. Archived from the original on 2020-06-05. Retrieved 2012-08-12.
↑ Kivity, Avi; Kamay, Yaniv; Laor, Dor; Lublin, Uri; Liguori, Anthony (June 2007). "KVM: the Linux Virtual Machine Monitor" (PDF). Proceedings of the Linux Symposium. Vol. 1. Ottawa, Ontario, Canada. pp. 225–230.
↑ Avi Cavity (April 23, 2007). "Interview: Avi Kivity". KernelTrap (Interview). Interviewed by Jeremy Andrews. Archived from the original on 2007-04-26.
↑ "Red Hat Advances Virtualization Leadership with Qumranet, Inc. Acquisition" (Press release). Red Hat. 4 September 2008. Retrieved 16 June 2015.
↑ "KVM 15 equipped with live migration". IT World Canada News. 7 March 2007. Archived from the original on July 28, 2019.
↑ Libby Clark (7 April 2015). "Git Success Stories and Tips from KVM Maintainer Paolo Bonzini". Linux.com. Archived from the original on 15 March 2016. Retrieved 17 June 2015.
↑ Khoa Huynh; Stefan Hajnoczi (2010). "KVM/QEMU Storage Stack Performance Discussion" (PDF). IBM. Linux Plumbers Conference. Retrieved January 3, 2015.^{[permanent dead link]}
↑ "SeaBIOS". seabios.org. 2013-12-21. Archived from the original on 2020-12-09. Retrieved 2014-06-16.
↑ "Hot Plugging Virtual CPUs with Red Hat Enterprise Virtualization Manager". 16 February 2016.
↑ "Faq - KVM".
↑ "KVM-15 release [LWN.net]".
↑ "Migration - KVM".
↑ "Daniel P. Berrangé » Blog Archive » Analysis of techniques for ensuring migration completion with KVM".
↑ "The Definitive KVM (Kernel-based Virtual Machine) API Documentation — the Linux Kernel documentation".
↑ "Linux kernel licensing rules — The Linux Kernel documentation". www.kernel.org. Archived from the original on 7 March 2020. Retrieved 2020-01-06.

Bibliography

Amit Shah (2016-11-02). "Ten years of KVM". lwn.net. Retrieved 2017-02-10.

External links

Best practices for the Kernel-based Virtual Machine Archived 2019-11-06 at the Wayback Machine, IBM, second edition, April 2012
Virtio-blk Performance Improvement, KVM Forum 2012, November 8, 2012, by Asias He
Wikibook QEMU & KVM
crosvm - Chrome OS virtual machine monitor
Firecracker VMM for KVM

[2620notes-1] 1 2 "Linux kernel 2.6.20, Section 2.2. Virtualization support through KVM". kernelnewbies.org. 2007-02-05. Retrieved 2014-06-16.

[2] "KVM FAQ: What do I need to use KVM?". www.linux-kvm.org. Retrieved 2026-04-24.

[3] "FreeBSD Quarterly Status Report: Porting Linux KVM to FreeBSD". freebsd.org. Retrieved 2026-04-24.

[4] "KVM on illumos". 15 August 2011.

[2626notes-5] 1 2 3 "Linux_2_6_26". kernelnewbies.org. 2008-07-13. 1.2. KVM ported to IA64, PPC and S390. Retrieved 2025-08-23.

[6] "KVM: s390: arch backend for the kvm kernel module". git.kernel.org. 2008-04-27. Retrieved 2026-04-24.

[7] "KVM/ARM: An Open-Source ARM Virtualization System".

[8] "KVM/ARM Open Source Project". Archived from the original on 2013-03-10. Retrieved 2017-11-01.

[9] Christoffer Dall; Jason Nieh (2014). "KVM/ARM: The Design and Implementation of the Linux ARM Hypervisor". SIGARCH Comput. Archit. News. 42 (1). ACM International Conference on Architectural Support for Programming Languages and Operating Systems: 333–348. doi:10.1145/2654822.2541946.

[10] "kernel/git/torvalds/linux.git: KVM: ia64: remove". git.kernel.org. 2014-11-19. Retrieved 2026-04-24.

[:0-11] 1 2 "KVM wiki: Guest support status". Retrieved 2007-05-27.

[12] "Running Mac OS X as a QEMU/KVM Guest". Retrieved 2014-08-20.

[13] "status". Gnu.org. Retrieved 2014-02-12.

[14] "OpenBSD man page virtio(4)". Retrieved 2018-02-04.

[15] "virtio binary packages for FreeBSD". Retrieved 2012-10-29.

[16] "NetBSD man page virtio(4)". Archived from the original on 2019-11-13. Retrieved 2013-07-15.

[17] "plan9front". Archived from the original on 2011-07-22. Retrieved 2013-02-11.

[18] "An API for virtual I/O: virtio". LWN.net. 2007-07-11. Retrieved 2014-04-16.

[19] "SCSI target for KVM wiki". linux-iscsi.org. 2012-08-07. Archived from the original on 2020-06-05. Retrieved 2012-08-12.

[20] Kivity, Avi; Kamay, Yaniv; Laor, Dor; Lublin, Uri; Liguori, Anthony (June 2007). "KVM: the Linux Virtual Machine Monitor" (PDF). Proceedings of the Linux Symposium. Vol. 1. Ottawa, Ontario, Canada. pp. 225–230.

[21] Avi Cavity (April 23, 2007). "Interview: Avi Kivity". KernelTrap (Interview). Interviewed by Jeremy Andrews. Archived from the original on 2007-04-26.

[22] "Red Hat Advances Virtualization Leadership with Qumranet, Inc. Acquisition" (Press release). Red Hat. 4 September 2008. Retrieved 16 June 2015.

[23] "KVM 15 equipped with live migration". IT World Canada News. 7 March 2007. Archived from the original on July 28, 2019.

[24] Libby Clark (7 April 2015). "Git Success Stories and Tips from KVM Maintainer Paolo Bonzini". Linux.com. Archived from the original on 15 March 2016. Retrieved 17 June 2015.

[25] Khoa Huynh; Stefan Hajnoczi (2010). "KVM/QEMU Storage Stack Performance Discussion" (PDF). IBM. Linux Plumbers Conference. Retrieved January 3, 2015.^{[permanent dead link]}

[26] "SeaBIOS". seabios.org. 2013-12-21. Archived from the original on 2020-12-09. Retrieved 2014-06-16.

[27] "Hot Plugging Virtual CPUs with Red Hat Enterprise Virtualization Manager". 16 February 2016.

[28] "Faq - KVM".

[29] "KVM-15 release [LWN.net]".

[30] "Migration - KVM".

[31] "Daniel P. Berrangé » Blog Archive » Analysis of techniques for ensuring migration completion with KVM".

[32] "The Definitive KVM (Kernel-based Virtual Machine) API Documentation — the Linux Kernel documentation".

[Linux_Licensing-33] "Linux kernel licensing rules — The Linux Kernel documentation". www.kernel.org. Archived from the original on 7 March 2020. Retrieved 2020-01-06.