Kernel-based Virtual Machine (KVM) is a virtualization infrastructure for the Linux kernel that turns it into a hypervisor. It was merged into the Linux kernel mainline in kernel version 2.6.20, which was released on February 5, 2007. KVM requires a processor with hardware virtualization extensions. KVM has also been ported to FreeBSD and illumos in the form of loadable kernel modules.
KVM originally supported x86 processors and has been ported to S/390, PowerPC, and IA-64. An ARM port was merged during the 3.9 kernel merge window.
A wide variety of guest operating systems work with KVM, including many flavours and versions of Linux, BSD, Solaris, Windows, Haiku, ReactOS, Plan 9, AROS Research Operating System and OS X. 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.
Paravirtualization support for certain devices is available for Linux, OpenBSD, FreeBSD, NetBSD, Plan 9 and Windows guests using the VirtIO API. This supports a paravirtual Ethernet card, a paravirtual disk I/O controller, a balloon device for adjusting guest memory usage, and a VGA graphics interface using SPICE or VMware drivers.
Internals
By itself, KVM does not perform any emulation. Instead, it exposes the /dev/kvm interface, which a userspace 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.
On Linux, QEMU versions 0.10.1 and later is one such userspace host. QEMU uses KVM when available to virtualize guests at near-native speeds, but otherwise falls back to software-only emulation.
Internally, KVM uses SeaBIOS as an open source implementation of a 16-bit x86 BIOS.
Licensing
KVM's parts are licensed under various GNU licenses:
- 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 that was acquired by Red Hat in 2008.
KVM was merged into the Linux kernel mainline in kernel version 2.6.20, which was released on 5 February 2007.
KVM is maintained by Paolo Bonzini.
Graphical management tools
- Kimchi â€" web-based virtualization management tool for KVM
- Virtual Machine Manager â€" 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 â€" 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 â€" management platform for managing heterogeneous data center infrastructures.
- GNOME Boxes â€" Gnome interface for managing libvirt guests on Linux.
- oVirt â€" open-source virtualization management tool for KVM built on top of libvirt
Emulated hardware
See also
References
Bibliography
- Amit Shah (2016-11-02). "Ten years of KVM". lwn.net. Retrieved 2017-02-10.Â
External links
- Official website
- Best practices for the Kernel-based Virtual Machine, IBM, second edition, April 2012
- Virtio-blk Performance Improvement, KVM Forum 2012, November 8, 2012, by Asias He
- Wikibook QEMU & KVM