A Kernel-based Virtual Machine is an open source virtualisation for the Linux kernel distributions.
The KVM was merged into the Linux kernel mainline in kernel version 2.6.20, with the use of a type-two hypervisor. It has also been ported to FreeBSD and illumos, activated in the form of loadable kernel modules.
In order for the Kernel-based Virtual Machine to work, it requires a processor with hardware virtualisation extensions.