Everything you wanted to know about Kernel-based Virtual Machine, but were afraid to ask

What is KVM?

KVM (short for Kernel-based Virtual Machine) refers to a set of open source kernel modules that turns the Linux kernel into a hypervisor. It requires the use of CPU extensions that are available in both Intel and AMD CPU’s. As such, KVM provides “full virtualization”, as opposed to para-virtualized virtualization.

Because it is part of the Linux kernel, as opposed to a separate layer above an operating system, it is a “type 1” or “bare-metal hypervisor.” Avi Kivity and others originally created KVM at Qumranet and it was officially accepted into the upstream Linux kernel in February of 2007, as part of the 2.6.20 kernel release. Red Hat subsequently purchased Qumranet in 2008.

KVM was designed from the ground up to be a secure and high performance hypervisor. To that end, KVM takes advantages of things that the Linux kernel already does well on it’s own such as memory management, driver support, security, scheduling, and other things. KVM simply adds in the missing components necessary to virtualize servers and/or desktops.

Acceptance into the Linux kernel is an important distinction to make for a few reasons. Architecturally speaking, this makes it much easier to take advantage of new kernel features and fixes.

As these features such as enhanced security, bug fixes, and hardware enablement are added, KVM can use them almost immediately. This is in stark contrast to other hypervisors that remain a separate layer and require guest kernel modification or recompiling of the host kernel in order to take full advantage of features. Under KVM, one can run multiple virtual machines running unmodified Linux, UNIX, or Windows guests.

Being part of the Linux kernel also means that a data center can use the same Linux operating system for virtual and native workloads. This cuts down on training and operational costs, as you don’t have to support a separate hypervisor. Additionally, the KVM architecture allows administrators to run native applications along side of virtual machines, providing true flexibility and datacenter consolidation. And finally, this also means that KVM enjoys wide spread use, regardless of the Linux distribution; almost all modern Linux distributions support and include KVM.

Technically the KVM hypervisor is comprised of the KVM kernel modules and the Qemu virtual machine environment. Qemu is an open-source computer emulator. In order to present virtual network, video, and block devices to KVM virtual machines, KVM uses the Qemu virtual machine environment, the most power feature of Qemu.

Most KVM developers are Qemu developers and vice versa. The two projects are designed to work together and we usually speak of them together as “KVM.” (KVM is released as part of the Linux kernel, while Qemu is released independently as a multi-platform emulator).

The flexibility, availability, and capability of KVM has also played a large part in the growth and success of cloud computing. Over 62% of OpenStack deployments use KVM as the hypervisor, as reported in the recent OpenStack User Survey.

What is Open Virtualization (oVirt)?
Open Virtualization, or oVirt, is both an open source project and community. oVirt the “community” provides development and governance for oVirt the “project” that develops an ecosystem and management system around the KVM hypervisor.
The most visible piece of oVirt is a product called “oVirt Engine”, which is a full-featured management platform that manages resources such as hypervisors, storage domains, virtual machines, virtual networks, and other related pieces. And while oVirt is quite capable of handling production workloads, it also serves as the “upstream” project for Red Hat Enterprise Virtualization (RHEV), which is a fully supported product of Red Hat. As new features are developed and hardened in oVirt, they are then pulled into RHEV. In this sense, oVirt is both a viable solution in and of itself, as well as a development sandbox.

While there are other open source solutions and some management products that support open source hypervisors, oVirt is the first comprehensive virtualization platform. From a project standpoint, the governance is modeled after the Apache Foundation. The board is comprised of people from Red Hat, SUSE, Intel, NetApp, Cisco, IBM, and Canonical. This board representation is important from the standpoint that in order to have a vibrant community, oVirt cannot be successful if it only represents Red Hat; it has to have support and contributions from other Linux distributions and technology leaders.

For more information about oVirt, visit:
http://www.ovirt.org/Home
What is the KVM Forum?
The KVM Forum is an annual technical conference that is co-located with either LinuxCon North America or LinuxCon EMEA. It brings together KVM developers, engineers, architects, and users in a single event meant to enable and further the ecosystem around KVM.

Like traditional trade conferences, there are speaking sessions, demonstrations, road map reviews, and many impromptu discussions.

This past October, the KVM Forum was held during the same week as LinuxCon EMEA in Edinburgh, Scotland; previous locations included Barcelona and Vancouver. While it might seem that KVM Forum would pull folks away from LinuxCon, it really does not.
There are many facets to Linux, of which one is KVM. KVM Forum attendees typically register for LinuxCon as well, and attend sessions from both conferences.

For more information and the Linux Foundation KVM, visit:
http://www.linux-kvm.org/page/Main_Page

The Open Virtualization Alliance
The Open Virtualization Alliance (OVA) was founded two years ago to help advance adoption of the Kernel-based Virtual Machine (KVM) hypervisor by providing education, best practices and nurturing a vibrant ecosystem. The mission of the OVA, now a Linux Foundation Collaborative Project, is to accelerate the adoption of KVM as on open alternative in enterprise-class virtualization and cloud solutions, through increasing overall awareness and understanding of KVM.

The OVA Governing Board, made up of HP, IBM, Intel, NetApp and Red Hat, and its 200+ Participating Members and Supporting Organizations are focused on fostering the use and ecosystem around the KVM hypervisor, and to provide context around KVM-based solutions. For more information about the Open Virtualization Alliance and its members, visit:

http://www.openvirtualizationalliance.org