Kernel-based Virtual Machine
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| Kernel-based Virtual Machine | |
|---|---|
 | |
| Name | Kernel-based Virtual Machine |
| Developer | Qumranet, Red Hat, Linus Torvalds |
| Released | 2007 |
| Operating system | Linux |
| Platform | x86, ARM, PowerPC, S390 |
| License | GNU General Public License |
Kernel-based Virtual Machine
Kernel-based Virtual Machine is a virtualization infrastructure integrated into the Linux kernel that turns the kernel into a hypervisor, enabling multiple operating system instances to run concurrently on a single physical host. It was developed by contributors from Qumranet, consolidated by Red Hat and merged upstream by Linus Torvalds; it leverages hardware extensions from vendors such as Intel and Advanced Micro Devices to provide near-native performance. Widely used across cloud platforms and enterprise deployments, it interoperates with management stacks from OpenStack, oVirt, Proxmox VE, and orchestration tools like libvirt.
Overview
KVM provides kernel-space virtualization for Linux by exposing a character device to user-space process managers such as QEMU and libvirt; these managers handle I/O and emulate devices while KVM supplies CPU and memory virtualization using hardware assist from Intel VT-x and AMD-V. The project started at Qumranet and became part of mainline Linux kernel releases, attracting contributions from organizations including IBM, Google, Canonical, and SUSE. KVM has been deployed by cloud providers like Amazon Web Services, Google Cloud Platform, Microsoft Azure, and private cloud stacks built with OpenStack and CloudStack.
Architecture
KVM’s architecture consists of a kernel module that implements the core virtual machine monitor and user-space components that perform device emulation; the kernel component registers as a pseudo-device accessible via /dev/kvm and communicates with processes such as QEMU or virt-manager. On supported processors, KVM uses Intel VT-x or AMD-V to run guest code in a special CPU mode while trapping privileged operations to the host; for ARM it relies on ARM virtualization extensions. Memory management integrates with Linux features like KSM, HugeTLBfs, and the IOMMU subsystem; device assignment uses VFIO to pass-through PCI devices from host to guests.
Features and Capabilities
KVM supports 64-bit and 32-bit guests on architectures including x86-64, ARM64, PowerPC, and s390x, offering live migration, snapshots, and virtual CPU hotplug. It interoperates with storage backends such as Ceph, GlusterFS, and LVM; networking capabilities include integration with Open vSwitch, Linux bridge, and SR-IOV for high-performance passthrough. Additional features include paravirtualized drivers from VirtIO for improved I/O, support for virtio-fs for shared filesystems, and integration with management stacks like oVirt and Proxmox VE.
Development and History
KVM originated at Qumranet in 2006–2007 and was merged into the Linux kernel mainline in 2007 after review by maintainers including Linus Torvalds. Early adoption and improvements were driven by companies such as Red Hat, IBM, and Canonical, while later expansions added support for architectures like ARM and s390x from IBM. The ecosystem matured with projects like libvirt, QEMU, and OpenStack providing management, emulation, and orchestration; major milestones include integration of VFIO for secure device assignment and upstreaming of performance features contributed by Google and Intel.
Performance and Use Cases
KVM achieves near-native performance for CPU- and memory-intensive workloads by using hardware virtualization extensions from Intel and Advanced Micro Devices and by offloading I/O to user-space processes like QEMU with VirtIO drivers. Common use cases span enterprise virtualization for vendors such as Red Hat Enterprise Linux, cloud infrastructure for providers like Amazon Web Services and Google Cloud Platform, container-hosting combinations with Kubernetes and CRI-O, and high-performance computing deployments on platforms from Dell Technologies and Hewlett Packard Enterprise. Benchmarks often compare KVM against hypervisors such as Xen and VMware ESXi for throughput, latency, and density.
Security and Isolation
Security mechanisms for KVM include kernel-enforced isolation via process separation, device isolation using VFIO and IOMMU mappings, and mitigations for microarchitectural vulnerabilities coordinated with Intel and AMD. The project benefits from Linux kernel security features like SELinux, AppArmor, and namespaces from systemd-adjacent tooling, while support for cryptographic acceleration uses hardware features available on platforms from Intel and IBM. Security hardening work has been contributed by firms such as Red Hat, Google, and IBM, and coordinated disclosures follow practices used by organizations like CVE numbering authorities.
Adoption and Ecosystem
KVM is integrated into distributions including Red Hat Enterprise Linux, CentOS Stream, Ubuntu, and SUSE Linux Enterprise Server, and is supported by cloud providers like Amazon Web Services and Google Cloud Platform. The surrounding ecosystem comprises management and orchestration projects such as libvirt, QEMU, OpenStack, oVirt, Proxmox VE, Ansible, and Kubernetes integrations for VM lifecycle. Commercial offerings and services are provided by vendors including Red Hat, Canonical, SUSE, and system integrators like IBM and Dell Technologies.
Category:Virtualization software