What is KVM?

Kernel-based Virtual Machine (KVM) is a virtualisation module within the Linux kernel that enables a Linux host to run multiple isolated virtual machines using CPU hardware virtualisation extensions like Intel VT-x and AMD-V. Operating as a Type 1.5 hypervisor, KVM allows the Linux kernel to function as both a host OS and a hypervisor, providing near-native performance by directly executing guest code on the CPU hardware. KVM serves as the foundational virtualisation layer for technologies such as Firecracker, QEMU, and Cloud Hypervisor, and is crucial for running microVMs and container sandboxes, offering hardware-enforced isolation for workloads. It has been integrated into the mainline Linux kernel since version 2.6.20 in 2007, requiring hardware support and user-space tooling for operation. KVM's open-source nature has made it a dominant choice in cloud infrastructure, enabling significant use in environments where isolation and security are paramount, such as Northflank's sandbox infrastructure that leverages KVM-backed technologies for scalable and secure deployments.