KVM is a Linux kernel module that turns the operating system into a hypervisor. Introduced in 2007, it allows a user-space program (like QEMU) to utilize the hardware virtualization features of modern processors (Intel VT-x or AMD-V). Unlike pure emulation, KVM allows the guest operating system to run instructions directly on the host CPU, drastically reducing overhead and increasing speed to near-bare-metal levels. The Synergy: How They Work Together In a typical setup, the two roles are clearly defined:
QEMU is a hosted virtual machine monitor that performs hardware virtualization. Its primary strength is : it can mimic various hardware architectures (like ARM, SPARC, or x86) on a different host machine. However, pure software emulation is slow because every instruction must be translated by the CPU. To speed things up, QEMU can use an "accelerator" to execute instructions directly on the host hardware. This is where KVM comes in. KVM: The Performance Engine QEMU and Kernel-based Virtual Machine
acts as the "brawn," handling the CPU and memory management within the kernel. KVM is a Linux kernel module that turns