Kernel-based Virtual Machine
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Kernel-based Virtual Machine¶
Kernel-based Virtual Machine (KVM) is open source software that allows the Linux kernel to act as a virtual machine hypervisor – in other words, it allows the kernel to emulate other guest machines, itself acting as the host machine.
KVM provides full virtualisation at near native performance on a given architecture, but is only supported by certain processor types which allow for virtualistion extensions (Intel VT or AMD-V).
Table of Contents¶
KVM details¶
The KVM provides a kernel module kvm.ko for the virtualisation infrastructure, and a different kernel module kvm-intel.ko (vmx, virtual machine extensions) or kvm-amd.ko (svm, secure virtual machine) specific to the processor.
Once your have enabled BIOS virtualisation extensions, either Intel VT or AMD-V, you should be able to check your processor’s flags to see if your machine is able to run KVM
cat /proc/cpuinfo | grep --color -E "(vmx|svm)"
The userspace of KVM is QEMU, which leverages libkvm to /dev/kvm through an ioctl interface.
Intel VT¶
An overview of Intel Virtualisation Technology (VT) can be found on the Intel Website. At it’s most basic, it provides a suite of tools for allowing multiple systems to run on the same hardware, with minimal overhead. The VT is enacted through both hardware and software, and at its minimum covers
CPU abstraction to virtual machines, with zero overhead
memory abstraction, allowing isolation and host monitoring per virtual machine
I/O virtualisation, from networks to physical devices
GPU abstraction, allowing virtual machines to have full or shared access to GPUs
Most of the advanced features are targeted at enterprise use of servers, where multiple, potentially very different machines, are running on the same server. An application of this could be, for example, a remote desktop cluster.
At the machine level, the Intel VT introduces 10 new virtualisation CPU instructions. Recent processors also benefit from Extended Page Tables, which allows each virtual machine to keep track of its own memory address table (before address translation would have to be performed).
The Intel VT can be thought of as providing a BIOS to each virtual machine.
AMD-V¶
This section I will fill in if I ever find the time or need.
Installing KVM¶
sudo apt install qemu-kvm bridge-utils
bridge-utils installs tools for creating and managing ethernet and network bridges.