README.kvm.md

KVM Device Plugin

Introduction

This software is a kubernetes device plugin that exposes /dev/kvm from the system.

Building

NOTE: This process is not finalized yet.

Plain binary

cd cmd/kvm
go build .

Docker

docker build -t kvm:latest .

Running

NOTE: This process is not finalized yet.

Locally

cd cmd/kvm
sudo ./kvm -v 3 -logtostderr

Docker

docker run -it -v /var/lib/kubelet/device-plugins:/var/lib/kubelet/device-plugins --privileged --cap-add=ALL kvm:latest /bin/bash
(in docker image) ./kvm -v 3 -logtostderr

As a DaemonSet

# Deploy the device plugin
kubectl apply -f manifests/kvm-ds.yml

# Optionally you can now test it using an example consumer
kubectl apply -f examples/kvm-consumer.yml
kubectl exec -it kvm-consumer -- ls /dev/kvm

API

Node description:

Capacity:
 ...
 devices.kubevirt.io/kvm: "3"
 ...

Pod:

spec:
  containers:
  - name: demo
    ...
    resources:
      requests:
              devices.kubevirt.io/kvm: "1"
      limits:
              devices.kubevirt.io/kvm: "1"

Issues

KVM Quantity

Currently, Kubernetes device plugins can only expose quantifiable resources. KVM itself is "infinite" resource, so it cannot be properly expressed.

This fact is worked around by the plugin: it adds one more KVM resource each time VM is started. Because we have no way of detecting stopped VMs, the KVM counter never goes down -- that causes the plugin to consume excessive memory.