Tuesday, May 20, 2014

How do I enable nested virtualization on KVM?

Nested virtualization allows you to run virtual machines inside a virtual machine. Though this is not good for any kind of production use case because of the performance issues involved, this is usually good for testing purposes. Eg, students can be given virtual machines to test virtualization without allocating physical systems per head count.

I am only covering intel cpus in this blog post. The steps are very simple.

  • Verify that nested virtualization is not enabled already.
cat  /sys/module/kvm_intel/parameters/nested
  •  Add below line to /etc/modprobe.d/kvm-intel.conf
options kvm-intel nested=1
  • Reboot the host or do
modprobe -r kvm-intel
modprobe kvm-intel
  • Verify that nested virtualization is enabled.
cat  /sys/module/kvm_intel/parameters/nested


Brady said...

What should we do when we have the kvm-intel module, but don't have "nested" parameters in it ?

Sadique Puthen said...

Make sure that you use latest version of kvm-intel which has nested support. I think latest version has this parameter.

If kvm-intel is not compiled as a module, you would have to add a kernel parameter for same.