So, we are configuring some openstack and kvm stuff at work for some projects. We’re ‘cloudy’ guys. What can I say? 😀 One Issue I had when installing xenserver, underneath KVM.

(why would we do this?) In our testing environment we’re using a single OnMetal v2 server, and, instead of running xenserver directly on the server, and requiring additional servers, we are using a single 128GB RAM hypervisor for the test environment. One issue though is that Windows is only supported with xenserver when directly run on the ‘host’. Because Xen is running virtualized under KVM we have a problem.

Enter, tested virtualization support. Hardware virtualization assist support will now work for xenserver thru KVM, which means I can boot windows servers. YAY! uh.. 😉 kinda.

Check if Nested hardware virtualization assist is enabled

$cat /sys/module/kvm_intel/parameters/nested
N

It wasn’t 🙁 Lets enable it

Enable nested hardware virtualization assist

sudo rmmod kvm-intel
sudo sh -c "echo 'options kvm-intel nested=y' >> /etc/modprobe.d/dist.conf"
sudo modprobe kvm-intel

Ensure nested hardware virtualization is enabled

cat /sys/module/kvm_intel/parameters/nested
Y

modinfo kvm_intel | grep nested
parm:           nested:bool

It worked!

This can also be done for AMD systems simply substituting kvm_amd.

http://docs.openstack.org/developer/devstack/guides/devstack-with-nested-kvm.html