I'm running oracle VM server,3.2.7 - the UEK kernel, 2.6.39-300.32..6.el5uek, as a VM under vcenter 5.5..
I'm also running nested VM's off of that Oracle Vm server..rather easy to set up and to get working, you'll need to use the web client to config CPU virtualization..
probably unsupported,but I did get it to work,and the VMs boot..
networking is a question mark, but the rest of it works fine..