VM in VM: QEMU, Xen, VMware ESXi and HyperV

I am trying to test some virtualization technologies. I don't want to install them on the real hardware directly. It is hard to change and maintain. So I want to install a VM in another VM. Following is a short summary:

----------------------------------Xen------------ Hyper-V--------- VMware ESX i
Underlying virtualization:
QEMU 0.10.5 -----------------\/--------------- X-------------------------- X
Virtual Box 3 ------------------?-----------------X-------------------------- X
VMware WS 6.5 --------------\/----------------?---------------------------- \/

It means Xen can run in a QEMU VM, but hyper-v and ESXi cannot run on current QEMU.