A hypervisor is a very lightweight wrapper around a virtual machine that either requires a modified virtual machine (not the case here) or hardware support in the CPU so you get to run a VM with a performance hit on the order of 3%.
The newest intel CPUs have added hardware virtualization support, so if you have a discrete GPU (like for this box), you can give the integrated graphics to the host Linux system, and dedicate the discrete GPU to the virtual machine (again, performance within a few percent of native).
All of this is to say that you can run a virtual OSX system on top of linux, and get almost native performance like running a hackintosh, but without having to have a perfect match of already supported hardware components.