Another VM option for Mac OS X, Veertu:

Veertu is a 100% user-space implementation and leverages OS X for scheduling, CPU management, memory management and more. Since Veertu is the only solution that uses OS X’s hypervisor and VMNet framework (first introduced in OS X Yosemite), it is approved by Apple for sale in the App Store.

It is using Hypervisor.framework:

The Hypervisor framework allows virtualization vendors to build virtualization solutions on top of OS X without needing to deploy third-party kernel extensions (KEXTs). Included is a lightweight hypervisor that enables virtualization of the host CPUs.

I’m going to try this out with Ubuntu 15.10.