Oracle Solaris kernel zones on x86-based systems make use of hardware-assisted virtualization features like does. However, for kernel zones and to share this hardware resource, they need to cooperate.

By default, due to performance reasons, acquires the hardware-assisted virtualization resource (VT-x/AMD-V) globally on the host machine and uses it until the last VM that requires it is powered off. This prevents other software from using VT-x/AMD-V during the time has taken control of it.

can be instructed to relinquish use of hardware-assisted virtualization features when not executing guest code, thereby allowing kernel zones to make use of them. To do this, shutdown all VMs and execute the following command:

$ VBoxManage setproperty hwvirtexclusive off

This command needs to be executed only once as the setting is stored as part of the global settings which will continue to persist across host-reboots and upgrades.