1. A processor comprising: event microcode to recognize a virtualization event as a top-down virtualization event or a bottom-up virtualization event; and evaluation microcode to determine whether to transfer control of the processor from a child guest to an intervening monitor hosting the child guest in response to the recognized virtualization event, by checking, if the virtualization event is recognized as a top-down virtualization event, a control structure of the child guest before checking a control structure of the intervening virtual machine monitor hosting the child guest, and by checking, if the virtualization event is recognized as a bottom-up virtualization event, the control structure of the intervening monitor hosting the child guest before checking the control structure of the child guest.