1. A method of processing external interrupts for virtual processors using a host processor, the method comprising: configuring a virtual machine monitor (VMM) in a host processor, the host processor having at least one logical processor and the VMM controlling a plurality of virtual processors for the at least one logical processor, the controlling including: allocating at least two physical interrupt vectors in the host processor, including a running notification vector (RNV) for posting interrupts to running virtual processors and a blocked notification vector (BNV) for posting interrupts to blocked virtual processors; masking interrupts posted to preempted virtual processors, the preempted virtual processors including previously blocked virtual processors having at least one posted interrupt and previously running virtual processors; and enabling delivery of notifications for masked interrupts using the RNV upon transitioning a preempted virtual processor to a running virtual processor.