1. A method for responding to an event when emulating an interrupt controller in a computer system, the interrupt controller having associated therewith a first priority, the first priority having a current value, wherein the event gives rise to a new value for the first priority, wherein a plurality of interrupts are pending with the interrupt controller, a maximum interrupt priority value being defined as a priority value associated with a first interrupt of the plurality of pending interrupts, the first interrupt having the highest priority of all pending interrupts, the method comprising: comparing the current value and the new value for the first priority with the maximum interrupt priority value; and if the current value and the new value are both less than the maximum interrupt priority value or if the current value and the new value are both greater than the maximum interrupt priority value, abstaining from an emulation of the interrupt controller in response to the event without dispatching an interrupt in response to the event; or if one of the current value and the new value is greater than the maximum interrupt priority value and the other of the current value and the new value is less than the maximum interrupt priority value, running an emulation of the interrupt controller in response to the event and determining whether to dispatch an interrupt in response to the event based on this emulation, wherein running an emulation of the interrupt controller in response to the event comprises determining a new processor priority value based in part on the new value for the first priority and comparing the new processor priority value to the maximum interrupt priority value to determine whether to dispatch an interrupt in response to the event, and wherein a new processor priority value is not determined in response to the event if the current value and the new value are both less than the maximum interrupt priority value or if the current value and the new value are both greater than the maximum interrupt priority value.