1. A computer program product for processing interrupt requests in a computer system comprising at least one processor which supports simultaneous multithreading for a plurality of threads comprising at least a first thread and an interrupt request handling thread, the computer program product comprising a computer readable storage medium having program code embodied therewith, the program code executable to: disable, by firmware of the computer system, an interrupt request mask of the first thread and enable an interrupt request mask of the interrupt request handling thread; route, by the processor, in response to an interrupt condition occurring in hardware, a first interrupt request to the interrupt request handling thread, wherein the disabled interrupt request mask of the first thread prevents the first interrupt request from being routed to the first thread; pretest, by the interrupt request handling thread, the first interrupt request, wherein the program code executable to pretest the first interrupt request comprises program code executable to collect information about the first interrupt request and determine whether the first thread needs to process the first interrupt request; and present, by the interrupt request handling thread, the first interrupt request to the first thread in response to determining that the first thread needs to process the first interrupt request, wherein the program code executable to present the first interrupt request comprises program code executable to: determine whether the interrupt condition in hardware has been reset; in response to determining that the interrupt condition in hardware has not been reset, re-enable the interrupt request mask of the first thread causing the first interrupt request to also be routed to the first thread; and in response to determining that the interrupt condition in hardware has been reset, send a firmware interrupt and the collected information about the first interrupt request to the first thread.