According to one embodiment, a method comprises system firmware instructing a system's operating system to idle a processor, and responsive to the instructing, the operating system idling the processor and returning control over the processor to the system firmware. According to one embodiment, a method comprises detecting loss of lockstep (LOL) for a processor module in a system, and responsive to the detecting LOL for the processor module, system firmware instructing an operating system to idle the processor module.