1. A method comprising: detecting loss of lockstep (LOL) for a processor in a multi-processor system; determining that the processor for which said LOL is detected is assigned a role of boot processor; changing a system identifier, used by the system's operating system to recognize the boot processor, of said boot processor for which said LOL is detected, to a different value, which causes the system's operating system to not recognize the processor for which said LOL is detected as the boot processor; and changing a system identifier of the spare processor to that of the boot processor, thereby switching the role of boot processor to a spare processor without shutting down the system's operating system.