CPUNUM
#define ACTION_CLR_IPI(cpu, ipi) (0x2000 | CPUNUM(cpu, 9) | ((ipi) << 8))
#define ACTION_SET_IPI(cpu, ipi) (0x3000 | CPUNUM(cpu, 9) | ((ipi) << 8))
#define ACTION_BOOT_THREAD(cpu) (0x08 | CPUNUM(cpu, 0))