mp.c

void
mpinit(void)
{
  uchar *p, *e;
  int ismp;
  struct mp *mp;
  struct mpconf *conf;
  struct mpproc *proc;
  struct mpioapic *ioapic;

  if((conf = mpconfig(&mp)) == 0)
    panic("Expect to run on an SMP");
  ismp = 1;
  lapic = (uint*)conf->lapicaddr;
  for(p=(uchar*)(conf+1), e=(uchar*)conf+conf->length; p<e; ){
    switch(*p){
    case MPPROC:
      proc = (struct mpproc*)p;
      if(ncpu < NCPU) {
        cpus[ncpu].apicid = proc->apicid;  // apicid may differ from ncpu
        ncpu++;
      }
      p += sizeof(struct mpproc);
      continue;
    case MPIOAPIC:
      ioapic = (struct mpioapic*)p;
      ioapicid = ioapic->apicno;
      p += sizeof(struct mpioapic);
      continue;
    case MPBUS:
    case MPIOINTR:
    case MPLINTR:
      p += 8;
      continue;
    default:
      ismp = 0;
      break;
    }
  }
  if(!ismp)
    panic("Didn't find a suitable machine");

  if(mp->imcrp){
    // Bochs doesn't support IMCR, so this doesn't run on Bochs.
    // But it would on real hardware.
    outb(0x22, 0x70);   // Select IMCR
    outb(0x23, inb(0x23) | 1);  // Mask external interrupts.
  }
}