mp.c

   1 // Multiprocessor bootstrap.
   2 // Search memory for MP description structures.
   3 // http://developer.intel.com/design/pentium/datashts/24201606.pdf
   4
   5 #include "types.h"
   6 #include "defs.h"
   7 #include "param.h"
   8 #include "mp.h"
   9 #include "x86.h"
  10 #include "mmu.h"
  11 #include "proc.h"
  12
  13 struct cpu cpus[NCPU];
  14 static struct cpu *bcpu;
  15 int ismp;
  16 int ncpu;
  17 uchar ioapicid;
  18
  19 int
  20 mpbcpu(void)
  21 {
  22   return bcpu-cpus;
  23 }
  24
  25 static uchar
  26 sum(uchar *addr, int len)
  27 {
  28   int i, sum;
  29
  30   sum = 0;
  31   for(i=0; i<len; i++)
  32     sum += addr[i];
  33   return sum;
  34 }
  35
  36 // Look for an MP structure in the len bytes at addr.
  37 static struct mp*
  38 mpsearch1(uchar *addr, int len)
  39 {
  40   uchar *e, *p;
  41
  42   e = addr+len;
  43   for(p = addr; p < e; p += sizeof(struct mp))
  44     if(memcmp(p, "_MP_", 4) == 0 && sum(p, sizeof(struct mp)) == 0)
  45       return (struct mp*)p;
  46   return 0;
  47 }
  48
  49 // Search for the MP Floating Pointer Structure, which according to the
  50 // spec is in one of the following three locations:
  51 // 1) in the first KB of the EBDA;
  52 // 2) in the last KB of system base memory;
  53 // 3) in the BIOS ROM between 0xE0000 and 0xFFFFF.
  54 static struct mp*
  55 mpsearch(void)
  56 {
  57   uchar *bda;
  58   uint p;
  59   struct mp *mp;
  60
  61   bda = (uchar*)0x400;
  62   if((p = ((bda[0x0F]<<8)|bda[0x0E]) << 4)){
  63     if((mp = mpsearch1((uchar*)p, 1024)))
  64       return mp;
  65   } else {
  66     p = ((bda[0x14]<<8)|bda[0x13])*1024;
  67     if((mp = mpsearch1((uchar*)p-1024, 1024)))
  68       return mp;
  69   }
  70   return mpsearch1((uchar*)0xF0000, 0x10000);
  71 }
  72
  73 // Search for an MP configuration table.  For now,
  74 // don't accept the default configurations (physaddr == 0).
  75 // Check for correct signature, calculate the checksum and,
  76 // if correct, check the version.
  77 // To do: check extended table checksum.
  78 static struct mpconf*
  79 mpconfig(struct mp **pmp)
  80 {
  81   struct mpconf *conf;
  82   struct mp *mp;
  83
  84   if((mp = mpsearch()) == 0 || mp->physaddr == 0)
  85     return 0;
  86   conf = (struct mpconf*)mp->physaddr;
  87   if(memcmp(conf, "PCMP", 4) != 0)
  88     return 0;
  89   if(conf->version != 1 && conf->version != 4)
  90     return 0;
  91   if(sum((uchar*)conf, conf->length) != 0)
  92     return 0;
  93   *pmp = mp;
  94   return conf;
  95 }
  96
  97 void
  98 mpinit(void)
  99 {
 100   uchar *p, *e;
 101   struct mp *mp;
 102   struct mpconf *conf;
 103   struct mpproc *proc;
 104   struct mpioapic *ioapic;
 105
 106   bcpu = &cpus[0];
 107   if((conf = mpconfig(&mp)) == 0)
 108     return;
 109   ismp = 1;
 110   lapic = (uint*)conf->lapicaddr;
 111   for(p=(uchar*)(conf+1), e=(uchar*)conf+conf->length; p<e; ){
 112     switch(*p){
 113     case MPPROC:
 114       proc = (struct mpproc*)p;
 115       if(ncpu != proc->apicid){
 116         cprintf("mpinit: ncpu=%d apicid=%d\n", ncpu, proc->apicid);
 117         ismp = 0;
 118       }
 119       if(proc->flags & MPBOOT)
 120         bcpu = &cpus[ncpu];
 121       cpus[ncpu].id = ncpu;
 122       ncpu++;
 123       p += sizeof(struct mpproc);
 124       continue;
 125     case MPIOAPIC:
 126       ioapic = (struct mpioapic*)p;
 127       ioapicid = ioapic->apicno;
 128       p += sizeof(struct mpioapic);
 129       continue;
 130     case MPBUS:
 131     case MPIOINTR:
 132     case MPLINTR:
 133       p += 8;
 134       continue;
 135     default:
 136       cprintf("mpinit: unknown config type %x\n", *p);
 137       ismp = 0;
 138     }
 139   }
 140   if(!ismp){
 141     // Didn't like what we found; fall back to no MP.
 142     ncpu = 1;
 143     lapic = 0;
 144     ioapicid = 0;
 145     return;
 146   }
 147
 148   if(mp->imcrp){
 149     // Bochs doesn't support IMCR, so this doesn't run on Bochs.
 150     // But it would on real hardware.
 151     outb(0x22, 0x70);   // Select IMCR
 152     outb(0x23, inb(0x23) | 1);  // Mask external interrupts.
 153   }
 154 }