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mp.c
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mp.c
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// Multiprocessor support
// Search memory for MP description structures.
// http://developer.intel.com/design/pentium/datashts/24201606.pdf
#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mp.h"
#include "x86.h"
#include "mmu.h"
#include "proc.h"
struct cpu cpus[NCPU];
int ncpu;
uchar ioapicid;
static uchar
sum(uchar *addr, int len)
{
int i, sum;
sum = 0;
for (i = 0; i < len; i++)
sum += addr[i];
return sum;
}
// Look for an MP structure in the len bytes at addr.
static struct mp *
mpsearch1(uint a, int len)
{
uchar *e, *p, *addr;
addr = P2V(a);
e = addr + len;
for (p = addr; p < e; p += sizeof(struct mp))
if (memcmp(p, "_MP_", 4) == 0 && sum(p, sizeof(struct mp)) == 0)
return (struct mp *)p;
return 0;
}
// Search for the MP Floating Pointer Structure, which according to the
// spec is in one of the following three locations:
// 1) in the first KB of the EBDA;
// 2) in the last KB of system base memory;
// 3) in the BIOS ROM between 0xE0000 and 0xFFFFF.
static struct mp *
mpsearch(void)
{
uchar *bda;
uint p;
struct mp *mp;
bda = (uchar *)P2V(0x400);
if ((p = ((bda[0x0F] << 8) | bda[0x0E]) << 4))
{
if ((mp = mpsearch1(p, 1024)))
return mp;
}
else
{
p = ((bda[0x14] << 8) | bda[0x13]) * 1024;
if ((mp = mpsearch1(p - 1024, 1024)))
return mp;
}
return mpsearch1(0xF0000, 0x10000);
}
// Search for an MP configuration table. For now,
// don't accept the default configurations (physaddr == 0).
// Check for correct signature, calculate the checksum and,
// if correct, check the version.
// To do: check extended table checksum.
static struct mpconf *
mpconfig(struct mp **pmp)
{
struct mpconf *conf;
struct mp *mp;
if ((mp = mpsearch()) == 0 || mp->physaddr == 0)
return 0;
conf = (struct mpconf *)P2V((uint)mp->physaddr);
if (memcmp(conf, "PCMP", 4) != 0)
return 0;
if (conf->version != 1 && conf->version != 4)
return 0;
if (sum((uchar *)conf, conf->length) != 0)
return 0;
*pmp = mp;
return conf;
}
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.
}
}