xv6

commit 3121e29fbb5db64ed76b5682d9f99633776de500
parent 8bb7079c6bce55bab6c85408b33c56644e6930b0
Author: Brian Swetland <swetland@frotz.net>
Date:   Sat,  4 Jan 2014 18:35:00 -0800

support systems where cpu# != apicid

- add an apicid field to struct cpu, don't assume id == apicid
- startothers() uses cpu->apicid when calling lapicstartap()
- cpunum() now walks the cpu table to back-map apicid to id
  this isn't too bad because cpunum() is only called from
  seginit() to initialize the cpu-local pointer to its struct cpu.
  Everywhere else uses cpu->id.

Now booting with two cores on an i3-4010u.

Diffstat:
M
include/proc.h
 | 
3
++-
M
kernel/lapic.c
 | 
16
++++++++++++++--
M
kernel/main.c
 | 
2
+-
M
kernel/mp.c
 | 
6
++----

4 files changed, 19 insertions(+), 8 deletions(-)
diff --git a/include/proc.h b/include/proc.h
@@ -3,7 +3,8 @@
 
 // Per-CPU state
 struct cpu {
-  uchar id;                    // Local APIC ID; index into cpus[] below
+  uchar id;                    // index into cpus[] below
+  uchar apicid;                // Local APIC ID
   struct context *scheduler;   // swtch() here to enter scheduler
   struct taskstate ts;         // Used by x86 to find stack for interrupt
   struct segdesc gdt[NSEGS];   // x86 global descriptor table
diff --git a/kernel/lapic.c b/kernel/lapic.c
@@ -7,6 +7,8 @@
 #include "traps.h"
 #include "mmu.h"
 #include "x86.h"
+#include "param.h"
+#include "proc.h"
 
 // Local APIC registers, divided by 4 for use as uint[] indices.
 #define ID      (0x0020/4)   // ID
@@ -95,9 +97,13 @@ lapicinit(void)
   lapicw(TPR, 0);
 }
 
+// This is only used during secondary processor startup.
+// cpu->id is the fast way to get the cpu number, once the
+// processor is fully started.
 int
 cpunum(void)
 {
+  int n, id;
   // Cannot call cpu when interrupts are enabled:
   // result not guaranteed to last long enough to be used!
   // Would prefer to panic but even printing is chancy here:
@@ -110,8 +116,14 @@ cpunum(void)
         __builtin_return_address(0));
   }
 
-  if(lapic)
-    return lapic[ID]>>24;
+  if(!lapic)
+    return 0;
+
+  id = lapic[ID]>>24;
+  for (n = 0; n < ncpu; n++)
+    if (id == cpus[n].apicid)
+      return n;
+
   return 0;
 }
 
diff --git a/kernel/main.c b/kernel/main.c
@@ -99,7 +99,7 @@ startothers(void)
     *(int**)(code-12) = (void *) v2p(entrypgdir);
 #endif
 
-    lapicstartap(c->id, v2p(code));
+    lapicstartap(c->apicid, v2p(code));
 
     // wait for cpu to finish mpmain()
     while(c->started == 0)
diff --git a/kernel/mp.c b/kernel/mp.c
@@ -114,13 +114,11 @@ mpinit(void)
     switch(*p){
     case MPPROC:
       proc = (struct mpproc*)p;
-      if(ncpu != proc->apicid){
-        cprintf("mpinit: ncpu=%d apicid=%d\n", ncpu, proc->apicid);
-        ismp = 0;
-      }
+      cprintf("mpinit ncpu=%d apicid=%d\n", ncpu, proc->apicid);
       if(proc->flags & MPBOOT)
         bcpu = &cpus[ncpu];
       cpus[ncpu].id = ncpu;
+      cpus[ncpu].apicid = proc->apicid;
       ncpu++;
       p += sizeof(struct mpproc);
       continue;