Sync the APIC startup sequence with amd64:

- Register APIC enumerators at SI_SUB_TUNABLES - 1 instead of SI_SUB_CPU - 1.
- Probe CPUs at SI_SUB_TUNABLES - 1.  This allows i386 to set a truly
  accurate mp_maxid value rather than always setting it to MAXCPU - 1.

3 files changed, 19 insertions, 4 deletions

diff --git a/sys/i386/acpica/madt.c b/sys/i386/acpica/madt.c
index bcf60b1..13bbb55 100644
--- a/sys/i386/acpica/madt.c
+++ b/sys/i386/acpica/madt.c
@@ -203,7 +203,7 @@ madt_register(void *dummy __unused)
 
 	apic_register_enumerator(&madt_enumerator);
 }
-SYSINIT(madt_register, SI_SUB_CPU - 1, SI_ORDER_SECOND, madt_register, NULL);
+SYSINIT(madt_register, SI_SUB_TUNABLES - 1, SI_ORDER_FIRST, madt_register, NULL);
 
 /*
  * Call the handler routine for each entry in the MADT table.
diff --git a/sys/i386/i386/mp_machdep.c b/sys/i386/i386/mp_machdep.c
index c4d2672..871ccb4 100644
--- a/sys/i386/i386/mp_machdep.c
+++ b/sys/i386/i386/mp_machdep.c
@@ -465,8 +465,10 @@ cpu_add(u_int apic_id, char boot_cpu)
 		boot_cpu_id = apic_id;
 		cpu_info[apic_id].cpu_bsp = 1;
 	}
-	if (mp_ncpus < MAXCPU)
+	if (mp_ncpus < MAXCPU) {
 		mp_ncpus++;
+		mp_maxid = mp_ncpus - 1;
+	}
 	if (bootverbose)
 		printf("SMP: Added CPU %d (%s)\n", apic_id, boot_cpu ? "BSP" :
 		    "AP");
@@ -476,7 +478,19 @@ void
 cpu_mp_setmaxid(void)
 {
 
-	mp_maxid = MAXCPU - 1;
+	/*
+	 * mp_maxid should be already set by calls to cpu_add().
+	 * Just sanity check its value here.
+	 */
+	if (mp_ncpus == 0)
+		KASSERT(mp_maxid == 0,
+		    ("%s: mp_ncpus is zero, but mp_maxid is not", __func__));
+	else if (mp_ncpus == 1)
+		mp_maxid = 0;
+	else
+		KASSERT(mp_maxid >= mp_ncpus - 1,
+		    ("%s: counters out of sync: max %d, count %d", __func__,
+			mp_maxid, mp_ncpus));
 }
 
 int
@@ -504,6 +518,7 @@ cpu_mp_probe(void)
 		 * One CPU was found, so this must be a UP system with
 		 * an I/O APIC.
 		 */
+		mp_maxid = 0;
 		return (0);
 	}
 
diff --git a/sys/i386/xen/mptable.c b/sys/i386/xen/mptable.c
index fe01cd5..d9942ab 100644
--- a/sys/i386/xen/mptable.c
+++ b/sys/i386/xen/mptable.c
@@ -109,7 +109,7 @@ mptable_register(void *dummy __unused)
 
 	apic_register_enumerator(&mptable_enumerator);
 }
-SYSINIT(mptable_register, SI_SUB_CPU - 1, SI_ORDER_FIRST, mptable_register,
+SYSINIT(mptable_register, SI_SUB_TUNABLES - 1, SI_ORDER_FIRST, mptable_register,
     NULL);