- Split cpu_mp_probe() into two parts. cpu_mp_setmaxid() is still called

very early (SI_SUB_TUNABLES - 1) and is responsible for setting mp_maxid.
  cpu_mp_probe() is now called at SI_SUB_CPU and determines if SMP is
  actually present and sets mp_ncpus and all_cpus.  Splitting these up
  allows an architecture to probe CPUs later than SI_SUB_TUNABLES by just
  setting mp_maxid to MAXCPU in cpu_mp_setmaxid().  This could allow the
  CPU probing code to live in a module, for example, since modules
  sysinit's in modules cannot be invoked prior to SI_SUB_KLD.  This is
  needed to re-enable the ACPI module on i386.
- For the alpha SMP probing code, use LOCATE_PCS() instead of duplicating
  its contents in a few places.  Also, add a smp_cpu_enabled() function
  to avoid duplicating some code.  There is room for further code
  reduction later since much of this code is also present in cpu_mp_start().
- All archs besides i386 still set mp_maxid to the same values they set it
  to before this change.  i386 now sets mp_maxid to MAXCPU.

Tested on:	alpha, amd64, i386, ia64, sparc64
Approved by:	re (scottl)

sys/alpha/alpha/mp_machdep.c

@@ -64,6 +64,7 @@ static struct mtx ap_boot_mtx;
 u_int boot_cpu_id;
 
 static void	release_aps(void *dummy);
+static int	smp_cpu_enabled(struct pcs *pcsp);
 extern void	smp_init_secondary_glue(void);
 static int	smp_send_secondary_command(const char *command, int cpuid);
 static int	smp_start_secondary(int cpuid);
@@ -301,10 +302,50 @@ smp_start_secondary(int cpuid)
 
 /* Other stuff */
 
+static int
+smp_cpu_enabled(struct pcs *pcsp)
+{
+
+	/* Is this CPU present? */
+	if ((pcsp->pcs_flags & PCS_PP) == 0)
+		return (0);
+
+	/* Is this CPU available? */
+	if ((pcsp->pcs_flags & PCS_PA) == 0)
+		/*
+		 * The TurboLaser PCS_PA bit doesn't seem to be set
+		 * correctly.
+		 */
+		if (hwrpb->rpb_type != ST_DEC_21000) 
+			return (0);
+
+	/* Is this CPU's PALcode valid? */
+	if ((pcsp->pcs_flags & PCS_PV) == 0)
+		return (0);
+
+	return (1);
+}
+
+void
+cpu_mp_setmaxid(void)
+{
+	int i;
+
+	mp_maxid = 0;
+	for (i = 0; i < hwrpb->rpb_pcs_cnt; i++) {
+		if (i == PCPU_GET(cpuid))
+			continue;
+		if (!smp_cpu_enabled(LOCATE_PCS(hwrpb, i)))
+			continue;
+		if (i > MAXCPU)
+			continue;
+		mp_maxid = i;
+	}
+}
+
 int
 cpu_mp_probe(void)
 {
-	struct pcs *pcsp;
 	int i, cpus;
 
 	/* XXX: Need to check for valid platforms here. */
@@ -315,33 +356,16 @@ cpu_mp_probe(void)
 	all_cpus = 1 << boot_cpu_id;
 
 	mp_ncpus = 1;
-	mp_maxid = 0;
 
 	/* Make sure we have at least one secondary CPU. */
 	cpus = 0;
 	for (i = 0; i < hwrpb->rpb_pcs_cnt; i++) {
 		if (i == PCPU_GET(cpuid))
 			continue;
-		pcsp = (struct pcs *)((char *)hwrpb + hwrpb->rpb_pcs_off +
+		if (!smp_cpu_enabled(LOCATE_PCS(hwrpb, i)))
-		    (i * hwrpb->rpb_pcs_size));
-		if ((pcsp->pcs_flags & PCS_PP) == 0) {
 			continue;
-		}
+		if (i > MAXCPU)
-		if ((pcsp->pcs_flags & PCS_PA) == 0) {
-			/*
-			 * The TurboLaser PCS_PA bit doesn't seem to be set
-			 * correctly.
-			 */
-			if (hwrpb->rpb_type != ST_DEC_21000) 
 			continue;
-		}
-		if ((pcsp->pcs_flags & PCS_PV) == 0) {
-			continue;
-		}
-		if (i > MAXCPU) {
-			continue;
-		}
-		mp_maxid = i;
 		cpus++;
 	}
 	return (cpus);
@@ -359,8 +383,7 @@ cpu_mp_start(void)
 
 		if (i == boot_cpu_id)
 			continue;
-		pcsp = (struct pcs *)((char *)hwrpb + hwrpb->rpb_pcs_off +
+		pcsp = LOCATE_PCS(hwrpb, i);
-		    (i * hwrpb->rpb_pcs_size));
 		if ((pcsp->pcs_flags & PCS_PP) == 0)
 			continue;
 		if ((pcsp->pcs_flags & PCS_PA) == 0) {

sys/amd64/amd64/mp_machdep.c

@@ -187,6 +187,26 @@ cpu_add(u_int apic_id, char boot_cpu)
 	
 }
 
+void
+cpu_mp_setmaxid(void)
+{
+
+	/*
+	 * 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
 cpu_mp_probe(void)
 {
@@ -202,8 +222,6 @@ cpu_mp_probe(void)
 		 * the variables to represent a system with a single CPU
 		 * with an id of 0.
 		 */
-		KASSERT(mp_maxid == 0,
-		    ("%s: mp_ncpus is zero, but mp_maxid is not", __func__));
 		mp_ncpus = 1;
 		return (0);
 	}
@@ -219,9 +237,6 @@ cpu_mp_probe(void)
 	}
 
 	/* At least two CPUs were found. */
-	KASSERT(mp_maxid >= mp_ncpus - 1,
-	    ("%s: counters out of sync: max %d, count %d", __func__, mp_maxid,
-	    mp_ncpus));
 	return (1);
 }
 

sys/i386/i386/mp_machdep.c

@@ -248,14 +248,19 @@ cpu_add(u_int apic_id, char boot_cpu)
 		cpu_info[apic_id].cpu_bsp = 1;
 	}
 	mp_ncpus++;
-	if (apic_id > mp_maxid)
-		mp_maxid = apic_id;
 	if (bootverbose)
 		printf("SMP: Added CPU %d (%s)\n", apic_id, boot_cpu ? "BSP" :
 		    "AP");
 	
 }
 
+void
+cpu_mp_setmaxid(void)
+{
+
+	mp_maxid = MAXCPU;
+}
+
 int
 cpu_mp_probe(void)
 {
@@ -271,8 +276,6 @@ cpu_mp_probe(void)
 		 * the variables to represent a system with a single CPU
 		 * with an id of 0.
 		 */
-		KASSERT(mp_maxid == 0,
-		    ("%s: mp_ncpus is zero, but mp_maxid is not", __func__));
 		mp_ncpus = 1;
 		return (0);
 	}
@@ -283,14 +286,10 @@ 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);
 	}
 
 	/* At least two CPUs were found. */
-	KASSERT(mp_maxid >= mp_ncpus - 1,
-	    ("%s: counters out of sync: max %d, count %d", __func__, mp_maxid,
-	    mp_ncpus));
 	return (1);
 }
 

sys/ia64/ia64/mp_machdep.c

@@ -132,9 +132,10 @@ ia64_ap_startup(void)
 	/* NOTREACHED */
 }
 
-int
+void
-cpu_mp_probe()
+cpu_mp_setmaxid(void)
 {
+
 	/*
 	 * Count the number of processors in the system by walking the ACPI
 	 * tables. Note that we record the actual number of processors, even
@@ -147,6 +148,11 @@ cpu_mp_probe()
 	 * VM initialization.
 	 */
 	mp_maxid = min(mp_ncpus, MAXCPU) - 1;
+}
+
+int
+cpu_mp_probe(void)
+{
 
 	/*
 	 * If there's only 1 processor, or we don't have a wake-up vector,

sys/kern/subr_smp.c

@@ -92,17 +92,16 @@ static void (*smp_rv_teardown_func)(void *arg);
 static void *smp_rv_func_arg;
 static volatile int smp_rv_waiters[2];
 static struct mtx smp_rv_mtx;
-static int mp_probe_status;
 
 /*
- * Initialize MI SMP variables.
+ * Let the MD SMP code initialize mp_maxid very early if it can.
  */
 static void
-mp_probe(void *dummy)
+mp_setmaxid(void *dummy)
 {
-	mp_probe_status = cpu_mp_probe();
+	cpu_mp_setmaxid();
 }
-SYSINIT(cpu_mp_probe, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_probe, NULL)
+SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL)
 
 /*
  * Call the MD SMP initialization code.
@@ -112,8 +111,9 @@ mp_start(void *dummy)
 {
 
 	/* Probe for MP hardware. */
-	if (mp_probe_status == 0 || smp_disabled != 0) {
+	if (smp_disabled != 0 || cpu_mp_probe() == 0) {
 		mp_ncpus = 1;
+		all_cpus = PCPU_GET(cpumask);
 		return;
 	}
 

sys/powerpc/powerpc/mp_machdep.c

@@ -47,6 +47,11 @@
 
 int			boot_cpu_id;
 
+void
+cpu_mp_setmaxid(void)
+{
+}
+
 int
 cpu_mp_probe(void)
 {

sys/sparc64/sparc64/mp_machdep.c

@@ -140,8 +140,8 @@ mp_tramp_alloc(void)
 /*
  * Probe for other cpus.
  */
-int
+void
-cpu_mp_probe(void)
+cpu_mp_setmaxid(void)
 {
 	phandle_t child;
 	phandle_t root;
@@ -160,7 +160,13 @@ cpu_mp_probe(void)
 			cpus++;
 	}
 	mp_maxid = cpus;
-	return (cpus > 1);
+}
+
+int
+cpu_mp_probe(void)
+{
+
+	return (mp_maxid > 1);
 }
 
 static void

sys/sys/smp.h

@@ -74,11 +74,17 @@ extern u_int mp_maxid;
  * executed and a simple message will be output to the console.  Finally,
  * cpu_mp_announce() will be called so that machine dependent messages about
  * the MP support may be output to the console if desired.
+ *
+ * The cpu_setmaxid() function is called very early during the boot process
+ * so that the MD code may set mp_maxid to provide an upper bound on CPU IDs
+ * that other subsystems may use.  If a platform is not able to determine
+ * the exact maximum ID that early, then it may set mp_maxid to MAXCPU.
  */
 struct thread;
 
 void	cpu_mp_announce(void);
 int	cpu_mp_probe(void);
+void	cpu_mp_setmaxid(void);
 void	cpu_mp_start(void);
 
 void	forward_signal(struct thread *);