Index: sys/sparc64/conf/GENERIC
===================================================================
--- sys/sparc64/conf/GENERIC
+++ sys/sparc64/conf/GENERIC
@@ -89,6 +89,7 @@
 
 # Make an SMP-capable kernel by default
 options 	SMP			# Symmetric MultiProcessor Kernel
+options 	EARLY_AP_STARTUP
 
 # Standard busses
 device		ebus
Index: sys/sparc64/sparc64/intr_machdep.c
===================================================================
--- sys/sparc64/sparc64/intr_machdep.c
+++ sys/sparc64/sparc64/intr_machdep.c
@@ -109,13 +109,16 @@
 /* protect intrcnt_index */
 static struct mtx intrcnt_lock;
 
-#ifdef SMP
+#if defined(SMP) && !defined(EARLY_AP_STARTUP)
 static int assign_cpu;
 
-static void intr_assign_next_cpu(struct intr_vector *iv);
 static void intr_shuffle_irqs(void *arg __unused);
 #endif
 
+#ifdef SMP
+static void intr_assign_next_cpu(struct intr_vector *iv);
+#endif
+
 static int intr_assign_cpu(void *arg, int cpu);
 static void intr_execute_handlers(void *);
 static void intr_stray_level(struct trapframe *);
@@ -262,11 +265,16 @@
 	struct pcpu *pc;
 	struct intr_vector *iv;
 
+#ifdef EARLY_AP_STARTUP
+	MPASS(mp_ncpus == 1 || smp_started);
+	if (cpu != NOCPU) {
+#else
 	/*
 	 * Don't do anything during early boot.  We will pick up the
 	 * assignment once the APs are started.
 	 */
 	if (assign_cpu && cpu != NOCPU) {
+#endif
 		pc = pcpu_find(cpu);
 		if (pc == NULL)
 			return (EINVAL);
@@ -383,9 +391,12 @@
 	}
 	intr_stray_count[vec] = 0;
 	intrcnt_updatename(vec, ie->ie_fullname, 0);
-#ifdef SMP
+#if defined(SMP) && !defined(EARLY_AP_STARTUP)
 	if (assign_cpu)
 		intr_assign_next_cpu(iv);
+#elif defined(SMP) && defined(EARLY_AP_STARTUP)
+	MPASS(mp_ncpus == 1 || smp_started);
+	intr_assign_next_cpu(iv);
 #endif
 	ic->ic_enable(iv);
 	/* Ensure the interrupt is cleared, it might have triggered before. */
@@ -517,6 +528,7 @@
 	CPU_SET(cpu, &intr_cpus);
 }
 
+#ifndef EARLY_AP_STARTUP
 /*
  * Distribute all the interrupt sources among the available CPUs once the
  * APs have been launched.
@@ -555,3 +567,4 @@
 SYSINIT(intr_shuffle_irqs, SI_SUB_SMP, SI_ORDER_SECOND, intr_shuffle_irqs,
     NULL);
 #endif
+#endif
Index: sys/sparc64/sparc64/mp_machdep.c
===================================================================
--- sys/sparc64/sparc64/mp_machdep.c
+++ sys/sparc64/sparc64/mp_machdep.c
@@ -471,8 +471,10 @@
 	if (smp_cpus == mp_ncpus)
 		atomic_store_rel_int(&smp_started, 1);
 
+#ifndef EARLY_AP_STARTUP
 	/* Start per-CPU event timers. */
 	cpu_initclocks_ap();
+#endif
 
 	/* Ok, now enter the scheduler. */
 	sched_throw(NULL);