diff --git a/sys/sparc64/sparc64/mp_machdep.c b/sys/sparc64/sparc64/mp_machdep.c
index bf79adfdb5cd..5470c113e55d 100644
--- a/sys/sparc64/sparc64/mp_machdep.c
+++ b/sys/sparc64/sparc64/mp_machdep.c
@@ -116,14 +116,12 @@ cpu_ipi_selected_t *cpu_ipi_selected;
 
 static vm_offset_t mp_tramp;
 static u_int cpuid_to_mid[MAXCPU];
-static int has_stopself;
 static int isjbus;
 static volatile u_int shutdown_cpus;
 
 static void cpu_mp_unleash(void *v);
 static void spitfire_ipi_send(u_int mid, u_long d0, u_long d1, u_long d2);
 static void sun4u_startcpu(phandle_t cpu, void *func, u_long arg);
-static void sun4u_stopself(void);
 
 static cpu_ipi_selected_t cheetah_ipi_selected;
 static cpu_ipi_selected_t spitfire_ipi_selected;
@@ -224,24 +222,6 @@ sun4u_startcpu(phandle_t cpu, void *func, u_long arg)
 	ofw_entry(&args);
 }
 
-/*
- * Stop the calling CPU.
- */
-static void
-sun4u_stopself(void)
-{
-	static struct {
-		cell_t	name;
-		cell_t	nargs;
-		cell_t	nreturns;
-	} args = {
-		(cell_t)SUNW_STOPSELF,
-	};
-
-	ofw_exit(&args);
-	panic("%s: failed.", __func__);
-}
-
 /*
  * Fire up any non-boot processors.
  */
@@ -260,9 +240,6 @@ cpu_mp_start(void)
 
 	mtx_init(&ipi_mtx, "ipi", NULL, MTX_SPIN);
 
-	if (OF_test(SUNW_STOPSELF) == 0)
-		has_stopself = 1;
-
 	intr_setup(PIL_AST, cpu_ipi_ast, -1, NULL, NULL);
 	intr_setup(PIL_RENDEZVOUS, (ih_func_t *)smp_rendezvous_action,
 	    -1, NULL, NULL);
@@ -457,8 +434,6 @@ cpu_ipi_stop(struct trapframe *tf)
 	while ((started_cpus & PCPU_GET(cpumask)) == 0) {
 		if ((shutdown_cpus & PCPU_GET(cpumask)) != 0) {
 			atomic_clear_int(&shutdown_cpus, PCPU_GET(cpumask));
-			if (has_stopself != 0)
-				sun4u_stopself();
 			(void)intr_disable();
 			for (;;)
 				;
@@ -538,7 +513,8 @@ spitfire_ipi_send(u_int mid, u_long d0, u_long d1, u_long d2)
 		printf("%s: couldn't send IPI to module 0x%u\n",
 		    __func__, mid);
 	else
-		panic("%s: couldn't send IPI", __func__);
+		panic("%s: couldn't send IPI to module 0x%u",
+		    __func__, mid);
 }
 
 static void
@@ -591,12 +567,19 @@ cheetah_ipi_selected(u_int cpus, u_long d0, u_long d1, u_long d2)
 				bnp++;
 			}
 		}
+		/*
+		 * On at least Fire V880 we may receive IDR_NACKs for
+		 * CPUs we actually haven't tried to send an IPI to,
+		 * but which apparently can be safely ignored.
+		 */
+		if (cpus == 0)
+			return;
 		/*
 		 * Leave interrupts enabled for a bit before retrying
 		 * in order to avoid deadlocks if the other CPUs are
 		 * also trying to send IPIs.
 		 */
-		DELAY(2 * bnp);
+		DELAY(2 * mp_ncpus);
 	}
 	if (
 #ifdef KDB
@@ -606,5 +589,6 @@ cheetah_ipi_selected(u_int cpus, u_long d0, u_long d1, u_long d2)
 		printf("%s: couldn't send IPI (cpus=0x%u ids=0x%lu)\n",
 		    __func__, cpus, ids);
 	else
-		panic("%s: couldn't send IPI", __func__);
+		panic("%s: couldn't send IPI (cpus=0x%u ids=0x%lu)",
+		    __func__, cpus, ids);
 }