Index: sys/kern/kern_shutdown.c
===================================================================
--- sys/kern/kern_shutdown.c
+++ sys/kern/kern_shutdown.c
@@ -119,9 +119,9 @@
 
 #ifdef KDB
 #ifdef KDB_UNATTENDED
-static int debugger_on_panic = 0;
+int debugger_on_panic = 0;
 #else
-static int debugger_on_panic = 1;
+int debugger_on_panic = 1;
 #endif
 SYSCTL_INT(_debug, OID_AUTO, debugger_on_panic,
     CTLFLAG_RWTUN | CTLFLAG_SECURE,
Index: sys/sys/kdb.h
===================================================================
--- sys/sys/kdb.h
+++ sys/sys/kdb.h
@@ -65,6 +65,7 @@
 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
 
 extern u_char kdb_active;		/* Non-zero while in debugger. */
+extern int debugger_on_panic;		/* enter the debugger on panic. */
 extern int debugger_on_trap;		/* enter the debugger on trap. */
 extern struct kdb_dbbe *kdb_dbbe;	/* Default debugger backend or NULL. */
 extern struct trapframe *kdb_frame;	/* Frame to kdb_trap(). */
Index: sys/x86/x86/cpu_machdep.c
===================================================================
--- sys/x86/x86/cpu_machdep.c
+++ sys/x86/x86/cpu_machdep.c
@@ -823,20 +823,14 @@
 }
 SYSINIT(cpu_idle_tun, SI_SUB_CPU, SI_ORDER_MIDDLE, cpu_idle_tun, NULL);
 
-static int panic_on_nmi = 1;
+static int panic_on_nmi = 0xff;
 SYSCTL_INT(_machdep, OID_AUTO, panic_on_nmi, CTLFLAG_RWTUN,
     &panic_on_nmi, 0,
-    "Panic on NMI raised by hardware failure");
+    "Panic on NMI: 1 = H/W failure; 2 = unknown; 0xff = all");
 int nmi_is_broadcast = 1;
 SYSCTL_INT(_machdep, OID_AUTO, nmi_is_broadcast, CTLFLAG_RWTUN,
     &nmi_is_broadcast, 0,
     "Chipset NMI is broadcast");
-#ifdef KDB
-int kdb_on_nmi = 1;
-SYSCTL_INT(_machdep, OID_AUTO, kdb_on_nmi, CTLFLAG_RWTUN,
-    &kdb_on_nmi, 0,
-    "Go to KDB on NMI with unknown source");
-#endif
 
 void
 nmi_call_kdb(u_int cpu, u_int type, struct trapframe *frame)
@@ -847,19 +841,31 @@
 	/* machine/parity/power fail/"kitchen sink" faults */
 	if (isa_nmi(frame->tf_err)) {
 		claimed = true;
-		if (panic_on_nmi)
+		if ((panic_on_nmi & 1) != 0)
 			panic("NMI indicates hardware failure");
 	}
 #endif /* DEV_ISA */
+
+	/*
+	 * NMIs can be useful for debugging.  They can be hooked up to a
+	 * pushbutton, usually on an ISA, PCI, or PCIe card.  They can also be
+	 * generated by an IPMI BMC, either manually or in response to a
+	 * watchdog timeout.  For example, see the "power diag" command in
+	 * ports/sysutils/ipmitool.  They can also be generated by a
+	 * hypervisor; see "bhyvectl --inject-nmi".
+	 */
+
 #ifdef KDB
-	if (!claimed && kdb_on_nmi) {
-		/*
-		 * NMI can be hooked up to a pushbutton for debugging.
-		 */
-		printf("NMI/cpu%d ... going to debugger\n", cpu);
-		kdb_trap(type, 0, frame);
+	if (!claimed && (panic_on_nmi & 2) != 0) {
+		if (debugger_on_panic) {
+			printf("NMI/cpu%d ... going to debugger\n", cpu);
+			claimed = kdb_trap(type, 0, frame);
+		}
 	}
 #endif /* KDB */
+
+	if (!claimed && panic_on_nmi != 0)
+		panic("NMI");
 }
 
 void