10597 would like a way to set NMI behavior at boot
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Andy Fiddaman <andy@omniosce.org>

@@ -21,11 +21,11 @@
 
 /*
  * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
  */
 /*
- * Copyright 2018 Joyent, Inc.
+ * Copyright 2019, Joyent, Inc.
  * Copyright (c) 2016, 2017 by Delphix. All rights reserved.
  */
 
 /*
  * PSMI 1.1 extensions are supported only in 2.6 and later versions.

@@ -806,10 +806,12 @@
 /* apic NMI handler */
 /*ARGSUSED*/
 void
 apic_nmi_intr(caddr_t arg, struct regs *rp)
 {
+        nmi_action_t action = nmi_action;
+
         if (apic_shutdown_processors) {
                 apic_disable_local_apic();
                 return;
         }
 

@@ -817,22 +819,45 @@
 
         if (!lock_try(&apic_nmi_lock))
                 return;
         apic_num_nmis++;
 
-        if (apic_kmdb_on_nmi && psm_debugger()) {
-                debug_enter("NMI received: entering kmdb\n");
-        } else if (apic_panic_on_nmi) {
-                /* Keep panic from entering kmdb. */
-                nopanicdebug = 1;
-                panic("NMI received\n");
-        } else {
                 /*
+         * "nmi_action" always over-rides the older way of doing this, unless we
+         * can't actually drop into kmdb when requested.
+         */
+        if (action == NMI_ACTION_KMDB && !psm_debugger())
+                action = NMI_ACTION_UNSET;
+
+        if (action == NMI_ACTION_UNSET) {
+                if (apic_kmdb_on_nmi && psm_debugger())
+                        action = NMI_ACTION_KMDB;
+                else if (apic_panic_on_nmi)
+                        action = NMI_ACTION_PANIC;
+                else
+                        action = NMI_ACTION_IGNORE;
+        }
+
+        switch (action) {
+        case NMI_ACTION_IGNORE:
+                /*
                  * prom_printf is the best shot we have of something which is
                  * problem free from high level/NMI type of interrupts
                  */
                 prom_printf("NMI received\n");
+                break;
+
+        case NMI_ACTION_PANIC:
+                /* Keep panic from entering kmdb. */
+                nopanicdebug = 1;
+                panic("NMI received\n");
+                break;
+
+        case NMI_ACTION_KMDB:
+        default:
+                debug_enter("NMI received: entering kmdb\n");
+                break;
         }
 
         lock_clear(&apic_nmi_lock);
 }