IPMI: new NMI handling

Convert over to the new NMI handling for getting IPMI watchdog timeouts via an
NMI. This add config options to know if there is the ability to receive NMIs
and if it has an NMI post processing call. Then it modifies the IPMI watchdog
to take advantage of this so that it can know if an NMI comes in.

It also adds testing that the IPMI NMI watchdog works.

Signed-off-by: Corey Minyard <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/IPMI.txt

···
 gets a pre-action.  During a panic or a reboot, the watchdog will
 start a 120 timer if it is running to make sure the reboot occurs.
 
-Note that if you use the NMI preaction for the watchdog, you MUST
-NOT use nmi watchdog mode 1.  If you use the NMI watchdog, you
-must use mode 2.
+Note that if you use the NMI preaction for the watchdog, you MUST NOT
+use the nmi watchdog.  There is no reasonable way to tell if an NMI
+comes from the IPMI controller, so it must assume that if it gets an
+otherwise unhandled NMI, it must be from IPMI and it will panic
+immediately.
 
 Once you open the watchdog timer, you must write a 'V' character to the
 device to close it, or the timer will not stop.  This is a new semantic

drivers/char/ipmi/ipmi_watchdog.c

···
 #include <linux/poll.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
+#include <linux/delay.h>
 #include <asm/atomic.h>
 
-#ifdef CONFIG_X86_LOCAL_APIC
-#include <asm/apic.h>
+#ifdef CONFIG_X86
+/* This is ugly, but I've determined that x86 is the only architecture
+   that can reasonably support the IPMI NMI watchdog timeout at this
+   time.  If another architecture adds this capability somehow, it
+   will have to be a somewhat different mechanism and I have no idea
+   how it will work.  So in the unlikely event that another
+   architecture supports this, we can figure out a good generic
+   mechanism for it at that time. */
+#include <asm/kdebug.h>
+#define HAVE_DIE_NMI
 #endif
 
 #define	PFX "IPMI Watchdog: "
···
 /* If a pretimeout occurs, this is used to allow only one panic to happen. */
 static atomic_t preop_panic_excl = ATOMIC_INIT(-1);
 
+#ifdef HAVE_DIE_NMI
+static int testing_nmi;
+static int nmi_handler_registered;
+#endif
+
 static int ipmi_heartbeat(void);
 
 /* We use a mutex to make sure that only one thing can send a set
···
 	struct ipmi_system_interface_addr addr;
 	int                               hbnow = 0;
 
+
+	/* These can be cleared as we are setting the timeout. */
+	pretimeout_since_last_heartbeat = 0;
 
 	data[0] = 0;
 	WDOG_SET_TIMER_USE(data[0], WDOG_TIMER_USE_SMS_OS);
···
 
 	wait_for_completion(&set_timeout_wait);
 
+	mutex_unlock(&set_timeout_lock);
+
 	if ((do_heartbeat == IPMI_SET_TIMEOUT_FORCE_HB)
 	    || ((send_heartbeat_now)
 		&& (do_heartbeat == IPMI_SET_TIMEOUT_HB_IF_NECESSARY)))
-	{
 		rv = ipmi_heartbeat();
-	}
-	mutex_unlock(&set_timeout_lock);
 
 out:
 	return rv;
···
 	int                               rv;
 	struct ipmi_system_interface_addr addr;
 
-	if (ipmi_ignore_heartbeat) {
+	if (ipmi_ignore_heartbeat)
 		return 0;
-	}
 
 	if (ipmi_start_timer_on_heartbeat) {
 		ipmi_start_timer_on_heartbeat = 0;
···
 		   We don't want to set the action, though, we want to
 		   leave that alone (thus it can't be combined with the
 		   above operation. */
-		pretimeout_since_last_heartbeat = 0;
 		return ipmi_set_timeout(IPMI_SET_TIMEOUT_HB_IF_NECESSARY);
 	}
 
···
 		printk(KERN_CRIT PFX "Unable to register misc device\n");
 	}
 
+#ifdef HAVE_DIE_NMI
+	if (nmi_handler_registered) {
+		int old_pretimeout = pretimeout;
+		int old_timeout = timeout;
+		int old_preop_val = preop_val;
+
+		/* Set the pretimeout to go off in a second and give
+		   ourselves plenty of time to stop the timer. */
+		ipmi_watchdog_state = WDOG_TIMEOUT_RESET;
+		preop_val = WDOG_PREOP_NONE; /* Make sure nothing happens */
+		pretimeout = 99;
+		timeout = 100;
+
+		testing_nmi = 1;
+
+		rv = ipmi_set_timeout(IPMI_SET_TIMEOUT_FORCE_HB);
+		if (rv) {
+			printk(KERN_WARNING PFX "Error starting timer to"
+			       " test NMI: 0x%x.  The NMI pretimeout will"
+			       " likely not work\n", rv);
+			rv = 0;
+			goto out_restore;
+		}
+
+		msleep(1500);
+
+		if (testing_nmi != 2) {
+			printk(KERN_WARNING PFX "IPMI NMI didn't seem to"
+			       " occur.  The NMI pretimeout will"
+			       " likely not work\n");
+		}
+	out_restore:
+		testing_nmi = 0;
+		preop_val = old_preop_val;
+		pretimeout = old_pretimeout;
+		timeout = old_timeout;
+	}
+#endif
+
  out:
 	if ((start_now) && (rv == 0)) {
 		/* Run from startup, so start the timer now. */
···
 		ipmi_watchdog_state = action_val;
 		ipmi_set_timeout(IPMI_SET_TIMEOUT_FORCE_HB);
 		printk(KERN_INFO PFX "Starting now!\n");
+	} else {
+		/* Stop the timer now. */
+		ipmi_watchdog_state = WDOG_TIMEOUT_NONE;
+		ipmi_set_timeout(IPMI_SET_TIMEOUT_NO_HB);
 	}
 }
 
···
 	return;
 }
 
-#ifdef HAVE_NMI_HANDLER
+#ifdef HAVE_DIE_NMI
 static int
-ipmi_nmi(void *dev_id, int cpu, int handled)
+ipmi_nmi(struct notifier_block *self, unsigned long val, void *data)
 {
+	struct die_args *args = data;
+
+	if (val != DIE_NMI)
+		return NOTIFY_OK;
+
+	/* Hack, if it's a memory or I/O error, ignore it. */
+	if (args->err & 0xc0)
+		return NOTIFY_OK;
+
+	/*
+	 * If we get here, it's an NMI that's not a memory or I/O
+	 * error.  We can't truly tell if it's from IPMI or not
+	 * without sending a message, and sending a message is almost
+	 * impossible because of locking.
+	 */
+
+	if (testing_nmi) {
+		testing_nmi = 2;
+		return NOTIFY_STOP;
+	}
+
         /* If we are not expecting a timeout, ignore it. */
 	if (ipmi_watchdog_state == WDOG_TIMEOUT_NONE)
-		return NOTIFY_DONE;
+		return NOTIFY_OK;
+
+	if (preaction_val != WDOG_PRETIMEOUT_NMI)
+		return NOTIFY_OK;
 
 	/* If no one else handled the NMI, we assume it was the IPMI
            watchdog. */
-	if ((!handled) && (preop_val == WDOG_PREOP_PANIC)) {
+	if (preop_val == WDOG_PREOP_PANIC) {
 		/* On some machines, the heartbeat will give
 		   an error and not work unless we re-enable
 		   the timer.   So do so. */
···
 			panic(PFX "pre-timeout");
 	}
 
-	return NOTIFY_DONE;
+	return NOTIFY_STOP;
 }
 
-static struct nmi_handler ipmi_nmi_handler =
-{
-	.link     = LIST_HEAD_INIT(ipmi_nmi_handler.link),
-	.dev_name = "ipmi_watchdog",
-	.dev_id   = NULL,
-	.handler  = ipmi_nmi,
-	.priority = 0, /* Call us last. */
+static struct notifier_block ipmi_nmi_handler = {
+	.notifier_call = ipmi_nmi
 };
-int nmi_handler_registered;
 #endif
 
 static int wdog_reboot_handler(struct notifier_block *this,
···
 		preaction_val = WDOG_PRETIMEOUT_NONE;
 	else if (strcmp(inval, "pre_smi") == 0)
 		preaction_val = WDOG_PRETIMEOUT_SMI;
-#ifdef HAVE_NMI_HANDLER
+#ifdef HAVE_DIE_NMI
 	else if (strcmp(inval, "pre_nmi") == 0)
 		preaction_val = WDOG_PRETIMEOUT_NMI;
 #endif
···
 
 static void check_parms(void)
 {
-#ifdef HAVE_NMI_HANDLER
+#ifdef HAVE_DIE_NMI
 	int do_nmi = 0;
 	int rv;
 
···
 			preop_op("preop_none", NULL);
 			do_nmi = 0;
 		}
-#ifdef CONFIG_X86_LOCAL_APIC
-		if (nmi_watchdog == NMI_IO_APIC) {
-			printk(KERN_WARNING PFX "nmi_watchdog is set to IO APIC"
-			       " mode (value is %d), that is incompatible"
-			       " with using NMI in the IPMI watchdog."
-			       " Disabling IPMI nmi pretimeout.\n",
-			       nmi_watchdog);
-			preaction_val = WDOG_PRETIMEOUT_NONE;
-			do_nmi = 0;
-		}
-#endif
 	}
 	if (do_nmi && !nmi_handler_registered) {
-		rv = request_nmi(&ipmi_nmi_handler);
+		rv = register_die_notifier(&ipmi_nmi_handler);
 		if (rv) {
 			printk(KERN_WARNING PFX
 			       "Can't register nmi handler\n");
···
 		} else
 			nmi_handler_registered = 1;
 	} else if (!do_nmi && nmi_handler_registered) {
-		release_nmi(&ipmi_nmi_handler);
+		unregister_die_notifier(&ipmi_nmi_handler);
 		nmi_handler_registered = 0;
 	}
 #endif
···
 
 	rv = ipmi_smi_watcher_register(&smi_watcher);
 	if (rv) {
-#ifdef HAVE_NMI_HANDLER
-		if (preaction_val == WDOG_PRETIMEOUT_NMI)
-			release_nmi(&ipmi_nmi_handler);
+#ifdef HAVE_DIE_NMI
+		if (nmi_handler_registered)
+			unregister_die_notifier(&ipmi_nmi_handler);
 #endif
 		atomic_notifier_chain_unregister(&panic_notifier_list,
 						 &wdog_panic_notifier);
···
 	ipmi_smi_watcher_unregister(&smi_watcher);
 	ipmi_unregister_watchdog(watchdog_ifnum);
 
-#ifdef HAVE_NMI_HANDLER
+#ifdef HAVE_DIE_NMI
 	if (nmi_handler_registered)
-		release_nmi(&ipmi_nmi_handler);
+		unregister_die_notifier(&ipmi_nmi_handler);
 #endif
 
 	atomic_notifier_chain_unregister(&panic_notifier_list,