[PATCH] Add SMP support on x86_64 to reservation framework

This patch includes the changes to make the nmi watchdog on x86_64 SMP
aware.  A bunch of code was moved around to make it simpler to read.  In
addition, it is now possible to determine if a particular NMI was the result
of the watchdog or not.  This feature allows the kernel to filter out
unknown NMIs easier.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>

arch/x86_64/kernel/apic.c

@@ -479,8 +479,7 @@ void __cpuinit setup_local_APIC (void)
 	}
 
 	nmi_watchdog_default();
-	if (nmi_watchdog == NMI_LOCAL_APIC)
-		setup_apic_nmi_watchdog();
+	setup_apic_nmi_watchdog(NULL);
 	apic_pm_activate();
 }
 

arch/x86_64/kernel/nmi.c

@@ -56,53 +56,29 @@ static unsigned int lapic_nmi_owner;
 #define LAPIC_NMI_RESERVED	(1<<1)
 
 /* nmi_active:
- * +1: the lapic NMI watchdog is active, but can be disabled
- *  0: the lapic NMI watchdog has not been set up, and cannot
+ * >0: the lapic NMI watchdog is active, but can be disabled
+ * <0: the lapic NMI watchdog has not been set up, and cannot
  *     be enabled
- * -1: the lapic NMI watchdog is disabled, but can be enabled
+ *  0: the lapic NMI watchdog is disabled, but can be enabled
  */
-int nmi_active;		/* oprofile uses this */
+atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */
 int panic_on_timeout;
 
 unsigned int nmi_watchdog = NMI_DEFAULT;
 static unsigned int nmi_hz = HZ;
-static unsigned int nmi_perfctr_msr;	/* the MSR to reset in NMI handler */
-static unsigned int nmi_p4_cccr_val;
 
-/* Note that these events don't tick when the CPU idles. This means
-   the frequency varies with CPU load. */
+struct nmi_watchdog_ctlblk {
+	int enabled;
+	u64 check_bit;
+	unsigned int cccr_msr;
+	unsigned int perfctr_msr;  /* the MSR to reset in NMI handler */
+	unsigned int evntsel_msr;  /* the MSR to select the events to handle */
+};
+static DEFINE_PER_CPU(struct nmi_watchdog_ctlblk, nmi_watchdog_ctlblk);
 
-#define K7_EVNTSEL_ENABLE	(1 << 22)
-#define K7_EVNTSEL_INT		(1 << 20)
-#define K7_EVNTSEL_OS		(1 << 17)
-#define K7_EVNTSEL_USR		(1 << 16)
-#define K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING	0x76
-#define K7_NMI_EVENT		K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING
-
-#define MSR_P4_MISC_ENABLE	0x1A0
-#define MSR_P4_MISC_ENABLE_PERF_AVAIL	(1<<7)
-#define MSR_P4_MISC_ENABLE_PEBS_UNAVAIL	(1<<12)
-#define MSR_P4_PERFCTR0		0x300
-#define MSR_P4_CCCR0		0x360
-#define P4_ESCR_EVENT_SELECT(N)	((N)<<25)
-#define P4_ESCR_OS		(1<<3)
-#define P4_ESCR_USR		(1<<2)
-#define P4_CCCR_OVF_PMI0	(1<<26)
-#define P4_CCCR_OVF_PMI1	(1<<27)
-#define P4_CCCR_THRESHOLD(N)	((N)<<20)
-#define P4_CCCR_COMPLEMENT	(1<<19)
-#define P4_CCCR_COMPARE		(1<<18)
-#define P4_CCCR_REQUIRED	(3<<16)
-#define P4_CCCR_ESCR_SELECT(N)	((N)<<13)
-#define P4_CCCR_ENABLE		(1<<12)
-/* Set up IQ_COUNTER0 to behave like a clock, by having IQ_CCCR0 filter
-   CRU_ESCR0 (with any non-null event selector) through a complemented
-   max threshold. [IA32-Vol3, Section 14.9.9] */
-#define MSR_P4_IQ_COUNTER0	0x30C
-#define P4_NMI_CRU_ESCR0	(P4_ESCR_EVENT_SELECT(0x3F)|P4_ESCR_OS|P4_ESCR_USR)
-#define P4_NMI_IQ_CCCR0	\
-	(P4_CCCR_OVF_PMI0|P4_CCCR_THRESHOLD(15)|P4_CCCR_COMPLEMENT|	\
-	 P4_CCCR_COMPARE|P4_CCCR_REQUIRED|P4_CCCR_ESCR_SELECT(4)|P4_CCCR_ENABLE)
+/* local prototypes */
+static void stop_apic_nmi_watchdog(void *unused);
+static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu);
 
 /* converts an msr to an appropriate reservation bit */
 static inline unsigned int nmi_perfctr_msr_to_bit(unsigned int msr)
@@ -241,6 +217,12 @@ int __init check_nmi_watchdog (void)
 	int *counts;
 	int cpu;
 
+	if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
+		return 0;
+
+	if (!atomic_read(&nmi_active))
+		return 0;
+
 	counts = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
 	if (!counts)
 		return -1;
@@ -258,19 +240,22 @@ int __init check_nmi_watchdog (void)
 	mdelay((10*1000)/nmi_hz); // wait 10 ticks
 
 	for_each_online_cpu(cpu) {
+		if (!per_cpu(nmi_watchdog_ctlblk, cpu).enabled)
+			continue;
 		if (cpu_pda(cpu)->__nmi_count - counts[cpu] <= 5) {
-			endflag = 1;
 			printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 			       cpu,
 			       counts[cpu],
 			       cpu_pda(cpu)->__nmi_count);
-			nmi_active = 0;
-			lapic_nmi_owner &= ~LAPIC_NMI_WATCHDOG;
-			nmi_perfctr_msr = 0;
+			per_cpu(nmi_watchdog_ctlblk, cpu).enabled = 0;
+			atomic_dec(&nmi_active);
+		}
+	}
+	if (!atomic_read(&nmi_active)) {
 		kfree(counts);
+		atomic_set(&nmi_active, -1);
 		return -1;
 	}
-	}
 	endflag = 1;
 	printk("OK.\n");
 
@@ -297,8 +282,11 @@ int __init setup_nmi_watchdog(char *str)
 
 	get_option(&str, &nmi);
 
-	if (nmi >= NMI_INVALID)
+	if ((nmi >= NMI_INVALID) || (nmi < NMI_NONE))
 		return 0;
+
+	if ((nmi == NMI_LOCAL_APIC) && (nmi_known_cpu() == 0))
+		return 0;  /* no lapic support */
 	nmi_watchdog = nmi;
 	return 1;
 }
@@ -307,31 +295,30 @@ __setup("nmi_watchdog=", setup_nmi_watchdog);
 
 static void disable_lapic_nmi_watchdog(void)
 {
-	if (nmi_active <= 0)
+	BUG_ON(nmi_watchdog != NMI_LOCAL_APIC);
+
+	if (atomic_read(&nmi_active) <= 0)
 		return;
-	switch (boot_cpu_data.x86_vendor) {
-	case X86_VENDOR_AMD:
-		wrmsr(MSR_K7_EVNTSEL0, 0, 0);
-		break;
-	case X86_VENDOR_INTEL:
-		if (boot_cpu_data.x86 == 15) {
-			wrmsr(MSR_P4_IQ_CCCR0, 0, 0);
-			wrmsr(MSR_P4_CRU_ESCR0, 0, 0);
-		}
-		break;
-	}
-	nmi_active = -1;
-	/* tell do_nmi() and others that we're not active any more */
-	nmi_watchdog = 0;
+
+	on_each_cpu(stop_apic_nmi_watchdog, NULL, 0, 1);
+
+	BUG_ON(atomic_read(&nmi_active) != 0);
 }
 
 static void enable_lapic_nmi_watchdog(void)
 {
-	if (nmi_active < 0) {
-		nmi_watchdog = NMI_LOCAL_APIC;
+	BUG_ON(nmi_watchdog != NMI_LOCAL_APIC);
+
+	/* are we already enabled */
+	if (atomic_read(&nmi_active) != 0)
+		return;
+
+	/* are we lapic aware */
+	if (nmi_known_cpu() <= 0)
+		return;
+
+	on_each_cpu(setup_apic_nmi_watchdog, NULL, 0, 1);
 	touch_nmi_watchdog();
-		setup_apic_nmi_watchdog();
-	}
 }
 
 int reserve_lapic_nmi(void)
@@ -363,21 +350,24 @@ void release_lapic_nmi(void)
 
 void disable_timer_nmi_watchdog(void)
 {
-	if ((nmi_watchdog != NMI_IO_APIC) || (nmi_active <= 0))
+	BUG_ON(nmi_watchdog != NMI_IO_APIC);
+
+	if (atomic_read(&nmi_active) <= 0)
 		return;
 
 	disable_irq(0);
-	unset_nmi_callback();
-	nmi_active = -1;
-	nmi_watchdog = NMI_NONE;
+	on_each_cpu(stop_apic_nmi_watchdog, NULL, 0, 1);
+
+	BUG_ON(atomic_read(&nmi_active) != 0);
 }
 
 void enable_timer_nmi_watchdog(void)
 {
-	if (nmi_active < 0) {
-		nmi_watchdog = NMI_IO_APIC;
+	BUG_ON(nmi_watchdog != NMI_IO_APIC);
+
+	if (atomic_read(&nmi_active) == 0) {
 		touch_nmi_watchdog();
-		nmi_active = 1;
+		on_each_cpu(setup_apic_nmi_watchdog, NULL, 0, 1);
 		enable_irq(0);
 	}
 }
@@ -388,7 +378,7 @@ static int nmi_pm_active; /* nmi_active before suspend */
 
 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
 {
-	nmi_pm_active = nmi_active;
+	nmi_pm_active = atomic_read(&nmi_active);
 	disable_lapic_nmi_watchdog();
 	return 0;
 }
@@ -415,7 +405,13 @@ static int __init init_lapic_nmi_sysfs(void)
 {
 	int error;
 
-	if (nmi_active == 0 || nmi_watchdog != NMI_LOCAL_APIC)
+	/* should really be a BUG_ON but b/c this is an
+	 * init call, it just doesn't work.  -dcz
+	 */
+	if (nmi_watchdog != NMI_LOCAL_APIC)
+		return 0;
+
+	if ( atomic_read(&nmi_active) < 0 )
 		return 0;
 
 	error = sysdev_class_register(&nmi_sysclass);
@@ -428,100 +424,232 @@ late_initcall(init_lapic_nmi_sysfs);
 
 #endif	/* CONFIG_PM */
 
+/*
+ * Activate the NMI watchdog via the local APIC.
+ * Original code written by Keith Owens.
+ */
+
+/* Note that these events don't tick when the CPU idles. This means
+   the frequency varies with CPU load. */
+
+#define K7_EVNTSEL_ENABLE	(1 << 22)
+#define K7_EVNTSEL_INT		(1 << 20)
+#define K7_EVNTSEL_OS		(1 << 17)
+#define K7_EVNTSEL_USR		(1 << 16)
+#define K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING	0x76
+#define K7_NMI_EVENT		K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING
+
 static int setup_k7_watchdog(void)
 {
+	unsigned int perfctr_msr, evntsel_msr;
 	unsigned int evntsel;
+	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
 
-	nmi_perfctr_msr = MSR_K7_PERFCTR0;
-
-	if (!reserve_perfctr_nmi(nmi_perfctr_msr))
+	perfctr_msr = MSR_K7_PERFCTR0;
+	evntsel_msr = MSR_K7_EVNTSEL0;
+	if (!reserve_perfctr_nmi(perfctr_msr))
 		goto fail;
 
-	if (!reserve_evntsel_nmi(MSR_K7_EVNTSEL0))
+	if (!reserve_evntsel_nmi(evntsel_msr))
 		goto fail1;
 
 	/* Simulator may not support it */
-	if (checking_wrmsrl(MSR_K7_EVNTSEL0, 0UL))
+	if (checking_wrmsrl(evntsel_msr, 0UL))
 		goto fail2;
-	wrmsrl(MSR_K7_PERFCTR0, 0UL);
+	wrmsrl(perfctr_msr, 0UL);
 
 	evntsel = K7_EVNTSEL_INT
 		| K7_EVNTSEL_OS
 		| K7_EVNTSEL_USR
 		| K7_NMI_EVENT;
 
-	wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
-	wrmsrl(MSR_K7_PERFCTR0, -((u64)cpu_khz * 1000 / nmi_hz));
+	/* setup the timer */
+	wrmsr(evntsel_msr, evntsel, 0);
+	wrmsrl(perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
 	apic_write(APIC_LVTPC, APIC_DM_NMI);
 	evntsel |= K7_EVNTSEL_ENABLE;
-	wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
+	wrmsr(evntsel_msr, evntsel, 0);
+
+	wd->perfctr_msr = perfctr_msr;
+	wd->evntsel_msr = evntsel_msr;
+	wd->cccr_msr = 0;  //unused
+	wd->check_bit = 1ULL<<63;
 	return 1;
 fail2:
-	release_evntsel_nmi(MSR_K7_EVNTSEL0);
+	release_evntsel_nmi(evntsel_msr);
 fail1:
-	release_perfctr_nmi(nmi_perfctr_msr);
+	release_perfctr_nmi(perfctr_msr);
 fail:
 	return 0;
 }
 
+static void stop_k7_watchdog(void)
+{
+	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
+
+	wrmsr(wd->evntsel_msr, 0, 0);
+
+	release_evntsel_nmi(wd->evntsel_msr);
+	release_perfctr_nmi(wd->perfctr_msr);
+}
+
+/* Note that these events don't tick when the CPU idles. This means
+   the frequency varies with CPU load. */
+
+#define MSR_P4_MISC_ENABLE_PERF_AVAIL	(1<<7)
+#define P4_ESCR_EVENT_SELECT(N)	((N)<<25)
+#define P4_ESCR_OS		(1<<3)
+#define P4_ESCR_USR		(1<<2)
+#define P4_CCCR_OVF_PMI0	(1<<26)
+#define P4_CCCR_OVF_PMI1	(1<<27)
+#define P4_CCCR_THRESHOLD(N)	((N)<<20)
+#define P4_CCCR_COMPLEMENT	(1<<19)
+#define P4_CCCR_COMPARE		(1<<18)
+#define P4_CCCR_REQUIRED	(3<<16)
+#define P4_CCCR_ESCR_SELECT(N)	((N)<<13)
+#define P4_CCCR_ENABLE		(1<<12)
+#define P4_CCCR_OVF 		(1<<31)
+/* Set up IQ_COUNTER0 to behave like a clock, by having IQ_CCCR0 filter
+   CRU_ESCR0 (with any non-null event selector) through a complemented
+   max threshold. [IA32-Vol3, Section 14.9.9] */
 
 static int setup_p4_watchdog(void)
 {
+	unsigned int perfctr_msr, evntsel_msr, cccr_msr;
+	unsigned int evntsel, cccr_val;
 	unsigned int misc_enable, dummy;
+	unsigned int ht_num;
+	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
 
-	rdmsr(MSR_P4_MISC_ENABLE, misc_enable, dummy);
+	rdmsr(MSR_IA32_MISC_ENABLE, misc_enable, dummy);
 	if (!(misc_enable & MSR_P4_MISC_ENABLE_PERF_AVAIL))
 		return 0;
 
-	nmi_perfctr_msr = MSR_P4_IQ_COUNTER0;
-	nmi_p4_cccr_val = P4_NMI_IQ_CCCR0;
 #ifdef CONFIG_SMP
-	if (smp_num_siblings == 2)
-		nmi_p4_cccr_val |= P4_CCCR_OVF_PMI1;
+	/* detect which hyperthread we are on */
+	if (smp_num_siblings == 2) {
+		unsigned int ebx, apicid;
+
+        	ebx = cpuid_ebx(1);
+	        apicid = (ebx >> 24) & 0xff;
+        	ht_num = apicid & 1;
+	} else
 #endif
+		ht_num = 0;
+
+	/* performance counters are shared resources
+	 * assign each hyperthread its own set
+	 * (re-use the ESCR0 register, seems safe
+	 * and keeps the cccr_val the same)
+	 */
+	if (!ht_num) {
+		/* logical cpu 0 */
+		perfctr_msr = MSR_P4_IQ_PERFCTR0;
+		evntsel_msr = MSR_P4_CRU_ESCR0;
+		cccr_msr = MSR_P4_IQ_CCCR0;
+		cccr_val = P4_CCCR_OVF_PMI0 | P4_CCCR_ESCR_SELECT(4);
+	} else {
+		/* logical cpu 1 */
+		perfctr_msr = MSR_P4_IQ_PERFCTR1;
+		evntsel_msr = MSR_P4_CRU_ESCR0;
+		cccr_msr = MSR_P4_IQ_CCCR1;
+		cccr_val = P4_CCCR_OVF_PMI1 | P4_CCCR_ESCR_SELECT(4);
+	}
 
-	if (!reserve_perfctr_nmi(nmi_perfctr_msr))
+	if (!reserve_perfctr_nmi(perfctr_msr))
 		goto fail;
 
-	if (!reserve_evntsel_nmi(MSR_P4_CRU_ESCR0))
+	if (!reserve_evntsel_nmi(evntsel_msr))
 		goto fail1;
 
-	wrmsr(MSR_P4_CRU_ESCR0, P4_NMI_CRU_ESCR0, 0);
-	wrmsr(MSR_P4_IQ_CCCR0, P4_NMI_IQ_CCCR0 & ~P4_CCCR_ENABLE, 0);
-	Dprintk("setting P4_IQ_COUNTER0 to 0x%08lx\n", -(cpu_khz * 1000UL / nmi_hz));
-	wrmsrl(MSR_P4_IQ_COUNTER0, -((u64)cpu_khz * 1000 / nmi_hz));
+	evntsel = P4_ESCR_EVENT_SELECT(0x3F)
+	 	| P4_ESCR_OS
+		| P4_ESCR_USR;
+
+	cccr_val |= P4_CCCR_THRESHOLD(15)
+		 | P4_CCCR_COMPLEMENT
+		 | P4_CCCR_COMPARE
+		 | P4_CCCR_REQUIRED;
+
+	wrmsr(evntsel_msr, evntsel, 0);
+	wrmsr(cccr_msr, cccr_val, 0);
+	wrmsrl(perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
 	apic_write(APIC_LVTPC, APIC_DM_NMI);
-	wrmsr(MSR_P4_IQ_CCCR0, nmi_p4_cccr_val, 0);
+	cccr_val |= P4_CCCR_ENABLE;
+	wrmsr(cccr_msr, cccr_val, 0);
+
+	wd->perfctr_msr = perfctr_msr;
+	wd->evntsel_msr = evntsel_msr;
+	wd->cccr_msr = cccr_msr;
+	wd->check_bit = 1ULL<<39;
 	return 1;
 fail1:
-	release_perfctr_nmi(nmi_perfctr_msr);
+	release_perfctr_nmi(perfctr_msr);
 fail:
 	return 0;
 }
 
-void setup_apic_nmi_watchdog(void)
+static void stop_p4_watchdog(void)
 {
+	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
+
+	wrmsr(wd->cccr_msr, 0, 0);
+	wrmsr(wd->evntsel_msr, 0, 0);
+
+	release_evntsel_nmi(wd->evntsel_msr);
+	release_perfctr_nmi(wd->perfctr_msr);
+}
+
+void setup_apic_nmi_watchdog(void *unused)
+{
+	/* only support LOCAL and IO APICs for now */
+	if ((nmi_watchdog != NMI_LOCAL_APIC) &&
+	    (nmi_watchdog != NMI_IO_APIC))
+	    	return;
+
+	if (nmi_watchdog == NMI_LOCAL_APIC) {
 		switch (boot_cpu_data.x86_vendor) {
 		case X86_VENDOR_AMD:
-		if (boot_cpu_data.x86 != 15)
-			return;
 			if (strstr(boot_cpu_data.x86_model_id, "Screwdriver"))
 				return;
 			if (!setup_k7_watchdog())
 				return;
 			break;
 		case X86_VENDOR_INTEL:
-		if (boot_cpu_data.x86 != 15)
-			return;
 			if (!setup_p4_watchdog())
 				return;
 			break;
+		default:
+			return;
+		}
+	}
+	__get_cpu_var(nmi_watchdog_ctlblk.enabled) = 1;
+	atomic_inc(&nmi_active);
+}
+
+static void stop_apic_nmi_watchdog(void *unused)
+{
+	/* only support LOCAL and IO APICs for now */
+	if ((nmi_watchdog != NMI_LOCAL_APIC) &&
+	    (nmi_watchdog != NMI_IO_APIC))
+	    	return;
 
+	if (nmi_watchdog == NMI_LOCAL_APIC) {
+		switch (boot_cpu_data.x86_vendor) {
+		case X86_VENDOR_AMD:
+			if (strstr(boot_cpu_data.x86_model_id, "Screwdriver"))
+				return;
+			stop_k7_watchdog();
+			break;
+		case X86_VENDOR_INTEL:
+			stop_p4_watchdog();
+			break;
 		default:
 			return;
 		}
-	lapic_nmi_owner = LAPIC_NMI_WATCHDOG;
-	nmi_active = 1;
+	}
+	__get_cpu_var(nmi_watchdog_ctlblk.enabled) = 0;
+	atomic_dec(&nmi_active);
 }
 
 /*
@@ -558,38 +686,52 @@ void __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
 {
 	int sum;
 	int touched = 0;
+	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
+	u64 dummy;
+
+	/* check for other users first */
+	if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
+			== NOTIFY_STOP) {
+		touched = 1;
+	}
 
 	sum = read_pda(apic_timer_irqs);
 	if (__get_cpu_var(nmi_touch)) {
 		__get_cpu_var(nmi_touch) = 0;
 		touched = 1;
 	}
+
 #ifdef CONFIG_X86_MCE
 	/* Could check oops_in_progress here too, but it's safer
 	   not too */
 	if (atomic_read(&mce_entry) > 0)
 		touched = 1;
 #endif
+	/* if the apic timer isn't firing, this cpu isn't doing much */
 	if (!touched && __get_cpu_var(last_irq_sum) == sum) {
 		/*
 		 * Ayiee, looks like this CPU is stuck ...
 		 * wait a few IRQs (5 seconds) before doing the oops ...
 		 */
 		local_inc(&__get_cpu_var(alert_counter));
-		if (local_read(&__get_cpu_var(alert_counter)) == 5*nmi_hz) {
-			if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
-							== NOTIFY_STOP) {
-				local_set(&__get_cpu_var(alert_counter), 0);
-				return;
-			}
+		if (local_read(&__get_cpu_var(alert_counter)) == 5*nmi_hz)
 			die_nmi("NMI Watchdog detected LOCKUP on CPU %d\n", regs);
-		}
 	} else {
 		__get_cpu_var(last_irq_sum) = sum;
 		local_set(&__get_cpu_var(alert_counter), 0);
 	}
-	if (nmi_perfctr_msr) {
- 		if (nmi_perfctr_msr == MSR_P4_IQ_COUNTER0) {
+
+	/* see if the nmi watchdog went off */
+	if (wd->enabled) {
+		if (nmi_watchdog == NMI_LOCAL_APIC) {
+			rdmsrl(wd->perfctr_msr, dummy);
+			if (dummy & wd->check_bit){
+				/* this wasn't a watchdog timer interrupt */
+				goto done;
+			}
+
+			/* only Intel uses the cccr msr */
+	 		if (wd->cccr_msr != 0) {
 	 			/*
 	 			 * P4 quirks:
 	 			 * - An overflown perfctr will assert its interrupt
@@ -597,11 +739,17 @@ void __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
 	 			 * - LVTPC is masked on interrupt and must be
 	 			 *   unmasked by the LVTPC handler.
 	 			 */
- 			wrmsr(MSR_P4_IQ_CCCR0, nmi_p4_cccr_val, 0);
+				rdmsrl(wd->cccr_msr, dummy);
+				dummy &= ~P4_CCCR_OVF;
+	 			wrmsrl(wd->cccr_msr, dummy);
 	 			apic_write(APIC_LVTPC, APIC_DM_NMI);
 	 		}
-		wrmsrl(nmi_perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
+			/* start the cycle over again */
+			wrmsrl(wd->perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
 		}
+	}
+done:
+	return;
 }
 
 static __kprobes int dummy_nmi_callback(struct pt_regs * regs, int cpu)

include/asm-x86_64/nmi.h

@@ -63,7 +63,7 @@ extern void release_perfctr_nmi(unsigned int);
 extern int reserve_evntsel_nmi(unsigned int);
 extern void release_evntsel_nmi(unsigned int);
 
-extern void setup_apic_nmi_watchdog (void);
+extern void setup_apic_nmi_watchdog (void *);
 extern int reserve_lapic_nmi(void);
 extern void release_lapic_nmi(void);
 extern void disable_timer_nmi_watchdog(void);
@@ -73,6 +73,7 @@ extern void nmi_watchdog_tick (struct pt_regs * regs, unsigned reason);
 extern void nmi_watchdog_default(void);
 extern int setup_nmi_watchdog(char *);
 
+extern atomic_t nmi_active;
 extern unsigned int nmi_watchdog;
 #define NMI_DEFAULT	-1
 #define NMI_NONE	0