[deliverable/linux.git] / arch / i386 / kernel / nmi.c

/*
 *  linux/arch/i386/nmi.c
 *
 *  NMI watchdog support on APIC systems
 *
 *  Started by Ingo Molnar <mingo@redhat.com>
 *
 *  Fixes:
 *  Mikael Pettersson   : AMD K7 support for local APIC NMI watchdog.
 *  Mikael Pettersson   : Power Management for local APIC NMI watchdog.
 *  Mikael Pettersson   : Pentium 4 support for local APIC NMI watchdog.
 *  Pavel Machek and
 *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
 */

#include <linux/config.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/sysdev.h>
#include <linux/sysctl.h>
#include <linux/percpu.h>

#include <asm/smp.h>
#include <asm/nmi.h>
#include <asm/kdebug.h>

#include "mach_traps.h"

/* perfctr_nmi_owner tracks the ownership of the perfctr registers:
 * evtsel_nmi_owner tracks the ownership of the event selection
 * - different performance counters/ event selection may be reserved for
 *   different subsystems this reservation system just tries to coordinate
 *   things a little
 */
static DEFINE_PER_CPU(unsigned long, perfctr_nmi_owner);
static DEFINE_PER_CPU(unsigned long, evntsel_nmi_owner[3]);

/* this number is calculated from Intel's MSR_P4_CRU_ESCR5 register and it's
 * offset from MSR_P4_BSU_ESCR0.  It will be the max for all platforms (for now)
 */
#define NMI_MAX_COUNTER_BITS 66

/* nmi_active:
 * >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
 *  0: the lapic NMI watchdog is disabled, but can be enabled
 */
atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */

unsigned int nmi_watchdog = NMI_DEFAULT;
static unsigned int nmi_hz = HZ;

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);

/* local prototypes */
static void stop_apic_nmi_watchdog(void *unused);
static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu);

extern void show_registers(struct pt_regs *regs);
extern int unknown_nmi_panic;

/* converts an msr to an appropriate reservation bit */
static inline unsigned int nmi_perfctr_msr_to_bit(unsigned int msr)
{
        /* returns the bit offset of the performance counter register */
        switch (boot_cpu_data.x86_vendor) {
        case X86_VENDOR_AMD:
                return (msr - MSR_K7_PERFCTR0);
        case X86_VENDOR_INTEL:
                switch (boot_cpu_data.x86) {
                case 6:
                        return (msr - MSR_P6_PERFCTR0);
                case 15:
                        return (msr - MSR_P4_BPU_PERFCTR0);
                }
        }
        return 0;
}

/* converts an msr to an appropriate reservation bit */
static inline unsigned int nmi_evntsel_msr_to_bit(unsigned int msr)
{
        /* returns the bit offset of the event selection register */
        switch (boot_cpu_data.x86_vendor) {
        case X86_VENDOR_AMD:
                return (msr - MSR_K7_EVNTSEL0);
        case X86_VENDOR_INTEL:
                switch (boot_cpu_data.x86) {
                case 6:
                        return (msr - MSR_P6_EVNTSEL0);
                case 15:
                        return (msr - MSR_P4_BSU_ESCR0);
                }
        }
        return 0;
}

/* checks for a bit availability (hack for oprofile) */
int avail_to_resrv_perfctr_nmi_bit(unsigned int counter)
{
        BUG_ON(counter > NMI_MAX_COUNTER_BITS);

        return (!test_bit(counter, &__get_cpu_var(perfctr_nmi_owner)));
}

/* checks the an msr for availability */
int avail_to_resrv_perfctr_nmi(unsigned int msr)
{
        unsigned int counter;

        counter = nmi_perfctr_msr_to_bit(msr);
        BUG_ON(counter > NMI_MAX_COUNTER_BITS);

        return (!test_bit(counter, &__get_cpu_var(perfctr_nmi_owner)));
}

int reserve_perfctr_nmi(unsigned int msr)
{
        unsigned int counter;

        counter = nmi_perfctr_msr_to_bit(msr);
        BUG_ON(counter > NMI_MAX_COUNTER_BITS);

        if (!test_and_set_bit(counter, &__get_cpu_var(perfctr_nmi_owner)))
                return 1;
        return 0;
}

void release_perfctr_nmi(unsigned int msr)
{
        unsigned int counter;

        counter = nmi_perfctr_msr_to_bit(msr);
        BUG_ON(counter > NMI_MAX_COUNTER_BITS);

        clear_bit(counter, &__get_cpu_var(perfctr_nmi_owner));
}

int reserve_evntsel_nmi(unsigned int msr)
{
        unsigned int counter;

        counter = nmi_evntsel_msr_to_bit(msr);
        BUG_ON(counter > NMI_MAX_COUNTER_BITS);

        if (!test_and_set_bit(counter, &__get_cpu_var(evntsel_nmi_owner)[0]))
                return 1;
        return 0;
}

void release_evntsel_nmi(unsigned int msr)
{
        unsigned int counter;

        counter = nmi_evntsel_msr_to_bit(msr);
        BUG_ON(counter > NMI_MAX_COUNTER_BITS);

        clear_bit(counter, &__get_cpu_var(evntsel_nmi_owner)[0]);
}

static __cpuinit inline int nmi_known_cpu(void)
{
        switch (boot_cpu_data.x86_vendor) {
        case X86_VENDOR_AMD:
                return ((boot_cpu_data.x86 == 15) || (boot_cpu_data.x86 == 6));
        case X86_VENDOR_INTEL:
                return ((boot_cpu_data.x86 == 15) || (boot_cpu_data.x86 == 6));
        }
        return 0;
}

#ifdef CONFIG_SMP
/* The performance counters used by NMI_LOCAL_APIC don't trigger when
 * the CPU is idle. To make sure the NMI watchdog really ticks on all
 * CPUs during the test make them busy.
 */
static __init void nmi_cpu_busy(void *data)
{
        volatile int *endflag = data;
        local_irq_enable_in_hardirq();
        /* Intentionally don't use cpu_relax here. This is
           to make sure that the performance counter really ticks,
           even if there is a simulator or similar that catches the
           pause instruction. On a real HT machine this is fine because
           all other CPUs are busy with "useless" delay loops and don't
           care if they get somewhat less cycles. */
        while (*endflag == 0)
                barrier();
}
#endif

static int __init check_nmi_watchdog(void)
{
        volatile int endflag = 0;
        unsigned int *prev_nmi_count;
        int cpu;

        if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
                return 0;

        if (!atomic_read(&nmi_active))
                return 0;

        prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
        if (!prev_nmi_count)
                return -1;

        printk(KERN_INFO "Testing NMI watchdog ... ");

        if (nmi_watchdog == NMI_LOCAL_APIC)
                smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);

        for_each_possible_cpu(cpu)
                prev_nmi_count[cpu] = per_cpu(irq_stat, cpu).__nmi_count;
        local_irq_enable();
        mdelay((10*1000)/nmi_hz); // wait 10 ticks

        for_each_possible_cpu(cpu) {
#ifdef CONFIG_SMP
                /* Check cpu_callin_map here because that is set
                   after the timer is started. */
                if (!cpu_isset(cpu, cpu_callin_map))
                        continue;
#endif
                if (!per_cpu(nmi_watchdog_ctlblk, cpu).enabled)
                        continue;
                if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
                        printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
                                cpu,
                                prev_nmi_count[cpu],
                                nmi_count(cpu));
                        per_cpu(nmi_watchdog_ctlblk, cpu).enabled = 0;
                        atomic_dec(&nmi_active);
                }
        }
        if (!atomic_read(&nmi_active)) {
                kfree(prev_nmi_count);
                atomic_set(&nmi_active, -1);
                return -1;
        }
        endflag = 1;
        printk("OK.\n");

        /* now that we know it works we can reduce NMI frequency to
           something more reasonable; makes a difference in some configs */
        if (nmi_watchdog == NMI_LOCAL_APIC)
                nmi_hz = 1;

        kfree(prev_nmi_count);
        return 0;
}
/* This needs to happen later in boot so counters are working */
late_initcall(check_nmi_watchdog);

static int __init setup_nmi_watchdog(char *str)
{
        int nmi;

        get_option(&str, &nmi);

        if ((nmi >= NMI_INVALID) || (nmi < NMI_NONE))
                return 0;
        /*
         * If any other x86 CPU has a local APIC, then
         * please test the NMI stuff there and send me the
         * missing bits. Right now Intel P6/P4 and AMD K7 only.
         */
        if ((nmi == NMI_LOCAL_APIC) && (nmi_known_cpu() == 0))
                return 0;  /* no lapic support */
        nmi_watchdog = nmi;
        return 1;
}

__setup("nmi_watchdog=", setup_nmi_watchdog);

static void disable_lapic_nmi_watchdog(void)
{
        BUG_ON(nmi_watchdog != NMI_LOCAL_APIC);

        if (atomic_read(&nmi_active) <= 0)
                return;

        on_each_cpu(stop_apic_nmi_watchdog, NULL, 0, 1);

        BUG_ON(atomic_read(&nmi_active) != 0);
}

static void enable_lapic_nmi_watchdog(void)
{
        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();
}

void disable_timer_nmi_watchdog(void)
{
        BUG_ON(nmi_watchdog != NMI_IO_APIC);

        if (atomic_read(&nmi_active) <= 0)
                return;

        disable_irq(0);
        on_each_cpu(stop_apic_nmi_watchdog, NULL, 0, 1);

        BUG_ON(atomic_read(&nmi_active) != 0);
}

void enable_timer_nmi_watchdog(void)
{
        BUG_ON(nmi_watchdog != NMI_IO_APIC);

        if (atomic_read(&nmi_active) == 0) {
                touch_nmi_watchdog();
                on_each_cpu(setup_apic_nmi_watchdog, NULL, 0, 1);
                enable_irq(0);
        }
}

#ifdef CONFIG_PM

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 = atomic_read(&nmi_active);
        disable_lapic_nmi_watchdog();
        return 0;
}

static int lapic_nmi_resume(struct sys_device *dev)
{
        if (nmi_pm_active > 0)
                enable_lapic_nmi_watchdog();
        return 0;
}


static struct sysdev_class nmi_sysclass = {
        set_kset_name("lapic_nmi"),
        .resume         = lapic_nmi_resume,
        .suspend        = lapic_nmi_suspend,
};

static struct sys_device device_lapic_nmi = {
        .id     = 0,
        .cls    = &nmi_sysclass,
};

static int __init init_lapic_nmi_sysfs(void)
{
        int error;

        /* 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);
        if (!error)
                error = sysdev_register(&device_lapic_nmi);
        return error;
}
/* must come after the local APIC's device_initcall() */
late_initcall(init_lapic_nmi_sysfs);

#endif  /* CONFIG_PM */

/*
 * Activate the NMI watchdog via the local APIC.
 * Original code written by Keith Owens.
 */

static void write_watchdog_counter(unsigned int perfctr_msr, const char *descr)
{
        u64 count = (u64)cpu_khz * 1000;

        do_div(count, nmi_hz);
        if(descr)
                Dprintk("setting %s to -0x%08Lx\n", descr, count);
        wrmsrl(perfctr_msr, 0 - count);
}

/* 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);

        perfctr_msr = MSR_K7_PERFCTR0;
        evntsel_msr = MSR_K7_EVNTSEL0;
        if (!reserve_perfctr_nmi(perfctr_msr))
                goto fail;

        if (!reserve_evntsel_nmi(evntsel_msr))
                goto fail1;

        wrmsrl(perfctr_msr, 0UL);

        evntsel = K7_EVNTSEL_INT
                | K7_EVNTSEL_OS
                | K7_EVNTSEL_USR
                | K7_NMI_EVENT;

        /* setup the timer */
        wrmsr(evntsel_msr, evntsel, 0);
        write_watchdog_counter(perfctr_msr, "K7_PERFCTR0");
        apic_write(APIC_LVTPC, APIC_DM_NMI);
        evntsel |= K7_EVNTSEL_ENABLE;
        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;
fail1:
        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);
}

#define P6_EVNTSEL0_ENABLE      (1 << 22)
#define P6_EVNTSEL_INT          (1 << 20)
#define P6_EVNTSEL_OS           (1 << 17)
#define P6_EVNTSEL_USR          (1 << 16)
#define P6_EVENT_CPU_CLOCKS_NOT_HALTED  0x79
#define P6_NMI_EVENT            P6_EVENT_CPU_CLOCKS_NOT_HALTED

static int setup_p6_watchdog(void)
{
        unsigned int perfctr_msr, evntsel_msr;
        unsigned int evntsel;
        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

        perfctr_msr = MSR_P6_PERFCTR0;
        evntsel_msr = MSR_P6_EVNTSEL0;
        if (!reserve_perfctr_nmi(perfctr_msr))
                goto fail;

        if (!reserve_evntsel_nmi(evntsel_msr))
                goto fail1;

        wrmsrl(perfctr_msr, 0UL);

        evntsel = P6_EVNTSEL_INT
                | P6_EVNTSEL_OS
                | P6_EVNTSEL_USR
                | P6_NMI_EVENT;

        /* setup the timer */
        wrmsr(evntsel_msr, evntsel, 0);
        write_watchdog_counter(perfctr_msr, "P6_PERFCTR0");
        apic_write(APIC_LVTPC, APIC_DM_NMI);
        evntsel |= P6_EVNTSEL0_ENABLE;
        wrmsr(evntsel_msr, evntsel, 0);

        wd->perfctr_msr = perfctr_msr;
        wd->evntsel_msr = evntsel_msr;
        wd->cccr_msr = 0;  //unused
        wd->check_bit = 1ULL<<39;
        return 1;
fail1:
        release_perfctr_nmi(perfctr_msr);
fail:
        return 0;
}

static void stop_p6_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_IA32_MISC_ENABLE, misc_enable, dummy);
        if (!(misc_enable & MSR_P4_MISC_ENABLE_PERF_AVAIL))
                return 0;

#ifdef CONFIG_SMP
        /* 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(perfctr_msr))
                goto fail;

        if (!reserve_evntsel_nmi(evntsel_msr))
                goto fail1;

        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);
        write_watchdog_counter(perfctr_msr, "P4_IQ_COUNTER0");
        apic_write(APIC_LVTPC, APIC_DM_NMI);
        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(perfctr_msr);
fail:
        return 0;
}

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 != 6 && boot_cpu_data.x86 != 15)
                                return;
                        if (!setup_k7_watchdog())
                                return;
                        break;
                case X86_VENDOR_INTEL:
                        switch (boot_cpu_data.x86) {
                        case 6:
                                if (boot_cpu_data.x86_model > 0xd)
                                        return;

                                if (!setup_p6_watchdog())
                                        return;
                                break;
                        case 15:
                                if (boot_cpu_data.x86_model > 0x4)
                                        return;

                                if (!setup_p4_watchdog())
                                        return;
                                break;
                        default:
                                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:
                        stop_k7_watchdog();
                        break;
                case X86_VENDOR_INTEL:
                        switch (boot_cpu_data.x86) {
                        case 6:
                                if (boot_cpu_data.x86_model > 0xd)
                                        break;
                                stop_p6_watchdog();
                                break;
                        case 15:
                                if (boot_cpu_data.x86_model > 0x4)
                                        break;
                                stop_p4_watchdog();
                                break;
                        }
                        break;
                default:
                        return;
                }
        }
        __get_cpu_var(nmi_watchdog_ctlblk.enabled) = 0;
        atomic_dec(&nmi_active);
}

/*
 * the best way to detect whether a CPU has a 'hard lockup' problem
 * is to check it's local APIC timer IRQ counts. If they are not
 * changing then that CPU has some problem.
 *
 * as these watchdog NMI IRQs are generated on every CPU, we only
 * have to check the current processor.
 *
 * since NMIs don't listen to _any_ locks, we have to be extremely
 * careful not to rely on unsafe variables. The printk might lock
 * up though, so we have to break up any console locks first ...
 * [when there will be more tty-related locks, break them up
 *  here too!]
 */

static unsigned int
        last_irq_sums [NR_CPUS],
        alert_counter [NR_CPUS];

void touch_nmi_watchdog (void)
{
        int i;

        /*
         * Just reset the alert counters, (other CPUs might be
         * spinning on locks we hold):
         */
        for_each_possible_cpu(i)
                alert_counter[i] = 0;

        /*
         * Tickle the softlockup detector too:
         */
        touch_softlockup_watchdog();
}
EXPORT_SYMBOL(touch_nmi_watchdog);

extern void die_nmi(struct pt_regs *, const char *msg);

int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason)
{

        /*
         * Since current_thread_info()-> is always on the stack, and we
         * always switch the stack NMI-atomically, it's safe to use
         * smp_processor_id().
         */
        unsigned int sum;
        int touched = 0;
        int cpu = smp_processor_id();
        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
        u64 dummy;
        int rc=0;

        /* check for other users first */
        if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
                        == NOTIFY_STOP) {
                rc = 1;
                touched = 1;
        }

        sum = per_cpu(irq_stat, cpu).apic_timer_irqs;

        /* if the apic timer isn't firing, this cpu isn't doing much */
        if (!touched && last_irq_sums[cpu] == sum) {
                /*
                 * Ayiee, looks like this CPU is stuck ...
                 * wait a few IRQs (5 seconds) before doing the oops ...
                 */
                alert_counter[cpu]++;
                if (alert_counter[cpu] == 5*nmi_hz)
                        /*
                         * die_nmi will return ONLY if NOTIFY_STOP happens..
                         */
                        die_nmi(regs, "BUG: NMI Watchdog detected LOCKUP");
        } else {
                last_irq_sums[cpu] = sum;
                alert_counter[cpu] = 0;
        }
        /* 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 P4 uses the cccr msr */
                        if (wd->cccr_msr != 0) {
                                /*
                                 * P4 quirks:
                                 * - An overflown perfctr will assert its interrupt
                                 *   until the OVF flag in its CCCR is cleared.
                                 * - LVTPC is masked on interrupt and must be
                                 *   unmasked by the LVTPC handler.
                                 */
                                rdmsrl(wd->cccr_msr, dummy);
                                dummy &= ~P4_CCCR_OVF;
                                wrmsrl(wd->cccr_msr, dummy);
                                apic_write(APIC_LVTPC, APIC_DM_NMI);
                        }
                        else if (wd->perfctr_msr == MSR_P6_PERFCTR0) {
                                /* Only P6 based Pentium M need to re-unmask
                                 * the apic vector but it doesn't hurt
                                 * other P6 variant */
                                apic_write(APIC_LVTPC, APIC_DM_NMI);
                        }
                        /* start the cycle over again */
                        write_watchdog_counter(wd->perfctr_msr, NULL);
                        rc = 1;
                } else if (nmi_watchdog == NMI_IO_APIC) {
                        /* don't know how to accurately check for this.
                         * just assume it was a watchdog timer interrupt
                         * This matches the old behaviour.
                         */
                        rc = 1;
                } else
                        printk(KERN_WARNING "Unknown enabled NMI hardware?!\n");
        }
done:
        return rc;
}

int do_nmi_callback(struct pt_regs * regs, int cpu)
{
#ifdef CONFIG_SYSCTL
        if (unknown_nmi_panic)
                return unknown_nmi_panic_callback(regs, cpu);
#endif
        return 0;
}

#ifdef CONFIG_SYSCTL

static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
{
        unsigned char reason = get_nmi_reason();
        char buf[64];

        sprintf(buf, "NMI received for unknown reason %02x\n", reason);
        die_nmi(regs, buf);
        return 0;
}

/*
 * proc handler for /proc/sys/kernel/nmi_watchdog
 */
int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
                        void __user *buffer, size_t *length, loff_t *ppos)
{
        int old_state;

        nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
        old_state = nmi_watchdog_enabled;
        proc_dointvec(table, write, file, buffer, length, ppos);
        if (!!old_state == !!nmi_watchdog_enabled)
                return 0;

        if (atomic_read(&nmi_active) < 0) {
                printk(KERN_WARNING "NMI watchdog is permanently disabled\n");
                return -EINVAL;
        }

        if (nmi_watchdog == NMI_DEFAULT) {
                if (nmi_known_cpu() > 0)
                        nmi_watchdog = NMI_LOCAL_APIC;
                else
                        nmi_watchdog = NMI_IO_APIC;
        }

        if (nmi_watchdog == NMI_LOCAL_APIC)
        {
                if (nmi_watchdog_enabled)
                        enable_lapic_nmi_watchdog();
                else
                        disable_lapic_nmi_watchdog();
        } else if (nmi_watchdog == NMI_IO_APIC) {
                /* FIXME
                 * for some reason these functions don't work
                 */
                printk("Can not enable/disable NMI on IO APIC\n");
                return -EINVAL;
#if 0
                if (nmi_watchdog_enabled)
                        enable_timer_nmi_watchdog();
                else
                        disable_timer_nmi_watchdog();
#endif
        } else {
                printk( KERN_WARNING
                        "NMI watchdog doesn't know what hardware to touch\n");
                return -EIO;
        }
        return 0;
}

#endif

EXPORT_SYMBOL(nmi_active);
EXPORT_SYMBOL(nmi_watchdog);
EXPORT_SYMBOL(avail_to_resrv_perfctr_nmi);
EXPORT_SYMBOL(avail_to_resrv_perfctr_nmi_bit);
EXPORT_SYMBOL(reserve_perfctr_nmi);
EXPORT_SYMBOL(release_perfctr_nmi);
EXPORT_SYMBOL(reserve_evntsel_nmi);
EXPORT_SYMBOL(release_evntsel_nmi);
EXPORT_SYMBOL(disable_timer_nmi_watchdog);
EXPORT_SYMBOL(enable_timer_nmi_watchdog);