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[hh.org.git] / arch / x86_64 / kernel / nmi.c

/*
 *  linux/arch/x86_64/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.
 *  Pavel Machek and
 *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
 */

#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/sysdev.h>
#include <linux/nmi.h>
#include <linux/sysctl.h>
#include <linux/kprobes.h>

#include <asm/smp.h>
#include <asm/nmi.h>
#include <asm/proto.h>
#include <asm/kdebug.h>
#include <asm/mce.h>
#include <asm/intel_arch_perfmon.h>

int unknown_nmi_panic;
int nmi_watchdog_enabled;
int panic_on_unrecovered_nmi;

/* 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, perfctr_nmi_owner);
static DEFINE_PER_CPU(unsigned, evntsel_nmi_owner[2]);

/* 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 */
int panic_on_timeout;

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 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)
{
        /* 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:
                if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
                        return (msr - MSR_ARCH_PERFMON_PERFCTR0);
                else
                        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:
                if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
                        return (msr - MSR_ARCH_PERFMON_EVENTSEL0);
                else
                        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)))
                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));
}

static __cpuinit inline int nmi_known_cpu(void)
{
        switch (boot_cpu_data.x86_vendor) {
        case X86_VENDOR_AMD:
                return boot_cpu_data.x86 == 15;
        case X86_VENDOR_INTEL:
                if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
                        return 1;
                else
                        return (boot_cpu_data.x86 == 15);
        }
        return 0;
}

/* Run after command line and cpu_init init, but before all other checks */
void nmi_watchdog_default(void)
{
        if (nmi_watchdog != NMI_DEFAULT)
                return;
        if (nmi_known_cpu())
                nmi_watchdog = NMI_LOCAL_APIC;
        else
                nmi_watchdog = NMI_IO_APIC;
}

#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

int __init check_nmi_watchdog (void)
{
        volatile int endflag = 0;
        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;

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

#ifdef CONFIG_SMP
        if (nmi_watchdog == NMI_LOCAL_APIC)
                smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
#endif

        for (cpu = 0; cpu < NR_CPUS; cpu++)
                counts[cpu] = cpu_pda(cpu)->__nmi_count;
        local_irq_enable();
        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) {
                        printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
                               cpu,
                               counts[cpu],
                               cpu_pda(cpu)->__nmi_count);
                        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");

        /* 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) {
                struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

                nmi_hz = 1;
                /*
                 * On Intel CPUs with ARCH_PERFMON only 32 bits in the counter
                 * are writable, with higher bits sign extending from bit 31.
                 * So, we can only program the counter with 31 bit values and
                 * 32nd bit should be 1, for 33.. to be 1.
                 * Find the appropriate nmi_hz
                 */
                if (wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0 &&
                        ((u64)cpu_khz * 1000) > 0x7fffffffULL) {
                        nmi_hz = ((u64)cpu_khz * 1000) / 0x7fffffffUL + 1;
                }
        }

        kfree(counts);
        return 0;
}

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

        if (!strncmp(str,"panic",5)) {
                panic_on_timeout = 1;
                str = strchr(str, ',');
                if (!str)
                        return 1;
                ++str;
        }

        get_option(&str, &nmi);

        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;
}

__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)
{
        /* only CPU0 goes here, other CPUs should be offline */
        nmi_pm_active = atomic_read(&nmi_active);
        stop_apic_nmi_watchdog(NULL);
        BUG_ON(atomic_read(&nmi_active) != 0);
        return 0;
}

static int lapic_nmi_resume(struct sys_device *dev)
{
        /* only CPU0 goes here, other CPUs should be offline */
        if (nmi_pm_active > 0) {
                setup_apic_nmi_watchdog(NULL);
                touch_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.
 */

/* 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;

        /* Simulator may not support it */
        if (checking_wrmsrl(evntsel_msr, 0UL))
                goto fail2;
        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);
        wrmsrl(perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
        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;
fail2:
        release_evntsel_nmi(evntsel_msr);
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);
}

/* 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);
        wrmsrl(perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
        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);
}

#define ARCH_PERFMON_NMI_EVENT_SEL      ARCH_PERFMON_UNHALTED_CORE_CYCLES_SEL
#define ARCH_PERFMON_NMI_EVENT_UMASK    ARCH_PERFMON_UNHALTED_CORE_CYCLES_UMASK

static int setup_intel_arch_watchdog(void)
{
        unsigned int ebx;
        union cpuid10_eax eax;
        unsigned int unused;
        unsigned int perfctr_msr, evntsel_msr;
        unsigned int evntsel;
        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

        /*
         * Check whether the Architectural PerfMon supports
         * Unhalted Core Cycles Event or not.
         * NOTE: Corresponding bit = 0 in ebx indicates event present.
         */
        cpuid(10, &(eax.full), &ebx, &unused, &unused);
        if ((eax.split.mask_length < (ARCH_PERFMON_UNHALTED_CORE_CYCLES_INDEX+1)) ||
            (ebx & ARCH_PERFMON_UNHALTED_CORE_CYCLES_PRESENT))
                goto fail;

        perfctr_msr = MSR_ARCH_PERFMON_PERFCTR0;
        evntsel_msr = MSR_ARCH_PERFMON_EVENTSEL0;

        if (!reserve_perfctr_nmi(perfctr_msr))
                goto fail;

        if (!reserve_evntsel_nmi(evntsel_msr))
                goto fail1;

        wrmsrl(perfctr_msr, 0UL);

        evntsel = ARCH_PERFMON_EVENTSEL_INT
                | ARCH_PERFMON_EVENTSEL_OS
                | ARCH_PERFMON_EVENTSEL_USR
                | ARCH_PERFMON_NMI_EVENT_SEL
                | ARCH_PERFMON_NMI_EVENT_UMASK;

        /* 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 |= ARCH_PERFMON_EVENTSEL0_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 << (eax.split.bit_width - 1);
        return 1;
fail1:
        release_perfctr_nmi(perfctr_msr);
fail:
        return 0;
}

static void stop_intel_arch_watchdog(void)
{
        unsigned int ebx;
        union cpuid10_eax eax;
        unsigned int unused;
        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

        /*
         * Check whether the Architectural PerfMon supports
         * Unhalted Core Cycles Event or not.
         * NOTE: Corresponding bit = 0 in ebx indicates event present.
         */
        cpuid(10, &(eax.full), &ebx, &unused, &unused);
        if ((eax.split.mask_length < (ARCH_PERFMON_UNHALTED_CORE_CYCLES_INDEX+1)) ||
            (ebx & ARCH_PERFMON_UNHALTED_CORE_CYCLES_PRESENT))
                return;

        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)
{
        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

        /* only support LOCAL and IO APICs for now */
        if ((nmi_watchdog != NMI_LOCAL_APIC) &&
            (nmi_watchdog != NMI_IO_APIC))
                return;

        if (wd->enabled == 1)
                return;

        /* cheap hack to support suspend/resume */
        /* if cpu0 is not active neither should the other cpus */
        if ((smp_processor_id() != 0) && (atomic_read(&nmi_active) <= 0))
                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;
                        if (!setup_k7_watchdog())
                                return;
                        break;
                case X86_VENDOR_INTEL:
                        if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
                                if (!setup_intel_arch_watchdog())
                                        return;
                                break;
                        }
                        if (!setup_p4_watchdog())
                                return;
                        break;
                default:
                        return;
                }
        }
        wd->enabled = 1;
        atomic_inc(&nmi_active);
}

void stop_apic_nmi_watchdog(void *unused)
{
        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

        /* only support LOCAL and IO APICs for now */
        if ((nmi_watchdog != NMI_LOCAL_APIC) &&
            (nmi_watchdog != NMI_IO_APIC))
                return;

        if (wd->enabled == 0)
                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:
                        if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
                                stop_intel_arch_watchdog();
                                break;
                        }
                        stop_p4_watchdog();
                        break;
                default:
                        return;
                }
        }
        wd->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.
 */

static DEFINE_PER_CPU(unsigned, last_irq_sum);
static DEFINE_PER_CPU(local_t, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);

void touch_nmi_watchdog (void)
{
        if (nmi_watchdog > 0) {
                unsigned cpu;

                /*
                 * Tell other CPUs to reset their alert counters. We cannot
                 * do it ourselves because the alert count increase is not
                 * atomic.
                 */
                for_each_present_cpu (cpu)
                        per_cpu(nmi_touch, cpu) = 1;
        }

        touch_softlockup_watchdog();
}

int __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;
        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 = 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)
                        die_nmi("NMI Watchdog detected LOCKUP on CPU %d\n", regs,
                                panic_on_timeout);
        } else {
                __get_cpu_var(last_irq_sum) = sum;
                local_set(&__get_cpu_var(alert_counter), 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 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_ARCH_PERFMON_PERFCTR0) {
                                /*
                                 * ArchPerfom/Core Duo needs to re-unmask
                                 * the apic vector
                                 */
                                apic_write(APIC_LVTPC, APIC_DM_NMI);
                        }
                        /* start the cycle over again */
                        wrmsrl(wd->perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
                        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;
}

asmlinkage __kprobes void do_nmi(struct pt_regs * regs, long error_code)
{
        nmi_enter();
        add_pda(__nmi_count,1);
        default_do_nmi(regs);
        nmi_exit();
}

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(buf, regs, 1);  /* Always panic here */
        return 0;
}

/*
 * proc handler for /proc/sys/kernel/nmi
 */
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 -EIO;
        }

        /* if nmi_watchdog is not set yet, then set it */
        nmi_watchdog_default();

        if (nmi_watchdog == NMI_LOCAL_APIC) {
                if (nmi_watchdog_enabled)
                        enable_lapic_nmi_watchdog();
                else
                        disable_lapic_nmi_watchdog();
        } 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);
EXPORT_SYMBOL(touch_nmi_watchdog);