arch/x86_64/kernel/nmi.c

   1 /*
   2  *  linux/arch/x86_64/nmi.c
   3  *
   4  *  NMI watchdog support on APIC systems
   5  *
   6  *  Started by Ingo Molnar <mingo@redhat.com>
   7  *
   8  *  Fixes:
   9  *  Mikael Pettersson   : AMD K7 support for local APIC NMI watchdog.
  10  *  Mikael Pettersson   : Power Management for local APIC NMI watchdog.
  11  *  Pavel Machek and
  12  *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
  13  */
  14
  15 #include <linux/mm.h>
  16 #include <linux/delay.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/module.h>
  19 #include <linux/sysdev.h>
  20 #include <linux/nmi.h>
  21 #include <linux/sysctl.h>
  22 #include <linux/kprobes.h>
  23
  24 #include <asm/smp.h>
  25 #include <asm/nmi.h>
  26 #include <asm/proto.h>
  27 #include <asm/kdebug.h>
  28 #include <asm/mce.h>
  29 #include <asm/intel_arch_perfmon.h>
  30
  31 /*
  32  * lapic_nmi_owner tracks the ownership of the lapic NMI hardware:
  33  * - it may be reserved by some other driver, or not
  34  * - when not reserved by some other driver, it may be used for
  35  *   the NMI watchdog, or not
  36  *
  37  * This is maintained separately from nmi_active because the NMI
  38  * watchdog may also be driven from the I/O APIC timer.
  39  */
  40 static DEFINE_SPINLOCK(lapic_nmi_owner_lock);
  41 static unsigned int lapic_nmi_owner;
  42 #define LAPIC_NMI_WATCHDOG      (1<<0)
  43 #define LAPIC_NMI_RESERVED      (1<<1)
  44
  45 /* nmi_active:
  46  * +1: the lapic NMI watchdog is active, but can be disabled
  47  *  0: the lapic NMI watchdog has not been set up, and cannot
  48  *     be enabled
  49  * -1: the lapic NMI watchdog is disabled, but can be enabled
  50  */
  51 int nmi_active;         /* oprofile uses this */
  52 int panic_on_timeout;
  53
  54 unsigned int nmi_watchdog = NMI_DEFAULT;
  55 static unsigned int nmi_hz = HZ;
  56 static unsigned int nmi_perfctr_msr;    /* the MSR to reset in NMI handler */
  57 static unsigned int nmi_p4_cccr_val;
  58
  59 /* Note that these events don't tick when the CPU idles. This means
  60    the frequency varies with CPU load. */
  61
  62 #define K7_EVNTSEL_ENABLE       (1 << 22)
  63 #define K7_EVNTSEL_INT          (1 << 20)
  64 #define K7_EVNTSEL_OS           (1 << 17)
  65 #define K7_EVNTSEL_USR          (1 << 16)
  66 #define K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING    0x76
  67 #define K7_NMI_EVENT            K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING
  68
  69 #define ARCH_PERFMON_NMI_EVENT_SEL      ARCH_PERFMON_UNHALTED_CORE_CYCLES_SEL
  70 #define ARCH_PERFMON_NMI_EVENT_UMASK    ARCH_PERFMON_UNHALTED_CORE_CYCLES_UMASK
  71
  72 #define MSR_P4_MISC_ENABLE      0x1A0
  73 #define MSR_P4_MISC_ENABLE_PERF_AVAIL   (1<<7)
  74 #define MSR_P4_MISC_ENABLE_PEBS_UNAVAIL (1<<12)
  75 #define MSR_P4_PERFCTR0         0x300
  76 #define MSR_P4_CCCR0            0x360
  77 #define P4_ESCR_EVENT_SELECT(N) ((N)<<25)
  78 #define P4_ESCR_OS              (1<<3)
  79 #define P4_ESCR_USR             (1<<2)
  80 #define P4_CCCR_OVF_PMI0        (1<<26)
  81 #define P4_CCCR_OVF_PMI1        (1<<27)
  82 #define P4_CCCR_THRESHOLD(N)    ((N)<<20)
  83 #define P4_CCCR_COMPLEMENT      (1<<19)
  84 #define P4_CCCR_COMPARE         (1<<18)
  85 #define P4_CCCR_REQUIRED        (3<<16)
  86 #define P4_CCCR_ESCR_SELECT(N)  ((N)<<13)
  87 #define P4_CCCR_ENABLE          (1<<12)
  88 /* Set up IQ_COUNTER0 to behave like a clock, by having IQ_CCCR0 filter
  89    CRU_ESCR0 (with any non-null event selector) through a complemented
  90    max threshold. [IA32-Vol3, Section 14.9.9] */
  91 #define MSR_P4_IQ_COUNTER0      0x30C
  92 #define P4_NMI_CRU_ESCR0        (P4_ESCR_EVENT_SELECT(0x3F)|P4_ESCR_OS|P4_ESCR_USR)
  93 #define P4_NMI_IQ_CCCR0 \
  94         (P4_CCCR_OVF_PMI0|P4_CCCR_THRESHOLD(15)|P4_CCCR_COMPLEMENT|     \
  95          P4_CCCR_COMPARE|P4_CCCR_REQUIRED|P4_CCCR_ESCR_SELECT(4)|P4_CCCR_ENABLE)
  96
  97 static __cpuinit inline int nmi_known_cpu(void)
  98 {
  99         switch (boot_cpu_data.x86_vendor) {
 100         case X86_VENDOR_AMD:
 101                 return boot_cpu_data.x86 == 15;
 102         case X86_VENDOR_INTEL:
 103                 if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
 104                         return 1;
 105                 else
 106                         return (boot_cpu_data.x86 == 15);
 107         }
 108         return 0;
 109 }
 110
 111 /* Run after command line and cpu_init init, but before all other checks */
 112 void __cpuinit nmi_watchdog_default(void)
 113 {
 114         if (nmi_watchdog != NMI_DEFAULT)
 115                 return;
 116         if (nmi_known_cpu())
 117                 nmi_watchdog = NMI_LOCAL_APIC;
 118         else
 119                 nmi_watchdog = NMI_IO_APIC;
 120 }
 121
 122 #ifdef CONFIG_SMP
 123 /* The performance counters used by NMI_LOCAL_APIC don't trigger when
 124  * the CPU is idle. To make sure the NMI watchdog really ticks on all
 125  * CPUs during the test make them busy.
 126  */
 127 static __init void nmi_cpu_busy(void *data)
 128 {
 129         volatile int *endflag = data;
 130         local_irq_enable_in_hardirq();
 131         /* Intentionally don't use cpu_relax here. This is
 132            to make sure that the performance counter really ticks,
 133            even if there is a simulator or similar that catches the
 134            pause instruction. On a real HT machine this is fine because
 135            all other CPUs are busy with "useless" delay loops and don't
 136            care if they get somewhat less cycles. */
 137         while (*endflag == 0)
 138                 barrier();
 139 }
 140 #endif
 141
 142 int __init check_nmi_watchdog (void)
 143 {
 144         volatile int endflag = 0;
 145         int *counts;
 146         int cpu;
 147
 148         counts = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
 149         if (!counts)
 150                 return -1;
 151
 152         printk(KERN_INFO "testing NMI watchdog ... ");
 153
 154 #ifdef CONFIG_SMP
 155         if (nmi_watchdog == NMI_LOCAL_APIC)
 156                 smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
 157 #endif
 158
 159         for (cpu = 0; cpu < NR_CPUS; cpu++)
 160                 counts[cpu] = cpu_pda(cpu)->__nmi_count;
 161         local_irq_enable();
 162         mdelay((10*1000)/nmi_hz); // wait 10 ticks
 163
 164         for_each_online_cpu(cpu) {
 165                 if (cpu_pda(cpu)->__nmi_count - counts[cpu] <= 5) {
 166                         endflag = 1;
 167                         printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 168                                cpu,
 169                                counts[cpu],
 170                                cpu_pda(cpu)->__nmi_count);
 171                         nmi_active = 0;
 172                         lapic_nmi_owner &= ~LAPIC_NMI_WATCHDOG;
 173                         nmi_perfctr_msr = 0;
 174                         kfree(counts);
 175                         return -1;
 176                 }
 177         }
 178         endflag = 1;
 179         printk("OK.\n");
 180
 181         /* now that we know it works we can reduce NMI frequency to
 182            something more reasonable; makes a difference in some configs */
 183         if (nmi_watchdog == NMI_LOCAL_APIC)
 184                 nmi_hz = 1;
 185
 186         kfree(counts);
 187         return 0;
 188 }
 189
 190 int __init setup_nmi_watchdog(char *str)
 191 {
 192         int nmi;
 193
 194         if (!strncmp(str,"panic",5)) {
 195                 panic_on_timeout = 1;
 196                 str = strchr(str, ',');
 197                 if (!str)
 198                         return 1;
 199                 ++str;
 200         }
 201
 202         get_option(&str, &nmi);
 203
 204         if (nmi >= NMI_INVALID)
 205                 return 0;
 206         nmi_watchdog = nmi;
 207         return 1;
 208 }
 209
 210 __setup("nmi_watchdog=", setup_nmi_watchdog);
 211
 212 static void disable_intel_arch_watchdog(void);
 213
 214 static void disable_lapic_nmi_watchdog(void)
 215 {
 216         if (nmi_active <= 0)
 217                 return;
 218         switch (boot_cpu_data.x86_vendor) {
 219         case X86_VENDOR_AMD:
 220                 wrmsr(MSR_K7_EVNTSEL0, 0, 0);
 221                 break;
 222         case X86_VENDOR_INTEL:
 223                 if (boot_cpu_data.x86 == 15) {
 224                         wrmsr(MSR_P4_IQ_CCCR0, 0, 0);
 225                         wrmsr(MSR_P4_CRU_ESCR0, 0, 0);
 226                 } else if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
 227                         disable_intel_arch_watchdog();
 228                 }
 229                 break;
 230         }
 231         nmi_active = -1;
 232         /* tell do_nmi() and others that we're not active any more */
 233         nmi_watchdog = 0;
 234 }
 235
 236 static void enable_lapic_nmi_watchdog(void)
 237 {
 238         if (nmi_active < 0) {
 239                 nmi_watchdog = NMI_LOCAL_APIC;
 240                 touch_nmi_watchdog();
 241                 setup_apic_nmi_watchdog();
 242         }
 243 }
 244
 245 int reserve_lapic_nmi(void)
 246 {
 247         unsigned int old_owner;
 248
 249         spin_lock(&lapic_nmi_owner_lock);
 250         old_owner = lapic_nmi_owner;
 251         lapic_nmi_owner |= LAPIC_NMI_RESERVED;
 252         spin_unlock(&lapic_nmi_owner_lock);
 253         if (old_owner & LAPIC_NMI_RESERVED)
 254                 return -EBUSY;
 255         if (old_owner & LAPIC_NMI_WATCHDOG)
 256                 disable_lapic_nmi_watchdog();
 257         return 0;
 258 }
 259
 260 void release_lapic_nmi(void)
 261 {
 262         unsigned int new_owner;
 263
 264         spin_lock(&lapic_nmi_owner_lock);
 265         new_owner = lapic_nmi_owner & ~LAPIC_NMI_RESERVED;
 266         lapic_nmi_owner = new_owner;
 267         spin_unlock(&lapic_nmi_owner_lock);
 268         if (new_owner & LAPIC_NMI_WATCHDOG)
 269                 enable_lapic_nmi_watchdog();
 270 }
 271
 272 void disable_timer_nmi_watchdog(void)
 273 {
 274         if ((nmi_watchdog != NMI_IO_APIC) || (nmi_active <= 0))
 275                 return;
 276
 277         disable_irq(0);
 278         unset_nmi_callback();
 279         nmi_active = -1;
 280         nmi_watchdog = NMI_NONE;
 281 }
 282
 283 void enable_timer_nmi_watchdog(void)
 284 {
 285         if (nmi_active < 0) {
 286                 nmi_watchdog = NMI_IO_APIC;
 287                 touch_nmi_watchdog();
 288                 nmi_active = 1;
 289                 enable_irq(0);
 290         }
 291 }
 292
 293 #ifdef CONFIG_PM
 294
 295 static int nmi_pm_active; /* nmi_active before suspend */
 296
 297 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
 298 {
 299         nmi_pm_active = nmi_active;
 300         disable_lapic_nmi_watchdog();
 301         return 0;
 302 }
 303
 304 static int lapic_nmi_resume(struct sys_device *dev)
 305 {
 306         if (nmi_pm_active > 0)
 307         enable_lapic_nmi_watchdog();
 308         return 0;
 309 }
 310
 311 static struct sysdev_class nmi_sysclass = {
 312         set_kset_name("lapic_nmi"),
 313         .resume         = lapic_nmi_resume,
 314         .suspend        = lapic_nmi_suspend,
 315 };
 316
 317 static struct sys_device device_lapic_nmi = {
 318         .id             = 0,
 319         .cls    = &nmi_sysclass,
 320 };
 321
 322 static int __init init_lapic_nmi_sysfs(void)
 323 {
 324         int error;
 325
 326         if (nmi_active == 0 || nmi_watchdog != NMI_LOCAL_APIC)
 327                 return 0;
 328
 329         error = sysdev_class_register(&nmi_sysclass);
 330         if (!error)
 331                 error = sysdev_register(&device_lapic_nmi);
 332         return error;
 333 }
 334 /* must come after the local APIC's device_initcall() */
 335 late_initcall(init_lapic_nmi_sysfs);
 336
 337 #endif  /* CONFIG_PM */
 338
 339 /*
 340  * Activate the NMI watchdog via the local APIC.
 341  * Original code written by Keith Owens.
 342  */
 343
 344 static void clear_msr_range(unsigned int base, unsigned int n)
 345 {
 346         unsigned int i;
 347
 348         for(i = 0; i < n; ++i)
 349                 wrmsr(base+i, 0, 0);
 350 }
 351
 352 static void setup_k7_watchdog(void)
 353 {
 354         int i;
 355         unsigned int evntsel;
 356
 357         nmi_perfctr_msr = MSR_K7_PERFCTR0;
 358
 359         for(i = 0; i < 4; ++i) {
 360                 /* Simulator may not support it */
 361                 if (checking_wrmsrl(MSR_K7_EVNTSEL0+i, 0UL)) {
 362                         nmi_perfctr_msr = 0;
 363                         return;
 364                 }
 365                 wrmsrl(MSR_K7_PERFCTR0+i, 0UL);
 366         }
 367
 368         evntsel = K7_EVNTSEL_INT
 369                 | K7_EVNTSEL_OS
 370                 | K7_EVNTSEL_USR
 371                 | K7_NMI_EVENT;
 372
 373         wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
 374         wrmsrl(MSR_K7_PERFCTR0, -((u64)cpu_khz * 1000 / nmi_hz));
 375         apic_write(APIC_LVTPC, APIC_DM_NMI);
 376         evntsel |= K7_EVNTSEL_ENABLE;
 377         wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
 378 }
 379
 380 static void disable_intel_arch_watchdog(void)
 381 {
 382         unsigned ebx;
 383
 384         /*
 385          * Check whether the Architectural PerfMon supports
 386          * Unhalted Core Cycles Event or not.
 387          * NOTE: Corresponding bit = 0 in ebp indicates event present.
 388          */
 389         ebx = cpuid_ebx(10);
 390         if (!(ebx & ARCH_PERFMON_UNHALTED_CORE_CYCLES_PRESENT))
 391                 wrmsr(MSR_ARCH_PERFMON_EVENTSEL0, 0, 0);
 392 }
 393
 394 static int setup_intel_arch_watchdog(void)
 395 {
 396         unsigned int evntsel;
 397         unsigned ebx;
 398
 399         /*
 400          * Check whether the Architectural PerfMon supports
 401          * Unhalted Core Cycles Event or not.
 402          * NOTE: Corresponding bit = 0 in ebp indicates event present.
 403          */
 404         ebx = cpuid_ebx(10);
 405         if ((ebx & ARCH_PERFMON_UNHALTED_CORE_CYCLES_PRESENT))
 406                 return 0;
 407
 408         nmi_perfctr_msr = MSR_ARCH_PERFMON_PERFCTR0;
 409
 410         clear_msr_range(MSR_ARCH_PERFMON_EVENTSEL0, 2);
 411         clear_msr_range(MSR_ARCH_PERFMON_PERFCTR0, 2);
 412
 413         evntsel = ARCH_PERFMON_EVENTSEL_INT
 414                 | ARCH_PERFMON_EVENTSEL_OS
 415                 | ARCH_PERFMON_EVENTSEL_USR
 416                 | ARCH_PERFMON_NMI_EVENT_SEL
 417                 | ARCH_PERFMON_NMI_EVENT_UMASK;
 418
 419         wrmsr(MSR_ARCH_PERFMON_EVENTSEL0, evntsel, 0);
 420         wrmsrl(MSR_ARCH_PERFMON_PERFCTR0, -((u64)cpu_khz * 1000 / nmi_hz));
 421         apic_write(APIC_LVTPC, APIC_DM_NMI);
 422         evntsel |= ARCH_PERFMON_EVENTSEL0_ENABLE;
 423         wrmsr(MSR_ARCH_PERFMON_EVENTSEL0, evntsel, 0);
 424         return 1;
 425 }
 426
 427
 428 static int setup_p4_watchdog(void)
 429 {
 430         unsigned int misc_enable, dummy;
 431
 432         rdmsr(MSR_P4_MISC_ENABLE, misc_enable, dummy);
 433         if (!(misc_enable & MSR_P4_MISC_ENABLE_PERF_AVAIL))
 434                 return 0;
 435
 436         nmi_perfctr_msr = MSR_P4_IQ_COUNTER0;
 437         nmi_p4_cccr_val = P4_NMI_IQ_CCCR0;
 438 #ifdef CONFIG_SMP
 439         if (smp_num_siblings == 2)
 440                 nmi_p4_cccr_val |= P4_CCCR_OVF_PMI1;
 441 #endif
 442
 443         if (!(misc_enable & MSR_P4_MISC_ENABLE_PEBS_UNAVAIL))
 444                 clear_msr_range(0x3F1, 2);
 445         /* MSR 0x3F0 seems to have a default value of 0xFC00, but current
 446            docs doesn't fully define it, so leave it alone for now. */
 447         if (boot_cpu_data.x86_model >= 0x3) {
 448                 /* MSR_P4_IQ_ESCR0/1 (0x3ba/0x3bb) removed */
 449                 clear_msr_range(0x3A0, 26);
 450                 clear_msr_range(0x3BC, 3);
 451         } else {
 452                 clear_msr_range(0x3A0, 31);
 453         }
 454         clear_msr_range(0x3C0, 6);
 455         clear_msr_range(0x3C8, 6);
 456         clear_msr_range(0x3E0, 2);
 457         clear_msr_range(MSR_P4_CCCR0, 18);
 458         clear_msr_range(MSR_P4_PERFCTR0, 18);
 459
 460         wrmsr(MSR_P4_CRU_ESCR0, P4_NMI_CRU_ESCR0, 0);
 461         wrmsr(MSR_P4_IQ_CCCR0, P4_NMI_IQ_CCCR0 & ~P4_CCCR_ENABLE, 0);
 462         Dprintk("setting P4_IQ_COUNTER0 to 0x%08lx\n", -(cpu_khz * 1000UL / nmi_hz));
 463         wrmsrl(MSR_P4_IQ_COUNTER0, -((u64)cpu_khz * 1000 / nmi_hz));
 464         apic_write(APIC_LVTPC, APIC_DM_NMI);
 465         wrmsr(MSR_P4_IQ_CCCR0, nmi_p4_cccr_val, 0);
 466         return 1;
 467 }
 468
 469 void setup_apic_nmi_watchdog(void)
 470 {
 471         switch (boot_cpu_data.x86_vendor) {
 472         case X86_VENDOR_AMD:
 473                 if (boot_cpu_data.x86 != 15)
 474                         return;
 475                 if (strstr(boot_cpu_data.x86_model_id, "Screwdriver"))
 476                         return;
 477                 setup_k7_watchdog();
 478                 break;
 479         case X86_VENDOR_INTEL:
 480                 if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
 481                         if (!setup_intel_arch_watchdog())
 482                                 return;
 483                 } else if (boot_cpu_data.x86 == 15) {
 484                         if (!setup_p4_watchdog())
 485                                 return;
 486                 } else {
 487                         return;
 488                 }
 489
 490                 break;
 491
 492         default:
 493                 return;
 494         }
 495         lapic_nmi_owner = LAPIC_NMI_WATCHDOG;
 496         nmi_active = 1;
 497 }
 498
 499 /*
 500  * the best way to detect whether a CPU has a 'hard lockup' problem
 501  * is to check it's local APIC timer IRQ counts. If they are not
 502  * changing then that CPU has some problem.
 503  *
 504  * as these watchdog NMI IRQs are generated on every CPU, we only
 505  * have to check the current processor.
 506  */
 507
 508 static DEFINE_PER_CPU(unsigned, last_irq_sum);
 509 static DEFINE_PER_CPU(local_t, alert_counter);
 510 static DEFINE_PER_CPU(int, nmi_touch);
 511
 512 void touch_nmi_watchdog (void)
 513 {
 514         if (nmi_watchdog > 0) {
 515                 unsigned cpu;
 516
 517                 /*
 518                  * Tell other CPUs to reset their alert counters. We cannot
 519                  * do it ourselves because the alert count increase is not
 520                  * atomic.
 521                  */
 522                 for_each_present_cpu (cpu)
 523                         per_cpu(nmi_touch, cpu) = 1;
 524         }
 525
 526         touch_softlockup_watchdog();
 527 }
 528
 529 void __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
 530 {
 531         int sum;
 532         int touched = 0;
 533
 534         sum = read_pda(apic_timer_irqs);
 535         if (__get_cpu_var(nmi_touch)) {
 536                 __get_cpu_var(nmi_touch) = 0;
 537                 touched = 1;
 538         }
 539 #ifdef CONFIG_X86_MCE
 540         /* Could check oops_in_progress here too, but it's safer
 541            not too */
 542         if (atomic_read(&mce_entry) > 0)
 543                 touched = 1;
 544 #endif
 545         if (!touched && __get_cpu_var(last_irq_sum) == sum) {
 546                 /*
 547                  * Ayiee, looks like this CPU is stuck ...
 548                  * wait a few IRQs (5 seconds) before doing the oops ...
 549                  */
 550                 local_inc(&__get_cpu_var(alert_counter));
 551                 if (local_read(&__get_cpu_var(alert_counter)) == 5*nmi_hz) {
 552                         if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
 553                                                         == NOTIFY_STOP) {
 554                                 local_set(&__get_cpu_var(alert_counter), 0);
 555                                 return;
 556                         }
 557                         die_nmi("NMI Watchdog detected LOCKUP on CPU %d\n", regs);
 558                 }
 559         } else {
 560                 __get_cpu_var(last_irq_sum) = sum;
 561                 local_set(&__get_cpu_var(alert_counter), 0);
 562         }
 563         if (nmi_perfctr_msr) {
 564                 if (nmi_perfctr_msr == MSR_P4_IQ_COUNTER0) {
 565                         /*
 566                          * P4 quirks:
 567                          * - An overflown perfctr will assert its interrupt
 568                          *   until the OVF flag in its CCCR is cleared.
 569                          * - LVTPC is masked on interrupt and must be
 570                          *   unmasked by the LVTPC handler.
 571                          */
 572                         wrmsr(MSR_P4_IQ_CCCR0, nmi_p4_cccr_val, 0);
 573                         apic_write(APIC_LVTPC, APIC_DM_NMI);
 574                 } else if (nmi_perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) {
 575                         /*
 576                          * For Intel based architectural perfmon
 577                          * - LVTPC is masked on interrupt and must be
 578                          *   unmasked by the LVTPC handler.
 579                          */
 580                         apic_write(APIC_LVTPC, APIC_DM_NMI);
 581                 }
 582                 wrmsrl(nmi_perfctr_msr, -((u64)cpu_khz * 1000 / nmi_hz));
 583         }
 584 }
 585
 586 static __kprobes int dummy_nmi_callback(struct pt_regs * regs, int cpu)
 587 {
 588         return 0;
 589 }
 590
 591 static nmi_callback_t nmi_callback = dummy_nmi_callback;
 592
 593 asmlinkage __kprobes void do_nmi(struct pt_regs * regs, long error_code)
 594 {
 595         int cpu = safe_smp_processor_id();
 596
 597         nmi_enter();
 598         add_pda(__nmi_count,1);
 599         if (!rcu_dereference(nmi_callback)(regs, cpu))
 600                 default_do_nmi(regs);
 601         nmi_exit();
 602 }
 603
 604 void set_nmi_callback(nmi_callback_t callback)
 605 {
 606         vmalloc_sync_all();
 607         rcu_assign_pointer(nmi_callback, callback);
 608 }
 609 EXPORT_SYMBOL_GPL(set_nmi_callback);
 610
 611 void unset_nmi_callback(void)
 612 {
 613         nmi_callback = dummy_nmi_callback;
 614 }
 615 EXPORT_SYMBOL_GPL(unset_nmi_callback);
 616
 617 #ifdef CONFIG_SYSCTL
 618
 619 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
 620 {
 621         unsigned char reason = get_nmi_reason();
 622         char buf[64];
 623
 624         if (!(reason & 0xc0)) {
 625                 sprintf(buf, "NMI received for unknown reason %02x\n", reason);
 626                 die_nmi(buf,regs);
 627         }
 628         return 0;
 629 }
 630
 631 /*
 632  * proc handler for /proc/sys/kernel/unknown_nmi_panic
 633  */
 634 int proc_unknown_nmi_panic(struct ctl_table *table, int write, struct file *file,
 635                         void __user *buffer, size_t *length, loff_t *ppos)
 636 {
 637         int old_state;
 638
 639         old_state = unknown_nmi_panic;
 640         proc_dointvec(table, write, file, buffer, length, ppos);
 641         if (!!old_state == !!unknown_nmi_panic)
 642                 return 0;
 643
 644         if (unknown_nmi_panic) {
 645                 if (reserve_lapic_nmi() < 0) {
 646                         unknown_nmi_panic = 0;
 647                         return -EBUSY;
 648                 } else {
 649                         set_nmi_callback(unknown_nmi_panic_callback);
 650                 }
 651         } else {
 652                 release_lapic_nmi();
 653                 unset_nmi_callback();
 654         }
 655         return 0;
 656 }
 657
 658 #endif
 659
 660 EXPORT_SYMBOL(nmi_active);
 661 EXPORT_SYMBOL(nmi_watchdog);
 662 EXPORT_SYMBOL(reserve_lapic_nmi);
 663 EXPORT_SYMBOL(release_lapic_nmi);
 664 EXPORT_SYMBOL(disable_timer_nmi_watchdog);
 665 EXPORT_SYMBOL(enable_timer_nmi_watchdog);
 666 EXPORT_SYMBOL(touch_nmi_watchdog);