arch/x86/kernel/cpu/mcheck/mce_amd.c

   1 /*
   2  *  (c) 2005, 2006 Advanced Micro Devices, Inc.
   3  *  Your use of this code is subject to the terms and conditions of the
   4  *  GNU general public license version 2. See "COPYING" or
   5  *  http://www.gnu.org/licenses/gpl.html
   6  *
   7  *  Written by Jacob Shin - AMD, Inc.
   8  *
   9  *  Support : jacob.shin@amd.com
  10  *
  11  *  April 2006
  12  *     - added support for AMD Family 0x10 processors
  13  *
  14  *  All MC4_MISCi registers are shared between multi-cores
  15  */
  16 #include <linux/interrupt.h>
  17 #include <linux/notifier.h>
  18 #include <linux/kobject.h>
  19 #include <linux/percpu.h>
  20 #include <linux/sysdev.h>
  21 #include <linux/errno.h>
  22 #include <linux/sched.h>
  23 #include <linux/sysfs.h>
  24 #include <linux/slab.h>
  25 #include <linux/init.h>
  26 #include <linux/cpu.h>
  27 #include <linux/smp.h>
  28
  29 #include <asm/apic.h>
  30 #include <asm/idle.h>
  31 #include <asm/mce.h>
  32 #include <asm/msr.h>
  33
  34 #define NR_BANKS          6
  35 #define NR_BLOCKS         9
  36 #define THRESHOLD_MAX     0xFFF
  37 #define INT_TYPE_APIC     0x00020000
  38 #define MASK_VALID_HI     0x80000000
  39 #define MASK_CNTP_HI      0x40000000
  40 #define MASK_LOCKED_HI    0x20000000
  41 #define MASK_LVTOFF_HI    0x00F00000
  42 #define MASK_COUNT_EN_HI  0x00080000
  43 #define MASK_INT_TYPE_HI  0x00060000
  44 #define MASK_OVERFLOW_HI  0x00010000
  45 #define MASK_ERR_COUNT_HI 0x00000FFF
  46 #define MASK_BLKPTR_LO    0xFF000000
  47 #define MCG_XBLK_ADDR     0xC0000400
  48
  49 struct threshold_block {
  50         unsigned int            block;
  51         unsigned int            bank;
  52         unsigned int            cpu;
  53         u32                     address;
  54         u16                     interrupt_enable;
  55         u16                     threshold_limit;
  56         struct kobject          kobj;
  57         struct list_head        miscj;
  58 };
  59
  60 struct threshold_bank {
  61         struct kobject          *kobj;
  62         struct threshold_block  *blocks;
  63         cpumask_var_t           cpus;
  64 };
  65 static DEFINE_PER_CPU(struct threshold_bank * [NR_BANKS], threshold_banks);
  66
  67 #ifdef CONFIG_SMP
  68 static unsigned char shared_bank[NR_BANKS] = {
  69         0, 0, 0, 0, 1
  70 };
  71 #endif
  72
  73 static DEFINE_PER_CPU(unsigned char, bank_map); /* see which banks are on */
  74
  75 static void amd_threshold_interrupt(void);
  76
  77 /*
  78  * CPU Initialization
  79  */
  80
  81 struct thresh_restart {
  82         struct threshold_block  *b;
  83         int                     reset;
  84         int                     set_lvt_off;
  85         int                     lvt_off;
  86         u16                     old_limit;
  87 };
  88
  89 static int lvt_off_valid(struct threshold_block *b, int apic, u32 lo, u32 hi)
  90 {
  91         int msr = (hi & MASK_LVTOFF_HI) >> 20;
  92
  93         if (apic < 0) {
  94                 pr_err(FW_BUG "cpu %d, failed to setup threshold interrupt "
  95                        "for bank %d, block %d (MSR%08X=0x%x%08x)\n", b->cpu,
  96                        b->bank, b->block, b->address, hi, lo);
  97                 return 0;
  98         }
  99
 100         if (apic != msr) {
 101                 pr_err(FW_BUG "cpu %d, invalid threshold interrupt offset %d "
 102                        "for bank %d, block %d (MSR%08X=0x%x%08x)\n",
 103                        b->cpu, apic, b->bank, b->block, b->address, hi, lo);
 104                 return 0;
 105         }
 106
 107         return 1;
 108 };
 109
 110 /* must be called with correct cpu affinity */
 111 /* Called via smp_call_function_single() */
 112 static void threshold_restart_bank(void *_tr)
 113 {
 114         struct thresh_restart *tr = _tr;
 115         u32 hi, lo;
 116
 117         rdmsr(tr->b->address, lo, hi);
 118
 119         if (tr->b->threshold_limit < (hi & THRESHOLD_MAX))
 120                 tr->reset = 1;  /* limit cannot be lower than err count */
 121
 122         if (tr->reset) {                /* reset err count and overflow bit */
 123                 hi =
 124                     (hi & ~(MASK_ERR_COUNT_HI | MASK_OVERFLOW_HI)) |
 125                     (THRESHOLD_MAX - tr->b->threshold_limit);
 126         } else if (tr->old_limit) {     /* change limit w/o reset */
 127                 int new_count = (hi & THRESHOLD_MAX) +
 128                     (tr->old_limit - tr->b->threshold_limit);
 129
 130                 hi = (hi & ~MASK_ERR_COUNT_HI) |
 131                     (new_count & THRESHOLD_MAX);
 132         }
 133
 134         if (tr->set_lvt_off) {
 135                 if (lvt_off_valid(tr->b, tr->lvt_off, lo, hi)) {
 136                         /* set new lvt offset */
 137                         hi &= ~MASK_LVTOFF_HI;
 138                         hi |= tr->lvt_off << 20;
 139                 }
 140         }
 141
 142         tr->b->interrupt_enable ?
 143             (hi = (hi & ~MASK_INT_TYPE_HI) | INT_TYPE_APIC) :
 144             (hi &= ~MASK_INT_TYPE_HI);
 145
 146         hi |= MASK_COUNT_EN_HI;
 147         wrmsr(tr->b->address, lo, hi);
 148 }
 149
 150 static void mce_threshold_block_init(struct threshold_block *b, int offset)
 151 {
 152         struct thresh_restart tr = {
 153                 .b                      = b,
 154                 .set_lvt_off            = 1,
 155                 .lvt_off                = offset,
 156         };
 157
 158         b->threshold_limit              = THRESHOLD_MAX;
 159         threshold_restart_bank(&tr);
 160 };
 161
 162 static int setup_APIC_mce(int reserved, int new)
 163 {
 164         if (reserved < 0 && !setup_APIC_eilvt(new, THRESHOLD_APIC_VECTOR,
 165                                               APIC_EILVT_MSG_FIX, 0))
 166                 return new;
 167
 168         return reserved;
 169 }
 170
 171 /* cpu init entry point, called from mce.c with preempt off */
 172 void mce_amd_feature_init(struct cpuinfo_x86 *c)
 173 {
 174         struct threshold_block b;
 175         unsigned int cpu = smp_processor_id();
 176         u32 low = 0, high = 0, address = 0;
 177         unsigned int bank, block;
 178         int offset = -1;
 179
 180         for (bank = 0; bank < NR_BANKS; ++bank) {
 181                 for (block = 0; block < NR_BLOCKS; ++block) {
 182                         if (block == 0)
 183                                 address = MSR_IA32_MC0_MISC + bank * 4;
 184                         else if (block == 1) {
 185                                 address = (low & MASK_BLKPTR_LO) >> 21;
 186                                 if (!address)
 187                                         break;
 188
 189                                 address += MCG_XBLK_ADDR;
 190                         } else
 191                                 ++address;
 192
 193                         if (rdmsr_safe(address, &low, &high))
 194                                 break;
 195
 196                         if (!(high & MASK_VALID_HI))
 197                                 continue;
 198
 199                         if (!(high & MASK_CNTP_HI)  ||
 200                              (high & MASK_LOCKED_HI))
 201                                 continue;
 202
 203                         if (!block)
 204                                 per_cpu(bank_map, cpu) |= (1 << bank);
 205 #ifdef CONFIG_SMP
 206                         if (shared_bank[bank] && c->cpu_core_id)
 207                                 break;
 208 #endif
 209                         offset = setup_APIC_mce(offset,
 210                                                 (high & MASK_LVTOFF_HI) >> 20);
 211
 212                         memset(&b, 0, sizeof(b));
 213                         b.cpu           = cpu;
 214                         b.bank          = bank;
 215                         b.block         = block;
 216                         b.address       = address;
 217
 218                         mce_threshold_block_init(&b, offset);
 219                         mce_threshold_vector = amd_threshold_interrupt;
 220                 }
 221         }
 222 }
 223
 224 /*
 225  * APIC Interrupt Handler
 226  */
 227
 228 /*
 229  * threshold interrupt handler will service THRESHOLD_APIC_VECTOR.
 230  * the interrupt goes off when error_count reaches threshold_limit.
 231  * the handler will simply log mcelog w/ software defined bank number.
 232  */
 233 static void amd_threshold_interrupt(void)
 234 {
 235         u32 low = 0, high = 0, address = 0;
 236         unsigned int bank, block;
 237         struct mce m;
 238
 239         mce_setup(&m);
 240
 241         /* assume first bank caused it */
 242         for (bank = 0; bank < NR_BANKS; ++bank) {
 243                 if (!(per_cpu(bank_map, m.cpu) & (1 << bank)))
 244                         continue;
 245                 for (block = 0; block < NR_BLOCKS; ++block) {
 246                         if (block == 0) {
 247                                 address = MSR_IA32_MC0_MISC + bank * 4;
 248                         } else if (block == 1) {
 249                                 address = (low & MASK_BLKPTR_LO) >> 21;
 250                                 if (!address)
 251                                         break;
 252                                 address += MCG_XBLK_ADDR;
 253                         } else {
 254                                 ++address;
 255                         }
 256
 257                         if (rdmsr_safe(address, &low, &high))
 258                                 break;
 259
 260                         if (!(high & MASK_VALID_HI)) {
 261                                 if (block)
 262                                         continue;
 263                                 else
 264                                         break;
 265                         }
 266
 267                         if (!(high & MASK_CNTP_HI)  ||
 268                              (high & MASK_LOCKED_HI))
 269                                 continue;
 270
 271                         /*
 272                          * Log the machine check that caused the threshold
 273                          * event.
 274                          */
 275                         machine_check_poll(MCP_TIMESTAMP,
 276                                         &__get_cpu_var(mce_poll_banks));
 277
 278                         if (high & MASK_OVERFLOW_HI) {
 279                                 rdmsrl(address, m.misc);
 280                                 rdmsrl(MSR_IA32_MC0_STATUS + bank * 4,
 281                                        m.status);
 282                                 m.bank = K8_MCE_THRESHOLD_BASE
 283                                        + bank * NR_BLOCKS
 284                                        + block;
 285                                 mce_log(&m);
 286                                 return;
 287                         }
 288                 }
 289         }
 290 }
 291
 292 /*
 293  * Sysfs Interface
 294  */
 295
 296 struct threshold_attr {
 297         struct attribute attr;
 298         ssize_t (*show) (struct threshold_block *, char *);
 299         ssize_t (*store) (struct threshold_block *, const char *, size_t count);
 300 };
 301
 302 #define SHOW_FIELDS(name)                                               \
 303 static ssize_t show_ ## name(struct threshold_block *b, char *buf)      \
 304 {                                                                       \
 305         return sprintf(buf, "%lx\n", (unsigned long) b->name);          \
 306 }
 307 SHOW_FIELDS(interrupt_enable)
 308 SHOW_FIELDS(threshold_limit)
 309
 310 static ssize_t
 311 store_interrupt_enable(struct threshold_block *b, const char *buf, size_t size)
 312 {
 313         struct thresh_restart tr;
 314         unsigned long new;
 315
 316         if (strict_strtoul(buf, 0, &new) < 0)
 317                 return -EINVAL;
 318
 319         b->interrupt_enable = !!new;
 320
 321         memset(&tr, 0, sizeof(tr));
 322         tr.b            = b;
 323
 324         smp_call_function_single(b->cpu, threshold_restart_bank, &tr, 1);
 325
 326         return size;
 327 }
 328
 329 static ssize_t
 330 store_threshold_limit(struct threshold_block *b, const char *buf, size_t size)
 331 {
 332         struct thresh_restart tr;
 333         unsigned long new;
 334
 335         if (strict_strtoul(buf, 0, &new) < 0)
 336                 return -EINVAL;
 337
 338         if (new > THRESHOLD_MAX)
 339                 new = THRESHOLD_MAX;
 340         if (new < 1)
 341                 new = 1;
 342
 343         memset(&tr, 0, sizeof(tr));
 344         tr.old_limit = b->threshold_limit;
 345         b->threshold_limit = new;
 346         tr.b = b;
 347
 348         smp_call_function_single(b->cpu, threshold_restart_bank, &tr, 1);
 349
 350         return size;
 351 }
 352
 353 struct threshold_block_cross_cpu {
 354         struct threshold_block  *tb;
 355         long                    retval;
 356 };
 357
 358 static void local_error_count_handler(void *_tbcc)
 359 {
 360         struct threshold_block_cross_cpu *tbcc = _tbcc;
 361         struct threshold_block *b = tbcc->tb;
 362         u32 low, high;
 363
 364         rdmsr(b->address, low, high);
 365         tbcc->retval = (high & 0xFFF) - (THRESHOLD_MAX - b->threshold_limit);
 366 }
 367
 368 static ssize_t show_error_count(struct threshold_block *b, char *buf)
 369 {
 370         struct threshold_block_cross_cpu tbcc = { .tb = b, };
 371
 372         smp_call_function_single(b->cpu, local_error_count_handler, &tbcc, 1);
 373         return sprintf(buf, "%lx\n", tbcc.retval);
 374 }
 375
 376 static ssize_t store_error_count(struct threshold_block *b,
 377                                  const char *buf, size_t count)
 378 {
 379         struct thresh_restart tr = { .b = b, .reset = 1, .old_limit = 0 };
 380
 381         smp_call_function_single(b->cpu, threshold_restart_bank, &tr, 1);
 382         return 1;
 383 }
 384
 385 #define RW_ATTR(val)                                                    \
 386 static struct threshold_attr val = {                                    \
 387         .attr   = {.name = __stringify(val), .mode = 0644 },            \
 388         .show   = show_## val,                                          \
 389         .store  = store_## val,                                         \
 390 };
 391
 392 RW_ATTR(interrupt_enable);
 393 RW_ATTR(threshold_limit);
 394 RW_ATTR(error_count);
 395
 396 static struct attribute *default_attrs[] = {
 397         &interrupt_enable.attr,
 398         &threshold_limit.attr,
 399         &error_count.attr,
 400         NULL
 401 };
 402
 403 #define to_block(k)     container_of(k, struct threshold_block, kobj)
 404 #define to_attr(a)      container_of(a, struct threshold_attr, attr)
 405
 406 static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 407 {
 408         struct threshold_block *b = to_block(kobj);
 409         struct threshold_attr *a = to_attr(attr);
 410         ssize_t ret;
 411
 412         ret = a->show ? a->show(b, buf) : -EIO;
 413
 414         return ret;
 415 }
 416
 417 static ssize_t store(struct kobject *kobj, struct attribute *attr,
 418                      const char *buf, size_t count)
 419 {
 420         struct threshold_block *b = to_block(kobj);
 421         struct threshold_attr *a = to_attr(attr);
 422         ssize_t ret;
 423
 424         ret = a->store ? a->store(b, buf, count) : -EIO;
 425
 426         return ret;
 427 }
 428
 429 static const struct sysfs_ops threshold_ops = {
 430         .show                   = show,
 431         .store                  = store,
 432 };
 433
 434 static struct kobj_type threshold_ktype = {
 435         .sysfs_ops              = &threshold_ops,
 436         .default_attrs          = default_attrs,
 437 };
 438
 439 static __cpuinit int allocate_threshold_blocks(unsigned int cpu,
 440                                                unsigned int bank,
 441                                                unsigned int block,
 442                                                u32 address)
 443 {
 444         struct threshold_block *b = NULL;
 445         u32 low, high;
 446         int err;
 447
 448         if ((bank >= NR_BANKS) || (block >= NR_BLOCKS))
 449                 return 0;
 450
 451         if (rdmsr_safe_on_cpu(cpu, address, &low, &high))
 452                 return 0;
 453
 454         if (!(high & MASK_VALID_HI)) {
 455                 if (block)
 456                         goto recurse;
 457                 else
 458                         return 0;
 459         }
 460
 461         if (!(high & MASK_CNTP_HI)  ||
 462              (high & MASK_LOCKED_HI))
 463                 goto recurse;
 464
 465         b = kzalloc(sizeof(struct threshold_block), GFP_KERNEL);
 466         if (!b)
 467                 return -ENOMEM;
 468
 469         b->block                = block;
 470         b->bank                 = bank;
 471         b->cpu                  = cpu;
 472         b->address              = address;
 473         b->interrupt_enable     = 0;
 474         b->threshold_limit      = THRESHOLD_MAX;
 475
 476         INIT_LIST_HEAD(&b->miscj);
 477
 478         if (per_cpu(threshold_banks, cpu)[bank]->blocks) {
 479                 list_add(&b->miscj,
 480                          &per_cpu(threshold_banks, cpu)[bank]->blocks->miscj);
 481         } else {
 482                 per_cpu(threshold_banks, cpu)[bank]->blocks = b;
 483         }
 484
 485         err = kobject_init_and_add(&b->kobj, &threshold_ktype,
 486                                    per_cpu(threshold_banks, cpu)[bank]->kobj,
 487                                    "misc%i", block);
 488         if (err)
 489                 goto out_free;
 490 recurse:
 491         if (!block) {
 492                 address = (low & MASK_BLKPTR_LO) >> 21;
 493                 if (!address)
 494                         return 0;
 495                 address += MCG_XBLK_ADDR;
 496         } else {
 497                 ++address;
 498         }
 499
 500         err = allocate_threshold_blocks(cpu, bank, ++block, address);
 501         if (err)
 502                 goto out_free;
 503
 504         if (b)
 505                 kobject_uevent(&b->kobj, KOBJ_ADD);
 506
 507         return err;
 508
 509 out_free:
 510         if (b) {
 511                 kobject_put(&b->kobj);
 512                 kfree(b);
 513         }
 514         return err;
 515 }
 516
 517 static __cpuinit long
 518 local_allocate_threshold_blocks(int cpu, unsigned int bank)
 519 {
 520         return allocate_threshold_blocks(cpu, bank, 0,
 521                                          MSR_IA32_MC0_MISC + bank * 4);
 522 }
 523
 524 /* symlinks sibling shared banks to first core.  first core owns dir/files. */
 525 static __cpuinit int threshold_create_bank(unsigned int cpu, unsigned int bank)
 526 {
 527         int i, err = 0;
 528         struct threshold_bank *b = NULL;
 529         char name[32];
 530 #ifdef CONFIG_SMP
 531         struct cpuinfo_x86 *c = &cpu_data(cpu);
 532 #endif
 533
 534         sprintf(name, "threshold_bank%i", bank);
 535
 536 #ifdef CONFIG_SMP
 537         if (cpu_data(cpu).cpu_core_id && shared_bank[bank]) {   /* symlink */
 538                 i = cpumask_first(c->llc_shared_map);
 539
 540                 /* first core not up yet */
 541                 if (cpu_data(i).cpu_core_id)
 542                         goto out;
 543
 544                 /* already linked */
 545                 if (per_cpu(threshold_banks, cpu)[bank])
 546                         goto out;
 547
 548                 b = per_cpu(threshold_banks, i)[bank];
 549
 550                 if (!b)
 551                         goto out;
 552
 553                 err = sysfs_create_link(&per_cpu(mce_dev, cpu).kobj,
 554                                         b->kobj, name);
 555                 if (err)
 556                         goto out;
 557
 558                 cpumask_copy(b->cpus, c->llc_shared_map);
 559                 per_cpu(threshold_banks, cpu)[bank] = b;
 560
 561                 goto out;
 562         }
 563 #endif
 564
 565         b = kzalloc(sizeof(struct threshold_bank), GFP_KERNEL);
 566         if (!b) {
 567                 err = -ENOMEM;
 568                 goto out;
 569         }
 570         if (!zalloc_cpumask_var(&b->cpus, GFP_KERNEL)) {
 571                 kfree(b);
 572                 err = -ENOMEM;
 573                 goto out;
 574         }
 575
 576         b->kobj = kobject_create_and_add(name, &per_cpu(mce_dev, cpu).kobj);
 577         if (!b->kobj)
 578                 goto out_free;
 579
 580 #ifndef CONFIG_SMP
 581         cpumask_setall(b->cpus);
 582 #else
 583         cpumask_set_cpu(cpu, b->cpus);
 584 #endif
 585
 586         per_cpu(threshold_banks, cpu)[bank] = b;
 587
 588         err = local_allocate_threshold_blocks(cpu, bank);
 589         if (err)
 590                 goto out_free;
 591
 592         for_each_cpu(i, b->cpus) {
 593                 if (i == cpu)
 594                         continue;
 595
 596                 err = sysfs_create_link(&per_cpu(mce_dev, i).kobj,
 597                                         b->kobj, name);
 598                 if (err)
 599                         goto out;
 600
 601                 per_cpu(threshold_banks, i)[bank] = b;
 602         }
 603
 604         goto out;
 605
 606 out_free:
 607         per_cpu(threshold_banks, cpu)[bank] = NULL;
 608         free_cpumask_var(b->cpus);
 609         kfree(b);
 610 out:
 611         return err;
 612 }
 613
 614 /* create dir/files for all valid threshold banks */
 615 static __cpuinit int threshold_create_device(unsigned int cpu)
 616 {
 617         unsigned int bank;
 618         int err = 0;
 619
 620         for (bank = 0; bank < NR_BANKS; ++bank) {
 621                 if (!(per_cpu(bank_map, cpu) & (1 << bank)))
 622                         continue;
 623                 err = threshold_create_bank(cpu, bank);
 624                 if (err)
 625                         return err;
 626         }
 627
 628         return err;
 629 }
 630
 631 /*
 632  * let's be hotplug friendly.
 633  * in case of multiple core processors, the first core always takes ownership
 634  *   of shared sysfs dir/files, and rest of the cores will be symlinked to it.
 635  */
 636
 637 static void deallocate_threshold_block(unsigned int cpu,
 638                                                  unsigned int bank)
 639 {
 640         struct threshold_block *pos = NULL;
 641         struct threshold_block *tmp = NULL;
 642         struct threshold_bank *head = per_cpu(threshold_banks, cpu)[bank];
 643
 644         if (!head)
 645                 return;
 646
 647         list_for_each_entry_safe(pos, tmp, &head->blocks->miscj, miscj) {
 648                 kobject_put(&pos->kobj);
 649                 list_del(&pos->miscj);
 650                 kfree(pos);
 651         }
 652
 653         kfree(per_cpu(threshold_banks, cpu)[bank]->blocks);
 654         per_cpu(threshold_banks, cpu)[bank]->blocks = NULL;
 655 }
 656
 657 static void threshold_remove_bank(unsigned int cpu, int bank)
 658 {
 659         struct threshold_bank *b;
 660         char name[32];
 661         int i = 0;
 662
 663         b = per_cpu(threshold_banks, cpu)[bank];
 664         if (!b)
 665                 return;
 666         if (!b->blocks)
 667                 goto free_out;
 668
 669         sprintf(name, "threshold_bank%i", bank);
 670
 671 #ifdef CONFIG_SMP
 672         /* sibling symlink */
 673         if (shared_bank[bank] && b->blocks->cpu != cpu) {
 674                 sysfs_remove_link(&per_cpu(mce_dev, cpu).kobj, name);
 675                 per_cpu(threshold_banks, cpu)[bank] = NULL;
 676
 677                 return;
 678         }
 679 #endif
 680
 681         /* remove all sibling symlinks before unregistering */
 682         for_each_cpu(i, b->cpus) {
 683                 if (i == cpu)
 684                         continue;
 685
 686                 sysfs_remove_link(&per_cpu(mce_dev, i).kobj, name);
 687                 per_cpu(threshold_banks, i)[bank] = NULL;
 688         }
 689
 690         deallocate_threshold_block(cpu, bank);
 691
 692 free_out:
 693         kobject_del(b->kobj);
 694         kobject_put(b->kobj);
 695         free_cpumask_var(b->cpus);
 696         kfree(b);
 697         per_cpu(threshold_banks, cpu)[bank] = NULL;
 698 }
 699
 700 static void threshold_remove_device(unsigned int cpu)
 701 {
 702         unsigned int bank;
 703
 704         for (bank = 0; bank < NR_BANKS; ++bank) {
 705                 if (!(per_cpu(bank_map, cpu) & (1 << bank)))
 706                         continue;
 707                 threshold_remove_bank(cpu, bank);
 708         }
 709 }
 710
 711 /* get notified when a cpu comes on/off */
 712 static void __cpuinit
 713 amd_64_threshold_cpu_callback(unsigned long action, unsigned int cpu)
 714 {
 715         switch (action) {
 716         case CPU_ONLINE:
 717         case CPU_ONLINE_FROZEN:
 718                 threshold_create_device(cpu);
 719                 break;
 720         case CPU_DEAD:
 721         case CPU_DEAD_FROZEN:
 722                 threshold_remove_device(cpu);
 723                 break;
 724         default:
 725                 break;
 726         }
 727 }
 728
 729 static __init int threshold_init_device(void)
 730 {
 731         unsigned lcpu = 0;
 732
 733         /* to hit CPUs online before the notifier is up */
 734         for_each_online_cpu(lcpu) {
 735                 int err = threshold_create_device(lcpu);
 736
 737                 if (err)
 738                         return err;
 739         }
 740         threshold_cpu_callback = amd_64_threshold_cpu_callback;
 741
 742         return 0;
 743 }
 744 device_initcall(threshold_init_device);