arch/x86/kernel/reboot.c

   1 #include <linux/module.h>
   2 #include <linux/reboot.h>
   3 #include <linux/init.h>
   4 #include <linux/pm.h>
   5 #include <linux/efi.h>
   6 #include <acpi/reboot.h>
   7 #include <asm/io.h>
   8 #include <asm/apic.h>
   9 #include <asm/desc.h>
  10 #include <asm/hpet.h>
  11 #include <asm/pgtable.h>
  12 #include <asm/proto.h>
  13 #include <asm/reboot_fixups.h>
  14 #include <asm/reboot.h>
  15 #include <asm/pci_x86.h>
  16 #include <asm/virtext.h>
  17
  18 #ifdef CONFIG_X86_32
  19 # include <linux/dmi.h>
  20 # include <linux/ctype.h>
  21 # include <linux/mc146818rtc.h>
  22 #else
  23 # include <asm/iommu.h>
  24 #endif
  25
  26 #include <mach_ipi.h>
  27
  28 /*
  29  * Power off function, if any
  30  */
  31 void (*pm_power_off)(void);
  32 EXPORT_SYMBOL(pm_power_off);
  33
  34 static const struct desc_ptr no_idt = {};
  35 static int reboot_mode;
  36 enum reboot_type reboot_type = BOOT_KBD;
  37 int reboot_force;
  38
  39 #if defined(CONFIG_X86_32) && defined(CONFIG_SMP)
  40 static int reboot_cpu = -1;
  41 #endif
  42
  43 /* This is set if we need to go through the 'emergency' path.
  44  * When machine_emergency_restart() is called, we may be on
  45  * an inconsistent state and won't be able to do a clean cleanup
  46  */
  47 static int reboot_emergency;
  48
  49 /* This is set by the PCI code if either type 1 or type 2 PCI is detected */
  50 bool port_cf9_safe = false;
  51
  52 /* reboot=b[ios] | s[mp] | t[riple] | k[bd] | e[fi] [, [w]arm | [c]old] | p[ci]
  53    warm   Don't set the cold reboot flag
  54    cold   Set the cold reboot flag
  55    bios   Reboot by jumping through the BIOS (only for X86_32)
  56    smp    Reboot by executing reset on BSP or other CPU (only for X86_32)
  57    triple Force a triple fault (init)
  58    kbd    Use the keyboard controller. cold reset (default)
  59    acpi   Use the RESET_REG in the FADT
  60    efi    Use efi reset_system runtime service
  61    pci    Use the so-called "PCI reset register", CF9
  62    force  Avoid anything that could hang.
  63  */
  64 static int __init reboot_setup(char *str)
  65 {
  66         for (;;) {
  67                 switch (*str) {
  68                 case 'w':
  69                         reboot_mode = 0x1234;
  70                         break;
  71
  72                 case 'c':
  73                         reboot_mode = 0;
  74                         break;
  75
  76 #ifdef CONFIG_X86_32
  77 #ifdef CONFIG_SMP
  78                 case 's':
  79                         if (isdigit(*(str+1))) {
  80                                 reboot_cpu = (int) (*(str+1) - '0');
  81                                 if (isdigit(*(str+2)))
  82                                         reboot_cpu = reboot_cpu*10 + (int)(*(str+2) - '0');
  83                         }
  84                                 /* we will leave sorting out the final value
  85                                    when we are ready to reboot, since we might not
  86                                    have set up boot_cpu_id or smp_num_cpu */
  87                         break;
  88 #endif /* CONFIG_SMP */
  89
  90                 case 'b':
  91 #endif
  92                 case 'a':
  93                 case 'k':
  94                 case 't':
  95                 case 'e':
  96                 case 'p':
  97                         reboot_type = *str;
  98                         break;
  99
 100                 case 'f':
 101                         reboot_force = 1;
 102                         break;
 103                 }
 104
 105                 str = strchr(str, ',');
 106                 if (str)
 107                         str++;
 108                 else
 109                         break;
 110         }
 111         return 1;
 112 }
 113
 114 __setup("reboot=", reboot_setup);
 115
 116
 117 #ifdef CONFIG_X86_32
 118 /*
 119  * Reboot options and system auto-detection code provided by
 120  * Dell Inc. so their systems "just work". :-)
 121  */
 122
 123 /*
 124  * Some machines require the "reboot=b"  commandline option,
 125  * this quirk makes that automatic.
 126  */
 127 static int __init set_bios_reboot(const struct dmi_system_id *d)
 128 {
 129         if (reboot_type != BOOT_BIOS) {
 130                 reboot_type = BOOT_BIOS;
 131                 printk(KERN_INFO "%s series board detected. Selecting BIOS-method for reboots.\n", d->ident);
 132         }
 133         return 0;
 134 }
 135
 136 static struct dmi_system_id __initdata reboot_dmi_table[] = {
 137         {       /* Handle problems with rebooting on Dell E520's */
 138                 .callback = set_bios_reboot,
 139                 .ident = "Dell E520",
 140                 .matches = {
 141                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 142                         DMI_MATCH(DMI_PRODUCT_NAME, "Dell DM061"),
 143                 },
 144         },
 145         {       /* Handle problems with rebooting on Dell 1300's */
 146                 .callback = set_bios_reboot,
 147                 .ident = "Dell PowerEdge 1300",
 148                 .matches = {
 149                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
 150                         DMI_MATCH(DMI_PRODUCT_NAME, "PowerEdge 1300/"),
 151                 },
 152         },
 153         {       /* Handle problems with rebooting on Dell 300's */
 154                 .callback = set_bios_reboot,
 155                 .ident = "Dell PowerEdge 300",
 156                 .matches = {
 157                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
 158                         DMI_MATCH(DMI_PRODUCT_NAME, "PowerEdge 300/"),
 159                 },
 160         },
 161         {       /* Handle problems with rebooting on Dell Optiplex 745's SFF*/
 162                 .callback = set_bios_reboot,
 163                 .ident = "Dell OptiPlex 745",
 164                 .matches = {
 165                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 166                         DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 745"),
 167                 },
 168         },
 169         {       /* Handle problems with rebooting on Dell Optiplex 745's DFF*/
 170                 .callback = set_bios_reboot,
 171                 .ident = "Dell OptiPlex 745",
 172                 .matches = {
 173                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 174                         DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 745"),
 175                         DMI_MATCH(DMI_BOARD_NAME, "0MM599"),
 176                 },
 177         },
 178         {       /* Handle problems with rebooting on Dell Optiplex 745 with 0KW626 */
 179                 .callback = set_bios_reboot,
 180                 .ident = "Dell OptiPlex 745",
 181                 .matches = {
 182                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 183                         DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 745"),
 184                         DMI_MATCH(DMI_BOARD_NAME, "0KW626"),
 185                 },
 186         },
 187         {   /* Handle problems with rebooting on Dell Optiplex 330 with 0KP561 */
 188                 .callback = set_bios_reboot,
 189                 .ident = "Dell OptiPlex 330",
 190                 .matches = {
 191                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 192                         DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 330"),
 193                         DMI_MATCH(DMI_BOARD_NAME, "0KP561"),
 194                 },
 195         },
 196         {       /* Handle problems with rebooting on Dell 2400's */
 197                 .callback = set_bios_reboot,
 198                 .ident = "Dell PowerEdge 2400",
 199                 .matches = {
 200                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
 201                         DMI_MATCH(DMI_PRODUCT_NAME, "PowerEdge 2400"),
 202                 },
 203         },
 204         {       /* Handle problems with rebooting on Dell T5400's */
 205                 .callback = set_bios_reboot,
 206                 .ident = "Dell Precision T5400",
 207                 .matches = {
 208                         DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
 209                         DMI_MATCH(DMI_PRODUCT_NAME, "Precision WorkStation T5400"),
 210                 },
 211         },
 212         {       /* Handle problems with rebooting on HP laptops */
 213                 .callback = set_bios_reboot,
 214                 .ident = "HP Compaq Laptop",
 215                 .matches = {
 216                         DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 217                         DMI_MATCH(DMI_PRODUCT_NAME, "HP Compaq"),
 218                 },
 219         },
 220         { }
 221 };
 222
 223 static int __init reboot_init(void)
 224 {
 225         dmi_check_system(reboot_dmi_table);
 226         return 0;
 227 }
 228 core_initcall(reboot_init);
 229
 230 /* The following code and data reboots the machine by switching to real
 231    mode and jumping to the BIOS reset entry point, as if the CPU has
 232    really been reset.  The previous version asked the keyboard
 233    controller to pulse the CPU reset line, which is more thorough, but
 234    doesn't work with at least one type of 486 motherboard.  It is easy
 235    to stop this code working; hence the copious comments. */
 236 static const unsigned long long
 237 real_mode_gdt_entries [3] =
 238 {
 239         0x0000000000000000ULL,  /* Null descriptor */
 240         0x00009b000000ffffULL,  /* 16-bit real-mode 64k code at 0x00000000 */
 241         0x000093000100ffffULL   /* 16-bit real-mode 64k data at 0x00000100 */
 242 };
 243
 244 static const struct desc_ptr
 245 real_mode_gdt = { sizeof (real_mode_gdt_entries) - 1, (long)real_mode_gdt_entries },
 246 real_mode_idt = { 0x3ff, 0 };
 247
 248 /* This is 16-bit protected mode code to disable paging and the cache,
 249    switch to real mode and jump to the BIOS reset code.
 250
 251    The instruction that switches to real mode by writing to CR0 must be
 252    followed immediately by a far jump instruction, which set CS to a
 253    valid value for real mode, and flushes the prefetch queue to avoid
 254    running instructions that have already been decoded in protected
 255    mode.
 256
 257    Clears all the flags except ET, especially PG (paging), PE
 258    (protected-mode enable) and TS (task switch for coprocessor state
 259    save).  Flushes the TLB after paging has been disabled.  Sets CD and
 260    NW, to disable the cache on a 486, and invalidates the cache.  This
 261    is more like the state of a 486 after reset.  I don't know if
 262    something else should be done for other chips.
 263
 264    More could be done here to set up the registers as if a CPU reset had
 265    occurred; hopefully real BIOSs don't assume much. */
 266 static const unsigned char real_mode_switch [] =
 267 {
 268         0x66, 0x0f, 0x20, 0xc0,                 /*    movl  %cr0,%eax        */
 269         0x66, 0x83, 0xe0, 0x11,                 /*    andl  $0x00000011,%eax */
 270         0x66, 0x0d, 0x00, 0x00, 0x00, 0x60,     /*    orl   $0x60000000,%eax */
 271         0x66, 0x0f, 0x22, 0xc0,                 /*    movl  %eax,%cr0        */
 272         0x66, 0x0f, 0x22, 0xd8,                 /*    movl  %eax,%cr3        */
 273         0x66, 0x0f, 0x20, 0xc3,                 /*    movl  %cr0,%ebx        */
 274         0x66, 0x81, 0xe3, 0x00, 0x00, 0x00, 0x60,       /*    andl  $0x60000000,%ebx */
 275         0x74, 0x02,                             /*    jz    f                */
 276         0x0f, 0x09,                             /*    wbinvd                 */
 277         0x24, 0x10,                             /* f: andb  $0x10,al         */
 278         0x66, 0x0f, 0x22, 0xc0                  /*    movl  %eax,%cr0        */
 279 };
 280 static const unsigned char jump_to_bios [] =
 281 {
 282         0xea, 0x00, 0x00, 0xff, 0xff            /*    ljmp  $0xffff,$0x0000  */
 283 };
 284
 285 /*
 286  * Switch to real mode and then execute the code
 287  * specified by the code and length parameters.
 288  * We assume that length will aways be less that 100!
 289  */
 290 void machine_real_restart(const unsigned char *code, int length)
 291 {
 292         local_irq_disable();
 293
 294         /* Write zero to CMOS register number 0x0f, which the BIOS POST
 295            routine will recognize as telling it to do a proper reboot.  (Well
 296            that's what this book in front of me says -- it may only apply to
 297            the Phoenix BIOS though, it's not clear).  At the same time,
 298            disable NMIs by setting the top bit in the CMOS address register,
 299            as we're about to do peculiar things to the CPU.  I'm not sure if
 300            `outb_p' is needed instead of just `outb'.  Use it to be on the
 301            safe side.  (Yes, CMOS_WRITE does outb_p's. -  Paul G.)
 302          */
 303         spin_lock(&rtc_lock);
 304         CMOS_WRITE(0x00, 0x8f);
 305         spin_unlock(&rtc_lock);
 306
 307         /* Remap the kernel at virtual address zero, as well as offset zero
 308            from the kernel segment.  This assumes the kernel segment starts at
 309            virtual address PAGE_OFFSET. */
 310         memcpy(swapper_pg_dir, swapper_pg_dir + KERNEL_PGD_BOUNDARY,
 311                 sizeof(swapper_pg_dir [0]) * KERNEL_PGD_PTRS);
 312
 313         /*
 314          * Use `swapper_pg_dir' as our page directory.
 315          */
 316         load_cr3(swapper_pg_dir);
 317
 318         /* Write 0x1234 to absolute memory location 0x472.  The BIOS reads
 319            this on booting to tell it to "Bypass memory test (also warm
 320            boot)".  This seems like a fairly standard thing that gets set by
 321            REBOOT.COM programs, and the previous reset routine did this
 322            too. */
 323         *((unsigned short *)0x472) = reboot_mode;
 324
 325         /* For the switch to real mode, copy some code to low memory.  It has
 326            to be in the first 64k because it is running in 16-bit mode, and it
 327            has to have the same physical and virtual address, because it turns
 328            off paging.  Copy it near the end of the first page, out of the way
 329            of BIOS variables. */
 330         memcpy((void *)(0x1000 - sizeof(real_mode_switch) - 100),
 331                 real_mode_switch, sizeof (real_mode_switch));
 332         memcpy((void *)(0x1000 - 100), code, length);
 333
 334         /* Set up the IDT for real mode. */
 335         load_idt(&real_mode_idt);
 336
 337         /* Set up a GDT from which we can load segment descriptors for real
 338            mode.  The GDT is not used in real mode; it is just needed here to
 339            prepare the descriptors. */
 340         load_gdt(&real_mode_gdt);
 341
 342         /* Load the data segment registers, and thus the descriptors ready for
 343            real mode.  The base address of each segment is 0x100, 16 times the
 344            selector value being loaded here.  This is so that the segment
 345            registers don't have to be reloaded after switching to real mode:
 346            the values are consistent for real mode operation already. */
 347         __asm__ __volatile__ ("movl $0x0010,%%eax\n"
 348                                 "\tmovl %%eax,%%ds\n"
 349                                 "\tmovl %%eax,%%es\n"
 350                                 "\tmovl %%eax,%%fs\n"
 351                                 "\tmovl %%eax,%%gs\n"
 352                                 "\tmovl %%eax,%%ss" : : : "eax");
 353
 354         /* Jump to the 16-bit code that we copied earlier.  It disables paging
 355            and the cache, switches to real mode, and jumps to the BIOS reset
 356            entry point. */
 357         __asm__ __volatile__ ("ljmp $0x0008,%0"
 358                                 :
 359                                 : "i" ((void *)(0x1000 - sizeof (real_mode_switch) - 100)));
 360 }
 361 #ifdef CONFIG_APM_MODULE
 362 EXPORT_SYMBOL(machine_real_restart);
 363 #endif
 364
 365 #endif /* CONFIG_X86_32 */
 366
 367 static inline void kb_wait(void)
 368 {
 369         int i;
 370
 371         for (i = 0; i < 0x10000; i++) {
 372                 if ((inb(0x64) & 0x02) == 0)
 373                         break;
 374                 udelay(2);
 375         }
 376 }
 377
 378 static void vmxoff_nmi(int cpu, struct die_args *args)
 379 {
 380         cpu_emergency_vmxoff();
 381 }
 382
 383 /* Use NMIs as IPIs to tell all CPUs to disable virtualization
 384  */
 385 static void emergency_vmx_disable_all(void)
 386 {
 387         /* Just make sure we won't change CPUs while doing this */
 388         local_irq_disable();
 389
 390         /* We need to disable VMX on all CPUs before rebooting, otherwise
 391          * we risk hanging up the machine, because the CPU ignore INIT
 392          * signals when VMX is enabled.
 393          *
 394          * We can't take any locks and we may be on an inconsistent
 395          * state, so we use NMIs as IPIs to tell the other CPUs to disable
 396          * VMX and halt.
 397          *
 398          * For safety, we will avoid running the nmi_shootdown_cpus()
 399          * stuff unnecessarily, but we don't have a way to check
 400          * if other CPUs have VMX enabled. So we will call it only if the
 401          * CPU we are running on has VMX enabled.
 402          *
 403          * We will miss cases where VMX is not enabled on all CPUs. This
 404          * shouldn't do much harm because KVM always enable VMX on all
 405          * CPUs anyway. But we can miss it on the small window where KVM
 406          * is still enabling VMX.
 407          */
 408         if (cpu_has_vmx() && cpu_vmx_enabled()) {
 409                 /* Disable VMX on this CPU.
 410                  */
 411                 cpu_vmxoff();
 412
 413                 /* Halt and disable VMX on the other CPUs */
 414                 nmi_shootdown_cpus(vmxoff_nmi);
 415
 416         }
 417 }
 418
 419
 420 void __attribute__((weak)) mach_reboot_fixups(void)
 421 {
 422 }
 423
 424 static void native_machine_emergency_restart(void)
 425 {
 426         int i;
 427
 428         if (reboot_emergency)
 429                 emergency_vmx_disable_all();
 430
 431         /* Tell the BIOS if we want cold or warm reboot */
 432         *((unsigned short *)__va(0x472)) = reboot_mode;
 433
 434         for (;;) {
 435                 /* Could also try the reset bit in the Hammer NB */
 436                 switch (reboot_type) {
 437                 case BOOT_KBD:
 438                         mach_reboot_fixups(); /* for board specific fixups */
 439
 440                         for (i = 0; i < 10; i++) {
 441                                 kb_wait();
 442                                 udelay(50);
 443                                 outb(0xfe, 0x64); /* pulse reset low */
 444                                 udelay(50);
 445                         }
 446
 447                 case BOOT_TRIPLE:
 448                         load_idt(&no_idt);
 449                         __asm__ __volatile__("int3");
 450
 451                         reboot_type = BOOT_KBD;
 452                         break;
 453
 454 #ifdef CONFIG_X86_32
 455                 case BOOT_BIOS:
 456                         machine_real_restart(jump_to_bios, sizeof(jump_to_bios));
 457
 458                         reboot_type = BOOT_KBD;
 459                         break;
 460 #endif
 461
 462                 case BOOT_ACPI:
 463                         acpi_reboot();
 464                         reboot_type = BOOT_KBD;
 465                         break;
 466
 467                 case BOOT_EFI:
 468                         if (efi_enabled)
 469                                 efi.reset_system(reboot_mode ?
 470                                                  EFI_RESET_WARM :
 471                                                  EFI_RESET_COLD,
 472                                                  EFI_SUCCESS, 0, NULL);
 473                         reboot_type = BOOT_KBD;
 474                         break;
 475
 476                 case BOOT_CF9:
 477                         port_cf9_safe = true;
 478                         /* fall through */
 479
 480                 case BOOT_CF9_COND:
 481                         if (port_cf9_safe) {
 482                                 u8 cf9 = inb(0xcf9) & ~6;
 483                                 outb(cf9|2, 0xcf9); /* Request hard reset */
 484                                 udelay(50);
 485                                 outb(cf9|6, 0xcf9); /* Actually do the reset */
 486                                 udelay(50);
 487                         }
 488                         reboot_type = BOOT_KBD;
 489                         break;
 490                 }
 491         }
 492 }
 493
 494 void native_machine_shutdown(void)
 495 {
 496         /* Stop the cpus and apics */
 497 #ifdef CONFIG_SMP
 498
 499         /* The boot cpu is always logical cpu 0 */
 500         int reboot_cpu_id = 0;
 501
 502 #ifdef CONFIG_X86_32
 503         /* See if there has been given a command line override */
 504         if ((reboot_cpu != -1) && (reboot_cpu < nr_cpu_ids) &&
 505                 cpu_online(reboot_cpu))
 506                 reboot_cpu_id = reboot_cpu;
 507 #endif
 508
 509         /* Make certain the cpu I'm about to reboot on is online */
 510         if (!cpu_online(reboot_cpu_id))
 511                 reboot_cpu_id = smp_processor_id();
 512
 513         /* Make certain I only run on the appropriate processor */
 514         set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id));
 515
 516         /* O.K Now that I'm on the appropriate processor,
 517          * stop all of the others.
 518          */
 519         smp_send_stop();
 520 #endif
 521
 522         lapic_shutdown();
 523
 524 #ifdef CONFIG_X86_IO_APIC
 525         disable_IO_APIC();
 526 #endif
 527
 528 #ifdef CONFIG_HPET_TIMER
 529         hpet_disable();
 530 #endif
 531
 532 #ifdef CONFIG_X86_64
 533         pci_iommu_shutdown();
 534 #endif
 535 }
 536
 537 static void __machine_emergency_restart(int emergency)
 538 {
 539         reboot_emergency = emergency;
 540         machine_ops.emergency_restart();
 541 }
 542
 543 static void native_machine_restart(char *__unused)
 544 {
 545         printk("machine restart\n");
 546
 547         if (!reboot_force)
 548                 machine_shutdown();
 549         __machine_emergency_restart(0);
 550 }
 551
 552 static void native_machine_halt(void)
 553 {
 554         /* stop other cpus and apics */
 555         machine_shutdown();
 556
 557         /* stop this cpu */
 558         stop_this_cpu(NULL);
 559 }
 560
 561 static void native_machine_power_off(void)
 562 {
 563         if (pm_power_off) {
 564                 if (!reboot_force)
 565                         machine_shutdown();
 566                 pm_power_off();
 567         }
 568 }
 569
 570 struct machine_ops machine_ops = {
 571         .power_off = native_machine_power_off,
 572         .shutdown = native_machine_shutdown,
 573         .emergency_restart = native_machine_emergency_restart,
 574         .restart = native_machine_restart,
 575         .halt = native_machine_halt,
 576 #ifdef CONFIG_KEXEC
 577         .crash_shutdown = native_machine_crash_shutdown,
 578 #endif
 579 };
 580
 581 void machine_power_off(void)
 582 {
 583         machine_ops.power_off();
 584 }
 585
 586 void machine_shutdown(void)
 587 {
 588         machine_ops.shutdown();
 589 }
 590
 591 void machine_emergency_restart(void)
 592 {
 593         __machine_emergency_restart(1);
 594 }
 595
 596 void machine_restart(char *cmd)
 597 {
 598         machine_ops.restart(cmd);
 599 }
 600
 601 void machine_halt(void)
 602 {
 603         machine_ops.halt();
 604 }
 605
 606 #ifdef CONFIG_KEXEC
 607 void machine_crash_shutdown(struct pt_regs *regs)
 608 {
 609         machine_ops.crash_shutdown(regs);
 610 }
 611 #endif
 612
 613
 614 #if defined(CONFIG_SMP)
 615
 616 /* This keeps a track of which one is crashing cpu. */
 617 static int crashing_cpu;
 618 static nmi_shootdown_cb shootdown_callback;
 619
 620 static atomic_t waiting_for_crash_ipi;
 621
 622 static int crash_nmi_callback(struct notifier_block *self,
 623                         unsigned long val, void *data)
 624 {
 625         int cpu;
 626
 627         if (val != DIE_NMI_IPI)
 628                 return NOTIFY_OK;
 629
 630         cpu = raw_smp_processor_id();
 631
 632         /* Don't do anything if this handler is invoked on crashing cpu.
 633          * Otherwise, system will completely hang. Crashing cpu can get
 634          * an NMI if system was initially booted with nmi_watchdog parameter.
 635          */
 636         if (cpu == crashing_cpu)
 637                 return NOTIFY_STOP;
 638         local_irq_disable();
 639
 640         shootdown_callback(cpu, (struct die_args *)data);
 641
 642         atomic_dec(&waiting_for_crash_ipi);
 643         /* Assume hlt works */
 644         halt();
 645         for (;;)
 646                 cpu_relax();
 647
 648         return 1;
 649 }
 650
 651 static void smp_send_nmi_allbutself(void)
 652 {
 653         send_IPI_allbutself(NMI_VECTOR);
 654 }
 655
 656 static struct notifier_block crash_nmi_nb = {
 657         .notifier_call = crash_nmi_callback,
 658 };
 659
 660 /* Halt all other CPUs, calling the specified function on each of them
 661  *
 662  * This function can be used to halt all other CPUs on crash
 663  * or emergency reboot time. The function passed as parameter
 664  * will be called inside a NMI handler on all CPUs.
 665  */
 666 void nmi_shootdown_cpus(nmi_shootdown_cb callback)
 667 {
 668         unsigned long msecs;
 669         local_irq_disable();
 670
 671         /* Make a note of crashing cpu. Will be used in NMI callback.*/
 672         crashing_cpu = safe_smp_processor_id();
 673
 674         shootdown_callback = callback;
 675
 676         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
 677         /* Would it be better to replace the trap vector here? */
 678         if (register_die_notifier(&crash_nmi_nb))
 679                 return;         /* return what? */
 680         /* Ensure the new callback function is set before sending
 681          * out the NMI
 682          */
 683         wmb();
 684
 685         smp_send_nmi_allbutself();
 686
 687         msecs = 1000; /* Wait at most a second for the other cpus to stop */
 688         while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
 689                 mdelay(1);
 690                 msecs--;
 691         }
 692
 693         /* Leave the nmi callback set */
 694 }
 695 #else /* !CONFIG_SMP */
 696 void nmi_shootdown_cpus(nmi_shootdown_cb callback)
 697 {
 698         /* No other CPUs to shoot down */
 699 }
 700 #endif