xref: /linux/arch/x86/kernel/reboot.c (revision b233b28eac0cc37d07c2d007ea08c86c778c5af4)
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
701