1/*
2 * Architecture specific (x86_64) functions for kexec based crash dumps.
3 *
4 * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
5 *
6 * Copyright (C) IBM Corporation, 2004. All rights reserved.
7 *
8 */
9
10#include <linux/init.h>
11#include <linux/types.h>
12#include <linux/kernel.h>
13#include <linux/smp.h>
14#include <linux/irq.h>
15#include <linux/reboot.h>
16#include <linux/kexec.h>
17#include <linux/delay.h>
18#include <linux/elf.h>
19#include <linux/elfcore.h>
20#include <linux/kdebug.h>
21
22#include <asm/processor.h>
23#include <asm/hardirq.h>
24#include <asm/nmi.h>
25#include <asm/hw_irq.h>
26#include <asm/mach_apic.h>
27
28/* This keeps a track of which one is crashing cpu. */
29static int crashing_cpu;
30
31#ifdef CONFIG_SMP
32static atomic_t waiting_for_crash_ipi;
33
34static int crash_nmi_callback(struct notifier_block *self,
35				unsigned long val, void *data)
36{
37	struct pt_regs *regs;
38	int cpu;
39
40	if (val != DIE_NMI_IPI)
41		return NOTIFY_OK;
42
43	regs = ((struct die_args *)data)->regs;
44	cpu = raw_smp_processor_id();
45
46	/*
47	 * Don't do anything if this handler is invoked on crashing cpu.
48	 * Otherwise, system will completely hang. Crashing cpu can get
49	 * an NMI if system was initially booted with nmi_watchdog parameter.
50	 */
51	if (cpu == crashing_cpu)
52		return NOTIFY_STOP;
53	local_irq_disable();
54
55	crash_save_cpu(regs, cpu);
56	disable_local_APIC();
57	atomic_dec(&waiting_for_crash_ipi);
58	/* Assume hlt works */
59	for(;;)
60		halt();
61
62	return 1;
63}
64
65static void smp_send_nmi_allbutself(void)
66{
67	send_IPI_allbutself(NMI_VECTOR);
68}
69
70/*
71 * This code is a best effort heuristic to get the
72 * other cpus to stop executing. So races with
73 * cpu hotplug shouldn't matter.
74 */
75
76static struct notifier_block crash_nmi_nb = {
77	.notifier_call = crash_nmi_callback,
78};
79
80static void nmi_shootdown_cpus(void)
81{
82	unsigned long msecs;
83
84	atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
85	if (register_die_notifier(&crash_nmi_nb))
86		return;         /* return what? */
87
88	/*
89	 * Ensure the new callback function is set before sending
90	 * out the NMI
91	 */
92	wmb();
93
94	smp_send_nmi_allbutself();
95
96	msecs = 1000; /* Wait at most a second for the other cpus to stop */
97	while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
98		mdelay(1);
99		msecs--;
100	}
101	/* Leave the nmi callback set */
102	disable_local_APIC();
103}
104#else
105static void nmi_shootdown_cpus(void)
106{
107	/* There are no cpus to shootdown */
108}
109#endif
110
111void machine_crash_shutdown(struct pt_regs *regs)
112{
113	/*
114	 * This function is only called after the system
115	 * has panicked or is otherwise in a critical state.
116	 * The minimum amount of code to allow a kexec'd kernel
117	 * to run successfully needs to happen here.
118	 *
119	 * In practice this means shooting down the other cpus in
120	 * an SMP system.
121	 */
122	/* The kernel is broken so disable interrupts */
123	local_irq_disable();
124
125	/* Make a note of crashing cpu. Will be used in NMI callback.*/
126	crashing_cpu = smp_processor_id();
127	nmi_shootdown_cpus();
128
129	if(cpu_has_apic)
130		 disable_local_APIC();
131
132	disable_IO_APIC();
133
134	crash_save_cpu(regs, smp_processor_id());
135}
136