arch/x86/kernel/cpu/mcheck/mce_64.c

/*
 * Machine check handler.
 * K8 parts Copyright 2002,2003 Andi Kleen, SuSE Labs.
 * Rest from unknown author(s).
 * 2004 Andi Kleen. Rewrote most of it.
 * Copyright 2008 Intel Corporation
 * Author: Andi Kleen
 */

#include <linux/init.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/string.h>
#include <linux/rcupdate.h>
#include <linux/kallsyms.h>
#include <linux/sysdev.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/percpu.h>
#include <linux/poll.h>
#include <linux/thread_info.h>
#include <linux/ctype.h>
#include <linux/kmod.h>
#include <linux/kdebug.h>
#include <linux/kobject.h>
#include <linux/sysfs.h>
#include <linux/ratelimit.h>
#include <asm/processor.h>
#include <asm/msr.h>
#include <asm/mce.h>
#include <asm/uaccess.h>
#include <asm/smp.h>
#include <asm/idle.h>

#define MISC_MCELOG_MINOR 227

atomic_t mce_entry;

static int mce_dont_init;

/*
 * Tolerant levels:
 *   0: always panic on uncorrected errors, log corrected errors
 *   1: panic or SIGBUS on uncorrected errors, log corrected errors
 *   2: SIGBUS or log uncorrected errors (if possible), log corrected errors
 *   3: never panic or SIGBUS, log all errors (for testing only)
 */
static int tolerant = 1;
static int banks;
static u64 *bank;
static unsigned long notify_user;
static int rip_msr;
static int mce_bootlog = -1;
static atomic_t mce_events;

static char trigger[128];
static char *trigger_argv[2] = { trigger, NULL };

static DECLARE_WAIT_QUEUE_HEAD(mce_wait);

/* MCA banks polled by the period polling timer for corrected events */
DEFINE_PER_CPU(mce_banks_t, mce_poll_banks) = {
	[0 ... BITS_TO_LONGS(MAX_NR_BANKS)-1] = ~0UL
};

/* Do initial initialization of a struct mce */
void mce_setup(struct mce *m)
{
	memset(m, 0, sizeof(struct mce));
	m->cpu = smp_processor_id();
	rdtscll(m->tsc);
}

/*
 * Lockless MCE logging infrastructure.
 * This avoids deadlocks on printk locks without having to break locks. Also
 * separate MCEs from kernel messages to avoid bogus bug reports.
 */

static struct mce_log mcelog = {
	MCE_LOG_SIGNATURE,
	MCE_LOG_LEN,
};

void mce_log(struct mce *mce)
{
	unsigned next, entry;
	atomic_inc(&mce_events);
	mce->finished = 0;
	wmb();
	for (;;) {
		entry = rcu_dereference(mcelog.next);
		for (;;) {
			/* When the buffer fills up discard new entries. Assume
			   that the earlier errors are the more interesting. */
			if (entry >= MCE_LOG_LEN) {
				set_bit(MCE_OVERFLOW, (unsigned long *)&mcelog.flags);
				return;
			}
			/* Old left over entry. Skip. */
			if (mcelog.entry[entry].finished) {
				entry++;
				continue;
			}
			break;
		}
		smp_rmb();
		next = entry + 1;
		if (cmpxchg(&mcelog.next, entry, next) == entry)
			break;
	}
	memcpy(mcelog.entry + entry, mce, sizeof(struct mce));
	wmb();
	mcelog.entry[entry].finished = 1;
	wmb();

	set_bit(0, &notify_user);
}

static void print_mce(struct mce *m)
{
	printk(KERN_EMERG "\n"
	       KERN_EMERG "HARDWARE ERROR\n"
	       KERN_EMERG
	       "CPU %d: Machine Check Exception: %16Lx Bank %d: %016Lx\n",
	       m->cpu, m->mcgstatus, m->bank, m->status);
	if (m->ip) {
		printk(KERN_EMERG "RIP%s %02x:<%016Lx> ",
		       !(m->mcgstatus & MCG_STATUS_EIPV) ? " !INEXACT!" : "",
		       m->cs, m->ip);
		if (m->cs == __KERNEL_CS)
			print_symbol("{%s}", m->ip);
		printk("\n");
	}
	printk(KERN_EMERG "TSC %llx ", m->tsc);
	if (m->addr)
		printk("ADDR %llx ", m->addr);
	if (m->misc)
		printk("MISC %llx ", m->misc);
	printk("\n");
	printk(KERN_EMERG "This is not a software problem!\n");
	printk(KERN_EMERG "Run through mcelog --ascii to decode "
	       "and contact your hardware vendor\n");
}

static void mce_panic(char *msg, struct mce *backup, unsigned long start)
{
	int i;

	oops_begin();
	for (i = 0; i < MCE_LOG_LEN; i++) {
		unsigned long tsc = mcelog.entry[i].tsc;

		if (time_before(tsc, start))
			continue;
		print_mce(&mcelog.entry[i]);
		if (backup && mcelog.entry[i].tsc == backup->tsc)
			backup = NULL;
	}
	if (backup)
		print_mce(backup);
	panic(msg);
}

int mce_available(struct cpuinfo_x86 *c)
{
	if (mce_dont_init)
		return 0;
	return cpu_has(c, X86_FEATURE_MCE) && cpu_has(c, X86_FEATURE_MCA);
}

static inline void mce_get_rip(struct mce *m, struct pt_regs *regs)
{
	if (regs && (m->mcgstatus & MCG_STATUS_RIPV)) {
		m->ip = regs->ip;
		m->cs = regs->cs;
	} else {
		m->ip = 0;
		m->cs = 0;
	}
	if (rip_msr) {
		/* Assume the RIP in the MSR is exact. Is this true? */
		m->mcgstatus |= MCG_STATUS_EIPV;
		rdmsrl(rip_msr, m->ip);
		m->cs = 0;
	}
}

/*
 * Poll for corrected events or events that happened before reset.
 * Those are just logged through /dev/mcelog.
 *
 * This is executed in standard interrupt context.
 */
void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
{
	struct mce m;
	int i;

	mce_setup(&m);

	rdmsrl(MSR_IA32_MCG_STATUS, m.mcgstatus);
	for (i = 0; i < banks; i++) {
		if (!bank[i] || !test_bit(i, *b))
			continue;

		m.misc = 0;
		m.addr = 0;
		m.bank = i;
		m.tsc = 0;

		barrier();
		rdmsrl(MSR_IA32_MC0_STATUS + i*4, m.status);
		if (!(m.status & MCI_STATUS_VAL))
			continue;

		/*
		 * Uncorrected events are handled by the exception handler
		 * when it is enabled. But when the exception is disabled log
		 * everything.
		 *
		 * TBD do the same check for MCI_STATUS_EN here?
		 */
		if ((m.status & MCI_STATUS_UC) && !(flags & MCP_UC))
			continue;

		if (m.status & MCI_STATUS_MISCV)
			rdmsrl(MSR_IA32_MC0_MISC + i*4, m.misc);
		if (m.status & MCI_STATUS_ADDRV)
			rdmsrl(MSR_IA32_MC0_ADDR + i*4, m.addr);

		if (!(flags & MCP_TIMESTAMP))
			m.tsc = 0;
		/*
		 * Don't get the IP here because it's unlikely to
		 * have anything to do with the actual error location.
		 */

		mce_log(&m);
		add_taint(TAINT_MACHINE_CHECK);

		/*
		 * Clear state for this bank.
		 */
		wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0);
	}

	/*
	 * Don't clear MCG_STATUS here because it's only defined for
	 * exceptions.
	 */
}

/*
 * The actual machine check handler. This only handles real
 * exceptions when something got corrupted coming in through int 18.
 *
 * This is executed in NMI context not subject to normal locking rules. This
 * implies that most kernel services cannot be safely used. Don't even
 * think about putting a printk in there!
 */
void do_machine_check(struct pt_regs * regs, long error_code)
{
	struct mce m, panicm;
	u64 mcestart = 0;
	int i;
	int panicm_found = 0;
	/*
	 * If no_way_out gets set, there is no safe way to recover from this
	 * MCE.  If tolerant is cranked up, we'll try anyway.
	 */
	int no_way_out = 0;
	/*
	 * If kill_it gets set, there might be a way to recover from this
	 * error.
	 */
	int kill_it = 0;
	DECLARE_BITMAP(toclear, MAX_NR_BANKS);

	atomic_inc(&mce_entry);

	if (notify_die(DIE_NMI, "machine check", regs, error_code,
			   18, SIGKILL) == NOTIFY_STOP)
		goto out2;
	if (!banks)
		goto out2;

	mce_setup(&m);

	rdmsrl(MSR_IA32_MCG_STATUS, m.mcgstatus);
	/* if the restart IP is not valid, we're done for */
	if (!(m.mcgstatus & MCG_STATUS_RIPV))
		no_way_out = 1;

	rdtscll(mcestart);
	barrier();

	for (i = 0; i < banks; i++) {
		__clear_bit(i, toclear);
		if (!bank[i])
			continue;

		m.misc = 0;
		m.addr = 0;
		m.bank = i;

		rdmsrl(MSR_IA32_MC0_STATUS + i*4, m.status);
		if ((m.status & MCI_STATUS_VAL) == 0)
			continue;

		/*
		 * Non uncorrected errors are handled by machine_check_poll
		 * Leave them alone.
		 */
		if ((m.status & MCI_STATUS_UC) == 0)
			continue;

		/*
		 * Set taint even when machine check was not enabled.
		 */
		add_taint(TAINT_MACHINE_CHECK);

		__set_bit(i, toclear);

		if (m.status & MCI_STATUS_EN) {
			/* if PCC was set, there's no way out */
			no_way_out |= !!(m.status & MCI_STATUS_PCC);
			/*
			 * If this error was uncorrectable and there was
			 * an overflow, we're in trouble.  If no overflow,
			 * we might get away with just killing a task.
			 */
			if (m.status & MCI_STATUS_UC) {
				if (tolerant < 1 || m.status & MCI_STATUS_OVER)
					no_way_out = 1;
				kill_it = 1;
			}
		} else {
			/*
			 * Machine check event was not enabled. Clear, but
			 * ignore.
			 */
			continue;
		}

		if (m.status & MCI_STATUS_MISCV)
			rdmsrl(MSR_IA32_MC0_MISC + i*4, m.misc);
		if (m.status & MCI_STATUS_ADDRV)
			rdmsrl(MSR_IA32_MC0_ADDR + i*4, m.addr);

		mce_get_rip(&m, regs);
		mce_log(&m);

		/* Did this bank cause the exception? */
		/* Assume that the bank with uncorrectable errors did it,
		   and that there is only a single one. */
		if ((m.status & MCI_STATUS_UC) && (m.status & MCI_STATUS_EN)) {
			panicm = m;
			panicm_found = 1;
		}
	}

	/* If we didn't find an uncorrectable error, pick
	   the last one (shouldn't happen, just being safe). */
	if (!panicm_found)
		panicm = m;

	/*
	 * If we have decided that we just CAN'T continue, and the user
	 *  has not set tolerant to an insane level, give up and die.
	 */
	if (no_way_out && tolerant < 3)
		mce_panic("Machine check", &panicm, mcestart);

	/*
	 * If the error seems to be unrecoverable, something should be
	 * done.  Try to kill as little as possible.  If we can kill just
	 * one task, do that.  If the user has set the tolerance very
	 * high, don't try to do anything at all.
	 */
	if (kill_it && tolerant < 3) {
		int user_space = 0;

		/*
		 * If the EIPV bit is set, it means the saved IP is the
		 * instruction which caused the MCE.
		 */
		if (m.mcgstatus & MCG_STATUS_EIPV)
			user_space = panicm.ip && (panicm.cs & 3);

		/*
		 * If we know that the error was in user space, send a
		 * SIGBUS.  Otherwise, panic if tolerance is low.
		 *
		 * force_sig() takes an awful lot of locks and has a slight
		 * risk of deadlocking.
		 */
		if (user_space) {
			force_sig(SIGBUS, current);
		} else if (panic_on_oops || tolerant < 2) {
			mce_panic("Uncorrected machine check",
				&panicm, mcestart);
		}
	}

	/* notify userspace ASAP */
	set_thread_flag(TIF_MCE_NOTIFY);

	/* the last thing we do is clear state */
	for (i = 0; i < banks; i++) {
		if (test_bit(i, toclear))
			wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0);
	}
	wrmsrl(MSR_IA32_MCG_STATUS, 0);
 out2:
	atomic_dec(&mce_entry);
}

#ifdef CONFIG_X86_MCE_INTEL
/***
 * mce_log_therm_throt_event - Logs the thermal throttling event to mcelog
 * @cpu: The CPU on which the event occurred.
 * @status: Event status information
 *
 * This function should be called by the thermal interrupt after the
 * event has been processed and the decision was made to log the event
 * further.
 *
 * The status parameter will be saved to the 'status' field of 'struct mce'
 * and historically has been the register value of the
 * MSR_IA32_THERMAL_STATUS (Intel) msr.
 */
void mce_log_therm_throt_event(__u64 status)
{
	struct mce m;

	mce_setup(&m);
	m.bank = MCE_THERMAL_BANK;
	m.status = status;
	mce_log(&m);
}
#endif /* CONFIG_X86_MCE_INTEL */

/*
 * Periodic polling timer for "silent" machine check errors.  If the
 * poller finds an MCE, poll 2x faster.  When the poller finds no more
 * errors, poll 2x slower (up to check_interval seconds).
 */

static int check_interval = 5 * 60; /* 5 minutes */
static int next_interval; /* in jiffies */
static void mcheck_timer(unsigned long);
static DEFINE_PER_CPU(struct timer_list, mce_timer);

static void mcheck_timer(unsigned long data)
{
	struct timer_list *t = &per_cpu(mce_timer, data);

	WARN_ON(smp_processor_id() != data);

	if (mce_available(&current_cpu_data))
		machine_check_poll(MCP_TIMESTAMP,
				&__get_cpu_var(mce_poll_banks));

	/*
	 * Alert userspace if needed.  If we logged an MCE, reduce the
	 * polling interval, otherwise increase the polling interval.
	 */
	if (mce_notify_user()) {
		next_interval = max(next_interval/2, HZ/100);
	} else {
		next_interval = min(next_interval * 2,
				(int)round_jiffies_relative(check_interval*HZ));
	}

	t->expires = jiffies + next_interval;
	add_timer(t);
}

static void mce_do_trigger(struct work_struct *work)
{
	call_usermodehelper(trigger, trigger_argv, NULL, UMH_NO_WAIT);
}

static DECLARE_WORK(mce_trigger_work, mce_do_trigger);

/*
 * Notify the user(s) about new machine check events.
 * Can be called from interrupt context, but not from machine check/NMI
 * context.
 */
int mce_notify_user(void)
{
	/* Not more than two messages every minute */
	static DEFINE_RATELIMIT_STATE(ratelimit, 60*HZ, 2);

	clear_thread_flag(TIF_MCE_NOTIFY);
	if (test_and_clear_bit(0, &notify_user)) {
		wake_up_interruptible(&mce_wait);

		/*
		 * There is no risk of missing notifications because
		 * work_pending is always cleared before the function is
		 * executed.
		 */
		if (trigger[0] && !work_pending(&mce_trigger_work))
			schedule_work(&mce_trigger_work);

		if (__ratelimit(&ratelimit))
			printk(KERN_INFO "Machine check events logged\n");

		return 1;
	}
	return 0;
}

/* see if the idle task needs to notify userspace */
static int
mce_idle_callback(struct notifier_block *nfb, unsigned long action, void *junk)
{
	/* IDLE_END should be safe - interrupts are back on */
	if (action == IDLE_END && test_thread_flag(TIF_MCE_NOTIFY))
		mce_notify_user();

	return NOTIFY_OK;
}

static struct notifier_block mce_idle_notifier = {
	.notifier_call = mce_idle_callback,
};

static __init int periodic_mcheck_init(void)
{
       idle_notifier_register(&mce_idle_notifier);
       return 0;
}
__initcall(periodic_mcheck_init);

/*
 * Initialize Machine Checks for a CPU.
 */
static int mce_cap_init(void)
{
	u64 cap;
	unsigned b;

	rdmsrl(MSR_IA32_MCG_CAP, cap);
	b = cap & 0xff;
	if (b > MAX_NR_BANKS) {
		printk(KERN_WARNING
		       "MCE: Using only %u machine check banks out of %u\n",
			MAX_NR_BANKS, b);
		b = MAX_NR_BANKS;
	}

	/* Don't support asymmetric configurations today */
	WARN_ON(banks != 0 && b != banks);
	banks = b;
	if (!bank) {
		bank = kmalloc(banks * sizeof(u64), GFP_KERNEL);
		if (!bank)
			return -ENOMEM;
		memset(bank, 0xff, banks * sizeof(u64));
	}

	/* Use accurate RIP reporting if available. */
	if ((cap & (1<<9)) && ((cap >> 16) & 0xff) >= 9)
		rip_msr = MSR_IA32_MCG_EIP;

	return 0;
}

static void mce_init(void *dummy)
{
	u64 cap;
	int i;
	mce_banks_t all_banks;

	/*
	 * Log the machine checks left over from the previous reset.
	 */
	bitmap_fill(all_banks, MAX_NR_BANKS);
	machine_check_poll(MCP_UC, &all_banks);

	set_in_cr4(X86_CR4_MCE);

	rdmsrl(MSR_IA32_MCG_CAP, cap);
	if (cap & MCG_CTL_P)
		wrmsr(MSR_IA32_MCG_CTL, 0xffffffff, 0xffffffff);

	for (i = 0; i < banks; i++) {
		wrmsrl(MSR_IA32_MC0_CTL+4*i, bank[i]);
		wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0);
	}
}

/* Add per CPU specific workarounds here */
static void mce_cpu_quirks(struct cpuinfo_x86 *c)
{
	/* This should be disabled by the BIOS, but isn't always */
	if (c->x86_vendor == X86_VENDOR_AMD) {
		if (c->x86 == 15 && banks > 4)
			/* disable GART TBL walk error reporting, which trips off
			   incorrectly with the IOMMU & 3ware & Cerberus. */
			clear_bit(10, (unsigned long *)&bank[4]);
		if(c->x86 <= 17 && mce_bootlog < 0)
			/* Lots of broken BIOS around that don't clear them
			   by default and leave crap in there. Don't log. */
			mce_bootlog = 0;
	}

}

static void mce_cpu_features(struct cpuinfo_x86 *c)
{
	switch (c->x86_vendor) {
	case X86_VENDOR_INTEL:
		mce_intel_feature_init(c);
		break;
	case X86_VENDOR_AMD:
		mce_amd_feature_init(c);
		break;
	default:
		break;
	}
}

static void mce_init_timer(void)
{
	struct timer_list *t = &__get_cpu_var(mce_timer);

	/* data race harmless because everyone sets to the same value */
	if (!next_interval)
		next_interval = check_interval * HZ;
	if (!next_interval)
		return;
	setup_timer(t, mcheck_timer, smp_processor_id());
	t->expires = round_jiffies(jiffies + next_interval);
	add_timer(t);
}

/*
 * Called for each booted CPU to set up machine checks.
 * Must be called with preempt off.
 */
void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
{
	if (!mce_available(c))
		return;

	if (mce_cap_init() < 0) {
		mce_dont_init = 1;
		return;
	}
	mce_cpu_quirks(c);

	mce_init(NULL);
	mce_cpu_features(c);
	mce_init_timer();
}

/*
 * Character device to read and clear the MCE log.
 */

static DEFINE_SPINLOCK(mce_state_lock);
static int open_count;	/* #times opened */
static int open_exclu;	/* already open exclusive? */

static int mce_open(struct inode *inode, struct file *file)
{
	lock_kernel();
	spin_lock(&mce_state_lock);

	if (open_exclu || (open_count && (file->f_flags & O_EXCL))) {
		spin_unlock(&mce_state_lock);
		unlock_kernel();
		return -EBUSY;
	}

	if (file->f_flags & O_EXCL)
		open_exclu = 1;
	open_count++;

	spin_unlock(&mce_state_lock);
	unlock_kernel();

	return nonseekable_open(inode, file);
}

static int mce_release(struct inode *inode, struct file *file)
{
	spin_lock(&mce_state_lock);

	open_count--;
	open_exclu = 0;

	spin_unlock(&mce_state_lock);

	return 0;
}

static void collect_tscs(void *data)
{
	unsigned long *cpu_tsc = (unsigned long *)data;

	rdtscll(cpu_tsc[smp_processor_id()]);
}

static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize,
			loff_t *off)
{
	unsigned long *cpu_tsc;
	static DEFINE_MUTEX(mce_read_mutex);
	unsigned prev, next;
	char __user *buf = ubuf;
	int i, err;

	cpu_tsc = kmalloc(nr_cpu_ids * sizeof(long), GFP_KERNEL);
	if (!cpu_tsc)
		return -ENOMEM;

	mutex_lock(&mce_read_mutex);
	next = rcu_dereference(mcelog.next);

	/* Only supports full reads right now */
	if (*off != 0 || usize < MCE_LOG_LEN*sizeof(struct mce)) {
		mutex_unlock(&mce_read_mutex);
		kfree(cpu_tsc);
		return -EINVAL;
	}

	err = 0;
	prev = 0;
	do {
		for (i = prev; i < next; i++) {
			unsigned long start = jiffies;

			while (!mcelog.entry[i].finished) {
				if (time_after_eq(jiffies, start + 2)) {
					memset(mcelog.entry + i, 0,
					       sizeof(struct mce));
					goto timeout;
				}
				cpu_relax();
			}
			smp_rmb();
			err |= copy_to_user(buf, mcelog.entry + i,
					    sizeof(struct mce));
			buf += sizeof(struct mce);
timeout:
			;
		}

		memset(mcelog.entry + prev, 0,
		       (next - prev) * sizeof(struct mce));
		prev = next;
		next = cmpxchg(&mcelog.next, prev, 0);
	} while (next != prev);

	synchronize_sched();

	/*
	 * Collect entries that were still getting written before the
	 * synchronize.
	 */
	on_each_cpu(collect_tscs, cpu_tsc, 1);
	for (i = next; i < MCE_LOG_LEN; i++) {
		if (mcelog.entry[i].finished &&
		    mcelog.entry[i].tsc < cpu_tsc[mcelog.entry[i].cpu]) {
			err |= copy_to_user(buf, mcelog.entry+i,
					    sizeof(struct mce));
			smp_rmb();
			buf += sizeof(struct mce);
			memset(&mcelog.entry[i], 0, sizeof(struct mce));
		}
	}
	mutex_unlock(&mce_read_mutex);
	kfree(cpu_tsc);
	return err ? -EFAULT : buf - ubuf;
}

static unsigned int mce_poll(struct file *file, poll_table *wait)
{
	poll_wait(file, &mce_wait, wait);
	if (rcu_dereference(mcelog.next))
		return POLLIN | POLLRDNORM;
	return 0;
}

static long mce_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
{
	int __user *p = (int __user *)arg;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	switch (cmd) {
	case MCE_GET_RECORD_LEN:
		return put_user(sizeof(struct mce), p);
	case MCE_GET_LOG_LEN:
		return put_user(MCE_LOG_LEN, p);
	case MCE_GETCLEAR_FLAGS: {
		unsigned flags;

		do {
			flags = mcelog.flags;
		} while (cmpxchg(&mcelog.flags, flags, 0) != flags);
		return put_user(flags, p);
	}
	default:
		return -ENOTTY;
	}
}

static const struct file_operations mce_chrdev_ops = {
	.open = mce_open,
	.release = mce_release,
	.read = mce_read,
	.poll = mce_poll,
	.unlocked_ioctl = mce_ioctl,
};

static struct miscdevice mce_log_device = {
	MISC_MCELOG_MINOR,
	"mcelog",
	&mce_chrdev_ops,
};

/*
 * Old style boot options parsing. Only for compatibility.
 */
static int __init mcheck_disable(char *str)
{
	mce_dont_init = 1;
	return 1;
}

/* mce=off disables machine check.
   mce=TOLERANCELEVEL (number, see above)
   mce=bootlog Log MCEs from before booting. Disabled by default on AMD.
   mce=nobootlog Don't log MCEs from before booting. */
static int __init mcheck_enable(char *str)
{
	if (!strcmp(str, "off"))
		mce_dont_init = 1;
	else if (!strcmp(str, "bootlog") || !strcmp(str,"nobootlog"))
		mce_bootlog = str[0] == 'b';
	else if (isdigit(str[0]))
		get_option(&str, &tolerant);
	else
		printk("mce= argument %s ignored. Please use /sys", str);
	return 1;
}

__setup("nomce", mcheck_disable);
__setup("mce=", mcheck_enable);

/*
 * Sysfs support
 */

/*
 * Disable machine checks on suspend and shutdown. We can't really handle
 * them later.
 */
static int mce_disable(void)
{
	int i;

	for (i = 0; i < banks; i++)
		wrmsrl(MSR_IA32_MC0_CTL + i*4, 0);
	return 0;
}

static int mce_suspend(struct sys_device *dev, pm_message_t state)
{
	return mce_disable();
}

static int mce_shutdown(struct sys_device *dev)
{
	return mce_disable();
}

/* On resume clear all MCE state. Don't want to see leftovers from the BIOS.
   Only one CPU is active at this time, the others get readded later using
   CPU hotplug. */
static int mce_resume(struct sys_device *dev)
{
	mce_init(NULL);
	mce_cpu_features(&current_cpu_data);
	return 0;
}

static void mce_cpu_restart(void *data)
{
	del_timer_sync(&__get_cpu_var(mce_timer));
	if (mce_available(&current_cpu_data))
		mce_init(NULL);
	mce_init_timer();
}

/* Reinit MCEs after user configuration changes */
static void mce_restart(void)
{
	next_interval = check_interval * HZ;
	on_each_cpu(mce_cpu_restart, NULL, 1);
}

static struct sysdev_class mce_sysclass = {
	.suspend = mce_suspend,
	.shutdown = mce_shutdown,
	.resume = mce_resume,
	.name = "machinecheck",
};

DEFINE_PER_CPU(struct sys_device, device_mce);
void (*threshold_cpu_callback)(unsigned long action, unsigned int cpu) __cpuinitdata;

/* Why are there no generic functions for this? */
#define ACCESSOR(name, var, start) \
	static ssize_t show_ ## name(struct sys_device *s,		\
				     struct sysdev_attribute *attr,	\
				     char *buf) {			\
		return sprintf(buf, "%lx\n", (unsigned long)var);	\
	}								\
	static ssize_t set_ ## name(struct sys_device *s,		\
				    struct sysdev_attribute *attr,	\
				    const char *buf, size_t siz) {	\
		char *end;						\
		unsigned long new = simple_strtoul(buf, &end, 0);	\
		if (end == buf) return -EINVAL;				\
		var = new;						\
		start;							\
		return end-buf;						\
	}								\
	static SYSDEV_ATTR(name, 0644, show_ ## name, set_ ## name);

static struct sysdev_attribute *bank_attrs;

static ssize_t show_bank(struct sys_device *s, struct sysdev_attribute *attr,
			 char *buf)
{
	u64 b = bank[attr - bank_attrs];
	return sprintf(buf, "%llx\n", b);
}

static ssize_t set_bank(struct sys_device *s, struct sysdev_attribute *attr,
			const char *buf, size_t siz)
{
	char *end;
	u64 new = simple_strtoull(buf, &end, 0);
	if (end == buf)
		return -EINVAL;
	bank[attr - bank_attrs] = new;
	mce_restart();
	return end-buf;
}

static ssize_t show_trigger(struct sys_device *s, struct sysdev_attribute *attr,
				char *buf)
{
	strcpy(buf, trigger);
	strcat(buf, "\n");
	return strlen(trigger) + 1;
}

static ssize_t set_trigger(struct sys_device *s, struct sysdev_attribute *attr,
				const char *buf,size_t siz)
{
	char *p;
	int len;
	strncpy(trigger, buf, sizeof(trigger));
	trigger[sizeof(trigger)-1] = 0;
	len = strlen(trigger);
	p = strchr(trigger, '\n');
	if (*p) *p = 0;
	return len;
}

static SYSDEV_ATTR(trigger, 0644, show_trigger, set_trigger);
static SYSDEV_INT_ATTR(tolerant, 0644, tolerant);
ACCESSOR(check_interval,check_interval,mce_restart())
static struct sysdev_attribute *mce_attributes[] = {
	&attr_tolerant.attr, &attr_check_interval, &attr_trigger,
	NULL
};

static cpumask_var_t mce_device_initialized;

/* Per cpu sysdev init.  All of the cpus still share the same ctl bank */
static __cpuinit int mce_create_device(unsigned int cpu)
{
	int err;
	int i;

	if (!mce_available(&boot_cpu_data))
		return -EIO;

	memset(&per_cpu(device_mce, cpu).kobj, 0, sizeof(struct kobject));
	per_cpu(device_mce,cpu).id = cpu;
	per_cpu(device_mce,cpu).cls = &mce_sysclass;

	err = sysdev_register(&per_cpu(device_mce,cpu));
	if (err)
		return err;

	for (i = 0; mce_attributes[i]; i++) {
		err = sysdev_create_file(&per_cpu(device_mce,cpu),
					 mce_attributes[i]);
		if (err)
			goto error;
	}
	for (i = 0; i < banks; i++) {
		err = sysdev_create_file(&per_cpu(device_mce, cpu),
					&bank_attrs[i]);
		if (err)
			goto error2;
	}
	cpumask_set_cpu(cpu, mce_device_initialized);

	return 0;
error2:
	while (--i >= 0) {
		sysdev_remove_file(&per_cpu(device_mce, cpu),
					&bank_attrs[i]);
	}
error:
	while (--i >= 0) {
		sysdev_remove_file(&per_cpu(device_mce,cpu),
				   mce_attributes[i]);
	}
	sysdev_unregister(&per_cpu(device_mce,cpu));

	return err;
}

static __cpuinit void mce_remove_device(unsigned int cpu)
{
	int i;

	if (!cpumask_test_cpu(cpu, mce_device_initialized))
		return;

	for (i = 0; mce_attributes[i]; i++)
		sysdev_remove_file(&per_cpu(device_mce,cpu),
			mce_attributes[i]);
	for (i = 0; i < banks; i++)
		sysdev_remove_file(&per_cpu(device_mce, cpu),
			&bank_attrs[i]);
	sysdev_unregister(&per_cpu(device_mce,cpu));
	cpumask_clear_cpu(cpu, mce_device_initialized);
}

/* Make sure there are no machine checks on offlined CPUs. */
static void mce_disable_cpu(void *h)
{
	int i;
	unsigned long action = *(unsigned long *)h;

	if (!mce_available(&current_cpu_data))
		return;
	if (!(action & CPU_TASKS_FROZEN))
		cmci_clear();
	for (i = 0; i < banks; i++)
		wrmsrl(MSR_IA32_MC0_CTL + i*4, 0);
}

static void mce_reenable_cpu(void *h)
{
	int i;
	unsigned long action = *(unsigned long *)h;

	if (!mce_available(&current_cpu_data))
		return;
	if (!(action & CPU_TASKS_FROZEN))
		cmci_reenable();
	for (i = 0; i < banks; i++)
		wrmsrl(MSR_IA32_MC0_CTL + i*4, bank[i]);
}

/* Get notified when a cpu comes on/off. Be hotplug friendly. */
static int __cpuinit mce_cpu_callback(struct notifier_block *nfb,
				      unsigned long action, void *hcpu)
{
	unsigned int cpu = (unsigned long)hcpu;
	struct timer_list *t = &per_cpu(mce_timer, cpu);

	switch (action) {
	case CPU_ONLINE:
	case CPU_ONLINE_FROZEN:
		mce_create_device(cpu);
		if (threshold_cpu_callback)
			threshold_cpu_callback(action, cpu);
		break;
	case CPU_DEAD:
	case CPU_DEAD_FROZEN:
		if (threshold_cpu_callback)
			threshold_cpu_callback(action, cpu);
		mce_remove_device(cpu);
		break;
	case CPU_DOWN_PREPARE:
	case CPU_DOWN_PREPARE_FROZEN:
		del_timer_sync(t);
		smp_call_function_single(cpu, mce_disable_cpu, &action, 1);
		break;
	case CPU_DOWN_FAILED:
	case CPU_DOWN_FAILED_FROZEN:
		t->expires = round_jiffies(jiffies + next_interval);
		add_timer_on(t, cpu);
		smp_call_function_single(cpu, mce_reenable_cpu, &action, 1);
		break;
	case CPU_POST_DEAD:
		/* intentionally ignoring frozen here */
		cmci_rediscover(cpu);
		break;
	}
	return NOTIFY_OK;
}

static struct notifier_block mce_cpu_notifier __cpuinitdata = {
	.notifier_call = mce_cpu_callback,
};

static __init int mce_init_banks(void)
{
	int i;

	bank_attrs = kzalloc(sizeof(struct sysdev_attribute) * banks,
				GFP_KERNEL);
	if (!bank_attrs)
		return -ENOMEM;

	for (i = 0; i < banks; i++) {
		struct sysdev_attribute *a = &bank_attrs[i];
		a->attr.name = kasprintf(GFP_KERNEL, "bank%d", i);
		if (!a->attr.name)
			goto nomem;
		a->attr.mode = 0644;
		a->show = show_bank;
		a->store = set_bank;
	}
	return 0;

nomem:
	while (--i >= 0)
		kfree(bank_attrs[i].attr.name);
	kfree(bank_attrs);
	bank_attrs = NULL;
	return -ENOMEM;
}

static __init int mce_init_device(void)
{
	int err;
	int i = 0;

	if (!mce_available(&boot_cpu_data))
		return -EIO;

	alloc_cpumask_var(&mce_device_initialized, GFP_KERNEL);

	err = mce_init_banks();
	if (err)
		return err;

	err = sysdev_class_register(&mce_sysclass);
	if (err)
		return err;

	for_each_online_cpu(i) {
		err = mce_create_device(i);
		if (err)
			return err;
	}

	register_hotcpu_notifier(&mce_cpu_notifier);
	misc_register(&mce_log_device);
	return err;
}

device_initcall(mce_init_device);