path: root/linux-2.6-xen-sparse/arch/i386/kernel/time-xen.c

/*
 *  linux/arch/i386/kernel/time.c
 *
 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
 *
 * This file contains the PC-specific time handling details:
 * reading the RTC at bootup, etc..
 * 1994-07-02    Alan Modra
 *	fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
 * 1995-03-26    Markus Kuhn
 *      fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
 *      precision CMOS clock update
 * 1996-05-03    Ingo Molnar
 *      fixed time warps in do_[slow|fast]_gettimeoffset()
 * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
 *		"A Kernel Model for Precision Timekeeping" by Dave Mills
 * 1998-09-05    (Various)
 *	More robust do_fast_gettimeoffset() algorithm implemented
 *	(works with APM, Cyrix 6x86MX and Centaur C6),
 *	monotonic gettimeofday() with fast_get_timeoffset(),
 *	drift-proof precision TSC calibration on boot
 *	(C. Scott Ananian <cananian@alumni.princeton.edu>, Andrew D.
 *	Balsa <andrebalsa@altern.org>, Philip Gladstone <philip@raptor.com>;
 *	ported from 2.0.35 Jumbo-9 by Michael Krause <m.krause@tu-harburg.de>).
 * 1998-12-16    Andrea Arcangeli
 *	Fixed Jumbo-9 code in 2.1.131: do_gettimeofday was missing 1 jiffy
 *	because was not accounting lost_ticks.
 * 1998-12-24 Copyright (C) 1998  Andrea Arcangeli
 *	Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
 *	serialize accesses to xtime/lost_ticks).
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/module.h>
#include <linux/sysdev.h>
#include <linux/bcd.h>
#include <linux/efi.h>
#include <linux/mca.h>
#include <linux/sysctl.h>
#include <linux/percpu.h>
#include <linux/kernel_stat.h>
#include <linux/posix-timers.h>

#include <asm/io.h>
#include <asm/smp.h>
#include <asm/irq.h>
#include <asm/msr.h>
#include <asm/delay.h>
#include <asm/mpspec.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
#include <asm/timer.h>
#include <asm/sections.h>

#include "mach_time.h"

#include <linux/timex.h>
#include <linux/config.h>

#include <asm/hpet.h>

#include <asm/arch_hooks.h>

#include <xen/evtchn.h>
#include <xen/interface/vcpu.h>

#if defined (__i386__)
#include <asm/i8259.h>
#endif

int pit_latch_buggy;              /* extern */

#if defined(__x86_64__)
unsigned long vxtime_hz = PIT_TICK_RATE;
struct vxtime_data __vxtime __section_vxtime;   /* for vsyscalls */
volatile unsigned long __jiffies __section_jiffies = INITIAL_JIFFIES;
unsigned long __wall_jiffies __section_wall_jiffies = INITIAL_JIFFIES;
struct timespec __xtime __section_xtime;
struct timezone __sys_tz __section_sys_tz;
#endif

unsigned int cpu_khz;	/* Detected as we calibrate the TSC */
EXPORT_SYMBOL(cpu_khz);

extern unsigned long wall_jiffies;

DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);

#if defined (__i386__)
#include <asm/i8253.h>
#endif

DEFINE_SPINLOCK(i8253_lock);
EXPORT_SYMBOL(i8253_lock);

extern struct init_timer_opts timer_tsc_init;
extern struct timer_opts timer_tsc;
#define timer_none timer_tsc
struct timer_opts *cur_timer __read_mostly = &timer_tsc;

/* These are peridically updated in shared_info, and then copied here. */
struct shadow_time_info {
	u64 tsc_timestamp;     /* TSC at last update of time vals.  */
	u64 system_timestamp;  /* Time, in nanosecs, since boot.    */
	u32 tsc_to_nsec_mul;
	u32 tsc_to_usec_mul;
	int tsc_shift;
	u32 version;
};
static DEFINE_PER_CPU(struct shadow_time_info, shadow_time);
static struct timespec shadow_tv;
static u32 shadow_tv_version;

/* Keep track of last time we did processing/updating of jiffies and xtime. */
static u64 processed_system_time;   /* System time (ns) at last processing. */
static DEFINE_PER_CPU(u64, processed_system_time);

/* How much CPU time was spent blocked and how much was 'stolen'? */
static DEFINE_PER_CPU(u64, processed_stolen_time);
static DEFINE_PER_CPU(u64, processed_blocked_time);

/* Current runstate of each CPU (updated automatically by the hypervisor). */
static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate);

/* Must be signed, as it's compared with s64 quantities which can be -ve. */
#define NS_PER_TICK (1000000000LL/HZ)

static inline void __normalize_time(time_t *sec, s64 *nsec)
{
	while (*nsec >= NSEC_PER_SEC) {
		(*nsec) -= NSEC_PER_SEC;
		(*sec)++;
	}
	while (*nsec < 0) {
		(*nsec) += NSEC_PER_SEC;
		(*sec)--;
	}
}

/* Does this guest OS track Xen time, or set its wall clock independently? */
static int independent_wallclock = 0;
static int __init __independent_wallclock(char *str)
{
	independent_wallclock = 1;
	return 1;
}
__setup("independent_wallclock", __independent_wallclock);

/* Permitted clock jitter, in nsecs, beyond which a warning will be printed. */
static unsigned long permitted_clock_jitter = 10000000UL; /* 10ms */
static int __init __permitted_clock_jitter(char *str)
{
	permitted_clock_jitter = simple_strtoul(str, NULL, 0);
	return 1;
}
__setup("permitted_clock_jitter=", __permitted_clock_jitter);

int tsc_disable __devinitdata = 0;

static void delay_tsc(unsigned long loops)
{
	unsigned long bclock, now;

	rdtscl(bclock);
	do {
		rep_nop();
		rdtscl(now);
	} while ((now - bclock) < loops);
}

struct timer_opts timer_tsc = {
	.name = "tsc",
	.delay = delay_tsc,
};

/*
 * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
 * yielding a 64-bit result.
 */
static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
{
	u64 product;
#ifdef __i386__
	u32 tmp1, tmp2;
#endif

	if (shift < 0)
		delta >>= -shift;
	else
		delta <<= shift;

#ifdef __i386__
	__asm__ (
		"mul  %5       ; "
		"mov  %4,%%eax ; "
		"mov  %%edx,%4 ; "
		"mul  %5       ; "
		"xor  %5,%5    ; "
		"add  %4,%%eax ; "
		"adc  %5,%%edx ; "
		: "=A" (product), "=r" (tmp1), "=r" (tmp2)
		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
#else
	__asm__ (
		"mul %%rdx ; shrd $32,%%rdx,%%rax"
		: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
#endif

	return product;
}

#if defined (__i386__)
int read_current_timer(unsigned long *timer_val)
{
	rdtscl(*timer_val);
	return 0;
}
#endif

void init_cpu_khz(void)
{
	u64 __cpu_khz = 1000000ULL << 32;
	struct vcpu_time_info *info;
	info = &HYPERVISOR_shared_info->vcpu_info[0].time;
	do_div(__cpu_khz, info->tsc_to_system_mul);
	if (info->tsc_shift < 0)
		cpu_khz = __cpu_khz << -info->tsc_shift;
	else
		cpu_khz = __cpu_khz >> info->tsc_shift;
}

static u64 get_nsec_offset(struct shadow_time_info *shadow)
{
	u64 now, delta;
	rdtscll(now);
	delta = now - shadow->tsc_timestamp;
	return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
}

static unsigned long get_usec_offset(struct shadow_time_info *shadow)
{
	u64 now, delta;
	rdtscll(now);
	delta = now - shadow->tsc_timestamp;
	return scale_delta(delta, shadow->tsc_to_usec_mul, shadow->tsc_shift);
}

static void __update_wallclock(time_t sec, long nsec)
{
	long wtm_nsec, xtime_nsec;
	time_t wtm_sec, xtime_sec;
	u64 tmp, wc_nsec;

	/* Adjust wall-clock time base based on wall_jiffies ticks. */
	wc_nsec = processed_system_time;
	wc_nsec += sec * (u64)NSEC_PER_SEC;
	wc_nsec += nsec;
	wc_nsec -= (jiffies - wall_jiffies) * (u64)NS_PER_TICK;

	/* Split wallclock base into seconds and nanoseconds. */
	tmp = wc_nsec;
	xtime_nsec = do_div(tmp, 1000000000);
	xtime_sec  = (time_t)tmp;

	wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - xtime_sec);
	wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - xtime_nsec);

	set_normalized_timespec(&xtime, xtime_sec, xtime_nsec);
	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);

	ntp_clear();
}

static void update_wallclock(void)
{
	shared_info_t *s = HYPERVISOR_shared_info;

	do {
		shadow_tv_version = s->wc_version;
		rmb();
		shadow_tv.tv_sec  = s->wc_sec;
		shadow_tv.tv_nsec = s->wc_nsec;
		rmb();
	} while ((s->wc_version & 1) | (shadow_tv_version ^ s->wc_version));

	if (!independent_wallclock)
		__update_wallclock(shadow_tv.tv_sec, shadow_tv.tv_nsec);
}

/*
 * Reads a consistent set of time-base values from Xen, into a shadow data
 * area.
 */
static void get_time_values_from_xen(void)
{
	shared_info_t           *s = HYPERVISOR_shared_info;
	struct vcpu_time_info   *src;
	struct shadow_time_info *dst;

	src = &s->vcpu_info[smp_processor_id()].time;
	dst = &per_cpu(shadow_time, smp_processor_id());

	do {
		dst->version = src->version;
		rmb();
		dst->tsc_timestamp     = src->tsc_timestamp;
		dst->system_timestamp  = src->system_time;
		dst->tsc_to_nsec_mul   = src->tsc_to_system_mul;
		dst->tsc_shift         = src->tsc_shift;
		rmb();
	} while ((src->version & 1) | (dst->version ^ src->version));

	dst->tsc_to_usec_mul = dst->tsc_to_nsec_mul / 1000;
}

static inline int time_values_up_to_date(int cpu)
{
	struct vcpu_time_info   *src;
	struct shadow_time_info *dst;

	src = &HYPERVISOR_shared_info->vcpu_info[cpu].time;
	dst = &per_cpu(shadow_time, cpu);

	rmb();
	return (dst->version == src->version);
}

/*
 * This is a special lock that is owned by the CPU and holds the index
 * register we are working with.  It is required for NMI access to the
 * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
 */
volatile unsigned long cmos_lock = 0;
EXPORT_SYMBOL(cmos_lock);

/* Routines for accessing the CMOS RAM/RTC. */
unsigned char rtc_cmos_read(unsigned char addr)
{
	unsigned char val;
	lock_cmos_prefix(addr);
	outb_p(addr, RTC_PORT(0));
	val = inb_p(RTC_PORT(1));
	lock_cmos_suffix(addr);
	return val;
}
EXPORT_SYMBOL(rtc_cmos_read);

void rtc_cmos_write(unsigned char val, unsigned char addr)
{
	lock_cmos_prefix(addr);
	outb_p(addr, RTC_PORT(0));
	outb_p(val, RTC_PORT(1));
	lock_cmos_suffix(addr);
}
EXPORT_SYMBOL(rtc_cmos_write);

/*
 * This version of gettimeofday has microsecond resolution
 * and better than microsecond precision on fast x86 machines with TSC.
 */
void do_gettimeofday(struct timeval *tv)
{
	unsigned long seq;
	unsigned long usec, sec;
	unsigned long max_ntp_tick;
	s64 nsec;
	unsigned int cpu;
	struct shadow_time_info *shadow;
	u32 local_time_version;

	cpu = get_cpu();
	shadow = &per_cpu(shadow_time, cpu);

	do {
		unsigned long lost;

		local_time_version = shadow->version;
		seq = read_seqbegin(&xtime_lock);

		usec = get_usec_offset(shadow);
		lost = jiffies - wall_jiffies;

		/*
		 * If time_adjust is negative then NTP is slowing the clock
		 * so make sure not to go into next possible interval.
		 * Better to lose some accuracy than have time go backwards..
		 */
		if (unlikely(time_adjust < 0)) {
			max_ntp_tick = (USEC_PER_SEC / HZ) - tickadj;
			usec = min(usec, max_ntp_tick);

			if (lost)
				usec += lost * max_ntp_tick;
		}
		else if (unlikely(lost))
			usec += lost * (USEC_PER_SEC / HZ);

		sec = xtime.tv_sec;
		usec += (xtime.tv_nsec / NSEC_PER_USEC);

		nsec = shadow->system_timestamp - processed_system_time;
		__normalize_time(&sec, &nsec);
		usec += (long)nsec / NSEC_PER_USEC;

		if (unlikely(!time_values_up_to_date(cpu))) {
			/*
			 * We may have blocked for a long time,
			 * rendering our calculations invalid
			 * (e.g. the time delta may have
			 * overflowed). Detect that and recalculate
			 * with fresh values.
			 */
			get_time_values_from_xen();
			continue;
		}
	} while (read_seqretry(&xtime_lock, seq) ||
		 (local_time_version != shadow->version));

	put_cpu();

	while (usec >= USEC_PER_SEC) {
		usec -= USEC_PER_SEC;
		sec++;
	}

	tv->tv_sec = sec;
	tv->tv_usec = usec;
}

EXPORT_SYMBOL(do_gettimeofday);

int do_settimeofday(struct timespec *tv)
{
	time_t sec;
	s64 nsec;
	unsigned int cpu;
	struct shadow_time_info *shadow;
	dom0_op_t op;

	if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
		return -EINVAL;

	cpu = get_cpu();
	shadow = &per_cpu(shadow_time, cpu);

	write_seqlock_irq(&xtime_lock);

	/*
	 * Ensure we don't get blocked for a long time so that our time delta
	 * overflows. If that were to happen then our shadow time values would
	 * be stale, so we can retry with fresh ones.
	 */
	for (;;) {
		nsec = tv->tv_nsec - get_nsec_offset(shadow);
		if (time_values_up_to_date(cpu))
			break;
		get_time_values_from_xen();
	}
	sec = tv->tv_sec;
	__normalize_time(&sec, &nsec);

	if (is_initial_xendomain() && !independent_wallclock) {
		op.cmd = DOM0_SETTIME;
		op.u.settime.secs        = sec;
		op.u.settime.nsecs       = nsec;
		op.u.settime.system_time = shadow->system_timestamp;
		HYPERVISOR_dom0_op(&op);
		update_wallclock();
	} else if (independent_wallclock) {
		nsec -= shadow->system_timestamp;
		__normalize_time(&sec, &nsec);
		__update_wallclock(sec, nsec);
	}

	write_sequnlock_irq(&xtime_lock);

	put_cpu();

	clock_was_set();
	return 0;
}

EXPORT_SYMBOL(do_settimeofday);

static void sync_xen_wallclock(unsigned long dummy);
static DEFINE_TIMER(sync_xen_wallclock_timer, sync_xen_wallclock, 0, 0);
static void sync_xen_wallclock(unsigned long dummy)
{
	time_t sec;
	s64 nsec;
	dom0_op_t op;

	if (!ntp_synced() || independent_wallclock || !is_initial_xendomain())
		return;

	write_seqlock_irq(&xtime_lock);

	sec  = xtime.tv_sec;
	nsec = xtime.tv_nsec + ((jiffies - wall_jiffies) * (u64)NS_PER_TICK);
	__normalize_time(&sec, &nsec);

	op.cmd = DOM0_SETTIME;
	op.u.settime.secs        = sec;
	op.u.settime.nsecs       = nsec;
	op.u.settime.system_time = processed_system_time;
	HYPERVISOR_dom0_op(&op);

	update_wallclock();

	write_sequnlock_irq(&xtime_lock);

	/* Once per minute. */
	mod_timer(&sync_xen_wallclock_timer, jiffies + 60*HZ);
}

static int set_rtc_mmss(unsigned long nowtime)
{
	int retval;

	WARN_ON(irqs_disabled());

	if (independent_wallclock || !is_initial_xendomain())
		return 0;

	/* gets recalled with irq locally disabled */
	spin_lock_irq(&rtc_lock);
	if (efi_enabled)
		retval = efi_set_rtc_mmss(nowtime);
	else
		retval = mach_set_rtc_mmss(nowtime);
	spin_unlock_irq(&rtc_lock);

	return retval;
}

/* monotonic_clock(): returns # of nanoseconds passed since time_init()
 *		Note: This function is required to return accurate
 *		time even in the absence of multiple timer ticks.
 */
unsigned long long monotonic_clock(void)
{
	int cpu = get_cpu();
	struct shadow_time_info *shadow = &per_cpu(shadow_time, cpu);
	u64 time;
	u32 local_time_version;

	do {
		local_time_version = shadow->version;
		barrier();
		time = shadow->system_timestamp + get_nsec_offset(shadow);
		if (!time_values_up_to_date(cpu))
			get_time_values_from_xen();
		barrier();
	} while (local_time_version != shadow->version);

	put_cpu();

	return time;
}
EXPORT_SYMBOL(monotonic_clock);

unsigned long long sched_clock(void)
{
	return monotonic_clock();
}

#if defined(CONFIG_SMP) && defined(CONFIG_FRAME_POINTER)
unsigned long profile_pc(struct pt_regs *regs)
{
	unsigned long pc = instruction_pointer(regs);

#ifdef __x86_64__
	/* Assume the lock function has either no stack frame or only a single word.
	   This checks if the address on the stack looks like a kernel text address.
	   There is a small window for false hits, but in that case the tick
	   is just accounted to the spinlock function.
	   Better would be to write these functions in assembler again
	   and check exactly. */
	if (in_lock_functions(pc)) {
		char *v = *(char **)regs->rsp;
		if ((v >= _stext && v <= _etext) ||
			(v >= _sinittext && v <= _einittext) ||
			(v >= (char *)MODULES_VADDR  && v <= (char *)MODULES_END))
			return (unsigned long)v;
		return ((unsigned long *)regs->rsp)[1];
	}
#else
	if (in_lock_functions(pc))
		return *(unsigned long *)(regs->ebp + 4);
#endif

	return pc;
}
EXPORT_SYMBOL(profile_pc);
#endif

irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	s64 delta, delta_cpu, stolen, blocked;
	u64 sched_time;
	int i, cpu = smp_processor_id();
	struct shadow_time_info *shadow = &per_cpu(shadow_time, cpu);
	struct vcpu_runstate_info *runstate = &per_cpu(runstate, cpu);

	write_seqlock(&xtime_lock);

	do {
		get_time_values_from_xen();

		/* Obtain a consistent snapshot of elapsed wallclock cycles. */
		delta = delta_cpu =
			shadow->system_timestamp + get_nsec_offset(shadow);
		delta     -= processed_system_time;
		delta_cpu -= per_cpu(processed_system_time, cpu);

		/*
		 * Obtain a consistent snapshot of stolen/blocked cycles. We
		 * can use state_entry_time to detect if we get preempted here.
		 */
		do {
			sched_time = runstate->state_entry_time;
			barrier();
			stolen = runstate->time[RUNSTATE_runnable] +
				runstate->time[RUNSTATE_offline] -
				per_cpu(processed_stolen_time, cpu);
			blocked = runstate->time[RUNSTATE_blocked] -
				per_cpu(processed_blocked_time, cpu);
			barrier();
		} while (sched_time != runstate->state_entry_time);
	} while (!time_values_up_to_date(cpu));

	if ((unlikely(delta < -(s64)permitted_clock_jitter) ||
	     unlikely(delta_cpu < -(s64)permitted_clock_jitter))
	    && printk_ratelimit()) {
		printk("Timer ISR/%d: Time went backwards: "
		       "delta=%lld delta_cpu=%lld shadow=%lld "
		       "off=%lld processed=%lld cpu_processed=%lld\n",
		       cpu, delta, delta_cpu, shadow->system_timestamp,
		       (s64)get_nsec_offset(shadow),
		       processed_system_time,
		       per_cpu(processed_system_time, cpu));
		for (i = 0; i < num_online_cpus(); i++)
			printk(" %d: %lld\n", i,
			       per_cpu(processed_system_time, i));
	}

	/* System-wide jiffy work. */
	while (delta >= NS_PER_TICK) {
		delta -= NS_PER_TICK;
		processed_system_time += NS_PER_TICK;
		do_timer(regs);
	}

	if (shadow_tv_version != HYPERVISOR_shared_info->wc_version) {
		update_wallclock();
		clock_was_set();
	}

	write_sequnlock(&xtime_lock);

	/*
	 * Account stolen ticks.
	 * HACK: Passing NULL to account_steal_time()
	 * ensures that the ticks are accounted as stolen.
	 */
	if ((stolen > 0) && (delta_cpu > 0)) {
		delta_cpu -= stolen;
		if (unlikely(delta_cpu < 0))
			stolen += delta_cpu; /* clamp local-time progress */
		do_div(stolen, NS_PER_TICK);
		per_cpu(processed_stolen_time, cpu) += stolen * NS_PER_TICK;
		per_cpu(processed_system_time, cpu) += stolen * NS_PER_TICK;
		account_steal_time(NULL, (cputime_t)stolen);
	}

	/*
	 * Account blocked ticks.
	 * HACK: Passing idle_task to account_steal_time()
	 * ensures that the ticks are accounted as idle/wait.
	 */
	if ((blocked > 0) && (delta_cpu > 0)) {
		delta_cpu -= blocked;
		if (unlikely(delta_cpu < 0))
			blocked += delta_cpu; /* clamp local-time progress */
		do_div(blocked, NS_PER_TICK);
		per_cpu(processed_blocked_time, cpu) += blocked * NS_PER_TICK;
		per_cpu(processed_system_time, cpu)  += blocked * NS_PER_TICK;
		account_steal_time(idle_task(cpu), (cputime_t)blocked);
	}

	/* Account user/system ticks. */
	if (delta_cpu > 0) {
		do_div(delta_cpu, NS_PER_TICK);
		per_cpu(processed_system_time, cpu) += delta_cpu * NS_PER_TICK;
		if (user_mode(regs))
			account_user_time(current, (cputime_t)delta_cpu);
		else
			account_system_time(current, HARDIRQ_OFFSET,
					    (cputime_t)delta_cpu);
	}

	/* Local timer processing (see update_process_times()). */
	run_local_timers();
	if (rcu_pending(cpu))
		rcu_check_callbacks(cpu, user_mode(regs));
	scheduler_tick();
	run_posix_cpu_timers(current);

	return IRQ_HANDLED;
}

static void init_missing_ticks_accounting(int cpu)
{
	struct vcpu_register_runstate_memory_area area;
	struct vcpu_runstate_info *runstate = &per_cpu(runstate, cpu);

	memset(runstate, 0, sizeof(*runstate));

	area.addr.v = runstate;
	HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, cpu, &area);

	per_cpu(processed_blocked_time, cpu) =
		runstate->time[RUNSTATE_blocked];
	per_cpu(processed_stolen_time, cpu) =
		runstate->time[RUNSTATE_runnable] +
		runstate->time[RUNSTATE_offline];
}

/* not static: needed by APM */
unsigned long get_cmos_time(void)
{
	unsigned long retval;

	spin_lock(&rtc_lock);

	if (efi_enabled)
		retval = efi_get_time();
	else
		retval = mach_get_cmos_time();

	spin_unlock(&rtc_lock);

	return retval;
}
EXPORT_SYMBOL(get_cmos_time);

static void sync_cmos_clock(unsigned long dummy);

static DEFINE_TIMER(sync_cmos_timer, sync_cmos_clock, 0, 0);

static void sync_cmos_clock(unsigned long dummy)
{
	struct timeval now, next;
	int fail = 1;

	/*
	 * If we have an externally synchronized Linux clock, then update
	 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
	 * called as close as possible to 500 ms before the new second starts.
	 * This code is run on a timer.  If the clock is set, that timer
	 * may not expire at the correct time.  Thus, we adjust...
	 */
	if (!ntp_synced())
		/*
		 * Not synced, exit, do not restart a timer (if one is
		 * running, let it run out).
		 */
		return;

	do_gettimeofday(&now);
	if (now.tv_usec >= USEC_AFTER - ((unsigned) TICK_SIZE) / 2 &&
	    now.tv_usec <= USEC_BEFORE + ((unsigned) TICK_SIZE) / 2)
		fail = set_rtc_mmss(now.tv_sec);

	next.tv_usec = USEC_AFTER - now.tv_usec;
	if (next.tv_usec <= 0)
		next.tv_usec += USEC_PER_SEC;

	if (!fail)
		next.tv_sec = 659;
	else
		next.tv_sec = 0;

	if (next.tv_usec >= USEC_PER_SEC) {
		next.tv_sec++;
		next.tv_usec -= USEC_PER_SEC;
	}
	mod_timer(&sync_cmos_timer, jiffies + timeval_to_jiffies(&next));
}

void notify_arch_cmos_timer(void)
{
	mod_timer(&sync_cmos_timer, jiffies + 1);
	mod_timer(&sync_xen_wallclock_timer, jiffies + 1);
}

static long clock_cmos_diff, sleep_start;

static struct timer_opts *last_timer;
static int timer_suspend(struct sys_device *dev, pm_message_t state)
{
	/*
	 * Estimate time zone so that set_time can update the clock
	 */
	clock_cmos_diff = -get_cmos_time();
	clock_cmos_diff += get_seconds();
	sleep_start = get_cmos_time();
	last_timer = cur_timer;
	cur_timer = &timer_none;
	if (last_timer->suspend)
		last_timer->suspend(state);
	return 0;
}

static int timer_resume(struct sys_device *dev)
{
	unsigned long flags;
	unsigned long sec;
	unsigned long sleep_length;

#ifdef CONFIG_HPET_TIMER
	if (is_hpet_enabled())
		hpet_reenable();
#endif
	sec = get_cmos_time() + clock_cmos_diff;
	sleep_length = (get_cmos_time() - sleep_start) * HZ;
	write_seqlock_irqsave(&xtime_lock, flags);
	xtime.tv_sec = sec;
	xtime.tv_nsec = 0;
	jiffies_64 += sleep_length;
	wall_jiffies += sleep_length;
	write_sequnlock_irqrestore(&xtime_lock, flags);
	if (last_timer->resume)
		last_timer->resume();
	cur_timer = last_timer;
	last_timer = NULL;
	touch_softlockup_watchdog();
	return 0;
}

static struct sysdev_class timer_sysclass = {
	.resume = timer_resume,
	.suspend = timer_suspend,
	set_kset_name("timer"),
};


/* XXX this driverfs stuff should probably go elsewhere later -john */
static struct sys_device device_timer = {
	.id	= 0,
	.cls	= &timer_sysclass,
};

static int time_init_device(void)
{
	int error = sysdev_class_register(&timer_sysclass);
	if (!error)
		error = sysdev_register(&device_timer);
	return error;
}

device_initcall(time_init_device);

#ifdef CONFIG_HPET_TIMER
extern void (*late_time_init)(void);
/* Duplicate of time_init() below, with hpet_enable part added */
static void __init hpet_time_init(void)
{
	xtime.tv_sec = get_cmos_time();
	xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
	set_normalized_timespec(&wall_to_monotonic,
		-xtime.tv_sec, -xtime.tv_nsec);

	if ((hpet_enable() >= 0) && hpet_use_timer) {
		printk("Using HPET for base-timer\n");
	}

	cur_timer = select_timer();
	printk(KERN_INFO "Using %s for high-res timesource\n",cur_timer->name);

	time_init_hook();
}
#endif

/* Dynamically-mapped IRQ. */
DEFINE_PER_CPU(int, timer_irq);

extern void (*late_time_init)(void);
static void setup_cpu0_timer_irq(void)
{
	per_cpu(timer_irq, 0) =
		bind_virq_to_irqhandler(
			VIRQ_TIMER,
			0,
			timer_interrupt,
			SA_INTERRUPT,
			"timer0",
			NULL);
	BUG_ON(per_cpu(timer_irq, 0) < 0);
}

void __init time_init(void)
{
#ifdef CONFIG_HPET_TIMER
	if (is_hpet_capable()) {
		/*
		 * HPET initialization needs to do memory-mapped io. So, let
		 * us do a late initialization after mem_init().
		 */
		late_time_init = hpet_time_init;
		return;
	}
#endif
	get_time_values_from_xen();

	processed_system_time = per_cpu(shadow_time, 0).system_timestamp;
	per_cpu(processed_system_time, 0) = processed_system_time;
	init_missing_ticks_accounting(0);

	update_wallclock();

	init_cpu_khz();
	printk(KERN_INFO "Xen reported: %u.%03u MHz processor.\n",
	       cpu_khz / 1000, cpu_khz % 1000);

#if defined(__x86_64__)
	vxtime.mode = VXTIME_TSC;
	vxtime.quot = (1000000L << 32) / vxtime_hz;
	vxtime.tsc_quot = (1000L << 32) / cpu_khz;
	sync_core();
	rdtscll(vxtime.last_tsc);
#endif

	/* Cannot request_irq() until kmem is initialised. */
	late_time_init = setup_cpu0_timer_irq;
}

/* Convert jiffies to system time. */
u64 jiffies_to_st(unsigned long j)
{
	unsigned long seq;
	long delta;
	u64 st;

	do {
		seq = read_seqbegin(&xtime_lock);
		delta = j - jiffies;
		if (delta < 1) {
			/* Triggers in some wrap-around cases, but that's okay:
			 * we just end up with a shorter timeout. */
			st = processed_system_time + NS_PER_TICK;
		} else if (((unsigned long)delta >> (BITS_PER_LONG-3)) != 0) {
			/* Very long timeout means there is no pending timer.
			 * We indicate this to Xen by passing zero timeout. */
			st = 0;
		} else {
			st = processed_system_time + delta * (u64)NS_PER_TICK;
		}
	} while (read_seqretry(&xtime_lock, seq));

	return st;
}
EXPORT_SYMBOL(jiffies_to_st);

/*
 * stop_hz_timer / start_hz_timer - enter/exit 'tickless mode' on an idle cpu
 * These functions are based on implementations from arch/s390/kernel/time.c
 */
static void stop_hz_timer(void)
{
	unsigned int cpu = smp_processor_id();
	unsigned long j;

	cpu_set(cpu, nohz_cpu_mask);

	/* See matching smp_mb in rcu_start_batch in rcupdate.c.  These mbs  */
	/* ensure that if __rcu_pending (nested in rcu_needs_cpu) fetches a  */
	/* value of rcp->cur that matches rdp->quiescbatch and allows us to  */
	/* stop the hz timer then the cpumasks created for subsequent values */
	/* of cur in rcu_start_batch are guaranteed to pick up the updated   */
	/* nohz_cpu_mask and so will not depend on this cpu.                 */

	smp_mb();

	/* Leave ourselves in tick mode if rcu or softirq or timer pending. */
	if (rcu_needs_cpu(cpu) || local_softirq_pending() ||
	    (j = next_timer_interrupt(), time_before_eq(j, jiffies))) {
		cpu_clear(cpu, nohz_cpu_mask);
		j = jiffies + 1;
	}

	if (HYPERVISOR_set_timer_op(jiffies_to_st(j)) != 0)
		BUG();
}

static void start_hz_timer(void)
{
	cpu_clear(smp_processor_id(), nohz_cpu_mask);
}

void safe_halt(void)
{
	stop_hz_timer();
	/* Blocking includes an implicit local_irq_enable(). */
	HYPERVISOR_block();
	start_hz_timer();
}
EXPORT_SYMBOL(safe_halt);

void halt(void)
{
	if (irqs_disabled())
		HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
}
EXPORT_SYMBOL(halt);

/* No locking required. We are only CPU running, and interrupts are off. */
void time_resume(void)
{
	init_cpu_khz();

	get_time_values_from_xen();

	processed_system_time = per_cpu(shadow_time, 0).system_timestamp;
	per_cpu(processed_system_time, 0) = processed_system_time;
	init_missing_ticks_accounting(0);

	update_wallclock();
}

#ifdef CONFIG_SMP
static char timer_name[NR_CPUS][15];

void local_setup_timer(unsigned int cpu)
{
	int seq;

	BUG_ON(cpu == 0);

	do {
		seq = read_seqbegin(&xtime_lock);
		/* Use cpu0 timestamp: cpu's shadow is not initialised yet. */
		per_cpu(processed_system_time, cpu) =
			per_cpu(shadow_time, 0).system_timestamp;
		init_missing_ticks_accounting(cpu);
	} while (read_seqretry(&xtime_lock, seq));

	sprintf(timer_name[cpu], "timer%d", cpu);
	per_cpu(timer_irq, cpu) =
		bind_virq_to_irqhandler(
			VIRQ_TIMER,
			cpu,
			timer_interrupt,
			SA_INTERRUPT,
			timer_name[cpu],
			NULL);
	BUG_ON(per_cpu(timer_irq, cpu) < 0);
}

void local_teardown_timer(unsigned int cpu)
{
	BUG_ON(cpu == 0);
	unbind_from_irqhandler(per_cpu(timer_irq, cpu), NULL);
}
#endif

/*
 * /proc/sys/xen: This really belongs in another file. It can stay here for
 * now however.
 */
static ctl_table xen_subtable[] = {
	{
		.ctl_name	= 1,
		.procname	= "independent_wallclock",
		.data		= &independent_wallclock,
		.maxlen		= sizeof(independent_wallclock),
		.mode		= 0644,
		.proc_handler	= proc_dointvec
	},
	{
		.ctl_name	= 2,
		.procname	= "permitted_clock_jitter",
		.data		= &permitted_clock_jitter,
		.maxlen		= sizeof(permitted_clock_jitter),
		.mode		= 0644,
		.proc_handler	= proc_doulongvec_minmax
	},
	{ 0 }
};
static ctl_table xen_table[] = {
	{
		.ctl_name	= 123,
		.procname	= "xen",
		.mode		= 0555,
		.child		= xen_subtable},
	{ 0 }
};
static int __init xen_sysctl_init(void)
{
	(void)register_sysctl_table(xen_table, 0);
	return 0;
}
__initcall(xen_sysctl_init);