[RFC PATCH 25/35] Add Xen time abstractions

[Chris Wright <chrisw@sous-sol.org>]

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Add support for Xen time abstractions. To avoid expensive traps into
the hypervisor, the passage of time is extrapolated from the local TSC
and a set of timestamps and scaling factors exported to the guest via
shared memory. Xen also provides a periodic interrupt facility which
is used to drive updates of xtime and jiffies, and perform the usual
process accounting and profiling.

Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
 arch/i386/kernel/Makefile |    6 
 drivers/xen/core/time.c   | 1045 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 1050 insertions(+), 1 deletion(-)

--- linus-2.6.orig/arch/i386/kernel/Makefile
+++ linus-2.6/arch/i386/kernel/Makefile
@@ -9,8 +9,11 @@ obj-y	:= process.o semaphore.o signal.o 
 		pci-dma.o i386_ksyms.o i387.o bootflag.o \
 		quirks.o i8237.o topology.o alternative.o
 
+timers-y			:= timers/
+timers-$(CONFIG_XEN)		:=
+
 obj-y				+= cpu/
-obj-y				+= timers/
+obj-y				+= $(timers-y)
 obj-y				+= acpi/
 obj-$(CONFIG_X86_BIOS_REBOOT)	+= reboot.o
 obj-$(CONFIG_MCA)		+= mca.o
@@ -45,6 +48,7 @@ obj-$(CONFIG_SCx200)		+= scx200.o
 hw_irq-y			:= i8259.o
 
 hw_irq-$(CONFIG_XEN)		:= ../../../drivers/xen/core/evtchn.o
+time-$(CONFIG_XEN)		:= ../../../drivers/xen/core/time.o
 
 # vsyscall.o contains the vsyscall DSO images as __initdata.
 # We must build both images before we can assemble it.
--- /dev/null
+++ linus-2.6/drivers/xen/core/time.c
@@ -0,0 +1,1045 @@
+/*
+ *  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)
+{
+	struct shared_info *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)
+{
+	struct shared_info *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;
+
+	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 (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 int set_rtc_mmss(unsigned long nowtime)
+{
+	int retval;
+
+	WARN_ON(irqs_disabled());
+
+	if (independent_wallclock || !(xen_start_info->flags & SIF_INITDOMAIN))
+		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);
+}
+
+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;
+	write_sequnlock_irqrestore(&xtime_lock, flags);
+	jiffies += sleep_length;
+	wall_jiffies += sleep_length;
+	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;
+		/* NB. The next check can trigger in some wrap-around cases,
+		 * but that's ok: we'll just end up with a shorter timeout. */
+		if (delta < 1)
+			delta = 1;
+		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
+ */
+void stop_hz_timer(void)
+{
+	unsigned int cpu = smp_processor_id();
+	unsigned long j;
+
+	/* We must do this /before/ checking rcu_pending(). */
+	cpu_set(cpu, nohz_cpu_mask);
+	smp_mb();
+
+	/* Leave ourselves in 'tick mode' if rcu or softirq pending. */
+	if (rcu_pending(cpu) || local_softirq_pending()) {
+		cpu_clear(cpu, nohz_cpu_mask);
+		j = jiffies + 1;
+	} else {
+		j = next_timer_interrupt();
+	}
+
+	BUG_ON(HYPERVISOR_set_timer_op(jiffies_to_st(j)) != 0);
+}
+
+void start_hz_timer(void)
+{
+	cpu_clear(smp_processor_id(), nohz_cpu_mask);
+}
+
+/* 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);

--