[PATCH] i386: vMI timer patches

VMI timer code.  It works by taking over the local APIC clock when APIC is
configured, which requires a couple hooks into the APIC code.  The backend
timer code could be commonized into the timer infrastructure, but there are
some pieces missing (stolen time, in particular), and the exact semantics of
when to do accounting for NO_IDLE need to be shared between different
hypervisors as well.  So for now, VMI timer is a separate module.

[Adrian Bunk: cleanups]

Subject: VMI timer patches
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>

10 files changed, 567 insertions, 5 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index a3b3f6e..595fb77 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -1272,3 +1272,12 @@ config X86_TRAMPOLINE
 config KTIME_SCALAR
 	bool
 	default y
+
+config NO_IDLE_HZ
+	bool
+	depends on PARAVIRT
+	default y
+	help
+	  Switches the regular HZ timer off when the system is going idle.
+	  This helps a hypervisor detect that the Linux system is idle,
+	  reducing the overhead of idle systems.
diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index 9cfb589..97f1e96 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -40,7 +40,7 @@ obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 obj-$(CONFIG_HPET_TIMER) 	+= hpet.o
 obj-$(CONFIG_K8_NB)		+= k8.o
 
-obj-$(CONFIG_VMI)		+= vmi.o
+obj-$(CONFIG_VMI)		+= vmi.o vmitime.o
 
 # Make sure this is linked after any other paravirt_ops structs: see head.S
 obj-$(CONFIG_PARAVIRT)		+= paravirt.o
diff --git a/arch/i386/kernel/apic.c b/arch/i386/kernel/apic.c
index 776d9be..629c5ed 100644
--- a/arch/i386/kernel/apic.c
+++ b/arch/i386/kernel/apic.c
@@ -1395,7 +1395,7 @@ int __init APIC_init_uniprocessor (void)
 		if (!skip_ioapic_setup && nr_ioapics)
 			setup_IO_APIC();
 #endif
-	setup_boot_APIC_clock();
+	setup_boot_clock();
 
 	return 0;
 }
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 8c6a22a..d4b4ffc 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -626,6 +626,11 @@ ENTRY(name)				\
 /* The include is where all of the SMP etc. interrupts come from */
 #include "entry_arch.h"
 
+/* This alternate entry is needed because we hijack the apic LVTT */
+#if defined(CONFIG_VMI) && defined(CONFIG_X86_LOCAL_APIC)
+BUILD_INTERRUPT(apic_vmi_timer_interrupt,LOCAL_TIMER_VECTOR)
+#endif
+
 KPROBE_ENTRY(page_fault)
 	RING0_EC_FRAME
 	pushl $do_page_fault
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index 5bf8105..2003733 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -544,6 +544,8 @@ struct paravirt_ops paravirt_ops = {
 	.apic_write = native_apic_write,
 	.apic_write_atomic = native_apic_write_atomic,
 	.apic_read = native_apic_read,
+	.setup_boot_clock = setup_boot_APIC_clock,
+	.setup_secondary_clock = setup_secondary_APIC_clock,
 #endif
 	.set_lazy_mode = (void *)native_nop,
 
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 42502d8..5a00b07 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -554,7 +554,7 @@ static void __cpuinit start_secondary(void *unused)
 	smp_callin();
 	while (!cpu_isset(smp_processor_id(), smp_commenced_mask))
 		rep_nop();
-	setup_secondary_APIC_clock();
+	setup_secondary_clock();
 	if (nmi_watchdog == NMI_IO_APIC) {
 		disable_8259A_irq(0);
 		enable_NMI_through_LVT0(NULL);
@@ -1331,7 +1331,7 @@ static void __init smp_boot_cpus(unsigned int max_cpus)
 
 	smpboot_setup_io_apic();
 
-	setup_boot_APIC_clock();
+	setup_boot_clock();
 
 	/*
 	 * Synchronize the TSC with the AP
diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index c505b16..9603cca 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -232,6 +232,7 @@ EXPORT_SYMBOL(get_cmos_time);
 static void sync_cmos_clock(unsigned long dummy);
 
 static DEFINE_TIMER(sync_cmos_timer, sync_cmos_clock, 0, 0);
+int no_sync_cmos_clock;
 
 static void sync_cmos_clock(unsigned long dummy)
 {
@@ -275,7 +276,8 @@ static void sync_cmos_clock(unsigned long dummy)
 
 void notify_arch_cmos_timer(void)
 {
-	mod_timer(&sync_cmos_timer, jiffies + 1);
+	if (!no_sync_cmos_clock)
+		mod_timer(&sync_cmos_timer, jiffies + 1);
 }
 
 static long clock_cmos_diff;
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 2cfc7b0..12fef14 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -23,6 +23,7 @@
  * an extra value to store the TSC freq
  */
 unsigned int tsc_khz;
+unsigned long long (*custom_sched_clock)(void);
 
 int tsc_disable;
 
@@ -107,6 +108,9 @@ unsigned long long sched_clock(void)
 {
 	unsigned long long this_offset;
 
+	if (unlikely(custom_sched_clock))
+		return (*custom_sched_clock)();
+
 	/*
 	 * in the NUMA case we dont use the TSC as they are not
 	 * synchronized across all CPUs.
diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c
index a94d64b..bb5a7ab 100644
--- a/arch/i386/kernel/vmi.c
+++ b/arch/i386/kernel/vmi.c
@@ -34,6 +34,7 @@
 #include <asm/apic.h>
 #include <asm/processor.h>
 #include <asm/timer.h>
+#include <asm/vmi_time.h>
 
 /* Convenient for calling VMI functions indirectly in the ROM */
 typedef u32 __attribute__((regparm(1))) (VROMFUNC)(void);
@@ -67,6 +68,7 @@ struct {
 	void (*set_linear_mapping)(int, u32, u32, u32);
 	void (*flush_tlb)(int);
 	void (*set_initial_ap_state)(int, int);
+	void (*halt)(void);
 } vmi_ops;
 
 /* XXX move this to alternative.h */
@@ -252,6 +254,19 @@ static void vmi_nop(void)
 {
 }
 
+/* For NO_IDLE_HZ, we stop the clock when halting the kernel */
+#ifdef CONFIG_NO_IDLE_HZ
+static fastcall void vmi_safe_halt(void)
+{
+	int idle = vmi_stop_hz_timer();
+	vmi_ops.halt();
+	if (idle) {
+		local_irq_disable();
+		vmi_account_time_restart_hz_timer();
+		local_irq_enable();
+	}
+}
+#endif
 
 #ifdef CONFIG_DEBUG_PAGE_TYPE
 
@@ -727,7 +742,12 @@ static inline int __init activate_vmi(void)
 		     (char *)paravirt_ops.save_fl);
 	patch_offset(&irq_save_disable_callout[IRQ_PATCH_DISABLE],
 		     (char *)paravirt_ops.irq_disable);
+#ifndef CONFIG_NO_IDLE_HZ
 	para_fill(safe_halt, Halt);
+#else
+	vmi_ops.halt = vmi_get_function(VMI_CALL_Halt);
+	paravirt_ops.safe_halt = vmi_safe_halt;
+#endif
 	para_fill(wbinvd, WBINVD);
 	/* paravirt_ops.read_msr = vmi_rdmsr */
 	/* paravirt_ops.write_msr = vmi_wrmsr */
@@ -838,6 +858,31 @@ static inline int __init activate_vmi(void)
 #endif
 
 	/*
+	 * Check for VMI timer functionality by probing for a cycle frequency method
+	 */
+	reloc = call_vrom_long_func(vmi_rom, get_reloc, VMI_CALL_GetCycleFrequency);
+	if (rel->type != VMI_RELOCATION_NONE) {
+		vmi_timer_ops.get_cycle_frequency = (void *)rel->eip;
+		vmi_timer_ops.get_cycle_counter =
+			vmi_get_function(VMI_CALL_GetCycleCounter);
+		vmi_timer_ops.get_wallclock =
+			vmi_get_function(VMI_CALL_GetWallclockTime);
+		vmi_timer_ops.wallclock_updated =
+			vmi_get_function(VMI_CALL_WallclockUpdated);
+		vmi_timer_ops.set_alarm = vmi_get_function(VMI_CALL_SetAlarm);
+		vmi_timer_ops.cancel_alarm =
+			 vmi_get_function(VMI_CALL_CancelAlarm);
+		paravirt_ops.time_init = vmi_time_init;
+		paravirt_ops.get_wallclock = vmi_get_wallclock;
+		paravirt_ops.set_wallclock = vmi_set_wallclock;
+#ifdef CONFIG_X86_LOCAL_APIC
+		paravirt_ops.setup_boot_clock = vmi_timer_setup_boot_alarm;
+		paravirt_ops.setup_secondary_clock = vmi_timer_setup_secondary_alarm;
+#endif
+		custom_sched_clock = vmi_sched_clock;
+	}
+
+	/*
 	 * Alternative instruction rewriting doesn't happen soon enough
 	 * to convert VMI_IRET to a call instead of a jump; so we have
 	 * to do this before IRQs get reenabled.  Fortunately, it is
diff --git a/arch/i386/kernel/vmitime.c b/arch/i386/kernel/vmitime.c
new file mode 100644
index 0000000..7c3033d
--- /dev/null
+++ b/arch/i386/kernel/vmitime.c
@@ -0,0 +1,495 @@
+/*
+ * VMI paravirtual timer support routines.
+ *
+ * Copyright (C) 2005, VMware, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * Send feedback to dhecht@vmware.com
+ *
+ */
+
+/*
+ * Portions of this code from arch/i386/kernel/timers/timer_tsc.c.
+ * Portions of the CONFIG_NO_IDLE_HZ code from arch/s390/kernel/time.c.
+ * See comments there for proper credits.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/jiffies.h>
+#include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
+#include <linux/rcupdate.h>
+#include <linux/clocksource.h>
+
+#include <asm/timer.h>
+#include <asm/io.h>
+#include <asm/apic.h>
+#include <asm/div64.h>
+#include <asm/timer.h>
+#include <asm/desc.h>
+
+#include <asm/vmi.h>
+#include <asm/vmi_time.h>
+
+#include <mach_timer.h>
+#include <io_ports.h>
+
+#ifdef CONFIG_X86_LOCAL_APIC
+#define VMI_ALARM_WIRING VMI_ALARM_WIRED_LVTT
+#else
+#define VMI_ALARM_WIRING VMI_ALARM_WIRED_IRQ0
+#endif
+
+/* Cached VMI operations */
+struct vmi_timer_ops vmi_timer_ops;
+
+#ifdef CONFIG_NO_IDLE_HZ
+
+/* /proc/sys/kernel/hz_timer state. */
+int sysctl_hz_timer;
+
+/* Some stats */
+static DEFINE_PER_CPU(unsigned long, vmi_idle_no_hz_irqs);
+static DEFINE_PER_CPU(unsigned long, vmi_idle_no_hz_jiffies);
+static DEFINE_PER_CPU(unsigned long, idle_start_jiffies);
+
+#endif /* CONFIG_NO_IDLE_HZ */
+
+/* Number of alarms per second. By default this is CONFIG_VMI_ALARM_HZ. */
+static int alarm_hz = CONFIG_VMI_ALARM_HZ;
+
+/* Cache of the value get_cycle_frequency / HZ. */
+static signed long long cycles_per_jiffy;
+
+/* Cache of the value get_cycle_frequency / alarm_hz. */
+static signed long long cycles_per_alarm;
+
+/* The number of cycles accounted for by the 'jiffies'/'xtime' count.
+ * Protected by xtime_lock. */
+static unsigned long long real_cycles_accounted_system;
+
+/* The number of cycles accounted for by update_process_times(), per cpu. */
+static DEFINE_PER_CPU(unsigned long long, process_times_cycles_accounted_cpu);
+
+/* The number of stolen cycles accounted, per cpu. */
+static DEFINE_PER_CPU(unsigned long long, stolen_cycles_accounted_cpu);
+
+/* Clock source. */
+static cycle_t read_real_cycles(void)
+{
+	return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
+}
+
+static cycle_t read_available_cycles(void)
+{
+	return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_AVAILABLE);
+}
+
+#if 0
+static cycle_t read_stolen_cycles(void)
+{
+	return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_STOLEN);
+}
+#endif  /*  0  */
+
+static struct clocksource clocksource_vmi = {
+	.name			= "vmi-timer",
+	.rating			= 450,
+	.read			= read_real_cycles,
+	.mask			= CLOCKSOURCE_MASK(64),
+	.mult			= 0, /* to be set */
+	.shift			= 22,
+	.is_continuous		= 1,
+};
+
+
+/* Timer interrupt handler. */
+static irqreturn_t vmi_timer_interrupt(int irq, void *dev_id);
+
+static struct irqaction vmi_timer_irq  = {
+	vmi_timer_interrupt,
+	SA_INTERRUPT,
+	CPU_MASK_NONE,
+	"VMI-alarm",
+	NULL,
+	NULL
+};
+
+/* Alarm rate */
+static int __init vmi_timer_alarm_rate_setup(char* str)
+{
+	int alarm_rate;
+	if (get_option(&str, &alarm_rate) == 1 && alarm_rate > 0) {
+		alarm_hz = alarm_rate;
+		printk(KERN_WARNING "VMI timer alarm HZ set to %d\n", alarm_hz);
+	}
+	return 1;
+}
+__setup("vmi_timer_alarm_hz=", vmi_timer_alarm_rate_setup);
+
+
+/* Initialization */
+static void vmi_get_wallclock_ts(struct timespec *ts)
+{
+	unsigned long long wallclock;
+	wallclock = vmi_timer_ops.get_wallclock(); // nsec units
+	ts->tv_nsec = do_div(wallclock, 1000000000);
+	ts->tv_sec = wallclock;
+}
+
+static void update_xtime_from_wallclock(void)
+{
+	struct timespec ts;
+	vmi_get_wallclock_ts(&ts);
+	do_settimeofday(&ts);
+}
+
+unsigned long vmi_get_wallclock(void)
+{
+	struct timespec ts;
+	vmi_get_wallclock_ts(&ts);
+	return ts.tv_sec;
+}
+
+int vmi_set_wallclock(unsigned long now)
+{
+	return -1;
+}
+
+unsigned long long vmi_sched_clock(void)
+{
+	return read_available_cycles();
+}
+
+void __init vmi_time_init(void)
+{
+	unsigned long long cycles_per_sec, cycles_per_msec;
+
+	setup_irq(0, &vmi_timer_irq);
+#ifdef CONFIG_X86_LOCAL_APIC
+	set_intr_gate(LOCAL_TIMER_VECTOR, apic_vmi_timer_interrupt);
+#endif
+
+	no_sync_cmos_clock = 1;
+
+	vmi_get_wallclock_ts(&xtime);
+	set_normalized_timespec(&wall_to_monotonic,
+		-xtime.tv_sec, -xtime.tv_nsec);
+
+	real_cycles_accounted_system = read_real_cycles();
+	update_xtime_from_wallclock();
+	per_cpu(process_times_cycles_accounted_cpu, 0) = read_available_cycles();
+
+	cycles_per_sec = vmi_timer_ops.get_cycle_frequency();
+
+	cycles_per_jiffy = cycles_per_sec;
+	(void)do_div(cycles_per_jiffy, HZ);
+	cycles_per_alarm = cycles_per_sec;
+	(void)do_div(cycles_per_alarm, alarm_hz);
+	cycles_per_msec = cycles_per_sec;
+	(void)do_div(cycles_per_msec, 1000);
+	cpu_khz = cycles_per_msec;
+
+	printk(KERN_WARNING "VMI timer cycles/sec = %llu ; cycles/jiffy = %llu ;"
+	       "cycles/alarm = %llu\n", cycles_per_sec, cycles_per_jiffy,
+	       cycles_per_alarm);
+
+	clocksource_vmi.mult = clocksource_khz2mult(cycles_per_msec,
+						    clocksource_vmi.shift);
+	if (clocksource_register(&clocksource_vmi))
+		printk(KERN_WARNING "Error registering VMITIME clocksource.");
+
+	/* Disable PIT. */
+	outb_p(0x3a, PIT_MODE); /* binary, mode 5, LSB/MSB, ch 0 */
+
+	/* schedule the alarm. do this in phase with process_times_cycles_accounted_cpu
+	 * reduce the latency calling update_process_times. */
+	vmi_timer_ops.set_alarm(
+		      VMI_ALARM_WIRED_IRQ0 | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
+		      per_cpu(process_times_cycles_accounted_cpu, 0) + cycles_per_alarm,
+		      cycles_per_alarm);
+}
+
+#ifdef CONFIG_X86_LOCAL_APIC
+
+void __init vmi_timer_setup_boot_alarm(void)
+{
+	local_irq_disable();
+
+	/* Route the interrupt to the correct vector. */
+	apic_write_around(APIC_LVTT, LOCAL_TIMER_VECTOR);
+
+	/* Cancel the IRQ0 wired alarm, and setup the LVTT alarm. */
+	vmi_timer_ops.cancel_alarm(VMI_CYCLES_AVAILABLE);
+	vmi_timer_ops.set_alarm(
+		      VMI_ALARM_WIRED_LVTT | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
+		      per_cpu(process_times_cycles_accounted_cpu, 0) + cycles_per_alarm,
+		      cycles_per_alarm);
+	local_irq_enable();
+}
+
+/* Initialize the time accounting variables for an AP on an SMP system.
+ * Also, set the local alarm for the AP. */
+void __init vmi_timer_setup_secondary_alarm(void)
+{
+	int cpu = smp_processor_id();
+
+	/* Route the interrupt to the correct vector. */
+	apic_write_around(APIC_LVTT, LOCAL_TIMER_VECTOR);
+
+	per_cpu(process_times_cycles_accounted_cpu, cpu) = read_available_cycles();
+
+	vmi_timer_ops.set_alarm(
+		      VMI_ALARM_WIRED_LVTT | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
+		      per_cpu(process_times_cycles_accounted_cpu, cpu) + cycles_per_alarm,
+		      cycles_per_alarm);
+}
+
+#endif
+
+/* Update system wide (real) time accounting (e.g. jiffies, xtime). */
+static void vmi_account_real_cycles(unsigned long long cur_real_cycles)
+{
+	long long cycles_not_accounted;
+
+	write_seqlock(&xtime_lock);
+
+	cycles_not_accounted = cur_real_cycles - real_cycles_accounted_system;
+	while (cycles_not_accounted >= cycles_per_jiffy) {
+		/* systems wide jiffies and wallclock. */
+		do_timer(1);
+
+		cycles_not_accounted -= cycles_per_jiffy;
+		real_cycles_accounted_system += cycles_per_jiffy;
+	}
+
+	if (vmi_timer_ops.wallclock_updated())
+		update_xtime_from_wallclock();
+
+	write_sequnlock(&xtime_lock);
+}
+
+/* Update per-cpu process times. */
+static void vmi_account_process_times_cycles(struct pt_regs *regs, int cpu,
+					     unsigned long long cur_process_times_cycles)
+{
+	long long cycles_not_accounted;
+	cycles_not_accounted = cur_process_times_cycles -
+		per_cpu(process_times_cycles_accounted_cpu, cpu);
+
+	while (cycles_not_accounted >= cycles_per_jiffy) {
+		/* Account time to the current process.  This includes
+		 * calling into the scheduler to decrement the timeslice
+		 * and possibly reschedule.*/
+		update_process_times(user_mode(regs));
+		/* XXX handle /proc/profile multiplier.  */
+		profile_tick(CPU_PROFILING);
+
+		cycles_not_accounted -= cycles_per_jiffy;
+		per_cpu(process_times_cycles_accounted_cpu, cpu) += cycles_per_jiffy;
+	}
+}
+
+#ifdef CONFIG_NO_IDLE_HZ
+/* Update per-cpu idle times.  Used when a no-hz halt is ended. */
+static void vmi_account_no_hz_idle_cycles(int cpu,
+					  unsigned long long cur_process_times_cycles)
+{
+	long long cycles_not_accounted;
+	unsigned long no_idle_hz_jiffies = 0;
+
+	cycles_not_accounted = cur_process_times_cycles -
+		per_cpu(process_times_cycles_accounted_cpu, cpu);
+
+	while (cycles_not_accounted >= cycles_per_jiffy) {
+		no_idle_hz_jiffies++;
+		cycles_not_accounted -= cycles_per_jiffy;
+		per_cpu(process_times_cycles_accounted_cpu, cpu) += cycles_per_jiffy;
+	}
+	/* Account time to the idle process. */
+	account_steal_time(idle_task(cpu), jiffies_to_cputime(no_idle_hz_jiffies));
+}
+#endif
+
+/* Update per-cpu stolen time. */
+static void vmi_account_stolen_cycles(int cpu,
+				      unsigned long long cur_real_cycles,
+				      unsigned long long cur_avail_cycles)
+{
+	long long stolen_cycles_not_accounted;
+	unsigned long stolen_jiffies = 0;
+
+	if (cur_real_cycles < cur_avail_cycles)
+		return;
+
+	stolen_cycles_not_accounted = cur_real_cycles - cur_avail_cycles -
+		per_cpu(stolen_cycles_accounted_cpu, cpu);
+
+	while (stolen_cycles_not_accounted >= cycles_per_jiffy) {
+		stolen_jiffies++;
+		stolen_cycles_not_accounted -= cycles_per_jiffy;
+		per_cpu(stolen_cycles_accounted_cpu, cpu) += cycles_per_jiffy;
+	}
+	/* HACK: pass NULL to force time onto cpustat->steal. */
+	account_steal_time(NULL, jiffies_to_cputime(stolen_jiffies));
+}
+
+/* Body of either IRQ0 interrupt handler (UP no local-APIC) or
+ * local-APIC LVTT interrupt handler (UP & local-APIC or SMP). */
+static void vmi_local_timer_interrupt(int cpu)
+{
+	unsigned long long cur_real_cycles, cur_process_times_cycles;
+
+	cur_real_cycles = read_real_cycles();
+	cur_process_times_cycles = read_available_cycles();
+	/* Update system wide (real) time state (xtime, jiffies). */
+	vmi_account_real_cycles(cur_real_cycles);
+	/* Update per-cpu process times. */
+	vmi_account_process_times_cycles(get_irq_regs(), cpu, cur_process_times_cycles);
+        /* Update time stolen from this cpu by the hypervisor. */
+	vmi_account_stolen_cycles(cpu, cur_real_cycles, cur_process_times_cycles);
+}
+
+#ifdef CONFIG_NO_IDLE_HZ
+
+/* Must be called only from idle loop, with interrupts disabled. */
+int vmi_stop_hz_timer(void)
+{
+	/* Note that cpu_set, cpu_clear are (SMP safe) atomic on x86. */
+
+	unsigned long seq, next;
+	unsigned long long real_cycles_expiry;
+	int cpu = smp_processor_id();
+	int idle;
+
+	BUG_ON(!irqs_disabled());
+	if (sysctl_hz_timer != 0)
+		return 0;
+
+	cpu_set(cpu, nohz_cpu_mask);
+	smp_mb();
+	if (rcu_needs_cpu(cpu) || local_softirq_pending() ||
+	    (next = next_timer_interrupt(), time_before_eq(next, jiffies))) {
+		cpu_clear(cpu, nohz_cpu_mask);
+		next = jiffies;
+		idle = 0;
+	} else
+		idle = 1;
+
+	/* Convert jiffies to the real cycle counter. */
+	do {
+		seq = read_seqbegin(&xtime_lock);
+		real_cycles_expiry = real_cycles_accounted_system +
+			(long)(next - jiffies) * cycles_per_jiffy;
+	} while (read_seqretry(&xtime_lock, seq));
+
+	/* This cpu is going idle. Disable the periodic alarm. */
+	if (idle) {
+		vmi_timer_ops.cancel_alarm(VMI_CYCLES_AVAILABLE);
+		per_cpu(idle_start_jiffies, cpu) = jiffies;
+	}
+
+	/* Set the real time alarm to expire at the next event. */
+	vmi_timer_ops.set_alarm(
+		      VMI_ALARM_WIRING | VMI_ALARM_IS_ONESHOT | VMI_CYCLES_REAL,
+		      real_cycles_expiry, 0);
+
+	return idle;
+}
+
+static void vmi_reenable_hz_timer(int cpu)
+{
+	/* For /proc/vmi/info idle_hz stat. */
+	per_cpu(vmi_idle_no_hz_jiffies, cpu) += jiffies - per_cpu(idle_start_jiffies, cpu);
+	per_cpu(vmi_idle_no_hz_irqs, cpu)++;
+
+	/* Don't bother explicitly cancelling the one-shot alarm -- at
+	 * worse we will receive a spurious timer interrupt. */
+	vmi_timer_ops.set_alarm(
+		      VMI_ALARM_WIRING | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
+		      per_cpu(process_times_cycles_accounted_cpu, cpu) + cycles_per_alarm,
+		      cycles_per_alarm);
+	/* Indicate this cpu is no longer nohz idle. */
+	cpu_clear(cpu, nohz_cpu_mask);
+}
+
+/* Called from interrupt handlers when (local) HZ timer is disabled. */
+void vmi_account_time_restart_hz_timer(void)
+{
+	unsigned long long cur_real_cycles, cur_process_times_cycles;
+	int cpu = smp_processor_id();
+
+	BUG_ON(!irqs_disabled());
+	/* Account the time during which the HZ timer was disabled. */
+	cur_real_cycles = read_real_cycles();
+	cur_process_times_cycles = read_available_cycles();
+	/* Update system wide (real) time state (xtime, jiffies). */
+	vmi_account_real_cycles(cur_real_cycles);
+	/* Update per-cpu idle times. */
+	vmi_account_no_hz_idle_cycles(cpu, cur_process_times_cycles);
+        /* Update time stolen from this cpu by the hypervisor. */
+	vmi_account_stolen_cycles(cpu, cur_real_cycles, cur_process_times_cycles);
+	/* Reenable the hz timer. */
+	vmi_reenable_hz_timer(cpu);
+}
+
+#endif /* CONFIG_NO_IDLE_HZ */
+
+/* UP (and no local-APIC) VMI-timer alarm interrupt handler.
+ * Handler for IRQ0. Not used when SMP or X86_LOCAL_APIC after
+ * APIC setup and setup_boot_vmi_alarm() is called.  */
+static irqreturn_t vmi_timer_interrupt(int irq, void *dev_id)
+{
+	vmi_local_timer_interrupt(smp_processor_id());
+	return IRQ_HANDLED;
+}
+
+#ifdef CONFIG_X86_LOCAL_APIC
+
+/* SMP VMI-timer alarm interrupt handler. Handler for LVTT vector.
+ * Also used in UP when CONFIG_X86_LOCAL_APIC.
+ * The wrapper code is from arch/i386/kernel/apic.c#smp_apic_timer_interrupt. */
+void smp_apic_vmi_timer_interrupt(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+	int cpu = smp_processor_id();
+
+	/*
+	 * the NMI deadlock-detector uses this.
+	 */
+        per_cpu(irq_stat,cpu).apic_timer_irqs++;
+
+	/*
+	 * NOTE! We'd better ACK the irq immediately,
+	 * because timer handling can be slow.
+	 */
+	ack_APIC_irq();
+
+	/*
+	 * update_process_times() expects us to have done irq_enter().
+	 * Besides, if we don't timer interrupts ignore the global
+	 * interrupt lock, which is the WrongThing (tm) to do.
+	 */
+	irq_enter();
+	vmi_local_timer_interrupt(cpu);
+	irq_exit();
+	set_irq_regs(old_regs);
+}
+
+#endif  /* CONFIG_X86_LOCAL_APIC */