10 files changed, 567 insertions, 5 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index a3b3f6ee3642..595fb771366e 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 9cfb58911f14..97f1e961d684 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 776d9be26af9..629c5ed94260 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 8c6a22a42d2e..d4b4ffc9eacb 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 5bf81059a7e6..2003733310dc 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 42502d820e4f..5a00b07e7194 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 c505b16c0990..9603ccaba997 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 2cfc7b09b925..12fef14995a5 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 a94d64b10f75..bb5a7abf949c 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 000000000000..7c3033dbe5f5
--- /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 */