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    Subject[PATCH 2/9] Sched clock paravirt op fix.patch
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    The custom_sched_clock hook is broken.  The result from sched_clock needs to be
    in nanoseconds, not in CPU cycles. The TSC is insufficient for this purpose,
    because TSC is poorly defined in a virtual environment, and mostly represents
    real world time instead of scheduled process time (which can be interrupted
    without notice when a virtual machine is descheduled).

    To make the scheduler consistent, we must expose a different nature of time,
    that is scheduled time. So deprecate this custom_sched_clock hack and turn it
    into a paravirt-op, as it should have been all along. This allows the tsc.c
    code which converts cycles to nanoseconds to be shared by all paravirt-ops
    backends.

    It is unfortunate to add a new paravirt-op, but this is a very distinct
    abstraction which is clearly different for all virtual machine implementations,
    and it gets rid of an ugly indirect function which I ashamedly admit I hacked
    in to try to get this to work earlier, and then even got in the wrong units.

    Please apply.

    Signed-off-by: Zachary Amsden <zach@vmware.com>

    diff -r d58e6ddfdfa9 arch/i386/kernel/paravirt.c
    --- a/arch/i386/kernel/paravirt.c Thu Feb 15 23:52:41 2007 -0800
    +++ b/arch/i386/kernel/paravirt.c Fri Feb 16 00:04:39 2007 -0800
    @@ -32,6 +32,7 @@
    #include <asm/fixmap.h>
    #include <asm/apic.h>
    #include <asm/tlbflush.h>
    +#include <asm/timer.h>

    /* nop stub */
    static void native_nop(void)
    @@ -520,6 +521,7 @@ struct paravirt_ops paravirt_ops = {
    .write_msr = native_write_msr,
    .read_tsc = native_read_tsc,
    .read_pmc = native_read_pmc,
    + .get_scheduled_cycles = native_read_tsc,
    .load_tr_desc = native_load_tr_desc,
    .set_ldt = native_set_ldt,
    .load_gdt = native_load_gdt,
    diff -r d58e6ddfdfa9 arch/i386/kernel/tsc.c
    --- a/arch/i386/kernel/tsc.c Thu Feb 15 23:52:41 2007 -0800
    +++ b/arch/i386/kernel/tsc.c Fri Feb 16 00:06:34 2007 -0800
    @@ -14,6 +14,7 @@
    #include <asm/delay.h>
    #include <asm/tsc.h>
    #include <asm/io.h>
    +#include <asm/timer.h>

    #include "mach_timer.h"

    @@ -108,9 +109,6 @@ unsigned long long sched_clock(void)
    {
    unsigned long long this_offset;

    - if (unlikely(custom_sched_clock))
    - return (*custom_sched_clock)();
    -
    /*
    * Fall back to jiffies if there's no TSC available:
    */
    @@ -119,7 +117,7 @@ unsigned long long sched_clock(void)
    return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);

    /* read the Time Stamp Counter: */
    - rdtscll(this_offset);
    + get_scheduled_cycles(this_offset);

    /* return the value in ns */
    return cycles_2_ns(this_offset);
    diff -r d58e6ddfdfa9 arch/i386/kernel/vmi.c
    --- a/arch/i386/kernel/vmi.c Thu Feb 15 23:52:41 2007 -0800
    +++ b/arch/i386/kernel/vmi.c Fri Feb 16 00:02:48 2007 -0800
    @@ -873,7 +873,7 @@ static inline int __init activate_vmi(vo
    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;
    + paravirt_ops.get_scheduled_cycles = vmi_get_sched_cycles;
    }
    if (!disable_noidle)
    para_fill(safe_halt, Halt);
    diff -r d58e6ddfdfa9 arch/i386/kernel/vmitime.c
    --- a/arch/i386/kernel/vmitime.c Thu Feb 15 23:52:41 2007 -0800
    +++ b/arch/i386/kernel/vmitime.c Fri Feb 16 00:02:48 2007 -0800
    @@ -172,7 +172,7 @@ int vmi_set_wallclock(unsigned long now)
    return -1;
    }

    -unsigned long long vmi_sched_clock(void)
    +unsigned long long vmi_get_sched_cycles(void)
    {
    return read_available_cycles();
    }
    diff -r d58e6ddfdfa9 include/asm-i386/paravirt.h
    --- a/include/asm-i386/paravirt.h Thu Feb 15 23:52:41 2007 -0800
    +++ b/include/asm-i386/paravirt.h Fri Feb 16 00:07:22 2007 -0800
    @@ -94,6 +94,7 @@ struct paravirt_ops

    u64 (*read_tsc)(void);
    u64 (*read_pmc)(void);
    + u64 (*get_scheduled_cycles)(void);

    void (*load_tr_desc)(void);
    void (*load_gdt)(const struct Xgt_desc_struct *);
    @@ -273,6 +274,8 @@ static inline void halt(void)

    #define rdtscll(val) (val = paravirt_ops.read_tsc())

    +#define get_scheduled_cycles(val) (val = paravirt_ops.get_scheduled_cycles())
    +
    #define write_tsc(val1,val2) wrmsr(0x10, val1, val2)

    #define rdpmc(counter,low,high) do { \
    diff -r d58e6ddfdfa9 include/asm-i386/time.h
    --- a/include/asm-i386/time.h Thu Feb 15 23:52:41 2007 -0800
    +++ b/include/asm-i386/time.h Fri Feb 16 00:02:48 2007 -0800
    @@ -30,7 +30,6 @@ static inline int native_set_wallclock(u

    #ifdef CONFIG_PARAVIRT
    #include <asm/paravirt.h>
    -extern unsigned long long native_sched_clock(void);
    #else /* !CONFIG_PARAVIRT */

    #define get_wallclock() native_get_wallclock()
    diff -r d58e6ddfdfa9 include/asm-i386/timer.h
    --- a/include/asm-i386/timer.h Thu Feb 15 23:52:41 2007 -0800
    +++ b/include/asm-i386/timer.h Fri Feb 16 00:05:13 2007 -0800
    @@ -4,13 +4,19 @@
    #include <linux/pm.h>

    #define TICK_SIZE (tick_nsec / 1000)
    +
    void setup_pit_timer(void);
    +unsigned long long native_sched_clock(void);
    +
    /* Modifiers for buggy PIT handling */
    extern int pit_latch_buggy;
    extern int timer_ack;
    extern int no_timer_check;
    -extern unsigned long long (*custom_sched_clock)(void);
    extern int no_sync_cmos_clock;
    extern int recalibrate_cpu_khz(void);

    +#ifndef CONFIG_PARAVIRT
    +#define get_scheduled_cycles(val) rdtscll(val)
    #endif
    +
    +#endif
    diff -r d58e6ddfdfa9 include/asm-i386/vmi_time.h
    --- a/include/asm-i386/vmi_time.h Thu Feb 15 23:52:41 2007 -0800
    +++ b/include/asm-i386/vmi_time.h Fri Feb 16 00:02:48 2007 -0800
    @@ -49,7 +49,7 @@ extern void __init vmi_time_init(void);
    extern void __init vmi_time_init(void);
    extern unsigned long vmi_get_wallclock(void);
    extern int vmi_set_wallclock(unsigned long now);
    -extern unsigned long long vmi_sched_clock(void);
    +extern unsigned long long vmi_get_sched_cycles(void);

    #ifdef CONFIG_X86_LOCAL_APIC
    extern void __init vmi_timer_setup_boot_alarm(void);
    -
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