Commit:     e30fab3ad34aa8bfb55c9f0337d4a92a0595f41f
Parent:     eda08b1befaabcdfea1a9216ae13f9065e69baa7
Author:     Zachary Amsden <[EMAIL PROTECTED]>
AuthorDate: Mon Mar 5 00:30:39 2007 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Mon Mar 5 07:57:52 2007 -0800

    [PATCH] vmi: pit override
    The time_init_hook in paravirt-ops no longer functions in the correct manner
    after the integration of the hrtimers code.  The problem is that now the 
    path for time initialization is:
      time_init :
           late_time_init = hpet_time_init;
      late_time_init -> hpet_time_init:
           setup_pit_timer (BAD)
           do_time_init --> (via paravirt.h)
              time_init_hook --> (via arch_hooks.h)
                  time_init_hook (in SUBARCH/setup.c)
    If this isn't confusing enough, the paravirt case goes through an indirect
    function pointer in the paravirt-ops table.  The problem is, by the time the
    paravirt hook is called, the pit timer is already enabled.
    But paravirt guests have their own timer, and don't want to use the PIT.
    Rather than intensify the struggle for power going on here, just make it all
    nice and simple and just unconditionally do all timer setup in the
    late_time_init hook.  This also has the advantage of enabling timers in the
    same place in all code paths, so everyone has the same bugs and we don't 
    outliers who break other code because they turn on timer too early or too
    So the paravirt-ops time init function is now by default hpet_time_init, 
    is the time init function used for native hardware.  Paravirt guests have 
    chance to override this when they setup the paravirt-ops table, and should
    need no change.
    Signed-off-by: Zachary Amsden <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 arch/i386/kernel/paravirt.c |    2 +-
 arch/i386/kernel/time.c     |   14 +++++++++++---
 include/asm-i386/paravirt.h |    4 ++--
 include/asm-i386/time.h     |    5 ++++-
 4 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index 871448d..2ec331e 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -494,7 +494,7 @@ struct paravirt_ops paravirt_ops = {
        .memory_setup = machine_specific_memory_setup,
        .get_wallclock = native_get_wallclock,
        .set_wallclock = native_set_wallclock,
-       .time_init = time_init_hook,
+       .time_init = hpet_time_init,
        .init_IRQ = native_init_IRQ,
        .cpuid = native_cpuid,
diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index a535005..ccd3734 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -262,14 +262,22 @@ void notify_arch_cmos_timer(void)
 extern void (*late_time_init)(void);
 /* Duplicate of time_init() below, with hpet_enable part added */
-static void __init hpet_time_init(void)
+void __init hpet_time_init(void)
        if (!hpet_enable())
-       do_time_init();
+       time_init_hook();
+ * This is called directly from init code; we must delay timer setup in the
+ * HPET case as we can't make the decision to turn on HPET this early in the
+ * boot process.
+ *
+ * The chosen time_init function will usually be hpet_time_init, above, but
+ * in the case of virtual hardware, an alternative function may be substituted.
+ */
 void __init time_init(void)
-       late_time_init = hpet_time_init;
+       late_time_init = choose_time_init();
diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h
index 1e4226a..f8319ca 100644
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -186,9 +186,9 @@ static inline int set_wallclock(unsigned long nowtime)
        return paravirt_ops.set_wallclock(nowtime);
-static inline void do_time_init(void)
+static inline void (*choose_time_init(void))(void)
-       return paravirt_ops.time_init();
+       return paravirt_ops.time_init;
 /* The paravirtualized CPUID instruction. */
diff --git a/include/asm-i386/time.h b/include/asm-i386/time.h
index ea8065a..eac0113 100644
--- a/include/asm-i386/time.h
+++ b/include/asm-i386/time.h
@@ -28,13 +28,16 @@ static inline int native_set_wallclock(unsigned long 
        return retval;
+extern void (*late_time_init)(void);
+extern void hpet_time_init(void);
 #include <asm/paravirt.h>
 #else /* !CONFIG_PARAVIRT */
 #define get_wallclock() native_get_wallclock()
 #define set_wallclock(x) native_set_wallclock(x)
-#define do_time_init() time_init_hook()
+#define choose_time_init() hpet_time_init
 #endif /* CONFIG_PARAVIRT */
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