[Xen-ia64-devel] [PATCH 09/15] ia64/pv_ops/pv_time_ops: add sched_clock hook.

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

add sched_clock() hook to paravirtualize sched_clock().
ia64 sched_clock() is based on ar.itc which isn't stable
on virtualized environment because vcpu may move around on
pcpus. So it needs paravirtualization.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
---
 arch/ia64/include/asm/paravirt.h |    7 +++++++
 arch/ia64/include/asm/timex.h    |    1 +
 arch/ia64/kernel/head.S          |   10 ++++++++--
 arch/ia64/kernel/paravirt.c      |    1 +
 arch/ia64/kernel/time.c          |    9 +++++++++
 5 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/ia64/include/asm/paravirt.h b/arch/ia64/include/asm/paravirt.h
index 56f69f9..a73e77a 100644
--- a/arch/ia64/include/asm/paravirt.h
+++ b/arch/ia64/include/asm/paravirt.h
@@ -225,6 +225,8 @@ struct pv_time_ops {
        int (*do_steal_accounting)(unsigned long *new_itm);
 
        void (*clocksource_resume)(void);
+
+       unsigned long long (*sched_clock)(void);
 };
 
 extern struct pv_time_ops pv_time_ops;
@@ -242,6 +244,11 @@ paravirt_do_steal_accounting(unsigned long *new_itm)
        return pv_time_ops.do_steal_accounting(new_itm);
 }
 
+static inline unsigned long long paravirt_sched_clock(void)
+{
+       return pv_time_ops.sched_clock();
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #else
diff --git a/arch/ia64/include/asm/timex.h b/arch/ia64/include/asm/timex.h
index 4e03cfe..86c7db8 100644
--- a/arch/ia64/include/asm/timex.h
+++ b/arch/ia64/include/asm/timex.h
@@ -40,5 +40,6 @@ get_cycles (void)
 }
 
 extern void ia64_cpu_local_tick (void);
+extern unsigned long long ia64_native_sched_clock (void);
 
 #endif /* _ASM_IA64_TIMEX_H */
diff --git a/arch/ia64/kernel/head.S b/arch/ia64/kernel/head.S
index 59301c4..23f846d 100644
--- a/arch/ia64/kernel/head.S
+++ b/arch/ia64/kernel/head.S
@@ -1050,7 +1050,7 @@ END(ia64_delay_loop)
  * except that the multiplication and the shift are done with 128-bit
  * intermediate precision so that we can produce a full 64-bit result.
  */
-GLOBAL_ENTRY(sched_clock)
+GLOBAL_ENTRY(ia64_native_sched_clock)
        addl r8=THIS_CPU(cpu_info) + IA64_CPUINFO_NSEC_PER_CYC_OFFSET,r0
        mov.m r9=ar.itc         // fetch cycle-counter                          
(35 cyc)
        ;;
@@ -1066,7 +1066,13 @@ GLOBAL_ENTRY(sched_clock)
        ;;
        shrp r8=r9,r8,IA64_NSEC_PER_CYC_SHIFT
        br.ret.sptk.many rp
-END(sched_clock)
+END(ia64_native_sched_clock)
+#ifndef CONFIG_PARAVIRT
+       //unsigned long long
+       //sched_clock(void) __attribute__((alias("ia64_native_sched_clock")));
+       .global sched_clock
+sched_clock = ia64_native_sched_clock
+#endif
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
 GLOBAL_ENTRY(cycle_to_cputime)
diff --git a/arch/ia64/kernel/paravirt.c b/arch/ia64/kernel/paravirt.c
index 9f14c16..6bc33a6 100644
--- a/arch/ia64/kernel/paravirt.c
+++ b/arch/ia64/kernel/paravirt.c
@@ -366,4 +366,5 @@ ia64_native_do_steal_accounting(unsigned long *new_itm)
 
 struct pv_time_ops pv_time_ops = {
        .do_steal_accounting = ia64_native_do_steal_accounting,
+       .sched_clock = ia64_native_sched_clock,
 };
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 65c10a4..91047f8 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -50,6 +50,15 @@ EXPORT_SYMBOL(last_cli_ip);
 #endif
 
 #ifdef CONFIG_PARAVIRT
+/* We need to define a real function for sched_clock, to override the
+   weak default version */
+unsigned long long sched_clock(void)
+{
+        return paravirt_sched_clock();
+}
+#endif
+
+#ifdef CONFIG_PARAVIRT
 static void
 paravirt_clocksource_resume(void)
 {
-- 
1.6.0.2


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