ia64/pv_ops/pv_time_ops: add sched_clock hook.

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@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>

3 files changed, 18 insertions, 2 deletions

diff --git a/arch/ia64/kernel/head.S b/arch/ia64/kernel/head.S
index 59301c47280..23f846de62d 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 9f14c16f636..6bc33a6db75 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 f0ebb342409..c323c7b9c77 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)
 {