ia64/pv_ops/xen/pv_time_ops: implement sched_clock.

paravirtualize sched_clock.

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

1 files changed, 48 insertions, 0 deletions

diff --git a/arch/ia64/xen/time.c b/arch/ia64/xen/time.c
index 68d6204c3f16..fb8332690179 100644
--- a/arch/ia64/xen/time.c
+++ b/arch/ia64/xen/time.c
@@ -175,10 +175,58 @@ static void xen_itc_jitter_data_reset(void)
         } while (unlikely(ret != lcycle));
 }
 
+/* based on xen_sched_clock() in arch/x86/xen/time.c. */
+/*
+ * This relies on HAVE_UNSTABLE_SCHED_CLOCK. If it can't be defined,
+ * something similar logic should be implemented here.
+ */
+/*
+ * Xen sched_clock implementation.  Returns the number of unstolen
+ * nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED
+ * states.
+ */
+static unsigned long long xen_sched_clock(void)
+{
+        struct vcpu_runstate_info runstate;
+
+        unsigned long long now;
+        unsigned long long offset;
+        unsigned long long ret;
+
+        /*
+         * Ideally sched_clock should be called on a per-cpu basis
+         * anyway, so preempt should already be disabled, but that's
+         * not current practice at the moment.
+         */
+        preempt_disable();
+
+        /*
+         * both ia64_native_sched_clock() and xen's runstate are
+         * based on mAR.ITC. So difference of them makes sense.
+         */
+        now = ia64_native_sched_clock();
+
+        get_runstate_snapshot(&runstate);
+
+        WARN_ON(runstate.state != RUNSTATE_running);
+
+        offset = 0;
+        if (now > runstate.state_entry_time)
+                offset = now - runstate.state_entry_time;
+        ret = runstate.time[RUNSTATE_blocked] +
+                runstate.time[RUNSTATE_running] +
+                offset;
+
+        preempt_enable();
+
+        return ret;
+}
+
 struct pv_time_ops xen_time_ops __initdata = {
         .init_missing_ticks_accounting  = xen_init_missing_ticks_accounting,
         .do_steal_accounting            = xen_do_steal_accounting,
         .clocksource_resume             = xen_itc_jitter_data_reset,
+        .sched_clock                    = xen_sched_clock,
 };
 
 /* Called after suspend, to resume time.  */