[PATCH] xen: add steal_clock support on x86

[Juergen Gross]

With CONFIG_PARAVIRT_TIME_ACCOUNTING the kernel is capable to account
for time a thread wasn't able to run due to hypervisor scheduling.
Add support in Xen arch independent time handling for this feature by
moving it out of the arm arch into drivers/xen.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 arch/arm/xen/enlighten.c | 17 ++---------------
 arch/x86/xen/time.c      |  2 ++
 drivers/xen/time.c       | 19 +++++++++++++++++++
 include/xen/xen-ops.h    |  1 +
 4 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 75cd734..9163b94 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -84,19 +84,6 @@ int xen_unmap_domain_gfn_range(struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL_GPL(xen_unmap_domain_gfn_range);
 
-static unsigned long long xen_stolen_accounting(int cpu)
-{
-	struct vcpu_runstate_info state;
-
-	BUG_ON(cpu != smp_processor_id());
-
-	xen_get_runstate_snapshot(&state);
-
-	WARN_ON(state.state != RUNSTATE_running);
-
-	return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
-}
-
 static void xen_read_wallclock(struct timespec64 *ts)
 {
 	u32 version;
@@ -355,8 +342,8 @@ static int __init xen_guest_init(void)
 
 	register_cpu_notifier(&xen_cpu_notifier);
 
-	pv_time_ops.steal_clock = xen_stolen_accounting;
-	static_key_slow_inc(&paravirt_steal_enabled);
+	xen_time_setup_guest();
+
 	if (xen_initial_domain())
 		pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
 
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index a0a4e55..f478169 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -431,6 +431,8 @@ static void __init xen_time_init(void)
 	xen_setup_timer(cpu);
 	xen_setup_cpu_clockevents();
 
+	xen_time_setup_guest();
+
 	if (xen_initial_domain())
 		pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
 }
diff --git a/drivers/xen/time.c b/drivers/xen/time.c
index 7107842..6648a78 100644
--- a/drivers/xen/time.c
+++ b/drivers/xen/time.c
@@ -75,6 +75,15 @@ bool xen_vcpu_stolen(int vcpu)
 	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
 }
 
+static u64 xen_steal_clock(int cpu)
+{
+	struct vcpu_runstate_info state;
+
+	BUG_ON(cpu != smp_processor_id());
+	xen_get_runstate_snapshot(&state);
+	return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
+}
+
 void xen_setup_runstate_info(int cpu)
 {
 	struct vcpu_register_runstate_memory_area area;
@@ -86,3 +95,13 @@ void xen_setup_runstate_info(int cpu)
 		BUG();
 }
 
+void __init xen_time_setup_guest(void)
+{
+	pv_time_ops.steal_clock = xen_steal_clock;
+
+	static_key_slow_inc(&paravirt_steal_enabled);
+	/*
+	 * We can't set paravirt_steal_rq_enabled as this would require the
+	 * capability to read another cpu's runstate info.
+	 */
+}
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 86abe07..5ce51c2 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -21,6 +21,7 @@ void xen_resume_notifier_unregister(struct notifier_block *nb);
 
 bool xen_vcpu_stolen(int vcpu);
 void xen_setup_runstate_info(int cpu);
+void __init xen_time_setup_guest(void);
 void xen_get_runstate_snapshot(struct vcpu_runstate_info *res);
 
 int xen_setup_shutdown_event(void);
-- 
2.6.6