x86: pvclock: introduce helper to read flags

Acked-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 47e25d464104..ea27a8dd189c 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -6,6 +6,7 @@
 
 /* some helper functions for xen and kvm pv clock sources */
 cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
+u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
 void pvclock_set_flags(u8 flags);
 unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
 void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index a7d90910c61a..c8fb043a8695 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -45,6 +45,19 @@ void pvclock_resume(void)
         atomic64_set(&last_value, 0);
 }
 
+u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
+{
+        unsigned version;
+        cycle_t ret;
+        u8 flags;
+
+        do {
+                version = __pvclock_read_cycles(src, &ret, &flags);
+        } while ((src->version & 1) || version != src->version);
+
+        return flags & valid_flags;
+}
+
 cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
 {
         unsigned version;