x86: pvclock: introduce helper to read flags

Acked-by: Glauber Costa <glommer@parallels.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
git-mirror · Nov 28, 2012 · 2697902 · 2697902
1 parent dce2db0
commit 2697902
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diff --git 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
@@ -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;