x86: paravirt: factor out cpu_khz to common code

KVM intends to use paravirt code to calibrate khz. Xen
current code will do just fine. So as a first step, factor out
code to pvclock.c.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kernel/pvclock.c

@@ -97,6 +97,18 @@ static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst,
 	return dst->version;
 }
 
+unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
+{
+	u64 tsc_khz = 1000000ULL << 32;
+
+	do_div(tsc_khz, src->tsc_to_system_mul);
+	if (src->tsc_shift < 0)
+		tsc_khz <<= -src->tsc_shift;
+	else
+		tsc_khz >>= src->tsc_shift;
+	return tsc_khz;
+}
+
 cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
 {
 	struct pvclock_shadow_time shadow;

arch/x86/xen/time.c

@@ -198,17 +198,10 @@ unsigned long long xen_sched_clock(void)
 /* Get the TSC speed from Xen */
 unsigned long xen_tsc_khz(void)
 {
-	u64 xen_khz = 1000000ULL << 32;
-	const struct pvclock_vcpu_time_info *info =
+	struct pvclock_vcpu_time_info *info =
 		&HYPERVISOR_shared_info->vcpu_info[0].time;
 
-	do_div(xen_khz, info->tsc_to_system_mul);
-	if (info->tsc_shift < 0)
-		xen_khz <<= -info->tsc_shift;
-	else
-		xen_khz >>= info->tsc_shift;
-
-	return xen_khz;
+	return pvclock_tsc_khz(info);
 }
 
 cycle_t xen_clocksource_read(void)

include/asm-x86/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);
+unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
 void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
 			    struct pvclock_vcpu_time_info *vcpu,
 			    struct timespec *ts);