[PATCH v3 1/6] pvclock: add parameter to store cycles stamp to pvclock reading function

[Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx>]

The parameter is a pointer which is used to store cycles stamp value
used for time calulation on pvclock reading.

This is a part of the work aiming to move to a more simple scheme of
masterclock related values calculation in KVM.

Signed-off-by: Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx>
---
 arch/x86/include/asm/pvclock.h |  2 +-
 arch/x86/kernel/kvmclock.c     |  2 +-
 arch/x86/kernel/pvclock.c      | 12 +++++++++---
 arch/x86/xen/time.c            |  2 +-
 4 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 448cfe1..147b411 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -14,7 +14,7 @@ static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
 #endif
 
 /* some helper functions for xen and kvm pv clock sources */
-u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
+u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, u64 *cycles);
 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);
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index d889676..f5cfc5d 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -91,7 +91,7 @@ static u64 kvm_clock_read(void)
 	preempt_disable_notrace();
 	cpu = smp_processor_id();
 	src = &hv_clock[cpu].pvti;
-	ret = pvclock_clocksource_read(src);
+	ret = pvclock_clocksource_read(src, NULL);
 	preempt_enable_notrace();
 	return ret;
 }
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 5c3f6d6..a2c554a 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -73,19 +73,24 @@ u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
 	return flags & valid_flags;
 }
 
-u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
+u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, u64 *cycles)
 {
 	unsigned version;
 	u64 ret;
 	u64 last;
 	u8 flags;
+	u64 tsc;
 
 	do {
 		version = pvclock_read_begin(src);
-		ret = __pvclock_read_cycles(src, rdtsc_ordered());
+		tsc = rdtsc_ordered();
+		ret = __pvclock_read_cycles(src, tsc);
 		flags = src->flags;
 	} while (pvclock_read_retry(src, version));
 
+	if (cycles)
+		*cycles = tsc;
+
 	if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
 		src->flags &= ~PVCLOCK_GUEST_STOPPED;
 		pvclock_touch_watchdogs();
@@ -136,7 +141,8 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
 		rmb();		/* fetch time before checking version */
 	} while ((wall_clock->version & 1) || (version != wall_clock->version));
 
-	delta = pvclock_clocksource_read(vcpu_time);	/* time since system boot */
+	/* time since system boot */
+	delta = pvclock_clocksource_read(vcpu_time, NULL);
 	delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
 
 	now.tv_nsec = do_div(delta, NSEC_PER_SEC);
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 1ecb05d..145ac9a 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -46,7 +46,7 @@ u64 xen_clocksource_read(void)
 
 	preempt_disable_notrace();
 	src = &__this_cpu_read(xen_vcpu)->time;
-	ret = pvclock_clocksource_read(src);
+	ret = pvclock_clocksource_read(src, NULL);
 	preempt_enable_notrace();
 	return ret;
 }
-- 
2.7.4