[PATCH v4 08/10] pvclock: add parameters to store stamp data in pvclock reading function

Denis Plotnikov
2017-08-02T14:39:32Z

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

This is a part of the work aiming to make possible to use KVM
masterclock in L2 guests (those once running over kvmclock clocksource).

Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
---
arch/x86/include/asm/pvclock.h | 3 ++-
arch/x86/kernel/kvmclock.c | 2 +-
arch/x86/kernel/pvclock.c | 18 +++++++++++++++---
arch/x86/xen/time.c | 2 +-
4 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 448cfe1..f4ff2c0 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -14,7 +14,8 @@ 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_stamp, u8 *flags_stamp);
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..f692579 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, NULL);
preempt_enable_notrace();
return ret;
}
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 5c3f6d6..bece384 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -73,21 +73,32 @@ 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_stamp, u8 *flags_stamp)
{
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_stamp)
+ *cycles_stamp = tsc;
+
+ if (flags_stamp)
+ *flags_stamp = flags;
+
if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
src->flags &= ~PVCLOCK_GUEST_STOPPED;
+ if (flags_stamp)
+ *flags_stamp &= ~PVCLOCK_GUEST_STOPPED;
pvclock_touch_watchdogs();
}

@@ -136,7 +147,8 @@ 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, 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..3292cbc 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, NULL);
preempt_enable_notrace();
return ret;
}
--
2.7.4