[PATCH v4 04/10] tsc: implement the extended tsc reading function

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

By doing that, add tsc clocksource to a list of KVM clocksources
providing valid cycle values, meaning that KVM can use its masterclock.

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@virtuozzo.com>
---
arch/x86/kernel/tsc.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 796d96b..8786454 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1036,6 +1036,15 @@ static void tsc_cs_tick_stable(struct clocksource *cs)
sched_clock_tick_stable();
}

+static bool tsc_read_with_stamp(struct clocksource *cs,
+ u64 *cycles, u64 *cycles_stamp)
+{
+ u64 tsc = read_tsc(cs);
+ *cycles = tsc;
+ *cycles_stamp = tsc;
+ return true;
+}
+
/*
* .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
*/
@@ -1043,6 +1052,7 @@ static struct clocksource clocksource_tsc = {
.name = "tsc",
.rating = 300,
.read = read_tsc,
+ .read_with_stamp = tsc_read_with_stamp,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS |
CLOCK_SOURCE_MUST_VERIFY,
--
2.7.4