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Subject[PATCH 05/12] xen/pvclock: add monotonicity check
Date
Other tsc-based clocksources add a monotonicity test to make sure there's
no regression in the returned cycles.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/xen/time.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 0a5aa44..00f06cc 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -213,9 +213,14 @@ cycle_t xen_clocksource_read(void)
return ret;
}

+static struct clocksource xen_clocksource;
+
static cycle_t xen_clocksource_get_cycles(struct clocksource *cs)
{
- return xen_clocksource_read();
+ cycle_t ret = xen_clocksource_read();
+
+ return ret >= xen_clocksource.cycle_last ?
+ ret : xen_clocksource.cycle_last;
}

static void xen_read_wallclock(struct timespec *ts)
--
1.6.2.5


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