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Subject[PATCH 04/12] kvm/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>
Cc: Avi Kivity <avi@redhat.com>
---
arch/x86/kernel/kvmclock.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 223af43..46cb77f 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -77,9 +77,14 @@ static cycle_t kvm_clock_read(void)
return ret;
}

+static struct clocksource kvm_clock;
+
static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
{
- return kvm_clock_read();
+ cycle_t ret = kvm_clock_read();
+
+ return ret >= kvm_clock.cycle_last ?
+ ret : kvm_clock.cycle_last;
}

/*
--
1.6.2.5


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