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xen-devel
[Xen-devel] [PATCH 04/12] kvm/pvclock: add monotonicity check
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To: |
Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] [PATCH 04/12] kvm/pvclock: add monotonicity check |
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From: |
Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx> |
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Date: |
Wed, 14 Oct 2009 12:28:28 -0700 |
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Cc: |
Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, kurt.hackel@xxxxxxxxxx, the arch/x86 maintainers <x86@xxxxxxxxxx>, Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, Chris Mason <chris.mason@xxxxxxxxxx> |
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Wed, 14 Oct 2009 12:32:46 -0700 |
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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@xxxxxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxx>
---
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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