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KVM: limit lapic periodic timer frequency

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Otherwise its possible to starve the host by programming lapic timer
with a very high frequency.

Cc: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Marcelo Tosatti 2009-07-27 23:41:01 -03:00 committed by Avi Kivity
parent 5f0269f5d7
commit 1444885a04
1 changed files with 9 additions and 0 deletions
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9
arch/x86/kvm/lapic.c
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@ -670,6 +670,15 @@ static void start_apic_timer(struct kvm_lapic *apic)
if (!apic->lapic_timer.period)
return;
/*
* Do not allow the guest to program periodic timers with small
* interval, since the hrtimers are not throttled by the host
* scheduler.
*/
if (apic_lvtt_period(apic)) {
if (apic->lapic_timer.period < NSEC_PER_MSEC/2)
apic->lapic_timer.period = NSEC_PER_MSEC/2;
}
hrtimer_start(&apic->lapic_timer.timer,
ktime_add_ns(now, apic->lapic_timer.period),