Messages in this thread Patch in this message | | | From | Avi Kivity <> | Subject | [PATCH 38/46] KVM: limit lapic periodic timer frequency | Date | Sun, 23 Aug 2009 14:56:37 +0300 |
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From: Marcelo Tosatti <mtosatti@redhat.com>
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> --- arch/x86/kvm/lapic.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index fdddf48..ce195f8 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -664,6 +664,15 @@ 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), -- 1.6.4.1
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