From 1444885a045fe3b1905a14ea1b52540bf556578b Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Mon, 27 Jul 2009 23:41:01 -0300 Subject: [PATCH] KVM: limit lapic periodic timer frequency 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 Signed-off-by: Avi Kivity --- arch/x86/kvm/lapic.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 66122bfc74a9..5b9d1ae09cad 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -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),