From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] KVM: x86: Avoid busy loops over uninjectable pending APIC timers Date: Sun, 17 Mar 2013 10:47:05 +0200 Message-ID: <20130317084705.GC11223@redhat.com> References: <5144DAC3.7080401@web.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Marcelo Tosatti , kvm To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:45041 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756099Ab3CQIrH (ORCPT ); Sun, 17 Mar 2013 04:47:07 -0400 Content-Disposition: inline In-Reply-To: <5144DAC3.7080401@web.de> Sender: kvm-owner@vger.kernel.org List-ID: On Sat, Mar 16, 2013 at 09:49:07PM +0100, Jan Kiszka wrote: > From: Jan Kiszka > > If the guest didn't take the last APIC timer interrupt yet and generates > another one on top, e.g. via periodic mode, we do not block the VCPU > even if the guest state is halted. The reason is that > apic_has_pending_timer continues to return a non-zero value. > > Fix this busy loop by taking the IRR content for the LVT vector in > apic_has_pending_timer into account. > Just drop coalescing tacking for lapic interrupt. After posted interrupt will be merged __apic_accept_irq() will not longer return coalescing information, so the code will be dead anyway. > Signed-off-by: Jan Kiszka > --- > > Not a critical issue, we are looping fully interruptible, but it's ugly > to do so IMHO. > > arch/x86/kvm/lapic.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index a8e9369..658abf5 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -1473,7 +1473,9 @@ int apic_has_pending_timer(struct kvm_vcpu *vcpu) > struct kvm_lapic *apic = vcpu->arch.apic; > > if (kvm_vcpu_has_lapic(vcpu) && apic_enabled(apic) && > - apic_lvt_enabled(apic, APIC_LVTT)) > + apic_lvt_enabled(apic, APIC_LVTT) && > + !apic_test_vector(apic_lvt_vector(apic, APIC_LVTT), > + apic->regs + APIC_IRR)) > return atomic_read(&apic->lapic_timer.pending); > > return 0; > -- > 1.7.3.4 -- Gleb.