From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH 1/6] KVM: Check for pending events before attempting injection Date: Wed, 28 Jul 2010 13:37:13 -0300 Message-ID: <20100728163713.GA26653@amt.cnet> References: <1280236780-5847-1-git-send-email-avi@redhat.com> <1280236780-5847-2-git-send-email-avi@redhat.com> <20100728162119.GA25224@amt.cnet> <4C505B47.5090405@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:1028 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751939Ab0G1QiD (ORCPT ); Wed, 28 Jul 2010 12:38:03 -0400 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o6SGc2ST016233 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 28 Jul 2010 12:38:03 -0400 Content-Disposition: inline In-Reply-To: <4C505B47.5090405@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Jul 28, 2010 at 07:31:03PM +0300, Avi Kivity wrote: > On 07/28/2010 07:21 PM, Marcelo Tosatti wrote: > >On Tue, Jul 27, 2010 at 04:19:35PM +0300, Avi Kivity wrote: > >>Instead of blindly attempting to inject an event before each guest entry, > >>check for a possible event first in vcpu->requests. Sites that can trigger > >>event injection are modified to set KVM_REQ_EVENT: > >> > >>- interrupt, nmi window opening > >>- ppr updates > >>- i8259 output changes > >>- local apic irr changes > >>- rflags updates > >>- gif flag set > >>- event set on exit > >> > >>This improves non-injecting entry performance, and sets the stage for > >>non-atomic injection. > >> > >>Signed-off-by: Avi Kivity > >>--- > >> arch/x86/kvm/i8259.c | 1 + > >> arch/x86/kvm/lapic.c | 12 ++++++++++-- > >> arch/x86/kvm/svm.c | 8 +++++++- > >> arch/x86/kvm/vmx.c | 6 ++++++ > >> arch/x86/kvm/x86.c | 35 ++++++++++++++++++++++++++--------- > >> include/linux/kvm_host.h | 1 + > >> 6 files changed, 51 insertions(+), 12 deletions(-) > >> > >>@@ -4731,17 +4737,19 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) > >> goto out; > >> } > >> > >>- inject_pending_event(vcpu); > >>+ if (kvm_check_request(KVM_REQ_EVENT, vcpu)) { > >>+ inject_pending_event(vcpu); > >> > >>- /* enable NMI/IRQ window open exits if needed */ > >>- if (vcpu->arch.nmi_pending) > >>- kvm_x86_ops->enable_nmi_window(vcpu); > >>- else if (kvm_cpu_has_interrupt(vcpu) || req_int_win) > >>- kvm_x86_ops->enable_irq_window(vcpu); > >>+ /* enable NMI/IRQ window open exits if needed */ > >>+ if (vcpu->arch.nmi_pending) > >>+ kvm_x86_ops->enable_nmi_window(vcpu); > >>+ else if (kvm_cpu_has_interrupt(vcpu) || req_int_win) > >>+ kvm_x86_ops->enable_irq_window(vcpu); > >Problem is it might not be possible to inject the event signalled by > >KVM_REQ_EVENT, say an interrupt from an irqchip, if there is an event > >that needs reinjection (or an exception). > > That can happen event now, no? A pending exception, interrupt comes > along, injection picks up the exception but leaves the interrupt. > > Now the situation can be more complicated: > > - pending exception > - injection > - interrupt, sets KVM_REQ_EVENT > - notices KVM_REQ_EVENT > - drops KVM_REQ_EVENT, cancels exception (made pending again) > - goes back > - injection (injects exception again, interrupt is pending) > > as far as I can tell, this is all fine. But you cleared KVM_REQ_EVENT. Which means you're not going to inject the pending interrupt on the next entry.