Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760087Ab2EPSIh (ORCPT ); Wed, 16 May 2012 14:08:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33283 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759768Ab2EPSIe (ORCPT ); Wed, 16 May 2012 14:08:34 -0400 Date: Wed, 16 May 2012 14:40:22 -0300 From: Marcelo Tosatti To: Gleb Natapov Cc: "Michael S. Tsirkin" , x86@kernel.org, kvm@vger.kernel.org, Ingo Molnar , "H. Peter Anvin" , Avi Kivity , Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: [PATCHv4 3/5] kvm: host side for eoi optimization Message-ID: <20120516174022.GA23332@amt.cnet> References: <42ba7beaa25855997e02fea91a11c9224c51720e.1337168687.git.mst@redhat.com> <20120516154940.GA20549@amt.cnet> <20120516162247.GA10676@redhat.com> <20120516163205.GB28798@redhat.com> <20120516165048.GA10769@redhat.com> <20120516170427.GA22784@amt.cnet> <20120516172155.GE28798@redhat.com> <20120516172345.GA23032@amt.cnet> <20120516173423.GF28798@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120516173423.GF28798@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3449 Lines: 74 On Wed, May 16, 2012 at 08:34:23PM +0300, Gleb Natapov wrote: > On Wed, May 16, 2012 at 02:23:45PM -0300, Marcelo Tosatti wrote: > > On Wed, May 16, 2012 at 08:21:55PM +0300, Gleb Natapov wrote: > > > On Wed, May 16, 2012 at 02:04:27PM -0300, Marcelo Tosatti wrote: > > > > On Wed, May 16, 2012 at 07:50:48PM +0300, Michael S. Tsirkin wrote: > > > > > On Wed, May 16, 2012 at 07:32:06PM +0300, Gleb Natapov wrote: > > > > > > On Wed, May 16, 2012 at 07:22:47PM +0300, Michael S. Tsirkin wrote: > > > > > > > On Wed, May 16, 2012 at 12:49:40PM -0300, Marcelo Tosatti wrote: > > > > > > > > > @@ -1245,9 +1306,20 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu) > > > > > > > > > int vector = kvm_apic_has_interrupt(vcpu); > > > > > > > > > struct kvm_lapic *apic = vcpu->arch.apic; > > > > > > > > > > > > > > > > > > - if (vector == -1) > > > > > > > > > + /* Detect interrupt nesting and disable EOI optimization */ > > > > > > > > > + if (pv_eoi_enabled(vcpu) && vector == -2) > > > > > > > > > + pv_eoi_clr_pending(vcpu); > > > > > > > > > + > > > > > > > > > + if (vector < 0) > > > > > > > > > > > > > > > > With interrupt window exiting, the guest will exit: > > > > > > > > > > > > > > > > - as soon as it sets RFLAGS.IF=1 and there is any > > > > > > > > interrupt pending in IRR. > > > > > > > > - any new interrupt is set in IRR will kick vcpu > > > > > > > > out of guest mode and recalculate interrupt-window-exiting. > > > > > > > > > > > > > > > > Doesnt this make this bit unnecessary ? > > > > > > > > > > > > > > Looks like we could cut it out. But I'm not sure how architectural it is > > > > > > > that we exit on interrupt window. > > > > > > We request exit on interrupt window only if there is pending irq that > > > > > > can be delivered on a guest entry. > > > > > > > > > > Aha. If so what Marcelo proposed won't work I think: if we inject A then B > > > > > which is lower priority, we need an exit on EOI, we can't inject > > > > > immediately. > > > > > > > > Please describe the scenario clearly, i can't see the problem. > > > > > > During vcpu entry there are two IRRs set 100 and 200. 200 is injected, > > > but irq window is not requested because 100 can't be injected, During > > > EOI exit 100 is injected. > > > > interrupt window exiting is always requested if IRR is pending. Except > > if NMI window is requested (which has higher priority). > > > This is where we enable irq window. We do it only if there is interrupt > pending: > if (kvm_cpu_has_interrupt(vcpu) || req_int_win) > kvm_x86_ops->enable_irq_window(vcpu); > > kvm_cpu_has_interrupt() checks apic by calling kvm_apic_has_interrupt() > > > kvm_apic_has_interrupt(): > apic_update_ppr(apic); > highest_irr = apic_find_highest_irr(apic); > if ((highest_irr == -1) || > ((highest_irr & 0xF0) <= apic_get_reg(apic, APIC_PROCPRI))) > return -1; > And above checks IRR priority, so we can have IRR set and do not enable > irq window exit. Right, but then you cannot inject interrupt anyway so EOI is not necessary. Instead TPR-below-threshold trap is set which handles that case. No? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/