Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758812Ab2EPRI6 (ORCPT ); Wed, 16 May 2012 13:08:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11642 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758226Ab2EPRIz (ORCPT ); Wed, 16 May 2012 13:08:55 -0400 Date: Wed, 16 May 2012 19:32:06 +0300 From: Gleb Natapov To: "Michael S. Tsirkin" Cc: Marcelo Tosatti , 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: <20120516163205.GB28798@redhat.com> References: <42ba7beaa25855997e02fea91a11c9224c51720e.1337168687.git.mst@redhat.com> <20120516154940.GA20549@amt.cnet> <20120516162247.GA10676@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120516162247.GA10676@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1576 Lines: 43 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. > I guess there are reasons to exit on interrupt window but > isn't it better to make the feature independent of it? > > This almost never happens in my testing anyway, so > however we handle it is unlikely to affect performance. > > -- > MST -- Gleb. -- 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/