Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759684AbcKCSIA (ORCPT ); Thu, 3 Nov 2016 14:08:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50674 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758404AbcKCSH6 (ORCPT ); Thu, 3 Nov 2016 14:07:58 -0400 Date: Thu, 3 Nov 2016 19:07:54 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, yang.zhang.wz@gmail.com, feng.wu@intel.com, mst@redhat.com Subject: Re: [PATCH 2/5] KVM: x86: do not scan IRR twice on APICv vmentry Message-ID: <20161103180753.GF7771@potion> References: <1476469291-5039-1-git-send-email-pbonzini@redhat.com> <1476469291-5039-3-git-send-email-pbonzini@redhat.com> <20161026195900.GC4212@potion> <00273a1a-ef5d-f814-3e02-24b4e855d229@redhat.com> <20161103150356.GE7771@potion> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Thu, 03 Nov 2016 18:07:57 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1223 Lines: 31 2016-11-03 17:00+0100, Paolo Bonzini: > On 03/11/2016 16:03, Radim Krčmář wrote: >> 2016-11-03 14:30+0100, Paolo Bonzini: >>> On 26/10/2016 21:59, Radim Krčmář wrote: >>>> 2016-10-14 20:21+0200, Paolo Bonzini: >>>>> Calling apic_find_highest_irr results in IRR being scanned twice, >>>>> once in vmx_sync_pir_from_irr and once in apic_search_irr. Change >>>>> sync_pir_from_irr to do the RVI write and kvm_apic_update_irr to >>>>> compute the new RVI on the fly. >>>>> >>>>> Signed-off-by: Paolo Bonzini >>>>> --- >>>> >>>> Reviewed-by: Radim Krčmář >>> >>> Nope, this breaks nested VMX exit on external interrupt. For now I'm >>> testing only patch 1 and will push that one only to kvm/next. Which hypervisor is being nested? >> Hm, does it also happen with this change? > > Probably not but I wanted to understand why. :) Yeah, I'm also looking forward to knowing the funny coincidence. I think a bug is likely for hypervisors that don't enable PIN_BASED_EXT_INTR_MASK. The bug would trigger when kvm_cpu_has_interrupt() in vmx_check_nested_events() in kvm_arch_vcpu_runnable() queues the interrupt ... but I didn't see how this would have caused a problem. :)