From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753726AbaCXR5O (ORCPT ); Mon, 24 Mar 2014 13:57:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43581 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752754AbaCXR5M (ORCPT ); Mon, 24 Mar 2014 13:57:12 -0400 Date: Mon, 24 Mar 2014 18:55:11 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, gleb@kernel.org, mtosatti@redhat.com, alex.williamson@redhat.com, jan.kiszka@siemens.com Subject: Re: [PATCH v2 3/4] KVM: ioapic: extract body of kvm_ioapic_set_irq Message-ID: <20140324175508.GA6143@potion.brq.redhat.com> References: <1395394081-16252-1-git-send-email-pbonzini@redhat.com> <1395394081-16252-4-git-send-email-pbonzini@redhat.com> <20140321185858.GA22118@potion.brq.redhat.com> <532E9EEF.2080906@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <532E9EEF.2080906@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014-03-23 09:44+0100, Paolo Bonzini: > Il 21/03/2014 19:58, Radim Krčmář ha scritto: > >>> + /* > >>> + * Return 0 for coalesced interrupts; for edge-triggered interrupts, > >>> + * this only happens if a previous edge has not been delivered due > >>> + * do masking. For level interrupts, the remote_irr field tells > > (^ to) > >>> + * us if the interrupt is waiting for an EOI. > > > >How do we know we haven't delivered an edge-triggered interrupt when > >ioapic_service() always clears this IRR bit? > > We know we have at least delivered it to the local APIC(s). If it > is masked in the ioredirtbl, ioapic_service doesn't clear the IRR. I see, LAPIC can't "refuse" an interrupt, so kvm_irq_delivery_to_apic() won't (mustn't) fail. (The code looks fragile if it returned -1.) Thanks.