From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757911Ab2IEOfs (ORCPT ); Wed, 5 Sep 2012 10:35:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20064 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752725Ab2IEOfq (ORCPT ); Wed, 5 Sep 2012 10:35:46 -0400 Message-ID: <5047633F.9020405@redhat.com> Date: Wed, 05 Sep 2012 17:35:43 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: Alex Williamson , gleb@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 1/2] kvm: Use a reserved IRQ source ID for irqfd References: <20120821190800.24958.74812.stgit@bling.home> <20120821192903.24958.90138.stgit@bling.home> <20120821195813.GD9027@redhat.com> <1345579579.29292.67.camel@ul30vt.home> <20120821204125.GF9027@redhat.com> <1345583694.29292.91.camel@ul30vt.home> <20120822004138.GM9027@redhat.com> In-Reply-To: <20120822004138.GM9027@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/22/2012 03:41 AM, Michael S. Tsirkin wrote: >> >> I assumed you were pointing out the level vs edge interaction. If we >> call that a userspace bug, I can just drop this. Thanks, >> >> Alex > > level is userspace bug I think :) I don't see how it's a bug. Suppose we have a vfio device that shares a gsi with an emulated device. The emulated device naturally uses KVM_IRQ_LINE (it has no need to re-sample on ADN), while vfio naturally has to use irqfd. Note one would expect that each irqfd gets its own irq source id, since they are all independent level sources. The reason they don't is that we shut them down anyway and let the sources re-trigger (it is more accurate to say that they have no irq source id, but that would just muddle the implementation). Alex, if the conclusion is that we do need this patch, then please add a comment explaining why we can share the source id among all irqfd users. -- error compiling committee.c: too many arguments to function