From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752656Ab2IEOuc (ORCPT ); Wed, 5 Sep 2012 10:50:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59053 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751179Ab2IEOua (ORCPT ); Wed, 5 Sep 2012 10:50:30 -0400 Date: Wed, 5 Sep 2012 17:51:53 +0300 From: "Michael S. Tsirkin" To: Avi Kivity 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 Message-ID: <20120905145153.GA11048@redhat.com> 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> <5047633F.9020405@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5047633F.9020405@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 05, 2012 at 05:35:43PM +0300, Avi Kivity wrote: > 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. Absolutely. But vfio needs to use irqfd with the new flag. Using existing irqfd for level is a bug. > 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