Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758169AbaKUKtR (ORCPT ); Fri, 21 Nov 2014 05:49:17 -0500 Received: from www.linutronix.de ([62.245.132.108]:56074 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750734AbaKUKtP (ORCPT ); Fri, 21 Nov 2014 05:49:15 -0500 Date: Fri, 21 Nov 2014 11:49:05 +0100 (CET) From: Thomas Gleixner To: Marc Zyngier cc: Yijing Wang , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Jiang Liu , Will Deacon , Catalin Marinas , "H. Peter Anvin" , Ingo Molnar , Arjan van de Ven , David Woodhouse Subject: Re: Removal of bus->msi assignment breaks MSI with stacked domains In-Reply-To: <546F140B.1050607@arm.com> Message-ID: References: <546E1771.4030201@arm.com> <546E93DC.8010902@huawei.com> <546F140B.1050607@arm.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Marc, On Fri, 21 Nov 2014, Marc Zyngier wrote: > On 21/11/14 01:46, Thomas Gleixner wrote: > > So the real question is: > > > > What is the association level requirement to properly identify the > > irqdomain for a specific device on any given architecture with and > > without IOMMU, interrupt redirection etc. > > > > To be honest: I don't know. > > > > My gut feeling tells me that it's at the device level, but I really > > leave that decision to the experts in that field. > > Given the above requirement (single device associated to DMAR), I can > see two possibilities: > - we represent DMAR as a single PCI bus: feels a bit artificial > - we move the MSI domain to the device, as you suggested. > > The second one seems a lot more attractive to me. And that's very useful if you want to support MSI on non PCI devices. > Also, it is not clear to me what is the advantage of getting rid of the > MSI controller. By doing so, we loose an important part of the topology > information (the irq domain is another level of abstraction). That was probably my misunderstanding of the msi controller. I had the impression it's just there to expose the MSI properties of a device, i.e. a magic wrapper which can be replaced by the MSI irqdomain work. If that handles other information as well, then it's probably a misnomer to begin with. Thanks, tglx -- 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/