From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH] kvmtool: don't use PCI config space IRQ line field Date: Fri, 6 Feb 2015 19:07:20 +0000 Message-ID: <20150206190719.GG24099@arm.com> References: <4324891.mqG6Yyfi6J@wuerfel> <1423064390-15269-1-git-send-email-andre.przywara@arm.com> <20150206185527.GC24099@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andre Przywara , "arnd@arndb.de" , "kvm@vger.kernel.org" , Marc Zyngier , "penberg@kernel.org" , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" To: Peter Maydell Return-path: Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:42483 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751083AbbBFTH2 (ORCPT ); Fri, 6 Feb 2015 14:07:28 -0500 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Fri, Feb 06, 2015 at 07:02:25PM +0000, Peter Maydell wrote: > On 6 February 2015 at 18:55, Will Deacon wrote: > > On Wed, Feb 04, 2015 at 03:39:50PM +0000, Andre Przywara wrote: > >> In PCI config space there is an interrupt line field (offset 0x3f), > >> which is used to initially communicate the IRQ line number from > >> firmware to the OS. _Hardware_ should never use this information, > >> as the OS is free to write any information in there. > > > > Is this true even with probe-only? I appreciate that this isn't a BAR, > > but it still feels odd for Linux to write this in that case. > > The hardware (model) shouldn't be doing anything with the value > in this register anyway, so I think this change to kvmtool is > correct regardless of Linux's behaviour. Well, kvmtool is also pretending to be firmware in this case, which is why it passes things like probe-only and PSCI nodes. Will