From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752917AbdCBOHY (ORCPT ); Thu, 2 Mar 2017 09:07:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43168 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751985AbdCBOHE (ORCPT ); Thu, 2 Mar 2017 09:07:04 -0500 Subject: Re: [PATCH 1/2] irqdomain: add empty irq_domain_check_msi_remap To: Mian Yousaf Kaukab , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, marc.zyngier@arm.com, alex.williamson@redhat.com References: <20170302100132.20502-1-yousaf.kaukab@suse.com> <7aa0b755-844d-f0f6-d733-276a38b53d11@suse.com> Cc: will.deacon@arm.com From: Auger Eric Message-ID: Date: Thu, 2 Mar 2017 14:12:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <7aa0b755-844d-f0f6-d733-276a38b53d11@suse.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Thu, 02 Mar 2017 13:12:18 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Yousaf, On 02/03/2017 13:23, Mian Yousaf Kaukab wrote: > On 03/02/2017 11:24 AM, Auger Eric wrote: >> Hi Mian Yousaf, >> >> On 02/03/2017 11:01, Mian Yousaf Kaukab wrote: >>> Fix following build error for s390: >>> drivers/vfio/vfio_iommu_type1.c: In function >>> 'vfio_iommu_type1_attach_group': >>> drivers/vfio/vfio_iommu_type1.c:1290:25: error: implicit declaration >>> of function 'irq_domain_check_msi_remap' >>> >>> Signed-off-by: Mian Yousaf Kaukab >>> --- >>> include/linux/irqdomain.h | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h >>> index 188eced6813e..137817b08cdc 100644 >>> --- a/include/linux/irqdomain.h >>> +++ b/include/linux/irqdomain.h >>> @@ -524,6 +524,10 @@ static inline struct irq_domain >>> *irq_find_matching_fwnode( >>> { >>> return NULL; >>> } >>> +static inline bool irq_domain_check_msi_remap(void) >>> +{ >>> + return true; >> By default you should rather return false, reporting there is no MSI >> remapping capability on irq domain side. Besides thank you for the fix. > I choose to return true based on the function header comments of > irq_domain_check_msi_remap. It says > > "Return: false if any MSI irq domain does not support IRQ remapping, > true otherwise (including if there is no MSI irq domain)" > > So function should return true in case of no MSI irq domain. Have I miss > understood this? This behavior is indeed mandated on ARM - where MSI are translated by the smmu - to allow safe device assignment if there is no MSI domain, ie. in this situation there is no risk an assigned device writes into an MSI doorbell. As the function is not implemented at all in your case, personally I would rather be defensive though and return false. You were not able to check the capability. Thanks Eric > > BR, > Yousaf