From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755329AbcFQJ1a (ORCPT ); Fri, 17 Jun 2016 05:27:30 -0400 Received: from foss.arm.com ([217.140.101.70]:48633 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753967AbcFQJ11 (ORCPT ); Fri, 17 Jun 2016 05:27:27 -0400 From: Robin Murphy Subject: Re: [RFC PATCH v2 03/15] arm64: mm: change IOMMU notifier action to attach DMA ops To: Lorenzo Pieralisi , iommu@lists.linux-foundation.org, Marek Szyprowski References: <1465306270-27076-1-git-send-email-lorenzo.pieralisi@arm.com> <1465306270-27076-4-git-send-email-lorenzo.pieralisi@arm.com> Cc: linux-arm-kernel@lists.infradead.org, "Rafael J. Wysocki" , Marc Zyngier , Catalin Marinas , Joerg Roedel , Will Deacon , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Sinan Kaya , linux-acpi@vger.kernel.org, Hanjun Guo , Tomasz Nowicki , Jon Masters Message-ID: <5763C27A.9030306@arm.com> Date: Fri, 17 Jun 2016 10:27:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: <1465306270-27076-4-git-send-email-lorenzo.pieralisi@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Lorenzo, I think this patch makes sense even independent of the rest of the series, one nit inline notwithstanding. Marek; I'm curious as to whether this could make the workaround in 722ec35f7 obsolete as well, or are all the drivers also bound super-early in the setup you had there? On 07/06/16 14:30, Lorenzo Pieralisi wrote: > Current bus notifier in ARM64 (__iommu_attach_notifier) > attempts to attach dma_ops to a device on BUS_NOTIFY_ADD_DEVICE > action notification. > > This causes issues on ACPI based systems, where PCI devices > can be added before the IOMMUs the devices are attached to > had a chance to be probed, causing failures on attempts to > attach dma_ops in that the domain for the respective IOMMU > may not be set-up yet by the time the bus notifier is run. > > Devices dma_ops do not require to be set-up till the matching > device drivers are probed. This means that instead of running > the notifier attaching dma_ops to devices (__iommu_attach_notifier) > on BUS_NOTIFY_ADD_DEVICE action, it can be run just before the > device driver is bound to the device in question (on action > BUS_NOTIFY_BIND_DRIVER) so that it is certain that its IOMMU > group and domain are set-up accordingly at the time the > notifier is triggered. > > This patch changes the notifier action upon which dma_ops > are attached to devices and defer it to driver binding time, > so that IOMMU devices have a chance to be probed and to register > their bus notifiers before the dma_ops attach sequence for a > device is actually carried out. > > Signed-off-by: Lorenzo Pieralisi > Cc: Will Deacon > Cc: Catalin Marinas > Cc: Robin Murphy > --- > arch/arm64/mm/dma-mapping.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c > index c566ec8..79b0882 100644 > --- a/arch/arm64/mm/dma-mapping.c > +++ b/arch/arm64/mm/dma-mapping.c > @@ -848,7 +848,7 @@ static int __iommu_attach_notifier(struct notifier_block *nb, > { > struct iommu_dma_notifier_data *master, *tmp; > > - if (action != BUS_NOTIFY_ADD_DEVICE) > + if (action != BUS_NOTIFY_BIND_DRIVER) With this, you can also get rid of the priority setting and big fat explanatory comment in register_iommu_dma_ops_notifier(). Robin. > return 0; > > mutex_lock(&iommu_dma_notifier_lock); >