From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B496C4332F for ; Thu, 14 Dec 2023 18:23:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231817AbjLNSWy (ORCPT ); Thu, 14 Dec 2023 13:22:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229519AbjLNSWv (ORCPT ); Thu, 14 Dec 2023 13:22:51 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 64C69120; Thu, 14 Dec 2023 10:22:57 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 77EACC15; Thu, 14 Dec 2023 10:23:42 -0800 (PST) Received: from [10.57.86.13] (unknown [10.57.86.13]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C1D713F738; Thu, 14 Dec 2023 10:22:51 -0800 (PST) Message-ID: <2d87c1dc-cc95-4d92-968c-9d6e6e6439ff@arm.com> Date: Thu, 14 Dec 2023 18:22:49 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/7] iommu/dma: Centralise iommu_setup_dma_ops() Content-Language: en-GB To: Jean-Philippe Brucker Cc: Joerg Roedel , Christoph Hellwig , Vineet Gupta , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , Paul Walmsley , Palmer Dabbelt , Albert Ou , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Suravee Suthikulpanit , David Woodhouse , Lu Baolu , Niklas Schnelle , Matthew Rosato , Gerald Schaefer , Rob Herring , Frank Rowand , Marek Szyprowski , Jason Gunthorpe , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org, iommu@lists.linux.dev, devicetree@vger.kernel.org References: <5d89190b35720bf5b66621f46b6d3c85323d8eab.1702486837.git.robin.murphy@arm.com> <20231214165126.GA3726750@myrica> From: Robin Murphy In-Reply-To: <20231214165126.GA3726750@myrica> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-12-14 4:51 pm, Jean-Philippe Brucker wrote: > On Wed, Dec 13, 2023 at 05:17:59PM +0000, Robin Murphy wrote: >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index 27a167f4cd3e..d808c8dcf5cb 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -1724,25 +1724,20 @@ static const struct dma_map_ops iommu_dma_ops = { >> .opt_mapping_size = iommu_dma_opt_mapping_size, >> }; >> >> -/* >> - * The IOMMU core code allocates the default DMA domain, which the underlying >> - * IOMMU driver needs to support via the dma-iommu layer. >> - */ >> -void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit) >> +void iommu_setup_dma_ops(struct device *dev) >> { >> struct iommu_domain *domain = iommu_get_domain_for_dev(dev); >> >> - if (!domain) >> - goto out_err; >> + if (dev_is_pci(dev)) >> + dev->iommu->pci_32bit_workaround = !iommu_dma_forcedac; >> >> - /* >> - * The IOMMU core code allocates the default DMA domain, which the >> - * underlying IOMMU driver needs to support via the dma-iommu layer. >> - */ >> if (iommu_is_dma_domain(domain)) { > > ... > >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index 824989874dee..43f630d0530e 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -560,10 +560,10 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list >> if (list_empty(&group->entry)) >> list_add_tail(&group->entry, group_list); >> } >> - mutex_unlock(&group->mutex); >> >> - if (dev_is_pci(dev)) >> - iommu_dma_set_pci_32bit_workaround(dev); >> + iommu_setup_dma_ops(dev); > > With Intel VT-d (QEMU emulation) I get a crash in iommu_setup_dma_ops() > because at this point group->domain and group->default_domain are still > NULL, group_list is non-NULL. Ugh, clearly I'd manage to confuse myself, since what I wrote in the changelog isn't even right... Taking yet another look, there's not actually one single place we can do this right now which will work in a manageable way for all cases. With 2 or 3 more levels of mess unpicked it's going to clean up much further (it's also becoming clear that iommu-dma wants better separation of its own per-device and per-domain bits), but for the immediate task in this series of finally getting out of arch code, I guess that continuing to echo the current probe_finalize flows is going to be safest. Something like the diff below (but I'll have a further think about it with a fresh head tomorrow). Thanks, Robin. ----->8----- diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 8972b7f22a9a..ba4cd5251205 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -562,7 +562,8 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list list_add_tail(&group->entry, group_list); } - iommu_setup_dma_ops(dev); + if (group->default_domain) + iommu_setup_dma_ops(dev); mutex_unlock(&group->mutex); @@ -1992,6 +1993,8 @@ int bus_iommu_probe(const struct bus_type *bus) mutex_unlock(&group->mutex); return ret; } + for_each_group_device(group, gdev) + iommu_setup_dma_ops(gdev->dev); mutex_unlock(&group->mutex); /* @@ -3217,18 +3220,9 @@ static ssize_t iommu_group_store_type(struct iommu_group *group, if (ret) goto out_unlock; - /* - * Release the mutex here because ops->probe_finalize() call-back of - * some vendor IOMMU drivers calls arm_iommu_attach_device() which - * in-turn might call back into IOMMU core code, where it tries to take - * group->mutex, resulting in a deadlock. - */ - mutex_unlock(&group->mutex); - /* Make sure dma_ops is appropriatley set */ for_each_group_device(group, gdev) - iommu_group_do_probe_finalize(gdev->dev); - return count; + iommu_setup_dma_ops(gdev->dev); out_unlock: mutex_unlock(&group->mutex);