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Date: Mon, 16 Jan 2023 17:24:56 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>,
Joerg Roedel <joro@...tes.org>,
Jason Gunthorpe <jgg@...dia.com>,
Christoph Hellwig <hch@...radead.org>,
Kevin Tian <kevin.tian@...el.com>,
Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
Vasant Hegde <vasant.hegde@....com>,
Hector Martin <marcan@...can.st>,
Sven Peter <sven@...npeter.dev>,
Rob Clark <robdclark@...il.com>,
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
Andy Gross <agross@...nel.org>,
Bjorn Andersson <andersson@...nel.org>,
Yong Wu <yong.wu@...iatek.com>,
Matthias Brugger <matthias.bgg@...il.com>,
Heiko Stuebner <heiko@...ech.de>,
Matthew Rosato <mjrosato@...ux.ibm.com>,
Orson Zhai <orsonzhai@...il.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
Chunyan Zhang <zhang.lyra@...il.com>,
Chen-Yu Tsai <wens@...e.org>,
Thierry Reding <thierry.reding@...il.com>,
iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/5] iommu: Retire detach_dev callback
Hi All,
On 10.01.2023 03:54, Lu Baolu wrote:
> Hi folks,
>
> The iommu core calls the driver's detach_dev domain op callback only when
> a device is finished assigning to user space and
> iommu_group_release_dma_owner() is called to return the device to the
> kernel, where iommu core wants to set the default domain to the device but
> the driver didn't provide one. The code looks like:
>
> /*
> * New drivers should support default domains and so the detach_dev() op
> * will never be called. Otherwise the NULL domain represents some
> * platform specific behavior.
> */
> if (!new_domain) {
> if (WARN_ON(!group->domain->ops->detach_dev))
> return -EINVAL;
> __iommu_group_for_each_dev(group, group->domain,
> iommu_group_do_detach_device);
> group->domain = NULL;
> return 0;
> }
>
> In other words, if the iommu driver provides default domains, the
> .detach_dev callback will never be called; Otherwise, the .detach_dev
> callback is actually called to return control back to the platform DMA
> ops, other than detaching the domain from device.
>
> This series cleanups this by:
>
> - If the IOMMU driver provides default domains, remove .detach_dev
> callback.
> - Adds a new set_platform_dma iommu op. Any IOMMU driver that doesn't
> provide default domain should implement set_platform_dma callback
> instead.
> - Retire .detach_dev callback.
>
> This series originates from various discussion in the community. Thanks
> to Jason, Robin and all others for their ideas.
I wonder how to handle the ARM 32bit case, which doesn't use the default
domain solution. Today, once this patchset has been merged to
linux-next, I've noticed that it broke booting of ARM 32bit Exynos based
boards.
The final solution would be to switch ARM 32bit to generic DMA-IOMMU
glue, but I'm not sure it this will happen soon. I will try to check if
any kind of quick workaround can be applied to get it working again.
> The whole series is available on github:
> https://protect2.fireeye.com/v1/url?k=ef2183b6-b0bababa-ef2008f9-000babff3563-336828b3433153d2&q=1&e=4ae5dae4-383f-4a82-9449-3f08f0422cb1&u=https%3A%2F%2Fgithub.com%2FLuBaolu%2Fintel-iommu%2Fcommits%2Fiommu-retire-detach_dev-v5
>
> Change log:
> v5:
> - Merge some patches to make the series cute. No functionality changes.
> - Check the op directly and WARN_ON the lack of any necessary
> callbacks. Get rid of the ret and EINVAL.
>
> v4:
> - https://lore.kernel.org/linux-iommu/20230104125725.271850-1-baolu.lu@linux.intel.com/
> - Drop the patch which renamed .attach_dev to .set_dev. As Robin said,
> "... I also wouldn't say that "attach" loses its meaning in a context
> where an equivalent "detach" operation is only ever implicit in
> reattaching to something else...". If we have a better name in the
> future, we can do it in other series.
> - Adjust the patch of "iommu: Add set_platform_dma_ops iommu ops"
> according to Jason's following suggestion " ... This is a bit ugly,
> it would be better to make the previous patch call set_platform_dma
> if it is set instead of detach_dev and then these patches should just
> rename the driver's fsl_pamu_detach_device to
> fsl_pamu_set_platform_dma ..."
> - Add a new patch to remove deferred attach check from
> __iommu_detach_domain() path. Make it a separate patch as the
> prerequisite to remove __iommu_detach_device() helper.
> - Rename set_platform_dma to set_platform_dma_ops to make it more
> meaningful.
>
> v3:
> - https://lore.kernel.org/linux-iommu/20221128064648.1934720-1-baolu.lu@linux.intel.com/
> - Setting blocking domain is not conceptually equal to detach_dev.
> Dropped all blocking domain related staffs in the previous version.
>
> v2:
> - https://lore.kernel.org/linux-iommu/20220826123014.52709-1-baolu.lu@linux.intel.com/
> - Replace .detach_dev callback with static block domain ops;
> - Rename .attach_dev to .set_dev.
>
> v1:
> - https://lore.kernel.org/linux-iommu/20220516015759.2952771-1-baolu.lu@linux.intel.com/
>
> Jason Gunthorpe (1):
> iommu: Remove deferred attach check from __iommu_detach_device()
>
> Lu Baolu (4):
> iommu: Remove detach_dev callbacks
> iommu: Add set_platform_dma_ops iommu ops
> iommu: Add set_platform_dma_ops callbacks
> iommu: Remove detach_dev callback
>
> include/linux/iommu.h | 8 ++-
> include/trace/events/iommu.h | 7 --
> drivers/iommu/amd/iommu.c | 26 -------
> drivers/iommu/apple-dart.c | 24 -------
> drivers/iommu/arm/arm-smmu/qcom_iommu.c | 23 ------
> drivers/iommu/exynos-iommu.c | 1 -
> drivers/iommu/fsl_pamu_domain.c | 6 +-
> drivers/iommu/iommu-traces.c | 1 -
> drivers/iommu/iommu.c | 94 ++++++++++++-------------
> drivers/iommu/ipmmu-vmsa.c | 16 -----
> drivers/iommu/msm_iommu.c | 6 +-
> drivers/iommu/mtk_iommu.c | 9 ---
> drivers/iommu/mtk_iommu_v1.c | 4 +-
> drivers/iommu/omap-iommu.c | 6 +-
> drivers/iommu/rockchip-iommu.c | 1 -
> drivers/iommu/s390-iommu.c | 7 +-
> drivers/iommu/sprd-iommu.c | 16 -----
> drivers/iommu/sun50i-iommu.c | 1 -
> drivers/iommu/tegra-gart.c | 6 +-
> drivers/iommu/tegra-smmu.c | 5 +-
> 20 files changed, 69 insertions(+), 198 deletions(-)
>
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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