[PATCH v5 0/5] iommu: Retire detach_dev callback

[Lu Baolu <baolu.lu@linux.intel.com>]

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.

The whole series is available on github:
https://github.com/LuBaolu/intel-iommu/commits/iommu-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(-)

-- 
2.34.1