[PATCH v4 00/19] iommu: Retire detach_dev callback

Lu Baolu
2023-01-04T13:06:01Z

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. Thank
Jason, Robin and all others for their ideas. This series looks very
long. It is necessary because I hope that change in each driver has a
confirmation from its stakeholder. I will then be able to merge some of
them to make the series cute.

The whole series is available on github:
https://github.com/LuBaolu/intel-iommu/commits/iommu-retire-detach_dev-v4

Please review and suggest.

Change log:
v4:
- 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 (18):
iommu/amd: Remove detach_dev callback
iommu/apple-dart: Remove detach_dev callback
iommu/qcom: Remove detach_dev callback
iommu/exynos: Remove detach_dev callback
iommu/ipmmu: Remove detach_dev callback
iommu/mtk: Remove detach_dev callback
iommu/rockchip: Remove detach_dev callback
iommu/sprd: Remove detach_dev callback
iommu/sun50i: Remove detach_dev callback
iommu: Add set_platform_dma_ops iommu ops
iommu/fsl_pamu: Add set_platform_dma_ops callback
iommu/msm: Add set_platform_dma_ops callback
iommu/mtk_v1: Add set_platform_dma_ops callback
iommu/omap: Add set_platform_dma_ops callback
iommu/s390: Add set_platform_dma_ops callback
iommu/gart: Add set_platform_dma_ops callback
iommu/tegra: Add set_platform_dma_ops callback
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 | 98 ++++++++++++-------------
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, 73 insertions(+), 198 deletions(-)

--
2.34.1