[PATCH v3 0/6] iommu: Extend changing default domain to normal group

[Lu Baolu]

The IOMMU group sysfs interface allows users to change the default
domain of a group. The current implementation uses device_lock() to make
sure that the devices in the group are not bound to any driver and won't
be bound during the process of changing the default domain. In order to
avoid a possible deadlock caused by lock order of device_lock and
group->mutex, it limits the functionality to singleton groups only.

The recently implemented DMA ownership framework can be applied here to
replace device_lock(). In addition, use group->mutex to ensure that the
iommu ops of the device are always valid during the process of changing
default domain.

With above replacement and enhancement, the device_lock() could be
removed and the singleton-group-only limitation could be removed.

This series is based on v6.3-rc1 with below series from Robin applied,
https://lore.kernel.org/linux-iommu/cover.1674753627.git.robin.murphy@xxxxxxx/

The whole series is also available on github:
https://github.com/LuBaolu/intel-iommu/commits/iommu-sysfs-default-domain-extension-v3

Please help to review and suggest.

Change log:
v3:
 - "arm_iommu_detach_device() is a noop" is not entirely right. It is
   used to to make the iommu driver stop using the domain that it is
   about to free. It cannot be a NOP or it is a UAF. [Jason]
 - Use Jason's new arm_iommu_release_device() proposal instead.

v2:
 - https://lore.kernel.org/linux-iommu/20230217094736.159005-1-baolu.lu@xxxxxxxxxxxxxxx/
 - Use group->mutex instead of an additional rw lock.

v1: initial post
 - https://lore.kernel.org/linux-iommu/20230213074941.919324-1-baolu.lu@xxxxxxxxxxxxxxx/

Lu Baolu (6):
  ARM/dma-mapping: Add arm_iommu_release_device()
  iommu: Split iommu_group_remove_device() into helpers
  iommu: Same critical region for device release and removal
  iommu: Move lock from iommu_change_dev_def_domain() to its caller
  iommu: Replace device_lock() with group->mutex
  iommu: Cleanup iommu_change_dev_def_domain()

 arch/arm/include/asm/dma-iommu.h              |   1 +
 arch/arm/mm/dma-mapping.c                     |  25 ++
 drivers/iommu/iommu.c                         | 270 ++++++++----------
 drivers/iommu/ipmmu-vmsa.c                    |  15 +-
 .../ABI/testing/sysfs-kernel-iommu_groups     |   1 -
 5 files changed, 156 insertions(+), 156 deletions(-)

-- 
2.34.1