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, add an rw lock to ensure that the
iommu ops of the devices is 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.

The whole series is also available on github:

https://github.com/LuBaolu/intel-iommu/commits/iommu-sysfs-default-domain-extension-v1

Please help to review and suggest.

Lu Baolu (4):
  iommu: Add dev_iommu->ops_rwsem
  iommu: Use group ownership to avoid driver attachment
  iommu: Remove unnecessary device_lock()
  iommu: Cleanup iommu_change_dev_def_domain()

 include/linux/iommu.h |   3 +
 drivers/iommu/iommu.c | 187 +++++++++++++++++-------------------------
 2 files changed, 78 insertions(+), 112 deletions(-)

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2.34.1