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    SubjectRe: [PATCH v2 0/6] iommu: Extend changing default domain to normal group
    On Fri, Feb 17, 2023 at 05:47:30PM +0800, Lu Baolu wrote:
    > 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 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-v2
    >
    > This series is on top of below series from Robin,
    > https://lore.kernel.org/linux-iommu/cover.1674753627.git.robin.murphy@arm.com/
    >
    > Please help to review and suggest.

    Given the overall situation, I think my suggestion to use
    arm_iommu_release_device() might be more short term practical.

    Jason

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