Re: [PATCH v2 05/10] iommu: Add iommu_init/deinit_device() paired functions

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

On 5/20/23 2:42 AM, Jason Gunthorpe wrote:
> Move the driver init and destruction code into two logically paired
> functions.
> 
> There is a subtle ordering dependency in how the group's domains are
> freed, the current code does the kobject_put() on the group which will
> hopefully trigger the free of the domains before the module_put() that
> protects the domain->ops.
> 
> Reorganize this to be explicit and documented. The domains are cleaned up
> by iommu_deinit_device() if it is the last device to be deinit'd from the
> group.  This must be done in a specific order - after
> ops->release_device() and before the module_put(). Make it very clear and
> obvious by putting the order directly in one function.
> 
> Leave WARN_ON's in case the refcounting gets messed up somehow.
> 
> This also moves the module_put() and dev_iommu_free() under the
> group->mutex to keep the code simple.
> 
> Building paired functions like this helps ensure that error cleanup flows
> in __iommu_probe_device() are correct because they share the same code
> that handles the normal flow. These details become relavent as following
> patches add more error unwind into __iommu_probe_device(), and ultimately
> a following series adds fine-grained locking to __iommu_probe_device().
> 
> Reviewed-by: Kevin Tian<kevin.tian@intel.com>
> Signed-off-by: Jason Gunthorpe<jgg@nvidia.com>

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu