RE: [PATCH v6 12/12] iommu: Improve iopf_queue_flush_dev()

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Thursday, September 28, 2023 12:28 PM
> 
> The iopf_queue_flush_dev() is called by the iommu driver before releasing
> a PASID. It ensures that all pending faults for this PASID have been
> handled or cancelled, and won't hit the address space that reuses this
> PASID. The driver must make sure that no new fault is added to the queue.
> 
> The SMMUv3 driver doesn't use it because it only implements the
> Arm-specific stall fault model where DMA transactions are held in the SMMU
> while waiting for the OS to handle iopf's. Since a device driver must
> complete all DMA transactions before detaching domain, there are no
> pending iopf's with the stall model. PRI support requires adding a call to
> iopf_queue_flush_dev() after flushing the hardware page fault queue.
> 
> The current implementation of iopf_queue_flush_dev() is a simplified
> version. It is only suitable for SVA case in which the processing of iopf
> is implemented in the inner loop of the iommu subsystem.
> 
> Improve this interface to make it also work for handling iopf out of the
> iommu core. Rename the function with a more meaningful name. Remove a
> warning message in iommu_page_response() since the iopf queue might get
> flushed before possible pending responses.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>