>> So the driver needs to use flush/drain operations to make sure all >> the in-flight work has completed before releasing/re-using the PASID. >> > Are you suggesting we should let driver also hold a reference of the > PASID?
The sequence for bare metal is: process is queuing requests to DSA process exits (either deliberately, or crashes, or is killed) kernel does exit processing DSA driver is called as part of tear down of "mm" issues drain/flush commands to ensure that all queued operations on the PASID for this mm have completed PASID can be freed There's a 1:1 map from "mm" to PASID ... so reference counting seems like overkill. Once the kernel is in the "exit" path, we know that no more work can be queued using this PASID. -Tony _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu