Re: [PATCH v4 1/6] iommu: Add a per domain PASID for DMA API

[Jason Gunthorpe]

On Tue, May 31, 2022 at 08:45:28PM +0800, Baolu Lu wrote:

> My understanding is that device driver owns its PASID policy.

I'm not sure this is actually useful, the core code should provide the
allocator as I can't think of any device that actually needs a special
allocator.

> If ENQCMD is supported on the device, the PASIDs should be allocated
> through ioasid_alloc(). Otherwise, the whole PASID pool is managed
> by the device driver.

This is OK only if we know in-advance that the device needs a global
PASID. ENQCMD is one reason, maybe there are others down the road.

Better to make this core code policy.

Jason