Re: [PATCH v2 17/19] iommu/arm-smmu-v3: Add arm_smmu_viommu_cache_invalidate

Jason Gunthorpe
2024-09-11T23:07:40Z

On Wed, Sep 11, 2024 at 08:13:01AM +0000, Tian, Kevin wrote:

> Probably there is a good reason e.g. for simplification or better
> aligned with hw accel stuff. But it's not explained clearly so far.

Probably the most concrete thing is if you have a direct assignment
invalidation queue (ie DMA'd directly by HW) then it only applies to a
single pIOMMU and invalidation commands placed there are unavoidably
limited in scope.

This creates a representation problem, if we have a vIOMMU that spans
many pIOMMUs but invalidations do some subset how to do we model
that. Just saying the vIOMMU is linked to the pIOMMU solves this
nicely.

Jason