On Wed, Apr 19, 2017 at 11:20:06AM +1000, Benjamin Herrenschmidt wrote: > That helper wouldn't perform the actual iommu mapping. It would simply > return something along the lines of: > > - "use that alternate bus address and don't map in the iommu" I was thinking only this one would be supported with a core code helper.. > - "use that alternate bus address and do map in the iommu" > - "proceed as normal" .. because I don't have an idea how a core code helper could figure out what the platform needs for the above two .. I think many of the iommu platforms will need to construct their own bus address in the iommu, and we already have easy access to the CPU address. Presumably once a transcation passes through the iommu it needs to be using the CPU address for the target bar, otherwise things are going to be ambiguous.. Jason
