Messages in this thread | | | Date | Wed, 19 Apr 2017 09:55:57 -0600 | From | Jason Gunthorpe <> | Subject | Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory |
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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
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