[openib-general] How to support IOMMUs for ipath driver

[Roland Dreier]

    Jason> I'm sure this must have been answered, but given a PCI
    Jason> domain:bus:device:function tuple and a DMA address,
    Jason> shouldn't any effects of an IOMMU be easially duplicated in
    Jason> software to result in a cpu-bus physical address? Ie on
    Jason> AMD64 it is just a matter of following the GART tables in
    Jason> software - assuming the address in question hits the GART
    Jason> region (which for ipath, I expect, it never would)

Yes, you could do this.  However there's no exported interface for
reversing a DMA mapping.  And it seems like a lot of unneeded
complexity to add -- why not just avoid the DMA mapping in the first place?

 - R.