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

[Jason Gunthorpe]

On Tue, Sep 12, 2006 at 05:40:10PM -0700, Ralph Campbell wrote:

> The ib_ipath driver needs kernel virtual addresses in order to be able
> to copy data to/from the posted work requests since it does not
> use HW DMA. It currently relies on the mapping being one-to-one
> and cannot reasonably reverse the mapping when an IOMMU is present.

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

Jason