Re: iommu dma mapping alignment requirements

Steve Wise
2007-12-20T21:02:35Z

Benjamin Herrenschmidt wrote:
> Adding A few more people to the discussion. You may well be right and we
> would have to provide the same alignment, though that sucks a bit as one
> of the reason we switched to 4K for the IOMMU is that the iommu space
> available on pSeries is very small and we were running out of it with
> 64K pages and lots of networking activity.
>

But smarter NIC drivers can resolve this too, I think, but perhaps
carving up full pages of mapped buffers instead of just assuming mapping
is free...

perhaps...