Messages in this thread | | | Subject | Re: [ofa-general] iommu dma mapping alignment requirements | From | Roland Dreier <> | Date | Thu, 20 Dec 2007 10:07:39 -0800 |
| |
> It appears that my problem boils down to a single host page of memory > that is mapped for dma, and the dma address returned by dma_map_sg() > is _not_ 64KB aligned. Here is an example:
> My first question is: Is there an assumption or requirement in linux > that dma_addressess should have the same alignment as the host address > they are mapped to? IE the rdma core is mapping the entire 64KB page, > but the mapping doesn't begin on a 64KB page boundary.
I don't think this is explicitly documented anywhere, but it certainly seems that we want the bus address to be page-aligned in this case. For mthca/mlx4 at least, we tell the adapter what the host page size is (so that it knows how to align doorbell pages etc) and I think this sort of thing would confuse the HW.
- R.
| |