lkml.org 
[lkml]   [2007]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [ofa-general] iommu dma mapping alignment requirements
From
Date
 > 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.


\
 
 \ /
  Last update: 2007-12-20 19:19    [W:0.116 / U:0.876 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site