[ewg] iommu issues with PPC64 and 2.6.23 and beyond

[Steve Wise]

 From today's conf call, I was asked to post info on the iommu issue I'm 
hitting on ppc64 systems.  This bug shows up as data corruption when I 
run stressful mvapich2 tests that force lots of dma mappings in the ppc 
iommu code.  The problem happens on kernels with the iommu size != host 
page size.  This is the default config for rh5.1 at least.    Workaround 
is to make the host page size 4KB.

Here is my original thread on this:

http://lkml.org/lkml/2007/12/20/368

Included in that thread is a proposed kernel fix from Ben that I tested ok.

Email if you have questions.

Steve.