Re: [PATCH][POWERPC] Workaround for iommu page alignment

On Tue, 2008-01-08 at 08:45 +1100, Benjamin Herrenschmidt wrote:

Our iommu page size is currently always 4K. That means with our current
code, drivers may do a dma_map_sg() of a 64K page and obtain a dma_addr_t
that is only 4K aligned.

This works fine in most cases except some infiniband HW it seems, where
they tell the HW about the page size and it ignores the low bits of the
DMA address.

This works around it by making our IOMMU code enforce a PAGE_SIZE alignment
for mappings of objects that are page aligned in the first place and whose
size is larger or equal to a page.

  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I don't see in the code where you implement the "size > PAGE_SIZE"
condition. But I only just got back from holidays .. :)

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person