Re: [PATCH 1/1] powerpc/pseries/iommu: Fix window size for direct mapping with pmem

On Tue, 2021-04-20 at 15:18 +1000, Alexey Kardashevskiy wrote:

On 20/04/2021 14:54, Leonardo Bras wrote:

quoted

As of today, if the DDW is big enough to fit (1 << MAX_PHYSMEM_BITS) it's
possible to use direct DMA mapping even with pmem region.

But, if that happens, the window size (len) is set to
(MAX_PHYSMEM_BITS - page_shift) instead of MAX_PHYSMEM_BITS, causing a
pagesize times smaller DDW to be created, being insufficient for correct
usage.

Fix this so the correct window size is used in this case.

Good find indeed.

afaict this does not create a huge problem though as 
query.largest_available_block is always smaller than (MAX_PHYSMEM_BITS - 
page_shift) where it matters (phyp).


Reviewed-by: Alexey Kardashevskiy <redacted>

Thanks for reviewing!

Leonardo Bras