Re: [PATCH v6 2/3] iommu/io-pgtable-arm-v7s: Request DMA32 memory, and improve debugging

[Will Deacon]

On Mon, Dec 10, 2018 at 09:15:03AM +0800, Nicolas Boichat wrote:
> IOMMUs using ARMv7 short-descriptor format require page tables
> (level 1 and 2) to be allocated within the first 4GB of RAM, even
> on 64-bit systems.
> 
> For level 1/2 pages, ensure GFP_DMA32 is used if CONFIG_ZONE_DMA32
> is defined (e.g. on arm64 platforms).
> 
> For level 2 pages, allocate a slab cache in SLAB_CACHE_DMA32. Note
> that we do not explicitly pass GFP_DMA[32] to kmem_cache_zalloc,
> as this is not strictly necessary, and would cause a warning
> in mm/sl*b.c, as we did not update GFP_SLAB_BUG_MASK.
> 
> Also, print an error when the physical address does not fit in
> 32-bit, to make debugging easier in the future.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")
> Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>

Assuming you're routing all of this via akpm:

Acked-by: Will Deacon <will.deacon@xxxxxxx>

Will