Re: [PATCH v2 3/3] iommu/io-pgtable-arm-v7s: Request DMA32 memory, and improve debugging

[Will Deacon <will.deacon@arm.com>]

On Sun, Nov 11, 2018 at 05:03:41PM +0800, Nicolas Boichat wrote:
> 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.
> 
> Also, print an error when the physical address does not fit in
> 32-bit, to make debugging easier in the future.
> 
> Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")
> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
> ---
> 
> Changes since v1:
>  - Changed approach to use SLAB_CACHE_DMA32 added by the previous
>    commit.
>  - Use DMA or DMA32 depending on the architecture (DMA for arm,
>    DMA32 for arm64).
> 
> drivers/iommu/io-pgtable-arm-v7s.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index 445c3bde04800c..996f7b6d00b44a 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -161,6 +161,14 @@
>  
>  #define ARM_V7S_TCR_PD1			BIT(5)
>  
> +#ifdef CONFIG_ZONE_DMA32
> +#define ARM_V7S_TABLE_GFP_DMA GFP_DMA32
> +#define ARM_V7S_TABLE_SLAB_CACHE SLAB_CACHE_DMA32
> +#else
> +#define ARM_V7S_TABLE_GFP_DMA GFP_DMA
> +#define ARM_V7S_TABLE_SLAB_CACHE SLAB_CACHE_DMA
> +#endif

It's a bit grotty that GFP_DMA32 doesn't just map to GFP_DMA on 32-bit
architectures, since then we wouldn't need this #ifdeffery afaict.

Will