[PATCH v2] arm64: dma-mapping: Fix dma_mapping_error() when bypassing SWIOTLB

[Aaro Koskinen]

Hi,

On Wed, Jan 25, 2017 at 06:31:31PM +0000, Robin Murphy wrote:
> When bypassing SWIOTLB on small-memory systems, we need to avoid calling
> into swiotlb_dma_mapping_error() in exactly the same way as we avoid
> swiotlb_dma_supported(), because the former also relies on SWIOTLB state
> being initialised.
> 
> Under the assumptions for which we skip SWIOTLB, dma_map_{single,page}()
> will only ever return the DMA-offset-adjusted physical address of the
> page passed in, thus we can report success unconditionally.
> 
> Fixes: b67a8b29df7e ("arm64: mm: only initialize swiotlb when necessary")
> CC: stable at vger.kernel.org
> CC: Jisheng Zhang <jszhang at marvell.com>
> Reported-by: Aaro Koskinen <aaro.koskinen at iki.fi>
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>

Tested-by: Aaro Koskinen <aaro.koskinen at iki.fi>

Thanks,

A.

> ---
> 
> v2: Get the return value the right way round this time... After some
>     careful reasoning it really is that simple.
> 
>  arch/arm64/mm/dma-mapping.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index e04082700bb1..1ffb7d5d299a 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -352,6 +352,13 @@ static int __swiotlb_dma_supported(struct device *hwdev, u64 mask)
>  	return 1;
>  }
>  
> +static int __swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t addr)
> +{
> +	if (swiotlb)
> +		return swiotlb_dma_mapping_error(hwdev, addr);
> +	return 0;
> +}
> +
>  static struct dma_map_ops swiotlb_dma_ops = {
>  	.alloc = __dma_alloc,
>  	.free = __dma_free,
> @@ -366,7 +373,7 @@ static struct dma_map_ops swiotlb_dma_ops = {
>  	.sync_sg_for_cpu = __swiotlb_sync_sg_for_cpu,
>  	.sync_sg_for_device = __swiotlb_sync_sg_for_device,
>  	.dma_supported = __swiotlb_dma_supported,
> -	.mapping_error = swiotlb_dma_mapping_error,
> +	.mapping_error = __swiotlb_dma_mapping_error,
>  };
>  
>  static int __init atomic_pool_init(void)
> -- 
> 2.11.0.dirty
>