Re: [PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to_phys

[Tom Lendacky]

On 2/19/25 16:07, Suzuki K Poulose wrote:
> phys_to_dma() sets the encryption bit on the translated DMA address. But
> dma_to_phys() clears the encryption bit after it has been translated back
> to the physical address, which could fail if the device uses DMA ranges.
> 
> Hopefully, AMD SME doesn't use it. Anyways, let us fix it, before cleanup
> the infrastructure for supporting other architectures.

I'm not aware of anything using DMA ranges on SME capable hardware. And
as you stated, this would have failed if there was.

Acked-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

> 
> Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxx>
> Link: https://lkml.kernel.org/r/yq5amsen9stc.fsf@xxxxxxxxxx
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Robin Murphy <robin.murphy@xxxxxxx>
> Cc: Steven Price <steven.price@xxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
>  include/linux/dma-direct.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
> index d7e30d4f7503..d20ecc24cb0f 100644
> --- a/include/linux/dma-direct.h
> +++ b/include/linux/dma-direct.h
> @@ -101,12 +101,13 @@ static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
>  {
>  	phys_addr_t paddr;
>  
> +	dma_addr = __sme_clr(dma_addr);
>  	if (dev->dma_range_map)
>  		paddr = translate_dma_to_phys(dev, dma_addr);
>  	else
>  		paddr = dma_addr;
>  
> -	return __sme_clr(paddr);
> +	return paddr;
>  }
>  #endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */
>