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

Suzuki K Poulose posted 3 patches 10 months ago
There is a newer version of this series
[PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to_phys
Posted by Suzuki K Poulose 10 months ago 
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.

Reported-by: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Link: https://lkml.kernel.org/r/yq5amsen9stc.fsf@kernel.org
Cc: Will Deacon <will@kernel.org>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 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 */
 
-- 
2.43.0
Re: [PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to_phys
Posted by Tom Lendacky 9 months, 3 weeks ago 
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@amd.com>

> 
> Reported-by: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
> Link: https://lkml.kernel.org/r/yq5amsen9stc.fsf@kernel.org
> Cc: Will Deacon <will@kernel.org>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
>  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 */
>
Re: [PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to_phys
Posted by Robin Murphy 9 months, 3 weeks ago 
On 2025-02-19 10:07 pm, 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.

...by which you mean we don't think any AMD systems are using the ACPI 
_DMA method to constrain physical DMA ranges, otherwise SME with 
dma-direct would presumably already be broken by this lookup going wrong.

> Anyways, let us fix it, before cleanup
> the infrastructure for supporting other architectures.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Reported-by: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
> Link: https://lkml.kernel.org/r/yq5amsen9stc.fsf@kernel.org
> Cc: Will Deacon <will@kernel.org>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
>   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 */
>
Re: [PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to_phys
Posted by Suzuki K Poulose 9 months, 3 weeks ago 
On 25/02/2025 11:25, Robin Murphy wrote:
> On 2025-02-19 10:07 pm, 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.
> 
> ...by which you mean we don't think any AMD systems are using the ACPI 
> _DMA method to constrain physical DMA ranges, otherwise SME with dma- 
> direct would presumably already be broken by this lookup going wrong.

Yep, that AMD systems aren't using DMA ranges.


> 
>> Anyways, let us fix it, before cleanup
>> the infrastructure for supporting other architectures.
> 
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>

Thanks

Suzuki

> 
>> Reported-by: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
>> Link: https://lkml.kernel.org/r/yq5amsen9stc.fsf@kernel.org
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Robin Murphy <robin.murphy@arm.com>
>> Cc: Steven Price <steven.price@arm.com>
>> Cc: Christoph Hellwig <hch@lst.de>
>> Cc: Tom Lendacky <thomas.lendacky@amd.com>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> ---
>>   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 */
>

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