linux-kernel - [PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to

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Message-ID: <20250219220751.1276854-2-suzuki.poulose@arm.com>
Date: Wed, 19 Feb 2025 22:07:49 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: will@...nel.org,
	robin.murphy@....com,
	catalin.marinas@....com
Cc: maz@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org,
	aneesh.kumar@...nel.org,
	steven.price@....com,
	suzuki.poulose@....com,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	Christoph Hellwig <hch@....de>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to_phys

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