Re: [PATCH v2 1/3] dma: Fix encryption bit clearing for dma_to_phys
From: Suzuki K Poulose
Date: Tue Feb 25 2025 - 09:07:03 EST
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@xxxxxxx>
Thanks
Suzuki
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 */