[PATCH v2] dma/pool: Ensure DMA_DIRECT_REMAP allocations are decrypted

[PATCH v2] dma/pool: Ensure DMA_DIRECT_REMAP allocations are decrypted

[Shanker Donthineni]

When CONFIG_DMA_DIRECT_REMAP is enabled, atomic pool pages are
remapped via dma_common_contiguous_remap() using the supplied
pgprot. Currently, the mapping uses
pgprot_dmacoherent(PAGE_KERNEL), which leaves the memory encrypted
on systems with memory encryption enabled (e.g., ARM CCA Realms).

This can cause the DMA layer to fail or crash when accessing the
memory, as the underlying physical pages are not configured as
expected.

Fix this by requesting a decrypted mapping in the vmap() call:
pgprot_decrypted(pgprot_dmacoherent(PAGE_KERNEL))

This ensures that atomic pool memory is consistently mapped
unencrypted.

Cc: stable@vger.kernel.org
Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
---
 kernel/dma/pool.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 7b04f7575796b..ee45dee33d491 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -102,8 +102,8 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
 
 #ifdef CONFIG_DMA_DIRECT_REMAP
 	addr = dma_common_contiguous_remap(page, pool_size,
-					   pgprot_dmacoherent(PAGE_KERNEL),
-					   __builtin_return_address(0));
+			pgprot_decrypted(pgprot_dmacoherent(PAGE_KERNEL)),
+			__builtin_return_address(0));
 	if (!addr)
 		goto free_page;
 #else
-- 
2.25.1

Re: [PATCH v2] dma/pool: Ensure DMA_DIRECT_REMAP allocations are decrypted

[Catalin Marinas]

On Mon, Aug 11, 2025 at 01:17:59PM -0500, Shanker Donthineni wrote:
> When CONFIG_DMA_DIRECT_REMAP is enabled, atomic pool pages are
> remapped via dma_common_contiguous_remap() using the supplied
> pgprot. Currently, the mapping uses
> pgprot_dmacoherent(PAGE_KERNEL), which leaves the memory encrypted
> on systems with memory encryption enabled (e.g., ARM CCA Realms).
> 
> This can cause the DMA layer to fail or crash when accessing the
> memory, as the underlying physical pages are not configured as
> expected.
> 
> Fix this by requesting a decrypted mapping in the vmap() call:
> pgprot_decrypted(pgprot_dmacoherent(PAGE_KERNEL))
> 
> This ensures that atomic pool memory is consistently mapped
> unencrypted.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Re: [PATCH v2] dma/pool: Ensure DMA_DIRECT_REMAP allocations are decrypted

[Marek Szyprowski]

On 11.08.2025 20:17, Shanker Donthineni wrote:
> When CONFIG_DMA_DIRECT_REMAP is enabled, atomic pool pages are
> remapped via dma_common_contiguous_remap() using the supplied
> pgprot. Currently, the mapping uses
> pgprot_dmacoherent(PAGE_KERNEL), which leaves the memory encrypted
> on systems with memory encryption enabled (e.g., ARM CCA Realms).
>
> This can cause the DMA layer to fail or crash when accessing the
> memory, as the underlying physical pages are not configured as
> expected.
>
> Fix this by requesting a decrypted mapping in the vmap() call:
> pgprot_decrypted(pgprot_dmacoherent(PAGE_KERNEL))
>
> This ensures that atomic pool memory is consistently mapped
> unencrypted.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>

Thanks, applied to dma-mapping-fixes branch.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland