linux-kernel - Re: [PATCH v2] dma/pool: Ensure DMA_DIRECT

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Message-ID: <aJsWnSm7un-EUmed@arm.com>
Date: Tue, 12 Aug 2025 11:25:33 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Shanker Donthineni <sdonthineni@...dia.com>
Cc: Will Deacon <will@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Steven Price <steven.price@....com>,
	linux-arm-kernel@...ts.infradead.org,
	Robin Murphy <robin.murphy@....com>, Gavin Shan <gshan@...hat.com>,
	Mike Rapoport <rppt@...nel.org>, Vikram Sethi <vsethi@...dia.com>,
	Jason Sequeira <jsequeira@...dia.com>, Dev Jain <dev.jain@....com>,
	David Rientjes <rientjes@...gle.com>, linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev, stable@...r.kernel.org
Subject: Re: [PATCH v2] dma/pool: Ensure DMA_DIRECT_REMAP allocations are
 decrypted

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@...r.kernel.org
> Signed-off-by: Shanker Donthineni <sdonthineni@...dia.com>

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