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Revert "Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()""

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This reverts commit b7d9aae404.

With the Qualcomm remoteproc driver now modified to use a carveout
memory region in 57f72170a2 ("remoteproc: qcom_q6v5_mss: Use a
carveout to authenticate modem headers"), we can reinstate c44094eee3
("arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()")
which relaxes the arm64 implementation of arch_dma_prep_coherent() to
perform only a data cache clean operation, rather than a
clean-and-invalidate.

Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon 2023-03-30 16:23:03 +01:00
parent 7cae569e62
commit 7bd6680b47
1 changed files with 1 additions and 16 deletions
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17
arch/arm64/mm/dma-mapping.c
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@ -36,22 +36,7 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
{
unsigned long start = (unsigned long)page_address(page);
/*
* The architecture only requires a clean to the PoC here in order to
* meet the requirements of the DMA API. However, some vendors (i.e.
* Qualcomm) abuse the DMA API for transferring buffers from the
* non-secure to the secure world, resetting the system if a non-secure
* access shows up after the buffer has been transferred:
*
* https://lore.kernel.org/r/20221114110329.68413-1-manivannan.sadhasivam@linaro.org
*
* Using clean+invalidate appears to make this issue less likely, but
* the drivers themselves still need fixing as the CPU could issue a
* speculative read from the buffer via the linear mapping irrespective
* of the cache maintenance we use. Once the drivers are fixed, we can
* relax this to a clean operation.
*/
dcache_clean_inval_poc(start, start + size);
dcache_clean_poc(start, start + size);
}
#ifdef CONFIG_IOMMU_DMA