Excerpts from Christoph Hellwig's message of March 31, 2022 2:06 am:
> pgprot_decrypted is used by AMD SME systems to allow access to memory
> that was set to not encrypted using set_memory_decrypted. That only
> happens for dma-direct memory as the IOMMU solves the addressing
> challenges for the encryption bit using its own remapping.
>
> Move the pgprot_decrypted call out of dma_pgprot which is also used
> by the IOMMU mappings and into dma-direct so that it is only used with
> memory that was set decrypted.
>
> Fixes: 5ff79fddf0ef ("dma-mapping: remove CONFIG_DMA_REMAP")
> Reported-by: Alex Xu (Hello71) <alex_y...@yahoo.ca>
> Signed-off-by: Christoph Hellwig <h...@lst.de>
> ---
> kernel/dma/direct.c | 10 ++++++++--
> kernel/dma/mapping.c | 2 --
> 2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 35a1d29d6a2e9..9743c6ccce1a9 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -277,12 +277,16 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> }
>
> if (remap) {
> + pgprot_t prot = dma_pgprot(dev, PAGE_KERNEL, attrs);
> +
> + if (force_dma_unencrypted(dev))
> + prot = pgprot_decrypted(prot);
> +
> /* remove any dirty cache lines on the kernel alias */
> arch_dma_prep_coherent(page, size);
>
> /* create a coherent mapping */
> - ret = dma_common_contiguous_remap(page, size,
> - dma_pgprot(dev, PAGE_KERNEL, attrs),
> + ret = dma_common_contiguous_remap(page, size, prot,
> __builtin_return_address(0));
> if (!ret)
> goto out_free_pages;
> @@ -535,6 +539,8 @@ int dma_direct_mmap(struct device *dev, struct
> vm_area_struct *vma,
> int ret = -ENXIO;
>
> vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
> + if (force_dma_unencrypted(dev))
> + vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
>
> if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
> return ret;
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index 559461a826bab..db7244291b745 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
> @@ -407,8 +407,6 @@ EXPORT_SYMBOL(dma_get_sgtable_attrs);
> */
> pgprot_t dma_pgprot(struct device *dev, pgprot_t prot, unsigned long attrs)
> {
> - if (force_dma_unencrypted(dev))
> - prot = pgprot_decrypted(prot);
> if (dev_is_dma_coherent(dev))
> return prot;
> #ifdef CONFIG_ARCH_HAS_DMA_WRITE_COMBINE
> --
> 2.30.2
>
>
Tested-by: Alex Xu (Hello71) <alex_y...@yahoo.ca>
Thanks,
Alex.
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