Re: [RFC PATCH 1/2] dma-mapping: Avoid double decrypting with DMA_RESTRICTED_POOL

[Mostafa Saleh <smostafa@google.com>]

On Tue, Mar 10, 2026 at 01:55:52PM +0000, Catalin Marinas wrote:
> On Tue, Mar 10, 2026 at 01:36:08PM +0000, Catalin Marinas wrote:
> > However, it's unclear to me whether we can get encrypted pages when
> > is_swiotlb_for_alloc() == false, remap == true and
> > force_dma_unencrypted() == true in dma_direct_alloc().
> > dma_set_decrypted() is only called on the !remap path.
> 
> Ah, I can see Anneesh trying to address this here:
> 
> https://lore.kernel.org/r/yq5abjjl4o0j.fsf@kernel.org

I see, thanks for pointing that out, the case Aneesh is fixing is the
missing decryption in the remap case. However, it’s not clear to me
how we can get there for CCA, I left a comment on his patch.

I can inline the is_swiotlb_for_alloc() checks outside, but I believe
adding this in the lowest level is better as indeed the memory is
decrypted and we don’t have to open code the check in other places are
dma_direct_alloc_pages()

Thanks,
Mostafa


> 
> -- 
> Catalin