Re: [RFC PATCH v3 3/5] dma-mapping: Decrypt memory on remap

[Catalin Marinas <catalin.marinas@arm.com>]

On Tue, Apr 14, 2026 at 03:01:15PM +0530, Aneesh Kumar K.V wrote:
> Mostafa Saleh <smostafa@google.com> writes:
> > In case memory needs to be remapped on systems with
> > force_dma_unencrypted(), where this memory is not allocated
> > from a restricted-dma pool, this was currently ignored, while only
> > setting the decrypted pgprot in the remapped alias.
> >
> > The memory still needs to be decrypted in that case.
> 
> For ARM CCA, we cannot mark a vmap address as decrypted. I don’t expect
> non-coherent DMA devices to be used in an ARM CCA configuration, but we
> may need a way to document this in the code.

I think you clarified what you meant later. The vmap here is just fine,
we pass pgprot_decrypted(). The key is the dma_set_decrypted() on the
page address before being remapped.

On arm64 we probably don't care but if we want to enforce it for all
architectures, dma_direct_alloc() could return NULL if
force_dma_unencrypted() && remap (maybe together with a WARN_ON_ONCE).
However, the proposed patch is small enough to cover this case as well.

-- 
Catalin