Commit 18fb5f1f authored Mar 21, 2026 by Danilo Krummrich Committed by Alexandre Courbot Mar 28, 2026

rust: dma: remove DMA_ATTR_NO_KERNEL_MAPPING from public attrs



When DMA_ATTR_NO_KERNEL_MAPPING is passed to dma_alloc_attrs(), the
returned CPU address is not a pointer to the allocated memory but an
opaque handle (e.g. struct page *).

Coherent<T> (or CoherentAllocation<T> respectively) stores this value as
NonNull<T> and exposes methods that dereference it and even modify its
contents.

Remove the flag from the public attrs module such that drivers cannot
pass it to Coherent<T> (or CoherentAllocation<T> respectively) in the
first place.

Instead DMA_ATTR_NO_KERNEL_MAPPING can be supported with an additional
opaque type (e.g. CoherentHandle) which does not provide access to the
allocated memory.

Cc: stable@vger.kernel.org
Fixes: ad2907b4 ("rust: add dma coherent allocator abstraction")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260321172749.592387-1-dakr@kernel.org


Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

parent 15a4bb87

rust/kernel/dma.rs

+0 −3

Original line number	Diff line number	Diff line
		@@ -267,9 +267,6 @@ pub mod attrs {
		/// Specifies that writes to the mapping may be buffered to improve performance.
		pub const DMA_ATTR_WRITE_COMBINE: Attrs = Attrs(bindings::DMA_ATTR_WRITE_COMBINE);

		/// Lets the platform to avoid creating a kernel virtual mapping for the allocated buffer.
		pub const DMA_ATTR_NO_KERNEL_MAPPING: Attrs = Attrs(bindings::DMA_ATTR_NO_KERNEL_MAPPING);

		/// Allows platform code to skip synchronization of the CPU cache for the given buffer assuming
		/// that it has been already transferred to 'device' domain.
		pub const DMA_ATTR_SKIP_CPU_SYNC: Attrs = Attrs(bindings::DMA_ATTR_SKIP_CPU_SYNC);