[PATCH v13 0/7] rust: add dma coherent allocator abstraction

Abdiel Janulgue
2025-03-07T11:08:36Z

This series adds the rust bindings for the dma coherent allocator which
is needed for nova-core[0]. For v13, the biggest change is to move out
the as_slice and write helpers for later discussion. The object is also
now wrapped in Devres to explicitly tie it to the lifetime of the
device[1]. This is tested on a Nvidia GA104 GPU device using PoC code
which parses and loads the GSP firmware via DMA.

Changes sinve v12:
- Move out the contentious functions: as_slice, as_slice_mut, and write
for later discussion as a separate patch. Make write unsafe as well.
Remove skip_drop, use volatile r/w for field_read and field_write
(Alice Ryhl, et al.).
- Documentation improvements, use markdown for intra-doc links
(Miguel Ojeda).
- Move dma addressing capabilities to a separate patch within device.rs
(Andreas Hindborg).
- Add a simple driver to excercise the basics of the api (Danilo).
- Link to v12: https://lore.kernel.org/lkml/20250224115007.2072043-1-abdiel.janulgue@gmail.com/

Changes since v11:
- Ensure robust handling for potential pointer arithmetic overflows
in bounds checking (Petr Tesařík).
- Add dma mask helpers (Daniel Almeida).
- Clarification in the safety aspects of the as_slice/as_slice_mut API,
Use ManuallyDrop trait as a replacement for into_parts(),
Add dma_read!/dma_write! helper macros (Alice Ryhl).

Changes since v10:
- rename read() to as_slice() (Boqun Feng)
- Do a bitwise copy of ARef<Device> in into_parts() when returning the
device reference (Alice Ryhl).

Changes since v9:
- Use ARef<Device> in the constructor arguments, docs clarification avoid
manually dropping the refcount for the device in into_parts(), use
add() instead of wrapping_add() in the pointer arithmetic for performance
(Alice Ryhl).

Changes since v8:
- Add MAINTAINERS entry
- Fix build issues due to switch from core::ffi to crate:ffi in bindgen.
- Ensure the wrapped attribute is non-pub in struct Attrs, declare it
#[repr(transparent)] as well (Daniel Sedlak)

Changes since v7:
- Remove cpu_buf() and cpu_buf_mut() as exporting a r/w interface via
a slice is undefined behaviour due to slice's requirement that the
underlying pointer should not be modified (Alice Ryhl, Robin Murphy).
- Reintroduce r/w helpers instead which includes proper safety
invariants (Daniel Almeida).

Changes since v6:
- Include the dma_attrs in the constructor, use alloc::Flags as inpiration

Changes since v5:
- Remove unnecessary lifetime annotation when returning the CPU buffer.

Changes since v4:
- Documentation and example fixes, use Markdown formatting (Miguel Ojeda).
- Discard read()/write() helpers to remove bound on Copy and fix overhead
(Daniel Almeida).
- Improve error-handling in the constructor block (Andreas Hindborg).

Changes since v3:
- Reject ZST types by checking the type size in the constructor in
addition to requiring FromBytes/AsBytes traits for the type (Alice Ryhl).

Changes since v2:
- Fixed missing header for generating the bindings.

Changes since v1:
- Fix missing info in commit log where EOVERFLOW is used.
- Restrict the dma coherent allocator to numeric types for now for valid
behaviour (Daniel Almeida).
- Build slice dynamically.

[0] https://lore.kernel.org/lkml/20250131220432.17717-1-dakr@kernel.org/
[1] https://lore.kernel.org/lkml/20250305174118.GA351188@nvidia.com/

Abdiel Janulgue (6):
rust: error: Add EOVERFLOW
rust: add dma coherent allocator abstraction.
rust: device: add dma addressing capabilities
samples: rust: add Rust dma test sample driver
MAINTAINERS: add entry for Rust dma mapping helpers device driver API
rust: dma: add as_slice/write functions for CoherentAllocation

Danilo Krummrich (1):
rust: pci: impl AsMut<Device> for pci::Device

MAINTAINERS | 12 +
rust/bindings/bindings_helper.h | 1 +
rust/helpers/dma.c | 8 +
rust/helpers/helpers.c | 1 +
rust/kernel/device.rs | 29 ++
rust/kernel/dma.rs | 464 ++++++++++++++++++++++++++++++++
rust/kernel/error.rs | 1 +
rust/kernel/lib.rs | 1 +
rust/kernel/pci.rs | 11 +
samples/rust/Kconfig | 11 +
samples/rust/Makefile | 1 +
samples/rust/rust_dma.rs | 104 +++++++
12 files changed, 644 insertions(+)
create mode 100644 rust/helpers/dma.c
create mode 100644 rust/kernel/dma.rs
create mode 100644 samples/rust/rust_dma.rs

base-commit: 6ad64bf91728502fe8a4d1419c0a3e4fd323f503
--
2.43.0