[PATCH v2 0/5] rust: Add Per-CPU Variable API

[Mitchell Levy <levymitchell0@gmail.com>]

This series adds an API for declaring an using per-CPU variables from
Rust, and it also adds support for Rust access to C per-CPU variables
(subject to some soundness requirements). It also adds a small test
module, lib/percpu_test_rust.rs, in the vein of lib/percpu_test.c.

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Signed-off-by: Mitchell Levy <levymitchell0@gmail.com>

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Changes in v2:
- Fix kernel test robot issues
- Fix documentation error
- Require `T: Zeroable` in the dynamic case
- Link to v1: https://lore.kernel.org/r/20250624-rust-percpu-v1-0-9c59b07d2a9c@gmail.com

Changes in v1:
- Use wrapping_add in `PerCpuPtr::get_ref` since overflow is expected.
- Separate the dynamic and static cases, with shared logic in a
  `PerCpuPtr` type.
- Implement pin-hole optimizations for numeric types
- Don't assume `GFP_KERNEL` when allocating the `Arc` in the dynamic
  case.
- Link to RFC v2: https://lore.kernel.org/r/20250414-rust-percpu-v2-0-5ea0d0de13a5@gmail.com

Changes in RFC v2:
- Renamed PerCpuVariable to StaticPerCpuSymbol to be more descriptive
- Support dynamically allocated per-CPU variables via the
  PerCpuAllocation type. Rework statically allocated variables to use
  this new type.
- Make use of a token/closure-based API via the PerCpu and PerCpuToken
  types, rather than an API based on PerCpuRef that automatically
  Deref(Mut)'s into a &(mut) T.
- Rebased
- Link to RFC: https://lore.kernel.org/r/20241219-rust-percpu-v1-0-209117e822b1@gmail.com

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Mitchell Levy (5):
      rust: percpu: introduce a rust API for per-CPU variables
      rust: rust-analyzer: add lib to dirs searched for crates
      rust: percpu: add a rust per-CPU variable test
      rust: percpu: Add pin-hole optimizations for numerics
      rust: percpu: cache per-CPU pointers in the dynamic case

 lib/Kconfig.debug                 |   9 ++
 lib/Makefile                      |   1 +
 lib/percpu_test_rust.rs           | 156 +++++++++++++++++++
 rust/helpers/helpers.c            |   2 +
 rust/helpers/percpu.c             |  20 +++
 rust/helpers/preempt.c            |  14 ++
 rust/kernel/lib.rs                |   3 +
 rust/kernel/percpu.rs             | 315 ++++++++++++++++++++++++++++++++++++++
 rust/kernel/percpu/cpu_guard.rs   |  35 +++++
 rust/kernel/percpu/numeric.rs     | 117 ++++++++++++++
 scripts/generate_rust_analyzer.py |   2 +-
 11 files changed, 673 insertions(+), 1 deletion(-)
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base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
change-id: 20240813-rust-percpu-ea2f54b5da33

Best regards,
-- 
Mitchell Levy <levymitchell0@gmail.com>