[PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[Ritvik Gupta]

Replace the following unsafe initializations:
1. `MaybeUninit::uninit().assume_init()` with `Opaque::uninit()`
2. `core::mem::zeroed()` with `Opaque::zeroed()`

Suggested-by: Benno Lossin <lossin@kernel.org>
Link: https://github.com/Rust-for-Linux/linux/issues/1178
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/rust-for-linux/CAH5fLgj0OoCn56OkNUmiPQ=RAVa_VmS-yMZ4TNBSpGPNtZ5D0A@mail.gmail.com/
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>
---

Carried forward 'Reviewed-by' tags from v1 since there're no substantial changes, just added suggested changes :)
(reviewers from v1 cc'd)

Changes in v2:
 - Replaced `core::mem::zeroed()` with `Opaque::zeroed()` in `CpumaskVar::new_zero()` (thanks, Alice!)

Link to v1: https://lore.kernel.org/rust-for-linux/20250710123836.146825-1-ritvikfoss@gmail.com/

---
 rust/kernel/cpumask.rs | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
index 4bce230a73b6..3fcbff438670 100644
--- a/rust/kernel/cpumask.rs
+++ b/rust/kernel/cpumask.rs
@@ -14,9 +14,6 @@
 #[cfg(CONFIG_CPUMASK_OFFSTACK)]
 use core::ptr::{self, NonNull};
 
-#[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
-use core::mem::MaybeUninit;
-
 use core::ops::{Deref, DerefMut};
 
 /// A CPU Mask.
@@ -239,10 +236,7 @@ pub fn new_zero(_flags: Flags) -> Result<Self, AllocError> {
             },
 
             #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
-            // SAFETY: FFI type is valid to be zero-initialized.
-            //
-            // INVARIANT: The associated memory is freed when the `CpumaskVar` goes out of scope.
-            mask: unsafe { core::mem::zeroed() },
+            mask: Cpumask(Opaque::zeroed()),
         })
     }
 
@@ -266,10 +260,7 @@ pub unsafe fn new(_flags: Flags) -> Result<Self, AllocError> {
                 NonNull::new(ptr.cast()).ok_or(AllocError)?
             },
             #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
-            // SAFETY: Guaranteed by the safety requirements of the function.
-            //
-            // INVARIANT: The associated memory is freed when the `CpumaskVar` goes out of scope.
-            mask: unsafe { MaybeUninit::uninit().assume_init() },
+            mask: Cpumask(Opaque::uninit()),
         })
     }
 

base-commit: 2009a2d5696944d85c34d75e691a6f3884e787c0
-- 
2.50.1

Re: [PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[Viresh Kumar]

On 14-07-25, 00:32, Ritvik Gupta wrote:
> Replace the following unsafe initializations:
> 1. `MaybeUninit::uninit().assume_init()` with `Opaque::uninit()`
> 2. `core::mem::zeroed()` with `Opaque::zeroed()`
> 
> Suggested-by: Benno Lossin <lossin@kernel.org>
> Link: https://github.com/Rust-for-Linux/linux/issues/1178
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Link: https://lore.kernel.org/rust-for-linux/CAH5fLgj0OoCn56OkNUmiPQ=RAVa_VmS-yMZ4TNBSpGPNtZ5D0A@mail.gmail.com/
> Reviewed-by: Benno Lossin <lossin@kernel.org>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

Re: [PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[Miguel Ojeda]

On Mon, Jul 14, 2025 at 6:54 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Wouldn't this go via your `pm` tree to Rafael? Or am I confused?

Thanks!

Cheers,
Miguel

Re: [PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[Viresh Kumar]

On 14-07-25, 18:53, Miguel Ojeda wrote:
> On Mon, Jul 14, 2025 at 6:54 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> >
> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> 
> Wouldn't this go via your `pm` tree to Rafael? Or am I confused?

Applied now.

I manage pull requests for cpufreq and OPP normally. I had to to
cpumask, clk, etc., as dependencies for my Rust stuff but I am not
sure about what's the best way to get them merged.

For now I can take this one though.

-- 
viresh

Re: [PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[Miguel Ojeda]

On Tue, Jul 15, 2025 at 5:06 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> Applied now.
>
> I manage pull requests for cpufreq and OPP normally. I had to to
> cpumask, clk, etc., as dependencies for my Rust stuff but I am not
> sure about what's the best way to get them merged.
>
> For now I can take this one though.

Ah, I thought the idea was to continue like that.

If that was not the case, then it should be clarified. Do you have a
pointer to the latest discussion on this?

Thanks!

Cheers,
Miguel

Re: [PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[Viresh Kumar]

On 15-07-25, 13:18, Miguel Ojeda wrote:
> Ah, I thought the idea was to continue like that.

I will keep pushing the changes via the PM tree for now.

-- 
viresh

Re: [PATCH v2] rust: cpumask: Replace `MaybeUninit` and `mem::zeroed` with `Opaque` APIs

[Miguel Ojeda]

On Wed, Jul 16, 2025 at 6:15 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> I will keep pushing the changes via the PM tree for now.

Ok, great, thanks -- please let me know if there is a renewed
discussion on that or if we can help somehow in the future.

Cheers,
Miguel