[PATCH v8 0/2] Rust allocator and kvec improvements

[PATCH v8 0/2] Rust allocator and kvec improvements

[Hui Zhu]

From: Hui Zhu <zhuhui@kylinos.cn>

This series adds tests and docs for Rust kernel components:
Patch 1 adds KUnit tests for allocator alignment guarantees.
and simplifies KVec test module naming convention.
Patch 2 documents KVec::as_slice with a usage example.

Both patches are co-developed with Geliang Tang. Based on [1].
Tested on x86_64 using KUnit.

Changelog:
v8:
Updated according to the comments of David.
v7:
Updated according to the comments of Miguel.
v6:
According to the comments of Danilo, updated test for allocator.rs
and allocator rebase onto [1].
v5:
According to the comments of Danilo, change to use generic struct and
allocator Generics in allocator.rs.
v4:
According to the comments of, add the error check for push.
v3:
According to the comments of Danilo and Boqun, move KVec test to doc
example and move VBox to allocator unit tests.
v2:
According to the comments of Danilo, updated the commit to samples the
usage of VBox and KVec.

[1] https://lore.kernel.org/lkml/20250715135645.2230065-1-vitaly.wool@konsulko.se/

Hui Zhu (2):
  rust: alloc: add alignment tests for allocators
  rust: alloc: kvec: add doc example for as_slice method

 rust/kernel/alloc/allocator.rs | 56 ++++++++++++++++++++++++++++++++++
 rust/kernel/alloc/kvec.rs      | 12 +++++++-
 2 files changed, 67 insertions(+), 1 deletion(-)

-- 
2.43.0

[PATCH v8 1/2] rust: alloc: add alignment tests for allocators

[Hui Zhu]

From: Hui Zhu <zhuhui@kylinos.cn>

Add unit tests to verify alignment guarantees of Kmalloc, Vmalloc,
and KVmallocallocators. Tests create types with explicit alignment
requirements (128B and 8192B) and validate allocations meet alignment.
Includes two test blobs with custom alignments and helper struct
TestAlignto abstract allocation and alignment checks.

Also updates kvec test macro name from rust_kvec_kunitto rust_kvec
for consistency with other test modules.

Co-developed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
Reviewed-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: David Gow <davidgow@google.com>
---
 rust/kernel/alloc/allocator.rs | 56 ++++++++++++++++++++++++++++++++++
 rust/kernel/alloc/kvec.rs      |  2 +-
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 63f271624428..a20111b40529 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -184,3 +184,59 @@ unsafe fn realloc(
         unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags, nid) }
     }
 }
+
+#[macros::kunit_tests(rust_allocator)]
+mod tests {
+    use super::*;
+    use core::mem::MaybeUninit;
+    use kernel::prelude::*;
+
+    #[test]
+    fn test_alignment() -> Result {
+        const TEST_SIZE: usize = 1024;
+        const TEST_LARGE_ALIGN_SIZE: usize = kernel::page::PAGE_SIZE * 4;
+
+        // These two structs are used to test allocating aligned memory.
+        // they don't need to be accessed, so they're marked as dead_code.
+        #[expect(dead_code)]
+        #[repr(align(128))]
+        struct Blob([u8; TEST_SIZE]);
+        #[expect(dead_code)]
+        #[repr(align(8192))]
+        struct LargeAlignBlob([u8; TEST_LARGE_ALIGN_SIZE]);
+
+        struct TestAlign<T, A: Allocator>(Box<MaybeUninit<T>, A>);
+        impl<T, A: Allocator> TestAlign<T, A> {
+            fn new() -> Result<Self> {
+                Ok(Self(Box::<_, A>::new_uninit(GFP_KERNEL)?))
+            }
+
+            fn is_aligned_to(&self, align: usize) -> bool {
+                assert!(align.is_power_of_two());
+
+                let addr = self.0.as_ptr() as usize;
+                addr & (align - 1) == 0
+            }
+        }
+
+        let ta = TestAlign::<Blob, Kmalloc>::new()?;
+        assert!(ta.is_aligned_to(128));
+
+        let ta = TestAlign::<LargeAlignBlob, Kmalloc>::new()?;
+        assert!(ta.is_aligned_to(8192));
+
+        let ta = TestAlign::<Blob, Vmalloc>::new()?;
+        assert!(ta.is_aligned_to(128));
+
+        let ta = TestAlign::<LargeAlignBlob, Vmalloc>::new()?;
+        assert!(ta.is_aligned_to(8192));
+
+        let ta = TestAlign::<Blob, KVmalloc>::new()?;
+        assert!(ta.is_aligned_to(128));
+
+        let ta = TestAlign::<LargeAlignBlob, KVmalloc>::new()?;
+        assert!(ta.is_aligned_to(8192));
+
+        Ok(())
+    }
+}
diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index 92d0ed3f302e..f912a9642969 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -1301,7 +1301,7 @@ fn drop(&mut self) {
     }
 }
 
-#[macros::kunit_tests(rust_kvec_kunit)]
+#[macros::kunit_tests(rust_kvec)]
 mod tests {
     use super::*;
     use crate::prelude::*;
-- 
2.43.0

[PATCH v8 2/2] rust: alloc: kvec: add doc example for as_slice method

[Hui Zhu]

From: Hui Zhu <zhuhui@kylinos.cn>

Add a practical usage example to the documentation of KVec::as_slice()
showing how to:
Create a new KVec.
Push elements into it.
Convert to a slice via as_slice().

Co-developed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: David Gow <davidgow@google.com>
---
 rust/kernel/alloc/kvec.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index f912a9642969..d71f6a1513e2 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -224,6 +224,16 @@ unsafe fn dec_len(&mut self, count: usize) -> &mut [T] {
     }
 
     /// Returns a slice of the entire vector.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut v = KVec::new();
+    /// v.push(1, GFP_KERNEL)?;
+    /// v.push(2, GFP_KERNEL)?;
+    /// assert_eq!(v.as_slice(), &[1, 2]);
+    /// # Ok::<(), Error>(())
+    /// ```
     #[inline]
     pub fn as_slice(&self) -> &[T] {
         self
-- 
2.43.0

Re: [PATCH v8 1/2] rust: alloc: add alignment tests for allocators

[Danilo Krummrich]

On Thu Jul 31, 2025 at 10:42 AM CEST, Hui Zhu wrote:
> diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
> index 63f271624428..a20111b40529 100644
> --- a/rust/kernel/alloc/allocator.rs
> +++ b/rust/kernel/alloc/allocator.rs
> @@ -184,3 +184,59 @@ unsafe fn realloc(
>          unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags, nid) }
>      }
>  }
> +
> +#[macros::kunit_tests(rust_allocator)]
> +mod tests {
> +    use super::*;
> +    use core::mem::MaybeUninit;
> +    use kernel::prelude::*;
> +

<snip>

> -#[macros::kunit_tests(rust_kvec_kunit)]
> +#[macros::kunit_tests(rust_kvec)]
>  mod tests {
>      use super::*;
>      use crate::prelude::*;

I think v7 was fine. David probably confused "rust_allocator" with "rust_kvec".
Renaming the kvec kunit tests should, as you correctly did in v7, indeed be a
separate patch.

No need to resend now, I think we can just pick v7.

In general, please send new version a little bit less frequent to leave some
time for people to comment.

Thanks,
Danilo