[PATCH v7 0/3] Rust allocator and kvec improvements

[PATCH v7 0/3] 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.
Patch 2 documents KVec::as_slice with a usage example.
Patch 3 simplifies KVec test module naming convention.

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

Changelog:
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.

Hui Zhu (3):
  rust: allocator: add KUnit tests for alignment guarantees
  rust: alloc: kvec: add doc example for as_slice method
  rust: alloc: kvec: simplify KUnit test module name to "rust_kvec"

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

-- 
2.43.0

[PATCH v7 1/3] rust: allocator: add KUnit tests for alignment guarantees

[Hui Zhu]

From: Hui Zhu <zhuhui@kylinos.cn>

Add a test module to verify memory alignment guarantees for Rust kernel
allocators.
The tests cover `Kmalloc`, `Vmalloc` and `KVmalloc` allocators
with both standard and large page-aligned allocations.

Key features of the tests:
1. Creates alignment-constrained types:
   - 128-byte aligned `Blob`
   - 8192-byte (4-page) aligned `LargeAlignBlob`
2. Validates allocators using `TestAlign` helper which:
   - Checks address alignment masks
   - Supports uninitialized allocations
3. Tests all three allocators with both alignment requirements:
   - Kmalloc with 128B and 8192B
   - Vmalloc with 128B and 8192B
   - KVmalloc with 128B and 8192B

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>
---
 rust/kernel/alloc/allocator.rs | 56 ++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

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(())
+    }
+}
-- 
2.43.0

Re: [PATCH v7 1/3] rust: allocator: add KUnit tests for alignment guarantees

[Danilo Krummrich]

On Thu Jul 31, 2025 at 4:50 AM CEST, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@kylinos.cn>
>
> Add a test module to verify memory alignment guarantees for Rust kernel
> allocators.
> The tests cover `Kmalloc`, `Vmalloc` and `KVmalloc` allocators
> with both standard and large page-aligned allocations.
>
> Key features of the tests:
> 1. Creates alignment-constrained types:
>    - 128-byte aligned `Blob`
>    - 8192-byte (4-page) aligned `LargeAlignBlob`
> 2. Validates allocators using `TestAlign` helper which:
>    - Checks address alignment masks
>    - Supports uninitialized allocations
> 3. Tests all three allocators with both alignment requirements:
>    - Kmalloc with 128B and 8192B
>    - Vmalloc with 128B and 8192B
>    - KVmalloc with 128B and 8192B
>
> 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>

Acked-by: Danilo Krummrich <dakr@kernel.org>

@Andrew: Can you please pick this one up once we land Vitaly's series [1]? I'll
take the other two patches of the series through the Rust alloc tree once -rc1
is out.

[1] https://lore.kernel.org/lkml/20250730191921.352591-1-vitaly.wool@konsulko.se/

Re: [PATCH v7 1/3] rust: allocator: add KUnit tests for alignment guarantees

[Danilo Krummrich]

On Thu Jul 31, 2025 at 11:19 AM CEST, Danilo Krummrich wrote:
> On Thu Jul 31, 2025 at 4:50 AM CEST, Hui Zhu wrote:
>> From: Hui Zhu <zhuhui@kylinos.cn>
>>
>> Add a test module to verify memory alignment guarantees for Rust kernel
>> allocators.
>> The tests cover `Kmalloc`, `Vmalloc` and `KVmalloc` allocators
>> with both standard and large page-aligned allocations.
>>
>> Key features of the tests:
>> 1. Creates alignment-constrained types:
>>    - 128-byte aligned `Blob`
>>    - 8192-byte (4-page) aligned `LargeAlignBlob`
>> 2. Validates allocators using `TestAlign` helper which:
>>    - Checks address alignment masks
>>    - Supports uninitialized allocations
>> 3. Tests all three allocators with both alignment requirements:
>>    - Kmalloc with 128B and 8192B
>>    - Vmalloc with 128B and 8192B
>>    - KVmalloc with 128B and 8192B
>>
>> 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>
>
> Acked-by: Danilo Krummrich <dakr@kernel.org>
>
> @Andrew: Can you please pick this one up once we land Vitaly's series [1]? I'll
> take the other two patches of the series through the Rust alloc tree once -rc1
> is out.

Just a reminder for this one to be picked up; I gave it a quick shot on top of
mm-everything and everything looks fine..

> [1] https://lore.kernel.org/lkml/20250730191921.352591-1-vitaly.wool@konsulko.se/

[PATCH v7 2/3] 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>
---
 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 92d0ed3f302e..f57e08c64929 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

[PATCH v7 3/3] rust: alloc: kvec: simplify KUnit test module name to "rust_kvec"

[Hui Zhu]

From: Hui Zhu <zhuhui@kylinos.cn>

Remove redundant "_kunit" suffix from test module name.

The naming is now consistent with other Rust components as the test
context is already implied by the #[kunit_tests] macro and test module
location.

Co-developed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
---
 rust/kernel/alloc/kvec.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index f57e08c64929..d71f6a1513e2 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -1311,7 +1311,7 @@ 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

Re: [PATCH v7 0/3] Rust allocator and kvec improvements

[David Gow]

[-- Attachment #1: Type: text/plain, Size: 1954 bytes --]

On Thu, 31 Jul 2025 at 10:51, Hui Zhu <hui.zhu@linux.dev> wrote:
>
> 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.
> Patch 2 documents KVec::as_slice with a usage example.
> Patch 3 simplifies KVec test module naming convention.
>
> Both patches are co-developed with Geliang Tang. Based on [1].
> Tested on x86_64 using KUnit.
>

This series looks good to me from a KUnit perspective. I've also
tested it out across a bunch of architectures (UML, x86_64, arm,
arm64) with no problems.

A few minor notes:
- You should squash patch 3 into patch 1: there's no need to introduce
the test with one name only to rename it in a later patch.
- The link to [1] is missing in this cover letter. (But at least the
test fails nicely without it!)

Otherwise, looks good!

The whole series is:
Reviewed-by: David Gow <davidgow@google.com>

Cheers,
-- David

> Changelog:
> 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.
>
> Hui Zhu (3):
>   rust: allocator: add KUnit tests for alignment guarantees
>   rust: alloc: kvec: add doc example for as_slice method
>   rust: alloc: kvec: simplify KUnit test module name to "rust_kvec"
>
>  rust/kernel/alloc/allocator.rs | 56 ++++++++++++++++++++++++++++++++++
>  rust/kernel/alloc/kvec.rs      | 12 +++++++-
>  2 files changed, 67 insertions(+), 1 deletion(-)
>
> --
> 2.43.0
>
>

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Re: [PATCH v7 0/3] Rust allocator and kvec improvements

[Danilo Krummrich]

On Thu Jul 31, 2025 at 6:14 AM CEST, David Gow wrote:
> On Thu, 31 Jul 2025 at 10:51, Hui Zhu <hui.zhu@linux.dev> wrote:
>>
>> 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.
>> Patch 2 documents KVec::as_slice with a usage example.
>> Patch 3 simplifies KVec test module naming convention.
>>
>> Both patches are co-developed with Geliang Tang. Based on [1].
>> Tested on x86_64 using KUnit.
>>
>
> This series looks good to me from a KUnit perspective. I've also
> tested it out across a bunch of architectures (UML, x86_64, arm,
> arm64) with no problems.
>
> A few minor notes:
> - You should squash patch 3 into patch 1: there's no need to introduce
> the test with one name only to rename it in a later patch.

The test introduced in patch 1 is not the one renamed in patch 3. :)

Re: [PATCH v7 0/3] Rust allocator and kvec improvements

[Danilo Krummrich]

On 7/31/25 4:50 AM, Hui Zhu wrote:
>    rust: alloc: kvec: add doc example for as_slice method
>    rust: alloc: kvec: simplify KUnit test module name to "rust_kvec"

Applied to alloc-next, thanks!