Re: [PATCH v14 1/2] rust: gpu: Add GPU buddy allocator bindings

["Gary Guo" <gary@garyguo.net>]

On Fri Mar 20, 2026 at 4:57 AM GMT, Joel Fernandes wrote:
> Add safe Rust abstractions over the Linux kernel's GPU buddy
> allocator for physical memory management. The GPU buddy allocator
> implements a binary buddy system useful for GPU physical memory
> allocation. nova-core will use it for physical memory allocation.
>
> Cc: Nikola Djukic <ndjukic@nvidia.com>
> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
> ---
>  MAINTAINERS                     |   6 +
>  rust/bindings/bindings_helper.h |  11 +
>  rust/helpers/gpu.c              |  23 ++
>  rust/helpers/helpers.c          |   1 +
>  rust/kernel/gpu.rs              |   6 +
>  rust/kernel/gpu/buddy.rs        | 613 ++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs              |   2 +
>  7 files changed, 662 insertions(+)
>  create mode 100644 rust/helpers/gpu.c
>  create mode 100644 rust/kernel/gpu.rs
>  create mode 100644 rust/kernel/gpu/buddy.rs
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e847099efcc2..cd9505d3be60 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8531,7 +8531,10 @@ T:	git https://gitlab.freedesktop.org/drm/rust/kernel.git
>  F:	drivers/gpu/drm/nova/
>  F:	drivers/gpu/drm/tyr/
>  F:	drivers/gpu/nova-core/
> +F:	rust/helpers/gpu.c
>  F:	rust/kernel/drm/
> +F:	rust/kernel/gpu.rs
> +F:	rust/kernel/gpu/
>  
>  DRM DRIVERS FOR ALLWINNER A10
>  M:	Chen-Yu Tsai <wens@kernel.org>
> @@ -8952,6 +8955,9 @@ F:	drivers/gpu/drm/drm_buddy.c
>  F:	drivers/gpu/tests/gpu_buddy_test.c
>  F:	include/drm/drm_buddy.h
>  F:	include/linux/gpu_buddy.h
> +F:	rust/helpers/gpu.c
> +F:	rust/kernel/gpu.rs
> +F:	rust/kernel/gpu/
>  
>  DRM AUTOMATED TESTING
>  M:	Helen Koike <helen.fornazier@gmail.com>
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 083cc44aa952..dbb765a9fdbd 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -29,6 +29,7 @@
>  #include <linux/hrtimer_types.h>
>  
>  #include <linux/acpi.h>
> +#include <linux/gpu_buddy.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_drv.h>
>  #include <drm/drm_file.h>
> @@ -146,6 +147,16 @@ const vm_flags_t RUST_CONST_HELPER_VM_MIXEDMAP = VM_MIXEDMAP;
>  const vm_flags_t RUST_CONST_HELPER_VM_HUGEPAGE = VM_HUGEPAGE;
>  const vm_flags_t RUST_CONST_HELPER_VM_NOHUGEPAGE = VM_NOHUGEPAGE;
>  
> +#if IS_ENABLED(CONFIG_GPU_BUDDY)
> +const unsigned long RUST_CONST_HELPER_GPU_BUDDY_RANGE_ALLOCATION = GPU_BUDDY_RANGE_ALLOCATION;
> +const unsigned long RUST_CONST_HELPER_GPU_BUDDY_TOPDOWN_ALLOCATION = GPU_BUDDY_TOPDOWN_ALLOCATION;
> +const unsigned long RUST_CONST_HELPER_GPU_BUDDY_CONTIGUOUS_ALLOCATION =
> +								GPU_BUDDY_CONTIGUOUS_ALLOCATION;
> +const unsigned long RUST_CONST_HELPER_GPU_BUDDY_CLEAR_ALLOCATION = GPU_BUDDY_CLEAR_ALLOCATION;
> +const unsigned long RUST_CONST_HELPER_GPU_BUDDY_CLEARED = GPU_BUDDY_CLEARED;
> +const unsigned long RUST_CONST_HELPER_GPU_BUDDY_TRIM_DISABLE = GPU_BUDDY_TRIM_DISABLE;
> +#endif
> +
>  #if IS_ENABLED(CONFIG_ANDROID_BINDER_IPC_RUST)
>  #include "../../drivers/android/binder/rust_binder.h"
>  #include "../../drivers/android/binder/rust_binder_events.h"
> diff --git a/rust/helpers/gpu.c b/rust/helpers/gpu.c
> new file mode 100644
> index 000000000000..38b1a4e6bef8
> --- /dev/null
> +++ b/rust/helpers/gpu.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/gpu_buddy.h>
> +
> +#ifdef CONFIG_GPU_BUDDY
> +
> +__rust_helper u64 rust_helper_gpu_buddy_block_offset(const struct gpu_buddy_block *block)
> +{
> +	return gpu_buddy_block_offset(block);
> +}
> +
> +__rust_helper unsigned int rust_helper_gpu_buddy_block_order(struct gpu_buddy_block *block)
> +{
> +	return gpu_buddy_block_order(block);
> +}
> +
> +__rust_helper u64 rust_helper_gpu_buddy_block_size(struct gpu_buddy *mm,
> +						   struct gpu_buddy_block *block)
> +{
> +	return gpu_buddy_block_size(mm, block);
> +}

From Sashiko:
https://sashiko.dev/#/patchset/20260320045711.43494-1-joelagnelf%40nvidia.com

    Does the Rust wrapper use this helper? It looks like AllocatedBlock::size()
    manually duplicates the bitwise logic (chunk_size << order) rather than
    calling this helper, which could create a divergence risk if the underlying C
    allocator implementation changes.

Many other review comments there seem to be false positive, but it might worth
confirming.

Best,
Gary

> +
> +#endif /* CONFIG_GPU_BUDDY */
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index 724fcb8240ac..a53929ce52a3 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -32,6 +32,7 @@
>  #include "err.c"
>  #include "irq.c"
>  #include "fs.c"
> +#include "gpu.c"
>  #include "io.c"
>  #include "jump_label.c"
>  #include "kunit.c"
> diff --git a/rust/kernel/gpu.rs b/rust/kernel/gpu.rs
> new file mode 100644
> index 000000000000..1dc5d0c8c09d
> --- /dev/null
> +++ b/rust/kernel/gpu.rs
> @@ -0,0 +1,6 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! GPU subsystem abstractions.
> +
> +#[cfg(CONFIG_GPU_BUDDY = "y")]
> +pub mod buddy;