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

On 3/20/2026 9:04 AM, Gary Guo wrote:

On Fri Mar 20, 2026 at 4:57 AM GMT, Joel Fernandes wrote:

quoted

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 <redacted>
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.

If Danilo is applying the patch, can we please remove the helper on apply? I
think in this case we do not need to call the helper. I don't think there is a
divergence risk here.

thanks,

--
Joel Fernandes