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

[Joel Fernandes <joelagnelf@nvidia.com>]

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