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.
Christian Koenig mentioned he'd like to step down from reviewer role for GPU buddy so updated accordingly. Arun/Matthew agree on the modified entry. Cc: Nikola Djukic <[email protected]> Signed-off-by: Joel Fernandes <[email protected]> --- MAINTAINERS | 6 +- rust/bindings/bindings_helper.h | 11 + rust/helpers/gpu.c | 23 ++ rust/helpers/helpers.c | 1 + rust/kernel/gpu/buddy.rs | 611 ++++++++++++++++++++++++++++++++ rust/kernel/gpu/mod.rs | 5 + rust/kernel/lib.rs | 2 + 7 files changed, 658 insertions(+), 1 deletion(-) create mode 100644 rust/helpers/gpu.c create mode 100644 rust/kernel/gpu/buddy.rs create mode 100644 rust/kernel/gpu/mod.rs diff --git a/MAINTAINERS b/MAINTAINERS index 4c66f8261ff2..b2600dd05fc2 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -8513,7 +8513,9 @@ 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/ DRM DRIVERS FOR ALLWINNER A10 M: Chen-Yu Tsai <[email protected]> @@ -8926,7 +8928,7 @@ F: include/drm/ttm/ GPU BUDDY ALLOCATOR M: Matthew Auld <[email protected]> M: Arun Pravin <[email protected]> -R: Christian Koenig <[email protected]> +R: Joel Fernandes <[email protected]> L: [email protected] S: Maintained T: git https://gitlab.freedesktop.org/drm/misc/kernel.git @@ -8935,6 +8937,8 @@ F: drivers/gpu/buddy.c F: drivers/gpu/tests/gpu_buddy_test.c F: include/linux/gpu_buddy.h F: include/drm/drm_buddy.h +F: rust/helpers/gpu.c +F: rust/kernel/gpu/ DRM AUTOMATED TESTING M: Helen Koike <[email protected]> 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); +} + +#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/buddy.rs b/rust/kernel/gpu/buddy.rs new file mode 100644 index 000000000000..9027c9a7778f --- /dev/null +++ b/rust/kernel/gpu/buddy.rs @@ -0,0 +1,611 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! GPU buddy allocator bindings. +//! +//! C header: [`include/linux/gpu_buddy.h`](srctree/include/linux/gpu_buddy.h) +//! +//! This module provides Rust abstractions over the Linux kernel's GPU buddy +//! allocator, which implements a binary buddy memory allocator. +//! +//! The buddy allocator manages a contiguous address space and allocates blocks +//! in power-of-two sizes, useful for GPU physical memory management. +//! +//! # Examples +//! +//! Create a buddy allocator and perform a basic range allocation: +//! +//! ``` +//! use kernel::{ +//! gpu::buddy::{GpuBuddy, GpuBuddyAllocMode, GpuBuddyAllocFlags, GpuBuddyParams}, +//! prelude::*, +//! ptr::Alignment, +//! sizes::*, // +//! }; +//! +//! // Create a 1GB buddy allocator with 4KB minimum chunk size. +//! let buddy = GpuBuddy::new(GpuBuddyParams { +//! base_offset: 0, +//! physical_memory_size: SZ_1G as u64, +//! chunk_size: SZ_4K, +//! })?; +//! +//! assert_eq!(buddy.size(), SZ_1G as u64); +//! assert_eq!(buddy.chunk_size(), SZ_4K); +//! let initial_free = buddy.free_memory(); +//! +//! // Allocate 16MB, results in a single 16MB block at offset 0. +//! let allocated = KBox::pin_init( +//! buddy.alloc_blocks( +//! GpuBuddyAllocMode::Range { start: 0, end: 0 }, +//! SZ_16M, +//! Alignment::new::<SZ_16M>(), +//! GpuBuddyAllocFlags::default(), +//! ), +//! GFP_KERNEL, +//! )?; +//! assert_eq!(buddy.free_memory(), initial_free - SZ_16M as u64); +//! +//! let block = allocated.iter().next().expect("expected one block"); +//! assert_eq!(block.offset(), 0); +//! assert_eq!(block.order(), 12); // 2^12 pages = 16MB +//! assert_eq!(block.size(), SZ_16M); +//! +//! // Dropping the allocation returns the memory to the buddy allocator. +//! drop(allocated); +//! assert_eq!(buddy.free_memory(), initial_free); +//! # Ok::<(), Error>(()) +//! ``` +//! +//! Top-down allocation allocates from the highest addresses: +//! +//! ``` +//! # use kernel::{ +//! # gpu::buddy::{GpuBuddy, GpuBuddyAllocMode, GpuBuddyAllocFlags, GpuBuddyParams}, +//! # prelude::*, +//! # ptr::Alignment, +//! # sizes::*, // +//! # }; +//! # let buddy = GpuBuddy::new(GpuBuddyParams { +//! # base_offset: 0, +//! # physical_memory_size: SZ_1G as u64, +//! # chunk_size: SZ_4K, +//! # })?; +//! # let initial_free = buddy.free_memory(); +//! let topdown = KBox::pin_init( +//! buddy.alloc_blocks( +//! GpuBuddyAllocMode::TopDown, +//! SZ_16M, +//! Alignment::new::<SZ_16M>(), +//! GpuBuddyAllocFlags::default(), +//! ), +//! GFP_KERNEL, +//! )?; +//! assert_eq!(buddy.free_memory(), initial_free - SZ_16M as u64); +//! +//! let block = topdown.iter().next().expect("expected one block"); +//! assert_eq!(block.offset(), (SZ_1G - SZ_16M) as u64); +//! assert_eq!(block.order(), 12); +//! assert_eq!(block.size(), SZ_16M); +//! +//! // Dropping the allocation returns the memory to the buddy allocator. +//! drop(topdown); +//! assert_eq!(buddy.free_memory(), initial_free); +//! # Ok::<(), Error>(()) +//! ``` +//! +//! Non-contiguous allocation can fill fragmented memory by returning multiple +//! blocks: +//! +//! ``` +//! # use kernel::{ +//! # gpu::buddy::{ +//! # GpuBuddy, GpuBuddyAllocFlags, GpuBuddyAllocMode, GpuBuddyParams, +//! # }, +//! # prelude::*, +//! # ptr::Alignment, +//! # sizes::*, // +//! # }; +//! # let buddy = GpuBuddy::new(GpuBuddyParams { +//! # base_offset: 0, +//! # physical_memory_size: SZ_1G as u64, +//! # chunk_size: SZ_4K, +//! # })?; +//! # let initial_free = buddy.free_memory(); +//! // Create fragmentation by allocating 4MB blocks at [0,4M) and [8M,12M). +//! let frag1 = KBox::pin_init( +//! buddy.alloc_blocks( +//! GpuBuddyAllocMode::Range { start: 0, end: SZ_4M as u64 }, +//! SZ_4M, +//! Alignment::new::<SZ_4M>(), +//! GpuBuddyAllocFlags::default(), +//! ), +//! GFP_KERNEL, +//! )?; +//! assert_eq!(buddy.free_memory(), initial_free - SZ_4M as u64); +//! +//! let frag2 = KBox::pin_init( +//! buddy.alloc_blocks( +//! GpuBuddyAllocMode::Range { +//! start: SZ_8M as u64, +//! end: (SZ_8M + SZ_4M) as u64, +//! }, +//! SZ_4M, +//! Alignment::new::<SZ_4M>(), +//! GpuBuddyAllocFlags::default(), +//! ), +//! GFP_KERNEL, +//! )?; +//! assert_eq!(buddy.free_memory(), initial_free - SZ_8M as u64); +//! +//! // Allocate 8MB, this returns 2 blocks from the holes. +//! let fragmented = KBox::pin_init( +//! buddy.alloc_blocks( +//! GpuBuddyAllocMode::Range { start: 0, end: SZ_16M as u64 }, +//! SZ_8M, +//! Alignment::new::<SZ_4M>(), +//! GpuBuddyAllocFlags::default(), +//! ), +//! GFP_KERNEL, +//! )?; +//! assert_eq!(buddy.free_memory(), initial_free - SZ_16M as u64); +//! +//! let (mut count, mut total) = (0u32, 0usize); +//! for block in fragmented.iter() { +//! assert_eq!(block.size(), SZ_4M); +//! total += block.size(); +//! count += 1; +//! } +//! assert_eq!(total, SZ_8M); +//! assert_eq!(count, 2); +//! # Ok::<(), Error>(()) +//! ``` +//! +//! Contiguous allocation fails when only fragmented space is available: +//! +//! ``` +//! # use kernel::{ +//! # gpu::buddy::{ +//! # GpuBuddy, GpuBuddyAllocFlag, GpuBuddyAllocMode, GpuBuddyParams, +//! # }, +//! # prelude::*, +//! # ptr::Alignment, +//! # sizes::*, // +//! # }; +//! // Create a small 16MB buddy allocator with fragmented memory. +//! let small = GpuBuddy::new(GpuBuddyParams { +//! base_offset: 0, +//! physical_memory_size: SZ_16M as u64, +//! chunk_size: SZ_4K, +//! })?; +//! +//! let _hole1 = KBox::pin_init( +//! small.alloc_blocks( +//! GpuBuddyAllocMode::Range { start: 0, end: SZ_4M as u64 }, +//! SZ_4M, +//! Alignment::new::<SZ_4M>(), +//! GpuBuddyAllocFlags::default(), +//! ), +//! GFP_KERNEL, +//! )?; +//! +//! let _hole2 = KBox::pin_init( +//! small.alloc_blocks( +//! GpuBuddyAllocMode::Range { +//! start: SZ_8M as u64, +//! end: (SZ_8M + SZ_4M) as u64, +//! }, +//! SZ_4M, +//! Alignment::new::<SZ_4M>(), +//! GpuBuddyAllocFlags::default(), +//! ), +//! GFP_KERNEL, +//! )?; +//! +//! // 8MB contiguous should fail, only two non-contiguous 4MB holes exist. +//! let result = KBox::pin_init( +//! small.alloc_blocks( +//! GpuBuddyAllocMode::Simple, +//! SZ_8M, +//! Alignment::new::<SZ_4M>(), +//! GpuBuddyAllocFlag::Contiguous.into(), +//! ), +//! GFP_KERNEL, +//! ); +//! assert!(result.is_err()); +//! # Ok::<(), Error>(()) +//! ``` + +use crate::{ + bindings, + clist_create, + error::to_result, + interop::list::CListHead, + new_mutex, + prelude::*, + ptr::Alignment, + sync::{ + lock::mutex::MutexGuard, + Arc, + Mutex, // + }, + types::Opaque, // +}; + +/// Allocation mode for the GPU buddy allocator. +/// +/// The mode determines the primary allocation strategy. Modes are mutually +/// exclusive: an allocation is either simple, range-constrained, or top-down. +/// +/// Orthogonal modifier flags (e.g., contiguous, clear) are specified separately +/// via [`GpuBuddyAllocFlags`]. +#[derive(Copy, Clone, Debug, PartialEq, Eq)] +pub enum GpuBuddyAllocMode { + /// Simple allocation without constraints. + Simple, + /// Range-based allocation between `start` and `end` addresses. + Range { + /// Start of the allocation range. + start: u64, + /// End of the allocation range. + end: u64, + }, + /// Allocate from top of address space downward. + TopDown, +} + +impl GpuBuddyAllocMode { + // Returns the C flags corresponding to the allocation mode. + fn into_flags(self) -> usize { + match self { + Self::Simple => 0, + Self::Range { .. } => bindings::GPU_BUDDY_RANGE_ALLOCATION as usize, + Self::TopDown => bindings::GPU_BUDDY_TOPDOWN_ALLOCATION as usize, + } + } + + // Extracts the range start/end, defaulting to (0, 0) for non-range modes. + fn range(self) -> (u64, u64) { + match self { + Self::Range { start, end } => (start, end), + _ => (0, 0), + } + } +} + +crate::impl_flags!( + /// Modifier flags for GPU buddy allocation. + /// + /// These flags can be combined with any [`GpuBuddyAllocMode`] to control + /// additional allocation behavior. + #[derive(Clone, Copy, Default, PartialEq, Eq)] + pub struct GpuBuddyAllocFlags(u32); + + /// Individual modifier flag for GPU buddy allocation. + #[derive(Clone, Copy, PartialEq, Eq)] + pub enum GpuBuddyAllocFlag { + /// Allocate physically contiguous blocks. + Contiguous = bindings::GPU_BUDDY_CONTIGUOUS_ALLOCATION as u32, + + /// Request allocation from cleared (zeroed) memory. + Clear = bindings::GPU_BUDDY_CLEAR_ALLOCATION as u32, + + /// Disable trimming of partially used blocks. + TrimDisable = bindings::GPU_BUDDY_TRIM_DISABLE as u32, + } +); + +/// Parameters for creating a GPU buddy allocator. +pub struct GpuBuddyParams { + /// Base offset (in bytes) where the managed memory region starts. + /// Allocations will be offset by this value. + pub base_offset: u64, + /// Total physical memory size (in bytes) managed by the allocator. + pub physical_memory_size: u64, + /// Minimum allocation unit / chunk size (in bytes), must be >= 4KB. + pub chunk_size: usize, +} + +/// Inner structure holding the actual buddy allocator. +/// +/// # Synchronization +/// +/// The C `gpu_buddy` API requires synchronization (see `include/linux/gpu_buddy.h`). +/// [`GpuBuddyGuard`] ensures that the lock is held for all +/// allocator and free operations, preventing races between concurrent allocations +/// and the freeing that occurs when [`AllocatedBlocks`] is dropped. +/// +/// # Invariants +/// +/// The inner [`Opaque`] contains an initialized buddy allocator. +#[pin_data(PinnedDrop)] +struct GpuBuddyInner { + #[pin] + inner: Opaque<bindings::gpu_buddy>, + + // TODO: Replace `Mutex<()>` with `Mutex<Opaque<..>>` once `Mutex::new()` + // accepts `impl PinInit<T>`. + #[pin] + lock: Mutex<()>, + /// Cached creation parameters (do not change after init). + params: GpuBuddyParams, +} + +impl GpuBuddyInner { + /// Create a pin-initializer for the buddy allocator. + fn new(params: GpuBuddyParams) -> impl PinInit<Self, Error> { + let size = params.physical_memory_size; + let chunk_size = params.chunk_size; + + // INVARIANT: `gpu_buddy_init` returns 0 on success, at which point the + // `gpu_buddy` structure is initialized and ready for use with all + // `gpu_buddy_*` APIs. `try_pin_init!` only completes if all fields succeed, + // so the invariant holds when construction finishes. + try_pin_init!(Self { + inner <- Opaque::try_ffi_init(|ptr| { + // SAFETY: `ptr` points to valid uninitialized memory from the pin-init + // infrastructure. `gpu_buddy_init` will initialize the structure. + to_result(unsafe { bindings::gpu_buddy_init(ptr, size, chunk_size as u64) }) + }), + lock <- new_mutex!(()), + params, + }) + } + + /// Lock the mutex and return a guard for accessing the allocator. + fn lock(&self) -> GpuBuddyGuard<'_> { + GpuBuddyGuard { + inner: self, + _guard: self.lock.lock(), + } + } +} + +#[pinned_drop] +impl PinnedDrop for GpuBuddyInner { + fn drop(self: Pin<&mut Self>) { + let guard = self.lock(); + + // SAFETY: Per the type invariant, `inner` contains an initialized + // allocator. `guard` provides exclusive access. + unsafe { + bindings::gpu_buddy_fini(guard.as_raw()); + } + } +} + +// SAFETY: GpuBuddyInner can be sent between threads. +unsafe impl Send for GpuBuddyInner {} + +// SAFETY: `GpuBuddyInner` is `Sync` because `GpuBuddyInner::lock` +// serializes all access to the C allocator, preventing data races. +unsafe impl Sync for GpuBuddyInner {} + +// Guard that proves the lock is held, enabling access to the allocator. +// The `_guard` holds the lock for the duration of this guard's lifetime. +struct GpuBuddyGuard<'a> { + inner: &'a GpuBuddyInner, + _guard: MutexGuard<'a, ()>, +} + +impl GpuBuddyGuard<'_> { + /// Get a raw pointer to the underlying C `gpu_buddy` structure. + fn as_raw(&self) -> *mut bindings::gpu_buddy { + self.inner.inner.get() + } +} + +/// GPU buddy allocator instance. +/// +/// This structure wraps the C `gpu_buddy` allocator using reference counting. +/// The allocator is automatically cleaned up when all references are dropped. +/// +/// Refer to the module-level documentation for usage examples. +pub struct GpuBuddy(Arc<GpuBuddyInner>); + +impl GpuBuddy { + /// Create a new buddy allocator. + /// + /// Creates a buddy allocator that manages a contiguous address space of the given + /// size, with the specified minimum allocation unit (chunk_size must be at least 4KB). + pub fn new(params: GpuBuddyParams) -> Result<Self> { + Ok(Self(Arc::pin_init(GpuBuddyInner::new(params), GFP_KERNEL)?)) + } + + /// Get the base offset for allocations. + pub fn base_offset(&self) -> u64 { + self.0.params.base_offset + } + + /// Get the chunk size (minimum allocation unit). + pub fn chunk_size(&self) -> usize { + self.0.params.chunk_size + } + + /// Get the total managed size. + pub fn size(&self) -> u64 { + self.0.params.physical_memory_size + } + + /// Get the available (free) memory in bytes. + pub fn free_memory(&self) -> u64 { + let guard = self.0.lock(); + + // SAFETY: Per the type invariant, `inner` contains an initialized allocator. + // `guard` provides exclusive access. + unsafe { (*guard.as_raw()).avail } + } + + /// Allocate blocks from the buddy allocator. + /// + /// Returns a pin-initializer for [`AllocatedBlocks`]. + /// + /// Takes `&self` instead of `&mut self` because the internal [`Mutex`] provides + /// synchronization - no external `&mut` exclusivity needed. + pub fn alloc_blocks( + &self, + mode: GpuBuddyAllocMode, + size: usize, + min_block_size: Alignment, + flags: GpuBuddyAllocFlags, + ) -> impl PinInit<AllocatedBlocks, Error> { + let buddy_arc = Arc::clone(&self.0); + let (start, end) = mode.range(); + let mode_flags = mode.into_flags(); + let modifier_flags = u32::from(flags) as usize; + + // Create pin-initializer that initializes list and allocates blocks. + try_pin_init!(AllocatedBlocks { + buddy: buddy_arc, + list <- CListHead::new(), + _: { + // Lock while allocating to serialize with concurrent frees. + let guard = buddy.lock(); + + // SAFETY: Per the type invariant, `inner` contains an initialized + // allocator. `guard` provides exclusive access. + to_result(unsafe { + bindings::gpu_buddy_alloc_blocks( + guard.as_raw(), + start, + end, + size as u64, + min_block_size.as_usize() as u64, + list.as_raw(), + mode_flags | modifier_flags, + ) + })? + } + }) + } +} + +/// Allocated blocks from the buddy allocator with automatic cleanup. +/// +/// This structure owns a list of allocated blocks and ensures they are +/// automatically freed when dropped. Use `iter()` to iterate over all +/// allocated blocks. +/// +/// # Invariants +/// +/// - `list` is an initialized, valid list head containing allocated blocks. +#[pin_data(PinnedDrop)] +pub struct AllocatedBlocks { + #[pin] + list: CListHead, + buddy: Arc<GpuBuddyInner>, +} + +impl AllocatedBlocks { + /// Check if the block list is empty. + pub fn is_empty(&self) -> bool { + // An empty list head points to itself. + !self.list.is_linked() + } + + /// Iterate over allocated blocks. + /// + /// Returns an iterator yielding [`AllocatedBlock`] values. Each [`AllocatedBlock`] + /// borrows `self` and is only valid for the duration of that borrow. + pub fn iter(&self) -> impl Iterator<Item = AllocatedBlock<'_>> + '_ { + // SAFETY: + // - Per the type invariant, `list` is an initialized sentinel `list_head` + // and is not concurrently modified (we hold a `&self` borrow). + // - The list contains `gpu_buddy_block` items linked via + // `__bindgen_anon_1.link`. + // - `Block` is `#[repr(transparent)]` over `gpu_buddy_block`. + let clist = clist_create!(unsafe { + self.list.as_raw(), + Block, + bindings::gpu_buddy_block, + __bindgen_anon_1.link + }); + + clist + .iter() + .map(|this| AllocatedBlock { this, blocks: self }) + } +} + +#[pinned_drop] +impl PinnedDrop for AllocatedBlocks { + fn drop(self: Pin<&mut Self>) { + let guard = self.buddy.lock(); + + // SAFETY: + // - list is valid per the type's invariants. + // - guard provides exclusive access to the allocator. + unsafe { + bindings::gpu_buddy_free_list(guard.as_raw(), self.list.as_raw(), 0); + } + } +} + +/// A GPU buddy block. +/// +/// Transparent wrapper over C `gpu_buddy_block` structure. This type is returned +/// as references during iteration over [`AllocatedBlocks`]. +/// +/// # Invariants +/// +/// The inner [`Opaque`] contains a valid, allocated `gpu_buddy_block`. +#[repr(transparent)] +struct Block(Opaque<bindings::gpu_buddy_block>); + +impl Block { + /// Get a raw pointer to the underlying C block. + fn as_raw(&self) -> *mut bindings::gpu_buddy_block { + self.0.get() + } + + /// Get the block's raw offset in the buddy address space (without base offset). + fn offset(&self) -> u64 { + // SAFETY: `self.as_raw()` is valid per the type's invariants. + unsafe { bindings::gpu_buddy_block_offset(self.as_raw()) } + } + + /// Get the block order. + fn order(&self) -> u32 { + // SAFETY: `self.as_raw()` is valid per the type's invariants. + unsafe { bindings::gpu_buddy_block_order(self.as_raw()) } + } +} + +// SAFETY: `Block` is a wrapper around `gpu_buddy_block` which can be +// sent across threads safely. +unsafe impl Send for Block {} + +// SAFETY: `Block` is only accessed through shared references after +// allocation, and thus safe to access concurrently across threads. +unsafe impl Sync for Block {} + +/// A buddy block paired with its owning [`AllocatedBlocks`] context. +/// +/// Unlike a raw block, which only knows its offset within the buddy address +/// space, an [`AllocatedBlock`] also has access to the allocator's `base_offset` +/// and `chunk_size`, enabling it to compute absolute offsets and byte sizes. +/// +/// Returned by [`AllocatedBlocks::iter()`]. +pub struct AllocatedBlock<'a> { + this: &'a Block, + blocks: &'a AllocatedBlocks, +} + +impl AllocatedBlock<'_> { + /// Get the block's offset in the address space. + /// + /// Returns the absolute offset including the allocator's base offset. + /// This is the actual address to use for accessing the allocated memory. + pub fn offset(&self) -> u64 { + self.blocks.buddy.params.base_offset + self.this.offset() + } + + /// Get the block order (size = chunk_size << order). + pub fn order(&self) -> u32 { + self.this.order() + } + + /// Get the block's size in bytes. + pub fn size(&self) -> usize { + self.blocks.buddy.params.chunk_size << self.this.order() + } +} diff --git a/rust/kernel/gpu/mod.rs b/rust/kernel/gpu/mod.rs new file mode 100644 index 000000000000..8f25e6367edc --- /dev/null +++ b/rust/kernel/gpu/mod.rs @@ -0,0 +1,5 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! GPU subsystem abstractions. + +pub mod buddy; diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index bb741f1e0dfd..63e3f656eb6c 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -98,6 +98,8 @@ pub mod firmware; pub mod fmt; pub mod fs; +#[cfg(CONFIG_GPU_BUDDY = "y")] +pub mod gpu; #[cfg(CONFIG_I2C = "y")] pub mod i2c; pub mod id_pool; -- 2.34.1
