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Reviewed-by: Alice Ryhl Reviewed-by: Yury Norov Signed-off-by: Eliot Courtney --- rust/kernel/bitmap.rs | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-) diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs index b27e0ec80d64..a43bfe0ec3dc 100644 --- a/rust/kernel/bitmap.rs +++ b/rust/kernel/bitmap.rs @@ -572,24 +572,21 @@ fn bitmap_set_clear_find() -> Result<(), AllocError> { } =20 #[test] + #[cfg(not(CONFIG_RUST_BITMAP_HARDENED))] fn owned_bitmap_out_of_bounds() -> Result<(), AllocError> { - // TODO: Kunit #[test]s do not support `cfg` yet, - // so we add it here in the body. - #[cfg(not(CONFIG_RUST_BITMAP_HARDENED))] - { - let mut b =3D BitmapVec::new(128, GFP_KERNEL)?; - b.set_bit(2048); - b.set_bit_atomic(2048); - b.clear_bit(2048); - b.clear_bit_atomic(2048); - assert_eq!(None, b.next_bit(2048)); - assert_eq!(None, b.next_zero_bit(2048)); - assert_eq!(None, b.last_bit()); - } + let mut b =3D BitmapVec::new(128, GFP_KERNEL)?; + + b.set_bit(2048); 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Restricting all bitmaps (even non-`BitmapVec` backed ones) to a maximum size of `i32::MAX` simplifies a few things and matches `BitmapVec::MAX_LEN`. Add that requirement to the unsafe requirements on `Bitmap::from_raw` and `Bitmap::from_raw_mut`, and to the invariants on `Bitmap`. This also fixes u32 casts truncating in `copy_and_extend`, which could otherwise lead to OOB writes. Fixes: 11eca92a2cae ("rust: add bitmap API.") Link: https://lore.kernel.org/DKG0U8RLO7LZ.2I1AIH0S38PAP@nvidia.com Reviewed-by: Yury Norov Signed-off-by: Eliot Courtney --- rust/kernel/bitmap.rs | 68 +++++++++++++++++++++++++++++++++++------------= ---- 1 file changed, 47 insertions(+), 21 deletions(-) diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs index a43bfe0ec3dc..fdcfc0409773 100644 --- a/rust/kernel/bitmap.rs +++ b/rust/kernel/bitmap.rs @@ -17,24 +17,57 @@ /// # Invariants /// /// Must reference a `[c_ulong]` long enough to fit `data.len()` bits. +/// Must not be longer than `i32::MAX` bits. #[cfg_attr(CONFIG_64BIT, repr(align(8)))] #[cfg_attr(not(CONFIG_64BIT), repr(align(4)))] pub struct Bitmap { data: [()], } =20 +macro_rules! bitmap_assert { + ($cond:expr, $($arg:tt)+) =3D> { + #[cfg(CONFIG_RUST_BITMAP_HARDENED)] + assert!($cond, $($arg)*); + } +} + +macro_rules! bitmap_assert_return { + ($cond:expr, $($arg:tt)+) =3D> { + #[cfg(CONFIG_RUST_BITMAP_HARDENED)] + assert!($cond, $($arg)*); + + #[cfg(not(CONFIG_RUST_BITMAP_HARDENED))] + if !($cond) { + pr_err!($($arg)*); + return + } + } +} + impl Bitmap { /// Borrows a C bitmap. /// + /// # Panics + /// + /// Panics if CONFIG_RUST_BITMAP_HARDENED is enabled and `nbits` excee= ds `i32::MAX`. + /// /// # Safety /// /// * `ptr` holds a non-null address of an initialized array of `unsig= ned long` /// that is large enough to hold `nbits` bits. + /// * `nbits` must not exceed `i32::MAX`. /// * the array must not be freed for the lifetime of this [`Bitmap`] /// * concurrent access only happens through atomic operations pub unsafe fn from_raw<'a>(ptr: *const usize, nbits: usize) -> &'a Bit= map { + bitmap_assert!( + nbits <=3D i32::MAX as usize, + "`nbits` must be <=3D {}, was {}", + i32::MAX, + nbits + ); let data: *const [()] =3D core::ptr::slice_from_raw_parts(ptr.cast= (), nbits); // INVARIANT: `data` references an initialized array that can hold= `nbits` bits. + // INVARIANT: the caller guarantees that `nbits` does not exceed `= i32::MAX`. // SAFETY: // The caller guarantees that `data` (derived from `ptr` and `nbit= s`) // points to a valid, initialized, and appropriately sized memory = region @@ -51,15 +84,27 @@ pub unsafe fn from_raw<'a>(ptr: *const usize, nbits: us= ize) -> &'a Bitmap { =20 /// Borrows a C bitmap exclusively. /// + /// # Panics + /// + /// Panics if CONFIG_RUST_BITMAP_HARDENED is enabled and `nbits` excee= ds `i32::MAX`. + /// /// # Safety /// /// * `ptr` holds a non-null address of an initialized array of `unsig= ned long` /// that is large enough to hold `nbits` bits. + /// * `nbits` must not exceed `i32::MAX`. /// * the array must not be freed for the lifetime of this [`Bitmap`] /// * no concurrent access may happen. pub unsafe fn from_raw_mut<'a>(ptr: *mut usize, nbits: usize) -> &'a m= ut Bitmap { + bitmap_assert!( + nbits <=3D i32::MAX as usize, + "`nbits` must be <=3D {}, was {}", + i32::MAX, + nbits + ); let data: *mut [()] =3D core::ptr::slice_from_raw_parts_mut(ptr.ca= st(), nbits); // INVARIANT: `data` references an initialized array that can hold= `nbits` bits. + // INVARIANT: the caller guarantees that `nbits` does not exceed `= i32::MAX`. // SAFETY: // The caller guarantees that `data` (derived from `ptr` and `nbit= s`) // points to a valid, initialized, and appropriately sized memory = region @@ -96,26 +141,6 @@ union BitmapRepr { ptr: NonNull, } =20 -macro_rules! bitmap_assert { - ($cond:expr, $($arg:tt)+) =3D> { - #[cfg(CONFIG_RUST_BITMAP_HARDENED)] - assert!($cond, $($arg)*); - } -} - -macro_rules! bitmap_assert_return { - ($cond:expr, $($arg:tt)+) =3D> { - #[cfg(CONFIG_RUST_BITMAP_HARDENED)] - assert!($cond, $($arg)*); - - #[cfg(not(CONFIG_RUST_BITMAP_HARDENED))] - if !($cond) { - pr_err!($($arg)*); - return - } - } -} - /// Represents an owned bitmap. /// /// Wraps underlying C bitmap API. See [`Bitmap`] for available @@ -415,7 +440,8 @@ pub fn clear_bit_atomic(&self, index: usize) { #[inline] pub fn copy_and_extend(&mut self, src: &Bitmap) { let len =3D core::cmp::min(src.len(), self.len()); - // SAFETY: access to `self` and `src` is within bounds. + // SAFETY: access to `self` and `src` is within bounds. 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Each one is made safe by adding some extra checks compared to the underlying C code (for example, checking bounds) and with additional checks to catch likely erroneous usage if `CONFIG_RUST_BITMAP_HARDENED` is on. Add tests demonstrating the edge cases. Signed-off-by: Eliot Courtney --- rust/kernel/bitmap.rs | 248 ++++++++++++++++++++++++++++++++++++++++++++++= +++- 1 file changed, 247 insertions(+), 1 deletion(-) diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs index fdcfc0409773..ad63f248a6ae 100644 --- a/rust/kernel/bitmap.rs +++ b/rust/kernel/bitmap.rs @@ -10,7 +10,11 @@ use crate::bindings; #[cfg(not(CONFIG_RUST_BITMAP_HARDENED))] use crate::pr_err; -use core::ptr::NonNull; +use crate::ptr::Alignment; +use core::{ + num::NonZero, + ptr::NonNull, // +}; =20 /// Represents a C bitmap. Wraps underlying C bitmap API. /// @@ -523,6 +527,148 @@ pub fn next_zero_bit(&self, start: usize) -> Option { Some(index) } } + + /// Finds a contiguous area of `nbits` zero bits at or after `start`, = where the area plus + /// `align_offset` is aligned to `align`. + /// + /// Returns the bit index of the start of the area, or [`None`] if no = such area fitting in + /// the bitmap exists. + /// + /// The returned index plus `align_offset` is a multiple of `align`. + /// + /// # Panics + /// + /// Panics if CONFIG_RUST_BITMAP_HARDENED is enabled and `start` is ou= t of bounds. + #[inline] + pub fn next_zero_area_off( + &self, + start: usize, + nbits: NonZero, + align: Alignment, + align_offset: usize, + ) -> Option { + bitmap_assert!( + start < self.len(), + "`start` must be < {}, was {}", + self.len(), + start + ); + + let nr =3D u32::try_from(nbits.get()).ok()?; + let align_mask =3D align.as_usize() - 1; + + // The C alignment and end arithmetic must not overflow, or it can= read out of bounds. + // Overflow is only possible on 32-bit. + #[cfg(not(CONFIG_64BIT))] + align_mask + .checked_add(self.len())? + .checked_add(nbits.get())?; + + // SAFETY: `bitmap_find_next_zero_area_off` is safe to use with an= out of bounds `start` + // value and, given the overflow check above, never reads beyond `= self.len()` bits. + let index =3D unsafe { + bindings::bitmap_find_next_zero_area_off( + self.as_ptr().cast_mut(), + self.len(), + start, + nr, + align_mask, + align_offset, + ) + }; + + (index < self.len()).then_some(index) + } + + /// Finds a contiguous area of `nbits` zero bits at or after `start`, = aligned to `align`. + /// + /// Returns the bit index of the start of the area, or [`None`] if no = such area fitting in + /// the bitmap exists. + /// + /// The returned index is a multiple of `align`. + /// + /// # Panics + /// + /// Panics if CONFIG_RUST_BITMAP_HARDENED is enabled and `start` is ou= t of bounds. + /// + /// # Examples + /// + /// ``` + /// use core::num::NonZero; + /// use kernel::alloc::{AllocError, flags::GFP_KERNEL}; + /// use kernel::bitmap::BitmapVec; + /// use kernel::ptr::Alignment; + /// + /// let mut b =3D BitmapVec::new(64, GFP_KERNEL)?; + /// let unaligned =3D Alignment::new::<1>(); + /// let eight =3D NonZero::new(8).unwrap(); + /// + /// assert_eq!(Some(0), b.next_zero_area(0, eight, unaligned)); + /// b.set(0, NonZero::new(5).unwrap()); + /// assert_eq!(Some(5), b.next_zero_area(0, eight, unaligned)); + /// assert_eq!(Some(8), b.next_zero_area(0, eight, Alignment::new::<8>= ())); + /// assert_eq!(None, b.next_zero_area(0, NonZero::new(65).unwrap(), un= aligned)); + /// # Ok::<(), AllocError>(()) + /// ``` + #[inline] + pub fn next_zero_area( + &self, + start: usize, + nbits: NonZero, + align: Alignment, + ) -> Option { + self.next_zero_area_off(start, nbits, align, 0) + } + + /// Sets a contiguous area of `nbits` bits starting at `start`. + /// + /// If CONFIG_RUST_BITMAP_HARDENED is not enabled and the area `start.= .start + nbits` is out of + /// bounds, does nothing. + /// + /// # Panics + /// + /// Panics if CONFIG_RUST_BITMAP_HARDENED is enabled and the area `sta= rt..start + nbits` is out + /// of bounds. + #[inline] + pub fn set(&mut self, start: usize, nbits: NonZero) { + bitmap_assert_return!( + start + .checked_add(nbits.get()) + .is_some_and(|end| end <=3D self.len()), + "Area `start..start + nbits` ({}..{}) must be within bounds {}= ", + start, + start.saturating_add(nbits.get()), + self.len() + ); + // SAFETY: The area `start..start + nbits` is within bounds and a = `Bitmap` is at most + // `i32::MAX` bits, so the casts are lossless. + unsafe { bindings::__bitmap_set(self.as_mut_ptr(), start as u32, n= bits.get() as i32) }; + } + + /// Clears a contiguous area of `nbits` bits starting at `start`. + /// + /// If CONFIG_RUST_BITMAP_HARDENED is not enabled and the area `start.= .start + nbits` is out of + /// bounds, does nothing. + /// + /// # Panics + /// + /// Panics if CONFIG_RUST_BITMAP_HARDENED is enabled and the area `sta= rt..start + nbits` is out + /// of bounds. + #[inline] + pub fn clear(&mut self, start: usize, nbits: NonZero) { + bitmap_assert_return!( + start + .checked_add(nbits.get()) + .is_some_and(|end| end <=3D self.len()), + "Area `start..start + nbits` ({}..{}) must be within bounds {}= ", + start, + start.saturating_add(nbits.get()), + self.len() + ); + // SAFETY: The area `start..start + nbits` is within bounds and a = `Bitmap` is at most + // `i32::MAX` bits, so the casts are lossless. + unsafe { bindings::__bitmap_clear(self.as_mut_ptr(), start as u32,= nbits.get() as i32) }; + } } =20 #[cfg(CONFIG_RUST_BITMAP_KUNIT_TEST)] @@ -531,6 +677,10 @@ mod tests { use super::*; use kernel::alloc::flags::GFP_KERNEL; =20 + const fn nz() -> NonZero { + const { NonZero::new(N).unwrap() } + } + #[test] fn bitmap_borrow() { let fake_bitmap: [usize; 2] =3D [0, 0]; @@ -640,4 +790,100 @@ fn bitmap_copy_and_extend() -> Result<(), AllocError>= { assert_eq!(Some(17), long_bitmap.last_bit()); Ok(()) } + + #[test] + fn bitmap_area_set_clear_find() -> Result<(), AllocError> { + let mut b =3D BitmapVec::new(128, GFP_KERNEL)?; + let unaligned =3D Alignment::new::<1>(); + + assert_eq!(Some(0), b.next_zero_area(0, nz::<5>(), unaligned)); + b.set(0, nz::<5>()); // Now contains {[0, 5)}. + + assert_eq!(Some(0), b.next_bit(0)); + assert_eq!(Some(4), b.next_bit(4)); + assert_eq!(Some(5), b.next_zero_bit(0)); + assert_eq!(Some(5), b.next_zero_area(0, nz::<5>(), unaligned)); + assert_eq!( + Some(8), + b.next_zero_area(0, nz::<5>(), Alignment::new::<8>()) + ); + + b.set(8, nz::<8>()); // Now contains {[0, 5), [8, 16)}. + assert_eq!( + Some(16), + b.next_zero_area(0, nz::<4>(), Alignment::new::<16>()) + ); + assert_eq!(Some(16), b.next_zero_area(0, nz::<4>(), unaligned)); + + b.clear(0, nz::<5>()); // Now contains {[8, 16)}. + assert_eq!(Some(0), b.next_zero_area(0, nz::<5>(), unaligned)); + assert_eq!(Some(8), b.next_bit(0)); + assert_eq!(Some(15), b.last_bit()); + + b.set(60, nz::<10>()); // Now contains {[8, 16), [60, 70)}. + assert_eq!(Some(60), b.next_bit(16)); + assert_eq!(Some(69), b.last_bit()); + assert_eq!(Some(16), b.next_zero_area(9, nz::<40>(), unaligned)); + assert_eq!(Some(70), b.next_zero_area(0, nz::<45>(), unaligned)); + + b.clear(62, nz::<6>()); // Now contains {[8, 16), [60, 62), [68, 7= 0)}. + assert_eq!(Some(62), b.next_zero_area(60, nz::<6>(), unaligned)); + assert_eq!(Some(61), b.next_bit(61)); + assert_eq!(Some(69), b.last_bit()); + Ok(()) + } + + #[test] + fn bitmap_area_exhaustion() -> Result<(), AllocError> { + let mut b =3D BitmapVec::new(64, GFP_KERNEL)?; + let unaligned =3D Alignment::new::<1>(); + + assert_eq!(None, b.next_zero_area(0, nz::<65>(), unaligned)); + assert_eq!(None, b.next_zero_area(0, nz::<{ usize::MAX }>(), unali= gned)); + assert_eq!(None, b.next_zero_area(1, nz::<{ usize::MAX }>(), unali= gned)); + + b.set_bit(0); // Now contains {[0, 1)}. + assert_eq!(None, b.next_zero_area(0, nz::<{ usize::MAX }>(), unali= gned)); + + b.set(0, nz::<61>()); // Now contains {[0, 61)}. + assert_eq!(None, b.next_zero_area(0, nz::<4>(), unaligned)); + assert_eq!(Some(61), b.next_zero_area(0, nz::<3>(), unaligned)); + assert_eq!(None, b.next_zero_area(0, nz::<1>(), Alignment::new::<6= 4>())); + Ok(()) + } + + #[test] + fn bitmap_area_off() -> Result<(), AllocError> { + let mut b =3D BitmapVec::new(64, GFP_KERNEL)?; + let align8 =3D Alignment::new::<8>(); + + b.set(0, nz::<5>()); // Now contains {[0, 5)}. + + // The area plus align_offset starts at a multiple of the alignmen= t. + assert_eq!(Some(7), b.next_zero_area_off(0, nz::<8>(), align8, 1)); + assert_eq!(Some(5), b.next_zero_area_off(0, nz::<8>(), align8, 3)); + + // A zero offset behaves like next_zero_area(). + assert_eq!( + b.next_zero_area(0, nz::<8>(), align8), + b.next_zero_area_off(0, nz::<8>(), align8, 0) + ); + Ok(()) + } + + #[test] + #[cfg(not(CONFIG_RUST_BITMAP_HARDENED))] + fn owned_bitmap_area_out_of_bounds() -> Result<(), AllocError> { + let mut b =3D BitmapVec::new(64, GFP_KERNEL)?; + + // Should be ignored since out of bounds. + b.set(64, nz::<4>()); + b.set(62, nz::<8>()); + b.set(usize::MAX, nz::<1>()); + b.clear(usize::MAX, nz::<1>()); + b.clear(2048, nz::<8>()); + assert_eq!(None, b.next_bit(0)); + assert_eq!(None, b.next_zero_area(64, nz::<1>(), Alignment::new::<= 1>())); + Ok(()) + } } --=20 2.55.0 From nobody Tue Sep 29 02:33:19 2026 Received: from SJ2PR03CU001.outbound.protection.outlook.com (mail-westusazon11012060.outbound.protection.outlook.com [52.101.43.60]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 15FBE375F96; Thu, 13 Aug 2026 07:34:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.43.60 ARC-Seal: i=2; a=rsa-sha256; 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Signed-off-by: Eliot Courtney --- rust/kernel/id_pool.rs | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs index 384753fe0e44..a4a2ff417fe8 100644 --- a/rust/kernel/id_pool.rs +++ b/rust/kernel/id_pool.rs @@ -4,8 +4,14 @@ =20 //! Rust API for an ID pool backed by a [`BitmapVec`]. =20 +use core::{ + num::NonZero, + ops::Range, // +}; + use crate::alloc::{AllocError, Flags}; use crate::bitmap::BitmapVec; +use crate::ptr::Alignment; =20 /// Represents a dynamic ID pool backed by a [`BitmapVec`]. /// @@ -240,6 +246,32 @@ pub fn find_unused_id(&mut self, offset: usize) -> Opt= ion> { pub fn release_id(&mut self, id: usize) { self.map.clear_bit(id); } + + /// Allocates a contiguous area of `count` IDs at or after `offset`. + /// + /// The start of the returned area is a multiple of `align`. + /// + /// Returns the allocated range upon success, or [`None`] if no such a= rea could be found. + #[inline] + #[must_use] + pub fn alloc_area( + &mut self, + offset: usize, + count: NonZero, + align: Alignment, + ) -> Option> { + let start =3D self.map.next_zero_area(offset, count, align)?; + self.map.set(start, count); + Some(start..start + count.get()) + } + + /// Releases a contiguous area of IDs. + #[inline] + pub fn release_area(&mut self, range: &Range) { + if let Some(nbits) =3D NonZero::new(range.len()) { + self.map.clear(range.start, nbits); 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Reflect this in IdPool::with_capacity. Signed-off-by: Eliot Courtney --- rust/kernel/id_pool.rs | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs index a4a2ff417fe8..1423a5fbca69 100644 --- a/rust/kernel/id_pool.rs +++ b/rust/kernel/id_pool.rs @@ -29,10 +29,11 @@ /// Basic usage /// /// ``` +/// use core::num::NonZero; /// use kernel::alloc::AllocError; /// use kernel::id_pool::{IdPool, UnusedId}; /// -/// let mut pool =3D IdPool::with_capacity(64, GFP_KERNEL)?; +/// let mut pool =3D IdPool::with_capacity(NonZero::new(64).unwrap(), GFP_= KERNEL)?; /// for i in 0..64 { /// assert_eq!(i, pool.find_unused_id(i).ok_or(ENOSPC)?.acquire()); /// } @@ -117,8 +118,8 @@ pub fn new() -> Self { /// /// [`MAX_INLINE_LEN`]: BitmapVec::MAX_INLINE_LEN #[inline] - pub fn with_capacity(num_ids: usize, flags: Flags) -> Result { - let num_ids =3D usize::max(num_ids, BitmapVec::MAX_INLINE_LEN); + pub fn with_capacity(num_ids: NonZero, flags: Flags) -> Result<= Self, AllocError> { + let num_ids =3D usize::max(num_ids.get(), BitmapVec::MAX_INLINE_LE= N); 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Remove this behaviour. Signed-off-by: Eliot Courtney --- rust/kernel/id_pool.rs | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs index 1423a5fbca69..9baafc1732be 100644 --- a/rust/kernel/id_pool.rs +++ b/rust/kernel/id_pool.rs @@ -113,14 +113,9 @@ pub fn new() -> Self { } =20 /// Constructs a new [`IdPool`] with space for a specific number of bi= ts. - /// - /// A capacity below [`MAX_INLINE_LEN`] is adjusted to [`MAX_INLINE_LE= N`]. - /// - /// [`MAX_INLINE_LEN`]: BitmapVec::MAX_INLINE_LEN #[inline] pub fn with_capacity(num_ids: NonZero, flags: Flags) -> Result<= Self, AllocError> { - let num_ids =3D usize::max(num_ids.get(), BitmapVec::MAX_INLINE_LE= N); - let map =3D BitmapVec::new(num_ids, flags)?; + let map =3D BitmapVec::new(num_ids.get(), flags)?; Ok(Self { map }) } =20 --=20 2.55.0 From nobody Tue Sep 29 02:33:19 2026 Received: from CH5PR02CU005.outbound.protection.outlook.com (mail-northcentralusazon11012063.outbound.protection.outlook.com [40.107.200.63]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E429F371877; 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This is necessary for apportioning ranges of channel IDs to be used in e.g. vGPU. Channel IDs are allocated as a contiguous sequence with a specific length and sometimes a specific alignment [1] for vGPU. The ID space is small (limited to 2048) and allocation is not on a hot path, so a bitmap-backed `IdPool` is a better fit than IDA/xarray (which allocate a single ID within a range, not a contiguous sequence) or a maple tree (where aligned allocation needs an alloc_range()+erase() retry loop that essentially reimplements bitmap_find_next_zero_area()) [2]. It is also faster than maple tree [3]. Link: https://lore.kernel.org/all/84bc8bd2-e292-4b84-9580-a1b5df4c5bdc@nvid= ia.com/ # [1] Link: https://lore.kernel.org/all/20260710-chid-maple-v1-1-4ee869055268@nvi= dia.com/ # [2] Link: https://lore.kernel.org/all/20260717053241.916441-1-ynorov@nvidia.com= / # [3] Signed-off-by: Eliot Courtney --- drivers/gpu/nova-core/gpu.rs | 2 + drivers/gpu/nova-core/gpu/channel.rs | 201 +++++++++++++++++++++++++++++++= ++++ 2 files changed, 203 insertions(+) diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs index 42a4cd7971fa..66ea697a89f8 100644 --- a/drivers/gpu/nova-core/gpu.rs +++ b/drivers/gpu/nova-core/gpu.rs @@ -33,6 +33,8 @@ vgpu::VgpuManager, // }; =20 +#[cfg_attr(not(CONFIG_KUNIT =3D "y"), expect(dead_code))] +mod channel; mod hal; =20 macro_rules! define_chipset { diff --git a/drivers/gpu/nova-core/gpu/channel.rs b/drivers/gpu/nova-core/g= pu/channel.rs new file mode 100644 index 000000000000..520436c6f6f2 --- /dev/null +++ b/drivers/gpu/nova-core/gpu/channel.rs @@ -0,0 +1,201 @@ +// SPDX-License-Identifier: GPL-2.0 +// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIA= TES. All rights reserved. + +//! Channel ID allocation. + +use core::{ + num::NonZero, + ops::{ + Deref, + Range, // + }, // +}; + +use kernel::{ + id_pool::IdPool, + prelude::*, + ptr::Alignment, + sync::{ + new_mutex, + Mutex, // + }, // +}; + +/// Pool for tracking reservations of channel IDs. +#[pin_data] +pub(crate) struct ChannelIdPool { + #[pin] + inner: Mutex, +} + +impl ChannelIdPool { + /// Creates a pool managing `num_chids` channel IDs. + pub(crate) fn new(num_chids: NonZero) -> impl PinInit { + try_pin_init!(Self { + inner <- new_mutex!(IdPool::with_capacity(num_chids, GFP_KERNE= L)?), + }) + } + + /// Reserves a contiguous area of `count` channel IDs starting at a mu= ltiple of `align`, + /// returning a guard that releases the area on drop. + pub(crate) fn alloc_area( + &self, + count: NonZero, + align: Alignment, + ) -> Result> { + let mut ids =3D self.inner.lock(); + let range =3D ids.alloc_area(0, count, align).ok_or(ENOSPC)?; + Ok(ChannelIdArea { pool: self, range }) + } +} + +/// A reserved contiguous area of channel IDs. +/// +/// Releases the whole area back to its [`ChannelIdPool`] when dropped. Re= leasing locks a +/// sleeping [`Mutex`], so the area must be dropped in a context that is a= llowed to sleep. +#[must_use =3D "the channel ID area is released immediately when unused"] +pub(crate) struct ChannelIdArea<'a> { + pool: &'a ChannelIdPool, + range: Range, +} + +impl Drop for ChannelIdArea<'_> { + fn drop(&mut self) { + self.pool.inner.lock().release_area(&self.range); + } +} + +impl Deref for ChannelIdArea<'_> { + type Target =3D Range; + + fn deref(&self) -> &Self::Target { + &self.range + } +} + +#[kunit_tests(nova_core_channel)] +mod tests { + use super::*; + + const fn nz() -> NonZero { + const { NonZero::new(N).unwrap() } + } + + #[test] + fn chid_area() -> Result { + let pool =3D KBox::pin_init(ChannelIdPool::new(nz::<2048>()), GFP_= KERNEL)?; + let unaligned =3D Alignment::new::<1>(); + + let first =3D pool.alloc_area(nz::<48>(), unaligned)?; + assert_eq!(0, first.start); + assert_eq!(48, first.len()); + assert_eq!(48, first.end); + + let second =3D pool.alloc_area(nz::<48>(), unaligned)?; + assert!(first.end <=3D second.start || second.end <=3D first.start= ); + + let first_start =3D first.start; + drop(first); + assert_eq!(first_start, pool.alloc_area(nz::<48>(), unaligned)?.st= art); + Ok(()) + } + + #[test] + fn chid_area_drop() -> Result { + let pool =3D KBox::pin_init(ChannelIdPool::new(nz::<8>()), GFP_KER= NEL)?; + let unaligned =3D Alignment::new::<1>(); + + let a =3D pool.alloc_area(nz::<3>(), unaligned)?; + let b =3D pool.alloc_area(nz::<3>(), unaligned)?; + let c =3D pool.alloc_area(nz::<2>(), unaligned)?; + assert_eq!(0, a.start); + assert_eq!(3, b.start); + assert_eq!(6, c.start); + + drop(b); + + // Only have space for 3 IDs right now. + assert_eq!( + Err(ENOSPC), + pool.alloc_area(nz::<4>(), unaligned).map(|_| ()) + ); + let b =3D pool.alloc_area(nz::<3>(), unaligned)?; + assert_eq!(3, b.start); + + drop(a); + drop(c); + drop(b); + + // Everything was dropped so the pool should be empty. + assert_eq!(0, pool.alloc_area(nz::<8>(), unaligned)?.start); + Ok(()) + } + + #[test] + fn chid_bounded_by_num_chids() -> Result { + let pool =3D KBox::pin_init(ChannelIdPool::new(nz::<4>()), GFP_KER= NEL)?; + let unaligned =3D Alignment::new::<1>(); + + { + let a =3D pool.alloc_area(nz::<1>(), unaligned)?; + let b =3D pool.alloc_area(nz::<1>(), unaligned)?; + let c =3D pool.alloc_area(nz::<1>(), unaligned)?; + let d =3D pool.alloc_area(nz::<1>(), unaligned)?; + assert_eq!(0, a.start); + assert_eq!(1, b.start); + assert_eq!(2, c.start); + assert_eq!(3, d.start); + assert_eq!( + Err(ENOSPC), + pool.alloc_area(nz::<1>(), unaligned).map(|_| ()) + ); + } + + assert_eq!(0, pool.alloc_area(nz::<4>(), unaligned)?.start); + assert_eq!( + Err(ENOSPC), + pool.alloc_area(nz::<5>(), unaligned).map(|_| ()) + ); + + let head =3D pool.alloc_area(nz::<3>(), unaligned)?; + assert_eq!(0, head.start); + assert_eq!( + Err(ENOSPC), + pool.alloc_area(nz::<2>(), unaligned).map(|_| ()) + ); + assert_eq!(3, pool.alloc_area(nz::<1>(), unaligned)?.start); + Ok(()) + } + + #[test] + fn chid_area_aligned() -> Result { + let pool =3D KBox::pin_init(ChannelIdPool::new(nz::<16>()), GFP_KE= RNEL)?; + let unaligned =3D Alignment::new::<1>(); + let align4 =3D Alignment::new::<4>(); + + // Alloc 0 so the first fit for the next area is unaligned. + let pad =3D pool.alloc_area(nz::<1>(), unaligned)?; + assert_eq!(0, pad.start); + + let a =3D pool.alloc_area(nz::<4>(), align4)?; + assert_eq!(4, a.start); + + // The area skipped over by the aligned allocation should still be= available. + let b =3D pool.alloc_area(nz::<1>(), unaligned)?; + assert_eq!(1, b.start); + + let c =3D pool.alloc_area(nz::<8>(), Alignment::new::<8>())?; + assert_eq!(8, c.start); + + // Only 2 IDs left. + assert_eq!(Err(ENOSPC), pool.alloc_area(nz::<4>(), align4).map(|_|= ())); + assert_eq!( + Err(ENOSPC), + pool.alloc_area(nz::<1>(), Alignment::new::<32>()) + .map(|_| ()) + ); + + assert_eq!(2, pool.alloc_area(nz::<2>(), unaligned)?.start); + Ok(()) + } +} --=20 2.55.0