On Tue, 05 May 2026 13:29:37 +0000 Alice Ryhl <[email protected]> wrote:
> This adds support for simple usage of drm_gpuvm_exec() for locking all > of the dma reservations and adding fences to them. For more complex > usage that does not involve locking all reservations, it is expected > that the ww-mutex abstractions will be used instead. > > Signed-off-by: Alice Ryhl <[email protected]> > --- > rust/bindings/bindings_helper.h | 2 ++ > rust/helpers/drm_gpuvm.c | 6 ++++ > rust/kernel/dma_buf/mod.rs | 17 ++++++++++ > rust/kernel/drm/gpuvm/mod.rs | 71 > +++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 96 insertions(+) > > diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h > index 1124785e210b..3978682a6f2e 100644 > --- a/rust/bindings/bindings_helper.h > +++ b/rust/bindings/bindings_helper.h > @@ -151,6 +151,8 @@ 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; > > +const u32 RUST_CONST_HELPER_DRM_EXEC_INTERRUPTIBLE_WAIT = > DRM_EXEC_INTERRUPTIBLE_WAIT; > + > #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; > diff --git a/rust/helpers/drm_gpuvm.c b/rust/helpers/drm_gpuvm.c > index 4130b6325213..30fb1777fbf2 100644 > --- a/rust/helpers/drm_gpuvm.c > +++ b/rust/helpers/drm_gpuvm.c > @@ -23,4 +23,10 @@ bool rust_helper_drm_gpuvm_is_extobj(struct drm_gpuvm > *gpuvm, > return drm_gpuvm_is_extobj(gpuvm, obj); > } > > +__rust_helper > +void rust_helper_drm_gpuvm_exec_unlock(struct drm_gpuvm_exec *vm_exec) > +{ > + drm_gpuvm_exec_unlock(vm_exec); > +} > + > #endif // CONFIG_RUST_DRM_GPUVM > diff --git a/rust/kernel/dma_buf/mod.rs b/rust/kernel/dma_buf/mod.rs > index b66e747c35ad..234936ba8265 100644 > --- a/rust/kernel/dma_buf/mod.rs > +++ b/rust/kernel/dma_buf/mod.rs > @@ -5,3 +5,20 @@ > pub mod dma_fence; > > pub use self::dma_fence::Fence; > + > +/// How the fences from a `dma_resv` obj are used. > +/// > +/// Please see [the C-side documentation][dma_resv_usage] for more details. > +/// > +/// [dma_resv_usage]: > https://docs.kernel.org/driver-api/dma-buf.html#c.dma_resv_usage > +#[repr(u32)] > +pub enum DmaResvUsage { > + /// For in kernel memory management only (e.g. copying, clearing memory). > + Kernel = bindings::dma_resv_usage_DMA_RESV_USAGE_KERNEL, > + /// Implicit write synchronization for userspace submissions. > + Write = bindings::dma_resv_usage_DMA_RESV_USAGE_WRITE, > + /// Implicit read synchronization for userspace submissions. > + Read = bindings::dma_resv_usage_DMA_RESV_USAGE_READ, > + /// No implicit sync (e.g. preemption fences, page table updates, TLB > flushes). > + Bookkeep = bindings::dma_resv_usage_DMA_RESV_USAGE_BOOKKEEP, > +} > diff --git a/rust/kernel/drm/gpuvm/mod.rs b/rust/kernel/drm/gpuvm/mod.rs > index ae58f6f667c1..a52fb25f22ff 100644 > --- a/rust/kernel/drm/gpuvm/mod.rs > +++ b/rust/kernel/drm/gpuvm/mod.rs > @@ -16,6 +16,7 @@ > Flags as AllocFlags, // > }, > bindings, > + dma_buf::{DmaResvUsage, Fence}, This can be handled vertically. > drm, > drm::gem::IntoGEMObject, > error::to_result, > @@ -216,6 +217,30 @@ pub fn obtain( > Ok(GpuVmBoAlloc::new(self, obj, data)?.obtain()) > } > > + /// Prepare this GPUVM. > + /// > + /// The parameter indicates how many fences to preallocate space for. > + #[inline] > + pub fn prepare(&self, num_fences: u32) -> impl PinInit<GpuVmExec<'_, T>, > Error> { > + try_pin_init!(GpuVmExec { > + exec <- Opaque::try_ffi_init(|exec: *mut > bindings::drm_gpuvm_exec| { > + // SAFETY: exec is valid but unused memory, so we can write. > + unsafe { > + ptr::write_bytes(exec, 0u8, 1usize); > + ptr::write(&raw mut (*exec).vm, self.as_raw()); > + ptr::write(&raw mut (*exec).flags, > bindings::DRM_EXEC_INTERRUPTIBLE_WAIT); > + ptr::write(&raw mut (*exec).num_fences, num_fences); > + } > + > + // SAFETY: If successful, this `struct drm_gpuvm_exec` > remains valid until this is > + // unlocked because it's pinned and unlocks it in drop. The > contained pointer to > + // `self` remains valid because `GpuVmExec` borrows from > `self`. > + to_result(unsafe { bindings::drm_gpuvm_exec_lock(exec) }) > + }), > + _gpuvm: PhantomData, > + }) > + } > + > /// Clean up buffer objects that are no longer used. > #[inline] > pub fn deferred_cleanup(&self) { > @@ -326,3 +351,49 @@ fn deref(&self) -> &GpuVm<T> { > &self.0 > } > } > + > +/// The exec token for preparing the objects. > +/// > +/// # Invariants > +/// > +/// Owns a GPUVM exec context. > +#[pin_data(PinnedDrop)] > +pub struct GpuVmExec<'vm, T: DriverGpuVm> { > + #[pin] > + exec: Opaque<bindings::drm_gpuvm_exec>, > + _gpuvm: PhantomData<&'vm mut GpuVm<T>>, > +} > + > +impl<'vm, T: DriverGpuVm> GpuVmExec<'vm, T> { > + /// Add a fence. > + /// > + /// The caller must ensure that the preallocated space for fences is > sufficient. > + #[inline] > + pub fn resv_add_fence( > + &self, > + fence: &Fence, > + private_usage: DmaResvUsage, > + extobj_usage: DmaResvUsage, > + ) { > + // SAFETY: This method takes a refcount on the fence, so it's only > required to be valid for > + // the duration of this method. If there is not enough space for the > pre-allocated fence, > + // then this leads to a BUG_ON() but does not trigger UB. Did you think about tracking the space of fences? We can store num_fences from prepare and a counter added_fences then compare them in this function to avoid this risk. > + unsafe { > + bindings::drm_gpuvm_resv_add_fence( > + (*self.exec.get()).vm, > + &raw mut (*self.exec.get()).exec, > + fence.as_raw(), > + private_usage as u32, > + extobj_usage as u32, > + ) > + } > + } > +} > + > +#[pinned_drop] > +impl<'vm, T: DriverGpuVm> PinnedDrop for GpuVmExec<'vm, T> { > + fn drop(self: Pin<&mut Self>) { > + // SAFETY: We hold the lock, so it's safe to unlock. > + unsafe { bindings::drm_gpuvm_exec_unlock(self.exec.get()) }; > + } > +} > > -- > 2.54.0.545.g6539524ca2-goog >
