[PATCH RFC 12/18] rust: drm: sched: Add GPU scheduler abstraction

Asahi Lina
2023-03-07T14:33:55Z

The GPU scheduler manages scheduling GPU jobs and dependencies between
them. This Rust abstraction allows Rust DRM drivers to use this
functionality.

Signed-off-by: Asahi Lina <lina@asahilina.net>
---
drivers/gpu/drm/Kconfig | 5 +
rust/bindings/bindings_helper.h | 1 +
rust/helpers.c | 6 +
rust/kernel/drm/mod.rs | 2 +
rust/kernel/drm/sched.rs | 358 ++++++++++++++++++++++++++++++++++++++++
5 files changed, 372 insertions(+)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 70a983a17ac2..8b5ad6aee126 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -39,6 +39,11 @@ config RUST_DRM_GEM_SHMEM_HELPER
depends on RUST_DRM
select DRM_GEM_SHMEM_HELPER

+config RUST_DRM_SCHED
+ bool
+ depends on RUST_DRM
+ select DRM_SCHED
+
config DRM_MIPI_DBI
tristate
depends on DRM
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index b6696011f3a4..dc01be08676e 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -13,6 +13,7 @@
#include <drm/drm_gem_shmem_helper.h>
#include <drm/drm_ioctl.h>
#include <drm/drm_syncobj.h>
+#include <drm/gpu_scheduler.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dma-fence.h>
diff --git a/rust/helpers.c b/rust/helpers.c
index 11965b1e2f4e..1b33ed602090 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -408,6 +408,12 @@ void rust_helper___spin_lock_init(spinlock_t *lock, const char *name,
}
EXPORT_SYMBOL_GPL(rust_helper___spin_lock_init);

+unsigned long rust_helper_msecs_to_jiffies(const unsigned int m)
+{
+ return msecs_to_jiffies(m);
+}
+EXPORT_SYMBOL_GPL(rust_helper_msecs_to_jiffies);
+
#ifdef CONFIG_DMA_SHARED_BUFFER

void rust_helper_dma_fence_get(struct dma_fence *fence)
diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs
index dae98826edfd..3ddf7712aab3 100644
--- a/rust/kernel/drm/mod.rs
+++ b/rust/kernel/drm/mod.rs
@@ -8,4 +8,6 @@ pub mod file;
pub mod gem;
pub mod ioctl;
pub mod mm;
+#[cfg(CONFIG_RUST_DRM_SCHED)]
+pub mod sched;
pub mod syncobj;
diff --git a/rust/kernel/drm/sched.rs b/rust/kernel/drm/sched.rs
new file mode 100644
index 000000000000..a5275cc16179
--- /dev/null
+++ b/rust/kernel/drm/sched.rs
@@ -0,0 +1,358 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+//! DRM Scheduler
+//!
+//! C header: [`include/linux/drm/gpu_scheduler.h`](../../../../include/linux/drm/gpu_scheduler.h)
+
+use crate::{
+ bindings, device,
+ dma_fence::*,
+ error::{to_result, Result},
+ prelude::*,
+ sync::{Arc, UniqueArc},
+};
+use alloc::boxed::Box;
+use core::marker::PhantomData;
+use core::mem::MaybeUninit;
+use core::ops::{Deref, DerefMut};
+use core::ptr::addr_of_mut;
+
+/// Scheduler status after timeout recovery
+#[repr(u32)]
+pub enum Status {
+ /// Device recovered from the timeout and can execute jobs again
+ Nominal = bindings::drm_gpu_sched_stat_DRM_GPU_SCHED_STAT_NOMINAL,
+ /// Device is no longer available
+ NoDevice = bindings::drm_gpu_sched_stat_DRM_GPU_SCHED_STAT_ENODEV,
+}
+
+/// Scheduler priorities
+#[repr(i32)]
+pub enum Priority {
+ /// Low userspace priority
+ Min = bindings::drm_sched_priority_DRM_SCHED_PRIORITY_MIN,
+ /// Normal userspace priority
+ Normal = bindings::drm_sched_priority_DRM_SCHED_PRIORITY_NORMAL,
+ /// High userspace priority
+ High = bindings::drm_sched_priority_DRM_SCHED_PRIORITY_HIGH,
+ /// Kernel priority (highest)
+ Kernel = bindings::drm_sched_priority_DRM_SCHED_PRIORITY_KERNEL,
+}
+
+/// Trait to be implemented by driver job objects.
+pub trait JobImpl: Sized {
+ /// Called when the scheduler is considering scheduling this job next, to get another Fence
+ /// for this job to block on. Once it returns None, run() may be called.
+ fn prepare(_job: &mut Job<Self>) -> Option<Fence> {
+ None // Equivalent to NULL function pointer
+ }
+
+ /// Called before job execution to check whether the hardware is free enough to run the job.
+ /// This can be used to implement more complex hardware resource policies than the hw_submission
+ /// limit.
+ fn can_run(_job: &mut Job<Self>) -> bool {
+ true
+ }
+
+ /// Called to execute the job once all of the dependencies have been resolved. This may be
+ /// called multiple times, if timed_out() has happened and drm_sched_job_recovery() decides
+ /// to try it again.
+ fn run(job: &mut Job<Self>) -> Result<Option<Fence>>;
+
+ /// Called when a job has taken too long to execute, to trigger GPU recovery.
+ ///
+ /// This method is called in a workqueue context.
+ fn timed_out(job: &mut Job<Self>) -> Status;
+}
+
+unsafe extern "C" fn prepare_job_cb<T: JobImpl>(
+ sched_job: *mut bindings::drm_sched_job,
+ _s_entity: *mut bindings::drm_sched_entity,
+) -> *mut bindings::dma_fence {
+ // SAFETY: All of our jobs are Job<T>.
+ let p = crate::container_of!(sched_job, Job<T>, job) as *mut Job<T>;
+
+ match T::prepare(unsafe { &mut *p }) {
+ None => core::ptr::null_mut(),
+ Some(fence) => fence.into_raw(),
+ }
+}
+
+unsafe extern "C" fn run_job_cb<T: JobImpl>(
+ sched_job: *mut bindings::drm_sched_job,
+) -> *mut bindings::dma_fence {
+ // SAFETY: All of our jobs are Job<T>.
+ let p = crate::container_of!(sched_job, Job<T>, job) as *mut Job<T>;
+
+ match T::run(unsafe { &mut *p }) {
+ Err(e) => e.to_ptr(),
+ Ok(None) => core::ptr::null_mut(),
+ Ok(Some(fence)) => fence.into_raw(),
+ }
+}
+
+unsafe extern "C" fn can_run_job_cb<T: JobImpl>(sched_job: *mut bindings::drm_sched_job) -> bool {
+ // SAFETY: All of our jobs are Job<T>.
+ let p = crate::container_of!(sched_job, Job<T>, job) as *mut Job<T>;
+
+ T::can_run(unsafe { &mut *p })
+}
+
+unsafe extern "C" fn timedout_job_cb<T: JobImpl>(
+ sched_job: *mut bindings::drm_sched_job,
+) -> bindings::drm_gpu_sched_stat {
+ // SAFETY: All of our jobs are Job<T>.
+ let p = crate::container_of!(sched_job, Job<T>, job) as *mut Job<T>;
+
+ T::timed_out(unsafe { &mut *p }) as bindings::drm_gpu_sched_stat
+}
+
+unsafe extern "C" fn free_job_cb<T: JobImpl>(sched_job: *mut bindings::drm_sched_job) {
+ // SAFETY: All of our jobs are Job<T>.
+ let p = crate::container_of!(sched_job, Job<T>, job) as *mut Job<T>;
+
+ // Convert the job back to a Box and drop it
+ // SAFETY: All of our Job<T>s are created inside a box.
+ unsafe { Box::from_raw(p) };
+}
+
+/// A DRM scheduler job.
+pub struct Job<T: JobImpl> {
+ job: bindings::drm_sched_job,
+ inner: T,
+}
+
+impl<T: JobImpl> Deref for Job<T> {
+ type Target = T;
+
+ fn deref(&self) -> &Self::Target {
+ &self.inner
+ }
+}
+
+impl<T: JobImpl> DerefMut for Job<T> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ &mut self.inner
+ }
+}
+
+impl<T: JobImpl> Drop for Job<T> {
+ fn drop(&mut self) {
+ // SAFETY: At this point the job has either been submitted and this is being called from
+ // `free_job_cb` above, or it hasn't and it is safe to call `drm_sched_job_cleanup`.
+ unsafe { bindings::drm_sched_job_cleanup(&mut self.job) };
+ }
+}
+
+/// A pending DRM scheduler job (not yet armed)
+pub struct PendingJob<'a, T: JobImpl>(Box<Job<T>>, PhantomData<&'a T>);
+
+impl<'a, T: JobImpl> PendingJob<'a, T> {
+ /// Add a fence as a dependency to the job
+ pub fn add_dependency(&mut self, fence: Fence) -> Result {
+ to_result(unsafe {
+ bindings::drm_sched_job_add_dependency(&mut self.0.job, fence.into_raw())
+ })
+ }
+
+ /// Arm the job to make it ready for execution
+ pub fn arm(mut self) -> ArmedJob<'a, T> {
+ unsafe { bindings::drm_sched_job_arm(&mut self.0.job) };
+ ArmedJob(self.0, PhantomData)
+ }
+}
+
+impl<'a, T: JobImpl> Deref for PendingJob<'a, T> {
+ type Target = Job<T>;
+
+ fn deref(&self) -> &Self::Target {
+ &self.0
+ }
+}
+
+impl<'a, T: JobImpl> DerefMut for PendingJob<'a, T> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ &mut self.0
+ }
+}
+
+/// An armed DRM scheduler job (not yet submitted)
+pub struct ArmedJob<'a, T: JobImpl>(Box<Job<T>>, PhantomData<&'a T>);
+
+impl<'a, T: JobImpl> ArmedJob<'a, T> {
+ /// Returns the job fences
+ pub fn fences(&self) -> JobFences<'_> {
+ JobFences(unsafe { &mut *self.0.job.s_fence })
+ }
+
+ /// Push the job for execution into the scheduler
+ pub fn push(self) {
+ // After this point, the job is submitted and owned by the scheduler
+ let ptr = match self {
+ ArmedJob(job, _) => Box::<Job<T>>::into_raw(job),
+ };
+
+ // SAFETY: We are passing in ownership of a valid Box raw pointer.
+ unsafe { bindings::drm_sched_entity_push_job(addr_of_mut!((*ptr).job)) };
+ }
+}
+impl<'a, T: JobImpl> Deref for ArmedJob<'a, T> {
+ type Target = Job<T>;
+
+ fn deref(&self) -> &Self::Target {
+ &self.0
+ }
+}
+
+impl<'a, T: JobImpl> DerefMut for ArmedJob<'a, T> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ &mut self.0
+ }
+}
+
+/// Reference to the bundle of fences attached to a DRM scheduler job
+pub struct JobFences<'a>(&'a mut bindings::drm_sched_fence);
+
+impl<'a> JobFences<'a> {
+ /// Returns a new reference to the job scheduled fence.
+ pub fn scheduled(&mut self) -> Fence {
+ unsafe { Fence::get_raw(&mut self.0.scheduled) }
+ }
+
+ /// Returns a new reference to the job finished fence.
+ pub fn finished(&mut self) -> Fence {
+ unsafe { Fence::get_raw(&mut self.0.finished) }
+ }
+}
+
+struct EntityInner<T: JobImpl> {
+ entity: bindings::drm_sched_entity,
+ // TODO: Allow users to share guilty flag between entities
+ sched: Arc<SchedulerInner<T>>,
+ guilty: bindings::atomic_t,
+ _p: PhantomData<T>,
+}
+
+impl<T: JobImpl> Drop for EntityInner<T> {
+ fn drop(&mut self) {
+ // SAFETY: The EntityInner is initialized. This will cancel/free all jobs.
+ unsafe { bindings::drm_sched_entity_destroy(&mut self.entity) };
+ }
+}
+
+// SAFETY: TODO
+unsafe impl<T: JobImpl> Sync for EntityInner<T> {}
+unsafe impl<T: JobImpl> Send for EntityInner<T> {}
+
+/// A DRM scheduler entity.
+pub struct Entity<T: JobImpl>(Pin<Box<EntityInner<T>>>);
+
+impl<T: JobImpl> Entity<T> {
+ /// Create a new scheduler entity.
+ pub fn new(sched: &Scheduler<T>, priority: Priority) -> Result<Self> {
+ let mut entity: Box<MaybeUninit<EntityInner<T>>> = Box::try_new_zeroed()?;
+
+ let mut sched_ptr = &sched.0.sched as *const _ as *mut _;
+
+ // SAFETY: The Box is allocated above and valid.
+ unsafe {
+ bindings::drm_sched_entity_init(
+ addr_of_mut!((*entity.as_mut_ptr()).entity),
+ priority as _,
+ &mut sched_ptr,
+ 1,
+ addr_of_mut!((*entity.as_mut_ptr()).guilty),
+ )
+ };
+
+ // SAFETY: The Box is allocated above and valid.
+ unsafe { addr_of_mut!((*entity.as_mut_ptr()).sched).write(sched.0.clone()) };
+
+ // SAFETY: entity is now initialized.
+ Ok(Self(Pin::from(unsafe { entity.assume_init() })))
+ }
+
+ /// Create a new job on this entity.
+ ///
+ /// The entity must outlive the pending job until it transitions into the submitted state,
+ /// after which the scheduler owns it.
+ pub fn new_job(&self, inner: T) -> Result<PendingJob<'_, T>> {
+ let mut job: Box<MaybeUninit<Job<T>>> = Box::try_new_zeroed()?;
+
+ // SAFETY: We hold a reference to the entity (which is a valid pointer),
+ // and the job object was just allocated above.
+ to_result(unsafe {
+ bindings::drm_sched_job_init(
+ addr_of_mut!((*job.as_mut_ptr()).job),
+ &self.0.as_ref().get_ref().entity as *const _ as *mut _,
+ core::ptr::null_mut(),
+ )
+ })?;
+
+ // SAFETY: The Box pointer is valid, and this initializes the inner member.
+ unsafe { addr_of_mut!((*job.as_mut_ptr()).inner).write(inner) };
+
+ // SAFETY: All fields of the Job<T> are now initialized.
+ Ok(PendingJob(unsafe { job.assume_init() }, PhantomData))
+ }
+}
+
+/// DRM scheduler inner data
+pub struct SchedulerInner<T: JobImpl> {
+ sched: bindings::drm_gpu_scheduler,
+ _p: PhantomData<T>,
+}
+
+impl<T: JobImpl> Drop for SchedulerInner<T> {
+ fn drop(&mut self) {
+ // SAFETY: The scheduler is valid. This assumes drm_sched_fini() will take care of
+ // freeing all in-progress jobs.
+ unsafe { bindings::drm_sched_fini(&mut self.sched) };
+ }
+}
+
+// SAFETY: TODO
+unsafe impl<T: JobImpl> Sync for SchedulerInner<T> {}
+unsafe impl<T: JobImpl> Send for SchedulerInner<T> {}
+
+/// A DRM Scheduler
+pub struct Scheduler<T: JobImpl>(Arc<SchedulerInner<T>>);
+
+impl<T: JobImpl> Scheduler<T> {
+ const OPS: bindings::drm_sched_backend_ops = bindings::drm_sched_backend_ops {
+ prepare_job: Some(prepare_job_cb::<T>),
+ can_run_job: Some(can_run_job_cb::<T>),
+ run_job: Some(run_job_cb::<T>),
+ timedout_job: Some(timedout_job_cb::<T>),
+ free_job: Some(free_job_cb::<T>),
+ };
+ /// Creates a new DRM Scheduler object
+ // TODO: Shared timeout workqueues & scores
+ pub fn new(
+ device: &impl device::RawDevice,
+ hw_submission: u32,
+ hang_limit: u32,
+ timeout_ms: usize,
+ name: &'static CStr,
+ ) -> Result<Scheduler<T>> {
+ let mut sched: UniqueArc<MaybeUninit<SchedulerInner<T>>> = UniqueArc::try_new_uninit()?;
+
+ // SAFETY: The drm_sched pointer is valid and pinned as it was just allocated above.
+ to_result(unsafe {
+ bindings::drm_sched_init(
+ addr_of_mut!((*sched.as_mut_ptr()).sched),
+ &Self::OPS,
+ hw_submission,
+ hang_limit,
+ bindings::msecs_to_jiffies(timeout_ms.try_into()?).try_into()?,
+ core::ptr::null_mut(),
+ core::ptr::null_mut(),
+ name.as_char_ptr(),
+ device.raw_device(),
+ )
+ })?;
+
+ // SAFETY: All fields of SchedulerInner are now initialized.
+ Ok(Scheduler(unsafe { sched.assume_init() }.into()))
+ }
+}

--
2.35.1