[PATCH v2] drm/amd/amdgpu: Add Annotations to Process Isolation functions

[Alex Deucher]

On Mon, Dec 2, 2024 at 11:42 AM Srinivasan Shanmugam
<srinivasan.shanmugam at amd.com> wrote:
>
> This update adds explanations to key functions that manage how the
> Kernel Fusion Driver (KFD) and Kernel Graphics Driver (KGD) share the
> GPU.
>
> amdgpu_gfx_enforce_isolation_wait_for_kfd: Controls the waiting period
> for KFD to ensure it takes turns with KGD in using the GPU. It uses a
> mutex to safely manage shared data, like timing and state, and tracks
> when KFD starts and stops waiting.
>
> amdgpu_gfx_enforce_isolation_ring_begin_use: Ensures KFD has enough time
> to run before new tasks are submitted to the GPU ring. It uses a mutex
> to synchronize access and may adjust the KFD scheduler.
>
> amdgpu_gfx_enforce_isolation_ring_end_use: Handles cleanup and state
> updates when finishing the use of a GPU ring. It may also adjust the KFD
> scheduler, using a mutex to manage shared data access.
>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
> Suggested-by: Alex Deucher <alexander.deucher at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
> v2:
>  - Incorporated feedbacks for function descriptions (Alex)
>
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c | 29 +++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> index e54f42e3797e..b1b133affbf9 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> @@ -1940,6 +1940,17 @@ void amdgpu_gfx_enforce_isolation_handler(struct work_struct *work)
>         mutex_unlock(&adev->enforce_isolation_mutex);
>  }
>
> +/**
> + * amdgpu_gfx_enforce_isolation_wait_for_kfd - Manage KFD wait period for process isolation
> + * @adev: amdgpu_device pointer
> + * @idx: Index of the GPU partition
> + *
> + * When kernel submissions come in, the jobs are given a time slice and once
> + * that time slice is up, if there are KFD user queues active, kernel
> + * submissions are blocked until KFD has had its time slice. Once the KFD time
> + * slice is up, KFD user queues are preempted and kernel submissions are
> + * unblocked and allowed to run again.
> + */
>  static void
>  amdgpu_gfx_enforce_isolation_wait_for_kfd(struct amdgpu_device *adev,
>                                           u32 idx)
> @@ -1985,6 +1996,15 @@ amdgpu_gfx_enforce_isolation_wait_for_kfd(struct amdgpu_device *adev,
>                 msleep(GFX_SLICE_PERIOD_MS);
>  }
>
> +/**
> + * amdgpu_gfx_enforce_isolation_ring_begin_use - Begin use of a ring with enforced isolation
> + * @ring: Pointer to the amdgpu_ring structure
> + *
> + * Ring begin_use helper implementation for gfx which serializes access to the
> + * gfx IP between kernel submission IOCTLs and KFD user queues when isolation
> + * enforcement is enabled. The kernel submission IOCTLs and KFD user queues
> + * each get a time slice when both are active.
> + */
>  void amdgpu_gfx_enforce_isolation_ring_begin_use(struct amdgpu_ring *ring)
>  {
>         struct amdgpu_device *adev = ring->adev;
> @@ -2012,6 +2032,15 @@ void amdgpu_gfx_enforce_isolation_ring_begin_use(struct amdgpu_ring *ring)
>         mutex_unlock(&adev->enforce_isolation_mutex);
>  }
>
> +/**
> + * amdgpu_gfx_enforce_isolation_ring_end_use - End use of a ring with enforced isolation
> + * @ring: Pointer to the amdgpu_ring structure
> + *
> + * Ring end_use helper implementation for gfx which serializes access to the
> + * gfx IP between kernel submission IOCTLs and KFD user queues when isolation
> + * enforcement is enabled. The kernel submission IOCTLs and KFD user queues
> + * each get a time slice when both are active.
> + */
>  void amdgpu_gfx_enforce_isolation_ring_end_use(struct amdgpu_ring *ring)
>  {
>         struct amdgpu_device *adev = ring->adev;
> --
> 2.34.1
>