Re: [PATCH v3 07/25] drm/xe: Update scheduler job layer to support PT jobs

["Summers, Stuart" <stuart.summers@intel.com>]

On Fri, 2026-02-27 at 17:34 -0800, Matthew Brost wrote:
> Update the scheduler job layer to support PT jobs. PT jobs are
> executed
> entirely on the CPU and do not require LRC fences or a batch address.
> Repurpose the LRC fence storage to hold PT‑job arguments and update
> the
> scheduler job layer to distinguish between PT jobs and jobs that
> require
> an LRC.
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_sched_job.c       | 92 ++++++++++++++++-------
> --
>  drivers/gpu/drm/xe/xe_sched_job_types.h | 31 ++++++++-
>  2 files changed, 88 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_sched_job.c
> b/drivers/gpu/drm/xe/xe_sched_job.c
> index ae5b38b2a884..a8ba7f90368f 100644
> --- a/drivers/gpu/drm/xe/xe_sched_job.c
> +++ b/drivers/gpu/drm/xe/xe_sched_job.c
> @@ -26,19 +26,22 @@ static struct kmem_cache
> *xe_sched_job_parallel_slab;
>  
>  int __init xe_sched_job_module_init(void)
>  {
> +       struct xe_sched_job *job;
> +       size_t size;
> +
> +       size = struct_size(job, ptrs, 1);

Nice..

>         xe_sched_job_slab =
> -               kmem_cache_create("xe_sched_job",
> -                                 sizeof(struct xe_sched_job) +
> -                                 sizeof(struct xe_job_ptrs), 0,
> +               kmem_cache_create("xe_sched_job", size, 0,
>                                   SLAB_HWCACHE_ALIGN, NULL);
>         if (!xe_sched_job_slab)
>                 return -ENOMEM;
>  
> +       size = max_t(size_t,
> +                    struct_size(job, ptrs,
> +                                XE_HW_ENGINE_MAX_INSTANCE),
> +                    struct_size(job, pt_update, 1));
>         xe_sched_job_parallel_slab =
> -               kmem_cache_create("xe_sched_job_parallel",
> -                                 sizeof(struct xe_sched_job) +
> -                                 sizeof(struct xe_job_ptrs) *
> -                                 XE_HW_ENGINE_MAX_INSTANCE, 0,
> +               kmem_cache_create("xe_sched_job_parallel", size, 0,
>                                   SLAB_HWCACHE_ALIGN, NULL);
>         if (!xe_sched_job_parallel_slab) {
>                 kmem_cache_destroy(xe_sched_job_slab);
> @@ -84,7 +87,7 @@ static void xe_sched_job_free_fences(struct
> xe_sched_job *job)
>  {
>         int i;
>  
> -       for (i = 0; i < job->q->width; ++i) {
> +       for (i = 0; !job->is_pt_job && i < job->q->width; ++i) {
>                 struct xe_job_ptrs *ptrs = &job->ptrs[i];
>  
>                 if (ptrs->lrc_fence)
> @@ -93,10 +96,23 @@ static void xe_sched_job_free_fences(struct
> xe_sched_job *job)
>         }
>  }
>  
> +/**
> + * xe_sched_job_create() - Create a scheduler job
> + * @q: exec queue to create the scheduler job for
> + * @batch: array of batch addresses for the job; must match the
> width of @q,
> + *         or NULL to indicate a PT job that does not require a
> batch address
> + *
> + * Create a scheduler job for submission.
> + *
> + * Context: Reclaim
> + *
> + * Return: a &xe_sched_job object on success, or an ERR_PTR on
> failure.
> + */
>  struct xe_sched_job *xe_sched_job_create(struct xe_exec_queue *q,
>                                          u64 *batch_addr)
>  {
>         bool is_migration = xe_sched_job_is_migration(q);
> +       struct xe_device *xe = gt_to_xe(q->gt);
>         struct xe_sched_job *job;
>         int err;
>         int i;
> @@ -105,6 +121,9 @@ struct xe_sched_job *xe_sched_job_create(struct
> xe_exec_queue *q,
>         /* only a kernel context can submit a vm-less job */
>         XE_WARN_ON(!q->vm && !(q->flags & EXEC_QUEUE_FLAG_KERNEL));
>  
> +       xe_assert(xe, batch_addr ||
> +                 q->flags & (EXEC_QUEUE_FLAG_VM |
> EXEC_QUEUE_FLAG_MIGRATE));

Ok..

> +
>         job = job_alloc(xe_exec_queue_is_parallel(q) ||
> is_migration);
>         if (!job)
>                 return ERR_PTR(-ENOMEM);
> @@ -119,34 +138,39 @@ struct xe_sched_job *xe_sched_job_create(struct
> xe_exec_queue *q,
>         if (err)
>                 goto err_free;
>  
> -       for (i = 0; i < q->width; ++i) {
> -               struct dma_fence *fence = xe_lrc_alloc_seqno_fence();
> -               struct dma_fence_chain *chain;
> -
> -               if (IS_ERR(fence)) {
> -                       err = PTR_ERR(fence);
> -                       goto err_sched_job;
> +       if (!batch_addr) {
> +               job->fence = dma_fence_get_stub();
> +               job->is_pt_job = true;
> +       } else {
> +               for (i = 0; i < q->width; ++i) {
> +                       struct dma_fence *fence =
> xe_lrc_alloc_seqno_fence();
> +                       struct dma_fence_chain *chain;
> +
> +                       if (IS_ERR(fence)) {
> +                               err = PTR_ERR(fence);
> +                               goto err_sched_job;
> +                       }
> +                       job->ptrs[i].lrc_fence = fence;
> +
> +                       if (i + 1 == q->width)
> +                               continue;
> +
> +                       chain = dma_fence_chain_alloc();
> +                       if (!chain) {
> +                               err = -ENOMEM;
> +                               goto err_sched_job;
> +                       }
> +                       job->ptrs[i].chain_fence = chain;
>                 }
> -               job->ptrs[i].lrc_fence = fence;
>  
> -               if (i + 1 == q->width)
> -                       continue;
> +               width = q->width;
> +               if (is_migration)
> +                       width = 2;
>  
> -               chain = dma_fence_chain_alloc();
> -               if (!chain) {
> -                       err = -ENOMEM;
> -                       goto err_sched_job;
> -               }
> -               job->ptrs[i].chain_fence = chain;
> +               for (i = 0; i < width; ++i)
> +                       job->ptrs[i].batch_addr = batch_addr[i];
>         }
>  
> -       width = q->width;
> -       if (is_migration)
> -               width = 2;
> -
> -       for (i = 0; i < width; ++i)
> -               job->ptrs[i].batch_addr = batch_addr[i];
> -
>         atomic_inc(&q->job_cnt);
>         xe_pm_runtime_get_noresume(job_to_xe(job));
>         trace_xe_sched_job_create(job);
> @@ -246,7 +270,7 @@ bool xe_sched_job_completed(struct xe_sched_job
> *job)
>  void xe_sched_job_arm(struct xe_sched_job *job)
>  {
>         struct xe_exec_queue *q = job->q;
> -       struct dma_fence *fence, *prev;
> +       struct dma_fence *fence = job->fence, *prev;

Looks like this was a bug where prev would be NULL in that first for
each queue width loop below? Would be nice for this to go into a
separate patch.

>         struct xe_vm *vm = q->vm;
>         u64 seqno = 0;
>         int i;
> @@ -266,6 +290,9 @@ void xe_sched_job_arm(struct xe_sched_job *job)
>                 job->ring_ops_flush_tlb = true;
>         }
>  
> +       if (job->is_pt_job)
> +               goto arm;
> +
>         /* Arm the pre-allocated fences */
>         for (i = 0; i < q->width; prev = fence, ++i) {

Can we either use the goto above or change this to align with what you
had earlier, something like:
for (i = 0; !job->is_pt_job && i < q->width; prev = fence, ++i) {

Just for consistency...

>                 struct dma_fence_chain *chain;
> @@ -286,6 +313,7 @@ void xe_sched_job_arm(struct xe_sched_job *job)
>                 fence = &chain->base;
>         }
>  
> +arm:
>         job->fence = dma_fence_get(fence);      /* Pairs with put in
> scheduler */
>         drm_sched_job_arm(&job->drm);
>  }
> diff --git a/drivers/gpu/drm/xe/xe_sched_job_types.h
> b/drivers/gpu/drm/xe/xe_sched_job_types.h
> index 13c2970e81a8..9be4e2c5989d 100644
> --- a/drivers/gpu/drm/xe/xe_sched_job_types.h
> +++ b/drivers/gpu/drm/xe/xe_sched_job_types.h
> @@ -10,10 +10,29 @@
>  
>  #include <drm/gpu_scheduler.h>
>  
> -struct xe_exec_queue;
>  struct dma_fence;
>  struct dma_fence_chain;
>  
> +struct xe_exec_queue;
> +struct xe_migrate_pt_update_ops;
> +struct xe_pt_job_ops;
> +struct xe_tile;
> +struct xe_vm;
> +
> +/**
> + * struct xe_pt_update_args - PT update arguments
> + */
> +struct xe_pt_update_args {
> +       /** @vm: VM which is being bound */
> +       struct xe_vm *vm;
> +       /** @tile: Tile which page tables belong to */
> +       struct xe_tile *tile;
> +       /** @ops: Migrate PT update ops */
> +       const struct xe_migrate_pt_update_ops *ops;
> +       /** @pt_job_ops: PT job ops state */
> +       struct xe_pt_job_ops *pt_job_ops;
> +};
> +
>  /**
>   * struct xe_job_ptrs - Per hw engine instance data
>   */
> @@ -69,8 +88,14 @@ struct xe_sched_job {
>         bool restore_replay;
>         /** @last_replay: last job being replayed */
>         bool last_replay;
> -       /** @ptrs: per instance pointers. */
> -       struct xe_job_ptrs ptrs[];
> +       /** @is_pt_job: is a PT job */
> +       bool is_pt_job;
> +       union {
> +               /** @ptrs: per instance pointers. */
> +               DECLARE_FLEX_ARRAY(struct xe_job_ptrs, ptrs);

Nice..

Thanks,
Stuart

> +               /** @pt_update: PT update arguments */
> +               DECLARE_FLEX_ARRAY(struct xe_pt_update_args,
> pt_update);
> +       };
>  };
>  
>  struct xe_sched_job_snapshot {