[RFC v1 3/9] drm/xe/hw_engine_group: Register hw engine group's exec queues

[Matthew Brost]

On Wed, Jul 17, 2024 at 03:07:24PM +0200, Francois Dugast wrote:
> Add helpers to safely add and delete the exec queues attached to a hw
> engine group, and make use them at the time of creation and destruction
> of the exec queues. Keeping track of them is required to control the
> execution mode of the hw engine group.
> 

Missed a few more things...

> Signed-off-by: Francois Dugast <francois.dugast at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_exec_queue.c |  7 +++++
>  drivers/gpu/drm/xe/xe_hw_engine.c  | 45 ++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_hw_engine.h  |  4 +++
>  3 files changed, 56 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
> index 0ba37835849b..645423a63434 100644
> --- a/drivers/gpu/drm/xe/xe_exec_queue.c
> +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
> @@ -192,6 +192,9 @@ void xe_exec_queue_destroy(struct kref *ref)
>  			xe_exec_queue_put(eq);
>  	}
>  
> +	if (q->vm)

I think this code path can be called GSC exec queues which don't have a
q->hwe->hw_engine_group. So I think:

if (q->vm && q->hwe->hw_engine_group)
	xe_hw_engine_group_del_exec_queue(q->hwe->hw_engine_group, q);

> +		xe_hw_engine_group_del_exec_queue(q->hwe->hw_engine_group, q);
> +
>  	q->ops->fini(q);
>  }
>  
> @@ -640,6 +643,10 @@ int xe_exec_queue_create_ioctl(struct drm_device *dev, void *data,
>  			if (XE_IOCTL_DBG(xe, err))
>  				goto put_exec_queue;
>  		}
> +
> +		err = xe_hw_engine_group_add_exec_queue(q->hwe->hw_engine_group, q);

So this only called on non-VM bind exec queues. I think techincally this
wrong as VM bind exec queues can use dma-fences plus the copy engine. I
plan dropping the copy engine for these [1] and I don't think it worth
fixing VM bind path with mode switching if we only are going to drop
this requirement soon. Let me just respin [1] and hopefully we can
prioritize though reviews so these two series land at roughly the same
time. 

[1] https://patchwork.freedesktop.org/patch/582003/?series=125608&rev=5

> +		if (err)
> +			goto put_exec_queue;
>  	}
>  
>  	mutex_lock(&xef->exec_queue.lock);
> diff --git a/drivers/gpu/drm/xe/xe_hw_engine.c b/drivers/gpu/drm/xe/xe_hw_engine.c
> index f8df85d25617..4dcc885a55c8 100644
> --- a/drivers/gpu/drm/xe/xe_hw_engine.c
> +++ b/drivers/gpu/drm/xe/xe_hw_engine.c
> @@ -1178,3 +1178,48 @@ u64 xe_hw_engine_read_timestamp(struct xe_hw_engine *hwe)
>  {
>  	return xe_mmio_read64_2x32(hwe->gt, RING_TIMESTAMP(hwe->mmio_base));
>  }
> +
> +/**
> + * xe_hw_engine_group_add_exec_queue() - Add an exec queue to a hw engine group
> + * @group: The hw engine group
> + * @q: The exec_queue
> + *
> + * Return: 0 on success,
> + *	    -EINTR if the lock could not be acquired
> + */
> +int xe_hw_engine_group_add_exec_queue(struct xe_hw_engine_group *group, struct xe_exec_queue *q)
> +{
> +	int err;
> +

Also assert here this is not a VM bind queue (e.g. EXEC_QUEUE_FLAG_VM is
clear).

> +	err = down_write_killable(&group->mode_sem);
> +	if (err)
> +		return err;
> +
> +	list_add(&q->hw_engine_group_link, &group->exec_queue_list);

I don't see where INIT_LIST_HEAD is called on group->exec_queue_list. I
think that should unconditionally be done in __xe_exec_queue_alloc.

Matt

> +	up_write(&group->mode_sem);
> +
> +	return 0;
> +}
> +
> +/**
> + * xe_hw_engine_group_del_exec_queue() - Delete an exec queue from a hw engine group
> + * @group: The hw engine group
> + * @q: The exec_queue
> + *
> + * Return: 0 on success,
> + *	    -EINTR if the lock could not be acquired
> + */
> +int xe_hw_engine_group_del_exec_queue(struct xe_hw_engine_group *group, struct xe_exec_queue *q)
> +{
> +	int err;
> +
> +	err = down_write_killable(&group->mode_sem);
> +	if (err)
> +		return err;
> +
> +	if (!list_empty(&group->exec_queue_list))
> +		list_del(&q->hw_engine_group_link);
> +	up_write(&group->mode_sem);
> +
> +	return 0;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_hw_engine.h b/drivers/gpu/drm/xe/xe_hw_engine.h
> index 7f2d27c0ba1a..ce59d83a75ad 100644
> --- a/drivers/gpu/drm/xe/xe_hw_engine.h
> +++ b/drivers/gpu/drm/xe/xe_hw_engine.h
> @@ -9,6 +9,7 @@
>  #include "xe_hw_engine_types.h"
>  
>  struct drm_printer;
> +struct xe_exec_queue;
>  
>  #ifdef CONFIG_DRM_XE_JOB_TIMEOUT_MIN
>  #define XE_HW_ENGINE_JOB_TIMEOUT_MIN CONFIG_DRM_XE_JOB_TIMEOUT_MIN
> @@ -70,4 +71,7 @@ static inline bool xe_hw_engine_is_valid(struct xe_hw_engine *hwe)
>  const char *xe_hw_engine_class_to_str(enum xe_engine_class class);
>  u64 xe_hw_engine_read_timestamp(struct xe_hw_engine *hwe);
>  
> +int xe_hw_engine_group_add_exec_queue(struct xe_hw_engine_group *group, struct xe_exec_queue *q);
> +int xe_hw_engine_group_del_exec_queue(struct xe_hw_engine_group *group, struct xe_exec_queue *q);
> +
>  #endif
> -- 
> 2.43.0
>