Re: [PATCH 2/2] drm/xe/oa/uapi: Allow preemption to be disabled on the stream exec queue

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Jun 26, 2024 at 11:18:17AM -0700, Ashutosh Dixit wrote:
> Mesa VK_KHR_performance_query use case requires preemption and timeslicing
> to be disabled for the stream exec queue. Implement this functionality
> here.
> 
> v2: Minor change to debug print to print both ret values (Umesh)
> 
> Acked-by: José Roberto de Souza <jose.souza@intel.com>

Acked-by: Matthew Brost <matthew.brost@intel.com>

> Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_oa.c       | 70 +++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/xe/xe_oa_types.h |  3 ++
>  include/uapi/drm/xe_drm.h        |  6 +++
>  3 files changed, 78 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_oa.c b/drivers/gpu/drm/xe/xe_oa.c
> index a68659fd5386..6cc3f0217341 100644
> --- a/drivers/gpu/drm/xe/xe_oa.c
> +++ b/drivers/gpu/drm/xe/xe_oa.c
> @@ -80,6 +80,7 @@ struct xe_oa_open_param {
>  	int engine_instance;
>  	struct xe_exec_queue *exec_q;
>  	struct xe_hw_engine *hwe;
> +	bool no_preempt;
>  };
>  
>  struct xe_oa_config_bo {
> @@ -1013,11 +1014,55 @@ static void xe_oa_stream_disable(struct xe_oa_stream *stream)
>  		hrtimer_cancel(&stream->poll_check_timer);
>  }
>  
> +static int xe_oa_enable_preempt_timeslice(struct xe_oa_stream *stream)
> +{
> +	struct xe_exec_queue *q = stream->exec_q;
> +	int ret1, ret2;
> +
> +	/* Best effort recovery: try to revert both to original, irrespective of error */
> +	ret1 = q->ops->set_timeslice(q, stream->hwe->eclass->sched_props.timeslice_us);
> +	ret2 = q->ops->set_preempt_timeout(q, stream->hwe->eclass->sched_props.preempt_timeout_us);
> +	if (ret1 || ret2)
> +		goto err;
> +	return 0;
> +err:
> +	drm_dbg(&stream->oa->xe->drm, "%s failed ret1 %d ret2 %d\n", __func__, ret1, ret2);
> +	return ret1 ?: ret2;
> +}
> +
> +static int xe_oa_disable_preempt_timeslice(struct xe_oa_stream *stream)
> +{
> +	struct xe_exec_queue *q = stream->exec_q;
> +	int ret;
> +
> +	/* Setting values to 0 will disable timeslice and preempt_timeout */
> +	ret = q->ops->set_timeslice(q, 0);
> +	if (ret)
> +		goto err;
> +
> +	ret = q->ops->set_preempt_timeout(q, 0);
> +	if (ret)
> +		goto err;
> +
> +	return 0;
> +err:
> +	xe_oa_enable_preempt_timeslice(stream);
> +	drm_dbg(&stream->oa->xe->drm, "%s failed %d\n", __func__, ret);
> +	return ret;
> +}
> +
>  static int xe_oa_enable_locked(struct xe_oa_stream *stream)
>  {
>  	if (stream->enabled)
>  		return 0;
>  
> +	if (stream->no_preempt) {
> +		int ret = xe_oa_disable_preempt_timeslice(stream);
> +
> +		if (ret)
> +			return ret;
> +	}
> +
>  	xe_oa_stream_enable(stream);
>  
>  	stream->enabled = true;
> @@ -1026,13 +1071,18 @@ static int xe_oa_enable_locked(struct xe_oa_stream *stream)
>  
>  static int xe_oa_disable_locked(struct xe_oa_stream *stream)
>  {
> +	int ret = 0;
> +
>  	if (!stream->enabled)
>  		return 0;
>  
>  	xe_oa_stream_disable(stream);
>  
> +	if (stream->no_preempt)
> +		ret = xe_oa_enable_preempt_timeslice(stream);
> +
>  	stream->enabled = false;
> -	return 0;
> +	return ret;
>  }
>  
>  static long xe_oa_config_locked(struct xe_oa_stream *stream, u64 arg)
> @@ -1307,6 +1357,7 @@ static int xe_oa_stream_init(struct xe_oa_stream *stream,
>  	stream->sample = param->sample;
>  	stream->periodic = param->period_exponent > 0;
>  	stream->period_exponent = param->period_exponent;
> +	stream->no_preempt = param->no_preempt;
>  
>  	/*
>  	 * For Xe2+, when overrun mode is enabled, there are no partial reports at the end
> @@ -1651,6 +1702,13 @@ static int xe_oa_set_prop_engine_instance(struct xe_oa *oa, u64 value,
>  	return 0;
>  }
>  
> +static int xe_oa_set_no_preempt(struct xe_oa *oa, u64 value,
> +				struct xe_oa_open_param *param)
> +{
> +	param->no_preempt = value;
> +	return 0;
> +}
> +
>  typedef int (*xe_oa_set_property_fn)(struct xe_oa *oa, u64 value,
>  				     struct xe_oa_open_param *param);
>  static const xe_oa_set_property_fn xe_oa_set_property_funcs[] = {
> @@ -1662,6 +1720,7 @@ static const xe_oa_set_property_fn xe_oa_set_property_funcs[] = {
>  	[DRM_XE_OA_PROPERTY_OA_DISABLED] = xe_oa_set_prop_disabled,
>  	[DRM_XE_OA_PROPERTY_EXEC_QUEUE_ID] = xe_oa_set_prop_exec_queue_id,
>  	[DRM_XE_OA_PROPERTY_OA_ENGINE_INSTANCE] = xe_oa_set_prop_engine_instance,
> +	[DRM_XE_OA_PROPERTY_NO_PREEMPT] = xe_oa_set_no_preempt,
>  };
>  
>  static int xe_oa_user_ext_set_property(struct xe_oa *oa, u64 extension,
> @@ -1766,6 +1825,15 @@ int xe_oa_stream_open_ioctl(struct drm_device *dev, u64 data, struct drm_file *f
>  	if (param.exec_q && !param.sample)
>  		privileged_op = false;
>  
> +	if (param.no_preempt) {
> +		if (!param.exec_q) {
> +			drm_dbg(&oa->xe->drm, "Preemption disable without exec_q!\n");
> +			ret = -EINVAL;
> +			goto err_exec_q;
> +		}
> +		privileged_op = true;
> +	}
> +
>  	if (privileged_op && xe_perf_stream_paranoid && !perfmon_capable()) {
>  		drm_dbg(&oa->xe->drm, "Insufficient privileges to open xe perf stream\n");
>  		ret = -EACCES;
> diff --git a/drivers/gpu/drm/xe/xe_oa_types.h b/drivers/gpu/drm/xe/xe_oa_types.h
> index 706d45577dae..540c3ec53a6d 100644
> --- a/drivers/gpu/drm/xe/xe_oa_types.h
> +++ b/drivers/gpu/drm/xe/xe_oa_types.h
> @@ -235,5 +235,8 @@ struct xe_oa_stream {
>  
>  	/** @oa_status: temporary storage for oa_status register value */
>  	u32 oa_status;
> +
> +	/** @no_preempt: Whether preemption and timeslicing is disabled for stream exec_q */
> +	u32 no_preempt;
>  };
>  #endif
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index b410553faa9b..12eaa8532b5c 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -1611,6 +1611,12 @@ enum drm_xe_oa_property_id {
>  	 * pass along with @DRM_XE_OA_PROPERTY_EXEC_QUEUE_ID or will default to 0.
>  	 */
>  	DRM_XE_OA_PROPERTY_OA_ENGINE_INSTANCE,
> +
> +	/**
> +	 * @DRM_XE_OA_PROPERTY_NO_PREEMPT: Allow preemption and timeslicing
> +	 * to be disabled for the stream exec queue.
> +	 */
> +	DRM_XE_OA_PROPERTY_NO_PREEMPT,
>  };
>  
>  /**
> -- 
> 2.41.0
>