Re: [Intel-gfx] [PATCH] drm/i915/execlists: Weak parallel submission support for execlists

[John Harrison <john.c.harrison@intel.com>]

On 11/11/2021 13:20, Matthew Brost wrote:
> A weak implementation of parallel submission (multi-bb execbuf IOCTL) for
> execlists. Doing as little as possible to support this interface for
> execlists - basically just passing submit fences between each request
> generated and virtual engines are not allowed. This is on par with what
> is there for the existing (hopefully soon deprecated) bonding interface.
>
> We perma-pin these execlists contexts to align with GuC implementation.
>
> v2:
>   (John Harrison)
>    - Drop siblings array as num_siblings must be 1
> v3:
>   (John Harrison)
>    - Drop single submission
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_context.c   | 10 +++--
>   drivers/gpu/drm/i915/gt/intel_context.c       |  4 +-
>   .../drm/i915/gt/intel_execlists_submission.c  | 40 +++++++++++++++++++
>   drivers/gpu/drm/i915/gt/intel_lrc.c           |  2 +
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c |  2 -
>   5 files changed, 50 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index ebd775cb1661c..d7bf6c8f70b7b 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -570,10 +570,6 @@ set_proto_ctx_engines_parallel_submit(struct i915_user_extension __user *base,
>   	struct intel_engine_cs **siblings = NULL;
>   	intel_engine_mask_t prev_mask;
>   
> -	/* FIXME: This is NIY for execlists */
> -	if (!(intel_uc_uses_guc_submission(&i915->gt.uc)))
> -		return -ENODEV;
> -
>   	if (get_user(slot, &ext->engine_index))
>   		return -EFAULT;
>   
> @@ -583,6 +579,12 @@ set_proto_ctx_engines_parallel_submit(struct i915_user_extension __user *base,
>   	if (get_user(num_siblings, &ext->num_siblings))
>   		return -EFAULT;
>   
> +	if (!intel_uc_uses_guc_submission(&i915->gt.uc) && num_siblings != 1) {
> +		drm_dbg(&i915->drm, "Only 1 sibling (%d) supported in non-GuC mode\n",
> +			num_siblings);
> +		return -EINVAL;
> +	}
> +
>   	if (slot >= set->num_engines) {
>   		drm_dbg(&i915->drm, "Invalid placement value, %d >= %d\n",
>   			slot, set->num_engines);
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> index 5634d14052bc9..1bec92e1d8e63 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.c
> +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> @@ -79,7 +79,8 @@ static int intel_context_active_acquire(struct intel_context *ce)
>   
>   	__i915_active_acquire(&ce->active);
>   
> -	if (intel_context_is_barrier(ce) || intel_engine_uses_guc(ce->engine))
> +	if (intel_context_is_barrier(ce) || intel_engine_uses_guc(ce->engine) ||
> +	    intel_context_is_parallel(ce))
>   		return 0;
>   
>   	/* Preallocate tracking nodes */
> @@ -563,7 +564,6 @@ void intel_context_bind_parent_child(struct intel_context *parent,
>   	 * Callers responsibility to validate that this function is used
>   	 * correctly but we use GEM_BUG_ON here ensure that they do.
>   	 */
> -	GEM_BUG_ON(!intel_engine_uses_guc(parent->engine));
>   	GEM_BUG_ON(intel_context_is_pinned(parent));
>   	GEM_BUG_ON(intel_context_is_child(parent));
>   	GEM_BUG_ON(intel_context_is_pinned(child));
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index ca03880fa7e49..5fd49ee47096d 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -2598,6 +2598,45 @@ static void execlists_context_cancel_request(struct intel_context *ce,
>   				      current->comm);
>   }
>   
> +static struct intel_context *
> +execlists_create_parallel(struct intel_engine_cs **engines,
> +			  unsigned int num_siblings,
> +			  unsigned int width)
> +{
> +	struct intel_context *parent = NULL, *ce, *err;
> +	int i;
> +
> +	GEM_BUG_ON(num_siblings != 1);
> +
> +	for (i = 0; i < width; ++i) {
> +		ce = intel_context_create(engines[i]);
> +		if (!ce) {
> +			err = ERR_PTR(-ENOMEM);
intel_context_create already checks for null and returns -ENOMEM. This 
needs to check for IS_ERR(ce).

> +			goto unwind;
> +		}
> +
> +		if (i == 0)
> +			parent = ce;
> +		else
> +			intel_context_bind_parent_child(parent, ce);
> +	}
> +
> +	parent->parallel.fence_context = dma_fence_context_alloc(1);
> +
> +	intel_context_set_nopreempt(parent);
> +	for_each_child(parent, ce) {
> +		intel_context_set_nopreempt(ce);
> +		intel_context_set_single_submission(ce);
I thought the single submission thing wasn't wanted anymore?

> +	}
> +
> +	return parent;
> +
> +unwind:
> +	if (parent)
> +		intel_context_put(parent);
> +	return err;
> +}
> +
>   static const struct intel_context_ops execlists_context_ops = {
>   	.flags = COPS_HAS_INFLIGHT,
>   
> @@ -2616,6 +2655,7 @@ static const struct intel_context_ops execlists_context_ops = {
>   	.reset = lrc_reset,
>   	.destroy = lrc_destroy,
>   
> +	.create_parallel = execlists_create_parallel,
>   	.create_virtual = execlists_create_virtual,
>   };
>   
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 56156cf18c413..70f4b309522d3 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1065,6 +1065,8 @@ lrc_pin(struct intel_context *ce,
>   
>   void lrc_unpin(struct intel_context *ce)
>   {
> +	if (unlikely(ce->parallel.last_rq))
> +		i915_request_put(ce->parallel.last_rq);
Should set this to null after to prevent the possibility of a double put?

John.

>   	check_redzone((void *)ce->lrc_reg_state - LRC_STATE_OFFSET,
>   		      ce->engine);
>   }
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 5cc49c0b38897..cd1784953d679 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -3235,8 +3235,6 @@ static void guc_parent_context_unpin(struct intel_context *ce)
>   	GEM_BUG_ON(!intel_context_is_parent(ce));
>   	GEM_BUG_ON(!intel_engine_is_virtual(ce->engine));
>   
> -	if (ce->parallel.last_rq)
> -		i915_request_put(ce->parallel.last_rq);
>   	unpin_guc_id(guc, ce);
>   	lrc_unpin(ce);
>   }