Re: [Intel-gfx] [PATCH 25/25] drm/i915/execlists: Weak parallel submission support for execlists

John Harrison
2021-10-14T18:42:53Z

On 10/14/2021 10:20, 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.
>
> 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 | 56 ++++++++++++++++++-
> drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +
> .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 2 -
> 5 files changed, 64 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index fb33d0322960..35e87a7d0ea9 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 5634d14052bc..1bec92e1d8e6 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 bedb80057046..8cd986bdf26c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -927,8 +927,7 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
>
> static bool ctx_single_port_submission(const struct intel_context *ce)
> {
> - return (IS_ENABLED(CONFIG_DRM_I915_GVT) &&
> - intel_context_force_single_submission(ce));
> + return intel_context_force_single_submission(ce);
Does this change not affect all execlist operation rather than just
parallel submission?

> }
>
> static bool can_merge_ctx(const struct intel_context *prev,
> @@ -2598,6 +2597,58 @@ 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_engine_cs **siblings = NULL;
> + struct intel_context *parent = NULL, *ce, *err;
> + int i, j;
> +
> + GEM_BUG_ON(num_siblings != 1);
> +
> + siblings = kmalloc_array(num_siblings,
> + sizeof(*siblings),
> + GFP_KERNEL);
> + if (!siblings)
> + return ERR_PTR(-ENOMEM);
> +
> + for (i = 0; i < width; ++i) {
> + for (j = 0; j < num_siblings; ++j)
> + siblings[j] = engines[i * num_siblings + j];
What is the purpose of this array? The only usage that I can see is
siblings[0] on the line below. The rest of the entries never seem to be
used. So you could just replace that with 'engines[i * num_siblings]'
and drop the siblings array itself completely?

John.

> +
> + ce = intel_context_create(siblings[0]);
> + if (!ce) {
> + err = ERR_PTR(-ENOMEM);
> + 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);
> + intel_context_set_single_submission(parent);
> + for_each_child(parent, ce) {
> + intel_context_set_nopreempt(ce);
> + intel_context_set_single_submission(ce);
> + }
> +
> + kfree(siblings);
> + return parent;
> +
> +unwind:
> + if (parent)
> + intel_context_put(parent);
> + kfree(siblings);
> + return err;
> +}
> +
> static const struct intel_context_ops execlists_context_ops = {
> .flags = COPS_HAS_INFLIGHT,
>
> @@ -2616,6 +2667,7 @@ 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 56156cf18c41..70f4b309522d 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);
> 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 d7710debcd47..145ffe265305 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -2960,8 +2960,6 @@ 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);
> }