drm/i915/gem: Disallow bonding of virtual engines (v3)

This adds a bunch of complexity which the media driver has never
actually used.  The media driver does technically bond a balanced engine
to another engine but the balanced engine only has one engine in the
sibling set.  This doesn't actually result in a virtual engine.

This functionality was originally added to handle cases where we may
have more than two video engines and media might want to load-balance
their bonded submits by, for instance, submitting to a balanced vcs0-1
as the primary and then vcs2-3 as the secondary.  However, no such
hardware has shipped thus far and, if we ever want to enable such
use-cases in the future, we'll use the up-and-coming parallel submit API
which targets GuC submission.

This makes I915_CONTEXT_ENGINES_EXT_BOND a total no-op.  We leave the
validation code in place in case we ever decide we want to do something
interesting with the bonding information.

v2 (Jason Ekstrand):
 - Don't delete quite as much code.

v3 (Tvrtko Ursulin):
 - Add some history to the commit message

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210708154835.528166-10-jason@jlekstrand.net

1 files changed, 0 insertions, 69 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
index 7dd7afccb3ad..98b256352c23 100644
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
@@ -182,18 +182,6 @@ struct virtual_engine {
 		int prio;
 	} nodes[I915_NUM_ENGINES];
 
-	/*
-	 * Keep track of bonded pairs -- restrictions upon on our selection
-	 * of physical engines any particular request may be submitted to.
-	 * If we receive a submit-fence from a master engine, we will only
-	 * use one of sibling_mask physical engines.
-	 */
-	struct ve_bond {
-		const struct intel_engine_cs *master;
-		intel_engine_mask_t sibling_mask;
-	} *bonds;
-	unsigned int num_bonds;
-
 	/* And finally, which physical engines this virtual engine maps onto. */
 	unsigned int num_siblings;
 	struct intel_engine_cs *siblings[];
@@ -3413,7 +3401,6 @@ static void rcu_virtual_context_destroy(struct work_struct *wrk)
 		i915_sched_engine_put(ve->base.sched_engine);
 	intel_engine_free_request_pool(&ve->base);
 
-	kfree(ve->bonds);
 	kfree(ve);
 }
 
@@ -3668,33 +3655,13 @@ unlock:
 	spin_unlock_irqrestore(&ve->base.sched_engine->lock, flags);
 }
 
-static struct ve_bond *
-virtual_find_bond(struct virtual_engine *ve,
-		  const struct intel_engine_cs *master)
-{
-	int i;
-
-	for (i = 0; i < ve->num_bonds; i++) {
-		if (ve->bonds[i].master == master)
-			return &ve->bonds[i];
-	}
-
-	return NULL;
-}
-
 static void
 virtual_bond_execute(struct i915_request *rq, struct dma_fence *signal)
 {
-	struct virtual_engine *ve = to_virtual_engine(rq->engine);
 	intel_engine_mask_t allowed, exec;
-	struct ve_bond *bond;
 
 	allowed = ~to_request(signal)->engine->mask;
 
-	bond = virtual_find_bond(ve, to_request(signal)->engine);
-	if (bond)
-		allowed &= bond->sibling_mask;
-
 	/* Restrict the bonded request to run on only the available engines */
 	exec = READ_ONCE(rq->execution_mask);
 	while (!try_cmpxchg(&rq->execution_mask, &exec, exec & allowed))
@@ -3850,42 +3817,6 @@ err_put:
 	return ERR_PTR(err);
 }
 
-int intel_virtual_engine_attach_bond(struct intel_engine_cs *engine,
-				     const struct intel_engine_cs *master,
-				     const struct intel_engine_cs *sibling)
-{
-	struct virtual_engine *ve = to_virtual_engine(engine);
-	struct ve_bond *bond;
-	int n;
-
-	/* Sanity check the sibling is part of the virtual engine */
-	for (n = 0; n < ve->num_siblings; n++)
-		if (sibling == ve->siblings[n])
-			break;
-	if (n == ve->num_siblings)
-		return -EINVAL;
-
-	bond = virtual_find_bond(ve, master);
-	if (bond) {
-		bond->sibling_mask |= sibling->mask;
-		return 0;
-	}
-
-	bond = krealloc(ve->bonds,
-			sizeof(*bond) * (ve->num_bonds + 1),
-			GFP_KERNEL);
-	if (!bond)
-		return -ENOMEM;
-
-	bond[ve->num_bonds].master = master;
-	bond[ve->num_bonds].sibling_mask = sibling->mask;
-
-	ve->bonds = bond;
-	ve->num_bonds++;
-
-	return 0;
-}
-
 void intel_execlists_show_requests(struct intel_engine_cs *engine,
 				   struct drm_printer *m,
 				   void (*show_request)(struct drm_printer *m,