From 5f21529a36bb26fab1bb75f89dde650d05afbf6e Mon Sep 17 00:00:00 2001
From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Date: Fri, 10 Sep 2021 18:18:15 -0700
Subject: [PATCH] sched/topology: Introduce sched_group::flags

References: jsc#SLE-18889
Patch-mainline: v5.16-rc1
Git-commit: 16d364ba6ef2aa59b409df70682770f3ed23f7c0

There exist situations in which the load balance needs to know the
properties of the CPUs in a scheduling group. When using asymmetric
packing, for instance, the load balancer needs to know not only the
state of dst_cpu but also of its SMT siblings, if any.

Use the flags of the child scheduling domains to initialize scheduling
group flags. This will reflect the properties of the CPUs in the
group.

A subsequent changeset will make use of these new flags. No functional
changes are introduced.

Originally-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-3-ricardo.neri-calderon@linux.intel.com
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 kernel/sched/sched.h    |  1 +
 kernel/sched/topology.c | 21 ++++++++++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 5dbfb349cbe2..fe5ccb484fde 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1805,6 +1805,7 @@ struct sched_group {
 	unsigned int		group_weight;
 	struct sched_group_capacity *sgc;
 	int			asym_prefer_cpu;	/* CPU of highest priority in group */
+	int			flags;
 
 	/*
 	 * The CPUs this group covers.
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 4e8698e62f07..c56faae461d9 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -716,8 +716,20 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
 		tmp = sd;
 		sd = sd->parent;
 		destroy_sched_domain(tmp);
-		if (sd)
+		if (sd) {
+			struct sched_group *sg = sd->groups;
+
+			/*
+			 * sched groups hold the flags of the child sched
+			 * domain for convenience. Clear such flags since
+			 * the child is being destroyed.
+			 */
+			do {
+				sg->flags = 0;
+			} while (sg != sd->groups);
+
 			sd->child = NULL;
+		}
 	}
 
 	for (tmp = sd; tmp; tmp = tmp->parent)
@@ -916,10 +928,12 @@ build_group_from_child_sched_domain(struct sched_domain *sd, int cpu)
 		return NULL;
 
 	sg_span = sched_group_span(sg);
-	if (sd->child)
+	if (sd->child) {
 		cpumask_copy(sg_span, sched_domain_span(sd->child));
-	else
+		sg->flags = sd->child->flags;
+	} else {
 		cpumask_copy(sg_span, sched_domain_span(sd));
+	}
 
 	atomic_inc(&sg->ref);
 	return sg;
@@ -1169,6 +1183,7 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd)
 	if (child) {
 		cpumask_copy(sched_group_span(sg), sched_domain_span(child));
 		cpumask_copy(group_balance_mask(sg), sched_group_span(sg));
+		sg->flags = child->flags;
 	} else {
 		cpumask_set_cpu(cpu, sched_group_span(sg));
 		cpumask_set_cpu(cpu, group_balance_mask(sg));