linux-kernel - [PATCH 1/2] sched/topology: Don't enable EAS on SMT systems

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Message-Id: <20200226164118.6405-2-valentin.schneider@arm.com>
Date:   Wed, 26 Feb 2020 16:41:17 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        morten.rasmussen@....com, qperret@...gle.com,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 1/2] sched/topology: Don't enable EAS on SMT systems

EAS already requires asymmetric CPU capacities to be enabled, and mixing
this with SMT is an aberration, but better be safe than sorry.

Signed-off-by: Valentin Schneider <valentin.schneider@....com>
---
 kernel/sched/topology.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 00911884b7e7..76cd0a370b9a 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -360,6 +360,10 @@ static bool build_perf_domains(const struct cpumask *cpu_map)
 		goto free;
 	}
 
+	/* EAS definitely does *not* handle SMT */
+	if (sched_smt_active())
+		goto free;
+
 	for_each_cpu(i, cpu_map) {
 		/* Skip already covered CPUs. */
 		if (find_pd(pd, i))
-- 
2.24.0