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Date:   Thu, 27 Feb 2020 13:00:01 +0000
From:   Quentin Perret <qperret@google.com>
To:     Valentin Schneider <valentin.schneider@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        morten.rasmussen@arm.com,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>, kernel-team@android.com
Subject: Re: [PATCH 1/2] sched/topology: Don't enable EAS on SMT systems
Message-ID: <20200227130001.GA107011@google.com>
References: <20200226164118.6405-1-valentin.schneider@arm.com>
 <20200226164118.6405-2-valentin.schneider@arm.com>
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On Wednesday 26 Feb 2020 at 16:41:17 (+0000), Valentin Schneider wrote:
> 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@arm.com>

Acked-by: Quentin Perret <qperret@google.com>

Thanks,
Quentin

> ---
>  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
>