linux-kernel - Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer

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Message-ID: <3b389423-4bc7-0706-660f-dbddf8445abd@arm.com>
Date:   Mon, 13 Jan 2020 15:15:28 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>,
        "Zengtao (B)" <prime.zeng@...ilicon.com>,
        Morten Rasmussen <morten.rasmussen@....com>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Linuxarm <linuxarm@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts with
 lower layer

On 13/01/2020 14:49, Dietmar Eggemann wrote:
> LGTM. This code detects the issue in cpu_coregroup_mask(), which is the
> the cpumask function of the sched domain MC level struct
> sched_domain_topology_level of ARM64's (and other archs)
> default_topology[].
> I wonder how x86 copes with such a config error?
> Maybe they do it inside their cpu_coregroup_mask()?
> 
> 
> We could move validate_topology_spans() into the existing
> 
> for_each_cpu(i, cpu_map)
>     for_each_sd_topology(tl)
> 
> loop in build_sched_domains() saving some code?
> 

[...]

Yeah that should work. Folks might want to gate it under SCHED_DEBUG, but
that's another discussion.