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From:   Valentin Schneider <valentin.schneider@arm.com>
To:     Barry Song <21cnbao@gmail.com>, dietmar.eggemann@arm.com,
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Subject: Re: [PATCH RESEND 1/3] topology: Represent clusters of CPUs within a die
In-Reply-To: <20210924085104.44806-2-21cnbao@gmail.com>
References: <20210924085104.44806-1-21cnbao@gmail.com> <20210924085104.44806-2-21cnbao@gmail.com>
Date:   Tue, 05 Oct 2021 17:33:59 +0100
Message-ID: <87o883l9c8.mognet@arm.com>
MIME-Version: 1.0
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On 24/09/21 20:51, Barry Song wrote:
>  void update_siblings_masks(unsigned int cpuid)
>  {
>       struct cpu_topology *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
> @@ -617,6 +622,11 @@ void update_siblings_masks(unsigned int cpuid)
>               if (cpuid_topo->package_id != cpu_topo->package_id)
>                       continue;
>
> +		if (cpuid_topo->cluster_id == cpu_topo->cluster_id) {
> +			cpumask_set_cpu(cpu, &cpuid_topo->cluster_sibling);
> +			cpumask_set_cpu(cpuid, &cpu_topo->cluster_sibling);
> +		}
> +

Hm so without cluster information (e.g. DT system), we have
->cluster_id=-1, we'll essentially copy the package mask into the cluster
mask.

The exposed cluster mask is still <= package mask which is sensible. Are we
fine with that, or do we need/want the mask to be empty in the -1 case? I'm
guessing userspace tools should check for either id!=-1 or if the exclusive
disjucntion of cluster vs package masks is non-empty.