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References: <20230126184157.27626-1-tony.luck@intel.com> <20230126184157.27626-8-tony.luck@intel.com>
In-Reply-To: <20230126184157.27626-8-tony.luck@intel.com>
From:   Peter Newman <peternewman@google.com>
Date:   Mon, 27 Feb 2023 14:30:38 +0100
Message-ID: <CALPaoCgnOWLdEqKtonNeq+d_Fj0yr3Y7tgwwmAHmuhL5xBhqyg@mail.gmail.com>
Subject: Re: [PATCH 7/7] x86/resctrl: Determine if Sub-NUMA Cluster is enabled
 and initialize.
To:     Tony Luck <tony.luck@intel.com>
Cc:     Fenghua Yu <fenghua.yu@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Jonathan Corbet <corbet@lwn.net>, x86@kernel.org,
        Shaopeng Tan <tan.shaopeng@fujitsu.com>,
        James Morse <james.morse@arm.com>,
        Jamie Iles <quic_jiles@quicinc.com>,
        Babu Moger <babu.moger@amd.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, patches@lists.linux.dev
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Hi Tony,

On Thu, Jan 26, 2023 at 7:42=E2=80=AFPM Tony Luck <tony.luck@intel.com> wro=
te:
> +static __init int find_snc_ways(void)
> +{
> +       unsigned long *node_caches;
> +       int cpu, node, ret;
> +
> +       node_caches =3D kcalloc(BITS_TO_LONGS(nr_node_ids), sizeof(*node_=
caches), GFP_KERNEL);
> +       if (!node_caches)
> +               return 1;
> +
> +       cpus_read_lock();
> +       for_each_node(node) {

Someone tried this patch on a machine with a CPU-less node...

We need to check for this:

+               if (cpumask_empty(cpumask_of_node(node)))
+                       continue;

> +               cpu =3D cpumask_first(cpumask_of_node(node));
> +               set_bit(get_cpu_cacheinfo_id(cpu, 3), node_caches);
> +       }
> +       cpus_read_unlock();

Thanks!
-Peter