linux-kernel - Re: [PATCH 7/7] x86/resctrl: Determine if Sub-NUMA Cluster is enabled and initialize.

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Message-ID: <CALPaoCgnOWLdEqKtonNeq+d_Fj0yr3Y7tgwwmAHmuhL5xBhqyg@mail.gmail.com>
Date:   Mon, 27 Feb 2023 14:30:38 +0100
From:   Peter Newman <peternewman@...gle.com>
To:     Tony Luck <tony.luck@...el.com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Jonathan Corbet <corbet@....net>, x86@...nel.org,
        Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Babu Moger <babu.moger@....com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH 7/7] x86/resctrl: Determine if Sub-NUMA Cluster is enabled
 and initialize.

Hi Tony,

On Thu, Jan 26, 2023 at 7:42 PM Tony Luck <tony.luck@...el.com> wrote:
> +static __init int find_snc_ways(void)
> +{
> +       unsigned long *node_caches;
> +       int cpu, node, ret;
> +
> +       node_caches = 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 = cpumask_first(cpumask_of_node(node));
> +               set_bit(get_cpu_cacheinfo_id(cpu, 3), node_caches);
> +       }
> +       cpus_read_unlock();

Thanks!
-Peter