Re: [Xen-devel] [PATCH v2 4/6] x86: bring up all CPUs even if not all are supposed to be used

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jul 18, 2018 at 02:21:53AM -0600, Jan Beulich wrote:
> --- a/xen/arch/x86/mpparse.c
> +++ b/xen/arch/x86/mpparse.c
> @@ -68,19 +68,26 @@ physid_mask_t phys_cpu_present_map;
>  
>  void __init set_nr_cpu_ids(unsigned int max_cpus)
>  {
> +     unsigned int tot_cpus = num_processors + disabled_cpus;
> +
>       if (!max_cpus)
> -             max_cpus = num_processors + disabled_cpus;
> +             max_cpus = tot_cpus;
>       if (max_cpus > NR_CPUS)
>               max_cpus = NR_CPUS;
>       else if (!max_cpus)
>               max_cpus = 1;
>       printk(XENLOG_INFO "SMP: Allowing %u CPUs (%d hotplug CPUs)\n",
>              max_cpus, max_t(int, max_cpus - num_processors, 0));
> -     nr_cpu_ids = max_cpus;
> +
> +     if (!park_offline_cpus)
> +             tot_cpus = max_cpus;
> +     nr_cpu_ids = min(tot_cpus, NR_CPUS + 0u);
> +     if (park_offline_cpus && nr_cpu_ids < num_processors)
> +             printk(XENLOG_WARNING "SMP: Cannot bring up %u further CPUs\n",
> +                    num_processors - nr_cpu_ids);

Minor nit:

Maybe it is just me, but "Cannot" is normally used when an operation
fails, I would use "Won't" to indicate this is a deliberate action, not
a consequence of failure, or say "Skip bringing up ...".

Whatever this log message ends up like:

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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