Messages in this thread | | | Date | Sun, 26 Jan 2014 10:09:26 +0100 | From | Ingo Molnar <> | Subject | Re: disabled APICs being counted as processors ? |
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* Yinghai Lu <yinghai@kernel.org> wrote:
> On Sun, Jan 26, 2014 at 12:36 AM, Ingo Molnar <mingo@kernel.org> wrote: > > > > No, this message is printed in prefill_possible_map() which > > _generates_ cpu_possible_map, so '8' is the number of bits in > > cpu_possible_map. > > > > So the problem is that the counting of disabled but hotpluggable CPUs > > is over-eager. Since I haven't actually seen _true_ hotplug CPU > > hardware yet, I'd argue we do the change below - allocating space for > > never-present CPUs is stupid. If there's true hot-plug CPUs around > > that could come online after we've booted, then we want to know about > > them explicitly. > > > > > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > > index a32da80..75a351a 100644 > > --- a/arch/x86/kernel/smpboot.c > > +++ b/arch/x86/kernel/smpboot.c > > @@ -1223,10 +1223,7 @@ __init void prefill_possible_map(void) > > i = setup_max_cpus ?: 1; > > if (setup_possible_cpus == -1) { > > possible = num_processors; > > -#ifdef CONFIG_HOTPLUG_CPU > > - if (setup_max_cpus) > > - possible += disabled_cpus; > > -#else > > +#ifndef CONFIG_HOTPLUG_CPU > > if (possible > i) > > possible = i; > > #endif > > Agreed.
A question would be kexec and virtualization: do any of those variants boot a kernel with 'disabled but working' CPUs, which could be hot-onlined later on?
Thanks,
Ingo
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