linux-kernel - Re: disabled APICs being counted as processors ?

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Message-ID: <20140125074107.GA10565@gmail.com>
Date:	Sat, 25 Jan 2014 08:41:07 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Dave Jones <davej@...hat.com>, x86@...nel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: disabled APICs being counted as processors ?


* Dave Jones <davej@...hat.com> wrote:

> I have a system with 4 cores (configured with CONFIG_NR_CPUS=4) that shows during boot..
> 
> [    0.000000] smpboot: 8 Processors exceeds NR_CPUS limit of 4
> 
> it looks like this is because..
> 
> [    0.000000] ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled)
> [    0.000000] ACPI: LAPIC (acpi_id[0x02] lapic_id[0x02] enabled)
> [    0.000000] ACPI: LAPIC (acpi_id[0x03] lapic_id[0x04] enabled)
> [    0.000000] ACPI: LAPIC (acpi_id[0x04] lapic_id[0x06] enabled)
> [    0.000000] ACPI: LAPIC (acpi_id[0x05] lapic_id[0xff] disabled)
> [    0.000000] ACPI: LAPIC (acpi_id[0x06] lapic_id[0xff] disabled)
> [    0.000000] ACPI: LAPIC (acpi_id[0x07] lapic_id[0xff] disabled)
> [    0.000000] ACPI: LAPIC (acpi_id[0x08] lapic_id[0xff] disabled)
> 
> Should the CPU counting code be ignoring those disabled APICs ?

Hm, so to the kernel it looks like as if those were 'possible CPUs', 
in theory hotpluggable. Not sure what they are - disabled cores in an 
8-core system? Or BIOS reporting crap?

But perhaps the boot message could be improved to say something like:

> [    0.000000] smpboot: 8 possible processors exceeds NR_CPUS limit of 4

?

Thanks,

	Ingo
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