linux-kernel - Re: [PATCH 34/35] x86: use num

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Message-ID: <4B7C98B9.1090903@zytor.com>
Date:	Wed, 17 Feb 2010 17:32:41 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 34/35] x86: use num_processors for possible cpus

On 02/10/2010 01:20 AM, Yinghai Lu wrote:
> some systems that have disable cpus entries because same
>   BIOS will support 2 sockets and 4 sockets and more at
>   same time, BIOS just leave some disable entries, but
>   those system do not support cpu hotplug. we don't need
>   treat disabled_cpus as hotplug cpus.
> so we can make nr_cpu_ids smaller and save more space
>   (pcpu data allocations), and could make some systems run
>   with logical flat instead of physical flat apic mode
> 
> -v2: change to black list instead
> -v3: just remove that, and the one use possible_cpus= directly.
> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>

I'm confused by this one.  This would seem to mean that unless you're
specifying possible_cpus= then you are not treating anything as
hotpluggable.

This is clearly wrong, and it would appear to go the wrong direction in
terms of what is safe.

What am I missing here?

	-hpa
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