linux-kernel - Re: [PATCH] Resurect proper handling of maxcpus= kernel option (take 2)

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Date:	Thu, 14 Aug 2008 11:11:20 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Max Krasnyansky <maxk@...lcomm.com>
Cc:	linux-kernel@...r.kernel.org, Max Krasnyansky <maxk@...lcomm.org>,
	lizf@...fujitsu.com, jeff.chua.linux@...il.com,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Resurect proper handling of maxcpus= kernel option
	(take 2)


* Max Krasnyansky <maxk@...lcomm.com> wrote:

> From: Max Krasnyansky <maxk@...lcomm.org>
> 
> For some reason we had two parsers registered for maxcpus=. One in init/main.c 
> and another in arch/x86/smpboot.c. So I nuked the one in arch/x86.
> 
> Also 64-bit kernels used to handle maxcpus= as documented in
> Documentation/cpu-hotplug.txt. CPUs with 'id > maxcpus' are initialized
> but not booted. 32-bit version for some reason ignored them even though
> all the infrastructure for booting them later is there.
> 
> In the current mainline both 64 and 32 bit versions are broken.
> This patch restores the correct behaviour. I've tested x86_64 version on
> 4- and 8- way Core2 and 2-way Opteron based machines. Various config
> combinations SMP, !SMP, CPU_HOTPLUG, !CPU_HOTPLUG.
> Booted with maxcpus=1 and maxcpus=4, etc. Everything is working as expected.
> 
> So far we've received two reports from different people confirming that 32-bit 
> version also works fine, both on dual core laptops and 16way server machines.
> 
> This version fixes visws breakage pointed out by Ingo.

applied to tip/x86/urgent, thanks Max.

	Ingo
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