linux-kernel - Re: [RFC PATCH 2/4] x86: use dmi check to treat disabled cpus as hotplug cpus.

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Message-ID: <6686.1263312874@localhost>
Date:	Tue, 12 Jan 2010 11:14:34 -0500
From:	Valdis.Kletnieks@...edu
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	"ananth@...ibm.com" <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/4] x86: use dmi check to treat disabled cpus as hotplug cpus.

On Mon, 11 Jan 2010 19:13:32 PST, Linus Torvalds said:

>  - only use that flat apic mode when you _know_ that you absolutely will 
>    never have more than 8 cpu's. Ie when CONFIG_NR_CPUS <= 8 (or, with 
>    1/3, when nr_cpu_ids <= 8) and/or when <= 8 CPU's were detected, and 
>    CPU hotplug is disabled entirely.

OK, I'll bite - how do you build an X86-64 kernel that doesn't have
CONFIG_HOTPLUG_CPU selected?  Try as I might, even if I have PM_SLEEP=n,
PM_SLEEP_SMP insists on being set, and then selecting HOTPLUG_SMP.  For the
record, I do *not* need/desire S2R, S2D, 'suspend', or similar functionality.

Is there some subtle reason why PM_SLEEP_SMP has to be on even without PM_SLEEP?

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