linux-kernel - Re: [PATCH 1/5] x86/smpboot: Add the missing description of possible

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Date:   Wed, 21 Mar 2018 13:33:24 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <linux-acpi@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <corbet@....net>,
        <rjw@...ysocki.net>, <lenb@...nel.org>, <hpa@...or.com>
Subject: Re: [PATCH 1/5] x86/smpboot: Add the missing description of
 possible_cpus

Hi Peter,

At 03/20/2018 08:37 PM, Peter Zijlstra wrote:
> On Tue, Mar 20, 2018 at 07:04:28PM +0800, Dou Liyang wrote:
> 
>> +	possible_cpus=	[s390,x86_64] Use this to set hotpluggable cpus.
>> +			This option sets possible_cpus bits in cpu_possible_map.
>> +			Thus keeping the numbers of bits set constant even if
>> +			the machine gets rebooted.
> 
> That description, esp. the last sentence, doesn't make any kind of sense
> to me. What?
> 

Ah, sure enough, I can't be lazy. :-) I stole that from the commit
   3b11ce7f542e ("x86: use possible_cpus=NUM to extend the possible cpus 
allowed")

How about:

possible_cpus=	[s390,x86_64] Set the number of possible CPUs which
		are determined by the ACPI tables MADT or mptables by
		default. possible_cpus=n : n >= 1 enforces the possible
		number to be 'n'.
		While nr_cpus is also be set: nr_cpus=m, choice the
		minimum one for the number of possible CPUs.

Thank,
	dou