linux-kernel - Re: [PATCH 4/5] x86, acpi, cpu-hotplug: Enable MADT APIs to return disabled apicid.

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Message-ID: <20150715220625.GN15934@mtj.duckdns.org>
Date:	Wed, 15 Jul 2015 18:06:25 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	mingo@...hat.com, akpm@...ux-foundation.org, rjw@...ysocki.net,
	hpa@...or.com, laijs@...fujitsu.com, yasu.isimatu@...il.com,
	isimatu.yasuaki@...fujitsu.com, kamezawa.hiroyu@...fujitsu.com,
	izumi.taku@...fujitsu.com, gongzhaogang@...pur.com,
	qiaonuohan@...fujitsu.com, x86@...nel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Gu Zheng <guz.fnst@...fujitsu.com>
Subject: Re: [PATCH 4/5] x86, acpi, cpu-hotplug: Enable MADT APIs to return
 disabled apicid.

Hello,

On Tue, Jul 07, 2015 at 05:30:24PM +0800, Tang Chen wrote:
> From: Gu Zheng <guz.fnst@...fujitsu.com>
> 
> All processors' apicids can be obtained by _MAT method or from MADT in ACPI.
> The current code ignores disabled processors and returns -ENODEV.
> 
> After this patch, a new parameter will be added to MADT APIs so that caller
> is able to control if disabled processors are ignored.

This describes what the patch does but doesn't really explain what the
patch is trying to achieve.

> @@ -282,8 +282,11 @@ static int acpi_processor_get_info(struct acpi_device *device)
>  	 *  Extra Processor objects may be enumerated on MP systems with
>  	 *  less than the max # of CPUs. They should be ignored _iff
>  	 *  they are physically not present.
> +	 *
> +	 *  NOTE: Even if the processor has a cpuid, it may not present because
                                                               ^
							       be
> +	 *  cpuid <-> apicid mapping is persistent now.

Saying "now" is kinda weird as this is how the code is gonna be
forever.

Thanks.

-- 
tejun
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