linux-kernel - Re: [PATCH RFC v2 0/3] add cpu physically hotplug driver

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Message-ID: <51B54D51.2070505@jp.fujitsu.com>
Date:	Mon, 10 Jun 2013 12:51:45 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	li guang <lig.fnst@...fujitsu.com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <lenb@...nel.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	<linux-kernel@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<platform-driver-x86@...r.kernel.org>,
	Andreas Färber <afaerber@...e.de>,
	Igor Mammedov <imammedo@...hat.com>
Subject: Re: [PATCH RFC v2 0/3] add cpu physically hotplug driver

2013/06/10 9:36, li guang wrote:
> Hi, Rafael
>
> 在 2013-06-06四的 13:00 +0200，Rafael J. Wysocki写道：
>> On Thursday, June 06, 2013 09:40:32 AM liguang wrote:
>>> This patch-set try to support physically hot-plug/unplug
>>> a cpu automatically, that is:
>>> if you offline a cpu, it will automatically actually remove
>>> a cpu, and if you hot-plug a cpu, then it will online this
>>> cpu automatically.
>>
>> No and no.
>
> Hmm... are you saying cpu online/offline designed to distinguish
> with real cpu plug/unplug?
> but, what the actual usage of online/offline?
> forgive my foolish.
>
>>
>> Why do you need this?
>>
>
> e.g. for QEMU case, if hot-plug a cpu,

> we have to online a cpu manually if there's
> no user space support like udev to do it automatically.

I could not understand why you do not use udev.
Please explain in detail.

> and also, I think maybe online/offline should be naturally
> integrated with real plug/unplug process of CPU.

I could not understand this explanation too.
Why do we need it?

Thanks,
Yasuaki Ishimatsu

>
>>
>>
>>> so, offline is just like eject, but eject attribute seems not
>>> available since recent kernel(can't figure out when), with
>>> this driver, if allowed, it will trigger a eject cpu process.
>>> and for automatically online, it was said there are objections,
>>> don't know the reason, so, send this patch-set boldly.
>>>
>>> of course, this approach is for QEMU 's hotplug cpu emulation
>>> only, but not limited, if someone like to explore ec space to
>>> implment cpu hot-plug/unplug for real platform please
>>> feel free to continue.
>>>
>>> Li Guang (3)
>>> 	 drivers/platform/x86: add cpu physically hotplug driver
>>> 	 ec: add ec space notifier
>>> 	 cpu_physic_hotplug: register handler for ec space notifier
>>>
>>> drivers/acpi/ec.c                         | 32 ++++++++++++++++++++++++++++++++
>>> drivers/platform/x86/Kconfig              |  8 ++++
>>> drivers/platform/x86/Makefile             |  1 +
>>> drivers/platform/x86/cpu_physic_hotplug.c | 90 +++++++++++++++++++++++++++++
>>> include/linux/acpi.h                      |  2 ++
>>> 5 files changed, 130 insertions(+), 3 deletions(-)
>>>   create mode 100644 drivers/platform/x86/cpu_physic_hotplug.c
>
>
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