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Subject: Re: [PATCH V3 0/4] genirq/affinity: irq vector spread among online
 CPUs as far as possible
To:     "Rafael J. Wysocki" <rafael@kernel.org>
CC:     Thomas Gleixner <tglx@linutronix.de>,
        Ming Lei <ming.lei@redhat.com>,
        Artem Bityutskiy <dedekind1@gmail.com>,
        Jens Axboe <axboe@kernel.dk>,
        Christoph Hellwig <hch@infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        <linux-block@vger.kernel.org>,
        Laurence Oberman <loberman@redhat.com>
References: <20180308105358.1506-1-ming.lei@redhat.com>
 <1520515113.20980.31.camel@gmail.com> <20180308133440.GA2713@ming.t460p>
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 <alpine.DEB.2.21.1803091107520.1364@nanos.tec.linutronix.de>
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 <CAJZ5v0hKYJY9W3Gjo-KZzmfXhT7JqBxbe=AGPSQOSd4DCThJVA@mail.gmail.com>
From:   Dou Liyang <douly.fnst@cn.fujitsu.com>
Message-ID: <b054b7da-baf0-3040-ffd4-47cab3300d51@cn.fujitsu.com>
Date:   Wed, 14 Mar 2018 11:30:56 +0800
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Hi Rafael,

Thank you so much for your reply.

At 03/13/2018 05:25 PM, Rafael J. Wysocki wrote:
> On Tue, Mar 13, 2018 at 4:11 AM, Dou Liyang <douly.fnst@cn.fujitsu.com> wrote:
>> Hi Thomas,
>>
>> At 03/09/2018 11:08 PM, Thomas Gleixner wrote:
>> [...]
>>>
>>>
>>> I'm not sure if there is a clear indicator whether physcial hotplug is
>>> supported or not, but the ACPI folks (x86) and architecture maintainers
>>
>> +cc Rafael
>>
>>> should be able to answer that question. I have a machine which says:
>>>
>>>      smpboot: Allowing 128 CPUs, 96 hotplug CPUs
>>>
>>> There is definitely no way to hotplug anything on that machine and sure
>>> the
>>
>>
>> AFAIK, in ACPI based dynamic reconfiguration, there is no clear
>> indicator. In theory, If the ACPI tables have the hotpluggable
>> CPU resources, the OS can support physical hotplug.
> 
> In order for the ACPI-based CPU hotplug (I mean physical, not just the
> software offline/online we do in the kernel) to work, there have to be
> objects in the ACPI namespace corresponding to all of the processors
> in question.
> 
> If they are not present, there is no way to signal insertion and eject
> the processors safely.

Yes, I see.

Thanks
	dou

> 
> 
>