linux-kernel - Re: [PATCH] x86, smpboot: allow manual hotplug of CPUs

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Message-ID: <50AD2A85.7030705@zytor.com>
Date:	Wed, 21 Nov 2012 11:24:53 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Sasha Levin <sasha.levin@...cle.com>
CC:	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, penberg@...nel.org
Subject: Re: [PATCH] x86, smpboot: allow manual hotplug of CPUs

On 11/21/2012 11:19 AM, Sasha Levin wrote:
>>
>> So, are there any mptables platforms which support hotplug?  If the
>> answer is "KVM" then the answer is that KVM needs to move to ACPI to get
>> the proper functionality; putting a hack in is really not okay.
> 
> There are no platforms which support actual hotplug, but you can still set
> existing processors as disabled in the table and without this patch there's
> no way enable them.
> 
> I'm not sure if it's a "hack" though - the presentation of hotpluggable cpus
> is the almost the same between mptable and acpi, and acpi provides a way to
> manually probe/release cpus as well. The only difference is that acpi also
> provides notifications about such events.
> 
> Actually, maybe acpi should start using probe/release as well... hmm...
> 

The bottom line is that I don't want the underlying implementation to
end up with a user-visible difference... therein lies madness and lots
of bugs.

	-hpa


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