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

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Message-ID: <50AD1F88.1010006@zytor.com>
Date:	Wed, 21 Nov 2012 10:38:00 -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 10:35 AM, Sasha Levin wrote:
>>
>> Reading between the lines, this sounds like would cause a user-visible
>> difference between mptable platforms and ACPI platforms?  If so, that is
>> totally unacceptable.  If not, the description is confusing.
> 
> With ACPI platforms you don't need probe/release because the hardware notifies
> on CPU insert/eject - this doesn't exist on mptable which is why you have to
> do it manually with probe/release.
> 
> The difference is already user visible: you can hotplug on ACPI, but can't on
> mptables.
> 
> Yes, reading back the subject does sound confusing - a better one would probably
> be "provide interface for CPU hotplug on mptable platforms" or something similar.
> 

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.

	-hpa


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