From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755851Ab2KUTZQ (ORCPT ); Wed, 21 Nov 2012 14:25:16 -0500 Received: from terminus.zytor.com ([198.137.202.10]:53927 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755755Ab2KUTZP (ORCPT ); Wed, 21 Nov 2012 14:25:15 -0500 Message-ID: <50AD2A85.7030705@zytor.com> Date: Wed, 21 Nov 2012 11:24:53 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121029 Thunderbird/16.0.2 MIME-Version: 1.0 To: Sasha Levin CC: tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org, penberg@kernel.org Subject: Re: [PATCH] x86, smpboot: allow manual hotplug of CPUs References: <1353522136-14944-1-git-send-email-sasha.levin@oracle.com> <50AD1CB6.9030707@zytor.com> <50AD1EE7.6020304@oracle.com> <50AD1F88.1010006@zytor.com> <50AD2953.5070700@oracle.com> In-Reply-To: <50AD2953.5070700@oracle.com> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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