From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755926Ab2KUTjZ (ORCPT ); Wed, 21 Nov 2012 14:39:25 -0500 Received: from terminus.zytor.com ([198.137.202.10]:54273 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755748Ab2KUTjY (ORCPT ); Wed, 21 Nov 2012 14:39:24 -0500 Message-ID: <50AD2DDB.1090107@zytor.com> Date: Wed, 21 Nov 2012 11:39:07 -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, "Brown, Len" 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> <50AD2A85.7030705@zytor.com> <50AD2D16.7050304@oracle.com> In-Reply-To: <50AD2D16.7050304@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 11:35 AM, Sasha Levin wrote: > On 11/21/2012 02:24 PM, H. Peter Anvin wrote: >> 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. > > Okay, so if in the case of ACPI, 'probe' will call acpi_processor_add() > and 'release' would call acpi_processor_remove() so the behaviour > would be the same for both ACPI and mptables. Is this okay? > Sounds reasonable to me. Adding Len to the Cc: list. -hpa