From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755891Ab2KUTgd (ORCPT ); Wed, 21 Nov 2012 14:36:33 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:51870 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755846Ab2KUTgc (ORCPT ); Wed, 21 Nov 2012 14:36:32 -0500 Message-ID: <50AD2D16.7050304@oracle.com> Date: Wed, 21 Nov 2012 14:35:50 -0500 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121112 Thunderbird/16.0.1 MIME-Version: 1.0 To: "H. Peter Anvin" 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> <50AD2A85.7030705@zytor.com> In-Reply-To: <50AD2A85.7030705@zytor.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Thanks, Sasha