From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King Subject: Re: [PATCH 01/14] Introduce cpu_enabled_map and friends Date: Tue, 15 Jul 2008 11:21:30 +0100 Message-ID: <20080715102130.GA22866@flint.arm.linux.org.uk> References: <20080715023344.2528.1836.stgit@blender.achiang> <20080715023349.2528.9423.stgit@blender.achiang> <20080715031512.GF14894@parisc-linux.org> <87wsjnxy4w.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:60376 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754806AbYGOK1L (ORCPT ); Tue, 15 Jul 2008 06:27:11 -0400 Content-Disposition: inline In-Reply-To: <87wsjnxy4w.fsf@basil.nowhere.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Andi Kleen Cc: Matthew Wilcox , Alex Chiang , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-acpi@vger.kernel.org On Tue, Jul 15, 2008 at 12:03:27PM +0200, Andi Kleen wrote: > Matthew Wilcox writes: > > > > I don't understand why we want to know about these CPUs. Surely they > > should be 'possible', but not 'present'? What useful thing can Linux do > > with them? > > He explained it in the intro, near the end (I nearly complained about > this too when I hadn't finished reading it completely :): > > |The big picture implication is that we can allow userspace > |to interact with disabled CPUs. In this particular example, > |we provide a knob that lets a sysadmin schedule any present > |CPU for firmware deconfiguration or enablement. > > The reason sounds pretty exotic, but ok. I don't see why this needs to be cross architecture then - shouldn't the generic kernel only be concerning itself with things that are possible, present and/or online? If you have an interface which allows you to change the machines configuration in a machine specific way, shouldn't that be something for that machine to support and forced upon the entire kernel? -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: