Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162985Ab3DEUu4 (ORCPT ); Fri, 5 Apr 2013 16:50:56 -0400 Received: from mail-ob0-f171.google.com ([209.85.214.171]:63695 "EHLO mail-ob0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162097Ab3DEUux (ORCPT ); Fri, 5 Apr 2013 16:50:53 -0400 Message-ID: <515F392B.1030200@gmail.com> Date: Fri, 05 Apr 2013 15:50:51 -0500 From: Rob Herring User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Nicolas Pitre CC: Stefano Stabellini , "xen-devel@lists.xensource.com" , "arnd@arndb.de" , "will.deacon@arm.com" , "linux-kernel@vger.kernel.org" , "rob.herring@calxeda.com" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v6 4/4] xen/arm: introduce xen_early_init, use PSCI on xen References: <1365167495-18508-4-git-send-email-stefano.stabellini@eu.citrix.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1650 Lines: 42 On 04/05/2013 02:36 PM, Nicolas Pitre wrote: > On Fri, 5 Apr 2013, Stefano Stabellini wrote: > >> This is what happens: >> >> - No Xen >> Xen is not running on the platform and a Xen hypervisor node is not >> available on device tree. >> Everything keeps working seamlessly, this patch doesn't change anything. >> >> - we are running on Xen >> Xen is running on the platform, we are running as a guest on Xen and an >> hypervisor node is available on device tree. >> Let's also assume that there aren't any "arm,cci" compatible nodes on >> device tree because Xen wouldn't export this kind of information to any >> guests right now. Therefore PSCI should be used to boot secondary cpus. >> Because the versatile express machine sets smp_init to >> vexpress_smp_init_ops, vexpress_smp_init_ops will be called. >> vexpress_smp_init_ops sets smp_ops to vexpress_smp_ops, that *break* >> Xen. > > OK I see. > >> With this patch, xen_smp_init will be called instead of >> vexpress_smp_init_ops, and smp_ops will be set to psci_smp_ops, >> therefore *unbreaking* Xen. > > However that breaks MCPM. You mean on bare metal, right? For the bare metal, "xen,xen" property would not be present and xen_smp_init is not used. So the vexpress MCPM ops will be used. Aren't Dom0 cpu's basically virtual cpus? If Xen ever needs the MCPM support, the Xen hook itself can figure out whether to use MCPM support. Rob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/