Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756683Ab3C2Rxj (ORCPT ); Fri, 29 Mar 2013 13:53:39 -0400 Received: from mail-qe0-f50.google.com ([209.85.128.50]:45540 "EHLO mail-qe0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756457Ab3C2Rxi (ORCPT ); Fri, 29 Mar 2013 13:53:38 -0400 Date: Fri, 29 Mar 2013 13:53:35 -0400 (EDT) From: Nicolas Pitre To: Stefano Stabellini cc: "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Will Deacon , Arnd Bergmann , "marc.zyngier@arm.com" , Russell King - ARM Linux Subject: Re: [PATCH v4 2/2] arm: prefer PSCI for SMP bringup In-Reply-To: Message-ID: References: <1364575371-8926-2-git-send-email-stefano.stabellini@eu.citrix.com> User-Agent: Alpine 2.03 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1986 Lines: 58 On Fri, 29 Mar 2013, Stefano Stabellini wrote: > On Fri, 29 Mar 2013, Nicolas Pitre wrote: > > On Fri, 29 Mar 2013, Stefano Stabellini wrote: > > > > > If PSCI initializes correctly and PSCI SMP operations are available, use them. > > > This is required for SMP support in Dom0 on Xen. > > > > > > Signed-off-by: Stefano Stabellini > > > CC: will.deacon@arm.com > > > CC: arnd@arndb.de > > > CC: marc.zyngier@arm.com > > > CC: linux@arm.linux.org.uk > > > CC: nico@linaro.org > > > > I'd suggest you also include in your series the patch I posted earlier > > providing a runtime mdesc->smp_init method as well. > > OK. > > > > This way the > > priority order would be: > > > > - If mdesc->smp_init is non null then use that. > > > > - Otherwise, if PSCI is available then use that. > > > > - Otherwise use mdesc->smp. > > > > This way, if the PSCI default has to be overriden (like in the MCPM case > > because it needs to wrap PSCI itself, or to cover Rob's concern) then > > this can be achieved at run time on a per mdesc basis. > > Actually that's not a bad idea, it could make everybody happy. > What about the following, in this precise order: > > - if a xen hypervisor node is present on device tree, use PSCI; > - otherwise if mdesc->smp_init is non null then use it; > - otherwise if PSCI is available then use it; > - otherwise use mdesc->smp. > > It's the most practical solution to satisfy everybody's needs. Maybe I'm missing something obvious, but why can't xen declare a mdesc of its own? Given it is going to tweak the DT passed to the kernel anyway that shouldn't be a problem. That would be more eleguant than adding xen exception hooks in generic code. Nicolas -- 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/