Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756922Ab3C2Tb4 (ORCPT ); Fri, 29 Mar 2013 15:31:56 -0400 Received: from mail-qa0-f48.google.com ([209.85.216.48]:63042 "EHLO mail-qa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756235Ab3C2Tby (ORCPT ); Fri, 29 Mar 2013 15:31:54 -0400 Message-ID: <5155EC28.8050608@gmail.com> Date: Fri, 29 Mar 2013 14:31:52 -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" , Russell King - ARM Linux , Arnd Bergmann , "marc.zyngier@arm.com" , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v4 2/2] arm: prefer PSCI for SMP bringup References: <1364575371-8926-2-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: 2603 Lines: 77 On 03/29/2013 12:53 PM, Nicolas Pitre wrote: > 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. Xen does have it's own mdesc. It is (or will be) mach-virt, but that is only for DomU guests. For Dom0, you still need all the platform specific code except smp_ops. However, I'm doubtful this would work without other changes on more complicated platforms like OMAP. I would say wait to add this until you have platforms that actually need the first case. Rob > > That would be more eleguant than adding xen exception hooks in generic > code. > > > Nicolas > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- 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/