Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753108Ab3C0SWW (ORCPT ); Wed, 27 Mar 2013 14:22:22 -0400 Received: from smtp.citrix.com ([66.165.176.89]:33178 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751791Ab3C0SWU (ORCPT ); Wed, 27 Mar 2013 14:22:20 -0400 X-IronPort-AV: E=Sophos;i="4.84,920,1355097600"; d="scan'208";a="15963434" Date: Wed, 27 Mar 2013 18:22:15 +0000 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Nicolas Pitre CC: Stefano Stabellini , Rob Herring , Will Deacon , "xen-devel@lists.xensource.com" , "linux@arm.linux.org.uk" , "arnd@arndb.de" , Marc Zyngier , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v3] [RFC] arm: use PSCI if available In-Reply-To: Message-ID: References: <1364388639-11210-1-git-send-email-stefano.stabellini@eu.citrix.com> <20130327133811.GE18429@mudshark.cambridge.arm.com> <51531FE3.8010905@gmail.com> User-Agent: Alpine 2.02 (DEB 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: 4393 Lines: 112 On Wed, 27 Mar 2013, Nicolas Pitre wrote: > On Wed, 27 Mar 2013, Stefano Stabellini wrote: > > > On Wed, 27 Mar 2013, Rob Herring wrote: > > > On 03/27/2013 11:23 AM, Stefano Stabellini wrote: > > > > Would you agree on a patch that moves virt_smp_ops out of mach-virt and > > > > renames them to psci_smp_ops (maybe to arch/arm/kernel/psci_smp_ops.c)? > > > > > > > > Would you agree on initializing psci from setup_arch, right after the > > > > call to arm_dt_init_cpu_maps()? > > > > > > > > Finally the most controversial point: would you agree on using > > > > psci_smp_ops by default if they are available? > > > > If not, would you at least agree on letting Xen overwrite the default > > > > machine smp_ops? > > > > We need one or the other for dom0 support. > > > > > > It should not be *always* use PSCI smp ops if available, but use them > > > only if the platform does not define its own smp ops. > > > > Well, that is the one additional problem that we have on Xen. > > > > On x86 Xen replaces a lot of core native function calls with its own > > implementations (see paravirt_ops). > > On ARM we only need *one* set of calls: the smp_ops calls. > > > > So if we don't want to give priority to PSCI over the platform smp_ops, > > then we need a simple workaround just for Xen in common code like the > > one appended below. > > Not pretty, but at least small: > [...] > > What about the patch below that I'm carying in my MCPM branch > which has been posted here already: It's a step in the right direction but it still wouldn't solve the problem. Let me describe the scenario again: - we have a versatile express machine with Xen running on it (or an exynos5, etc.); - Xen boots Linux as Dom0, passing a versatile express device tree with the Xen hypervisor node added to it; - Linux is booting, using the versatile express device tree for hardware discovery; - Linux can access the hardware described in the device tree because Xen remapped the MMIO regions appropriately; - Linux needs to bring secondary cpus up, but Xen only exports a PSCI interface, so the native versatile express smp_ops don't work; - Linux needs to detect that PSCI is available (or Xen is available with its set of xen_smp_ops) and preferable on this platform and uses it instead of the versatile express smp_ops. > From: Jon Medhurst > Date: Thu, 13 Dec 2012 13:23:13 +0000 > Subject: [PATCH] ARM: Enable selection of SMP operations at boot time > > Add a new 'smp_init' hook to machine_desc so platforms can specify a > function to be used to setup smp ops instead of having a statically > defined value. > > Signed-off-by: Jon Medhurst > Signed-off-by: Nicolas Pitre > Reviewed-by: Santosh Shilimkar > > diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h > index 308ad7d6f9..c01bf53b85 100644 > --- a/arch/arm/include/asm/mach/arch.h > +++ b/arch/arm/include/asm/mach/arch.h > @@ -16,8 +16,10 @@ struct pt_regs; > struct smp_operations; > #ifdef CONFIG_SMP > #define smp_ops(ops) (&(ops)) > +#define smp_init_ops(ops) (&(ops)) > #else > #define smp_ops(ops) (struct smp_operations *)NULL > +#define smp_init_ops(ops) (void (*)(void))NULL > #endif > > struct machine_desc { > @@ -41,6 +43,7 @@ struct machine_desc { > unsigned char reserve_lp2 :1; /* never has lp2 */ > char restart_mode; /* default restart mode */ > struct smp_operations *smp; /* SMP operations */ > + void (*smp_init)(void); > void (*fixup)(struct tag *, char **, > struct meminfo *); > void (*reserve)(void);/* reserve mem blocks */ > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c > index 3f6cbb2e3e..41edca8582 100644 > --- a/arch/arm/kernel/setup.c > +++ b/arch/arm/kernel/setup.c > @@ -768,7 +768,10 @@ void __init setup_arch(char **cmdline_p) > arm_dt_init_cpu_maps(); > #ifdef CONFIG_SMP > if (is_smp()) { > - smp_set_ops(mdesc->smp); > + if(mdesc->smp_init) > + (*mdesc->smp_init)(); > + else > + smp_set_ops(mdesc->smp); > smp_init_cpus(); > } > #endif > -- 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/