From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932622Ab2KNCim (ORCPT ); Tue, 13 Nov 2012 21:38:42 -0500 Received: from mga14.intel.com ([143.182.124.37]:37267 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932489Ab2KNCdl (ORCPT ); Tue, 13 Nov 2012 21:33:41 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.83,247,1352102400"; d="scan'208";a="217413906" From: "Fenghua Yu" To: "Ingo Molnar" , "Thomas Gleixner" , "H Peter Anvin" , "Linus Torvalds" , "Andrew Morton" , "Asit K Mallick" , "Tony Luck" , "Arjan Dan De Ven" , "Suresh B Siddha" , "Len Brown" , "Srivatssa S. Bhat" , "Randy Dunlap" , "Rafael J. Wysocki" , "Chen Gong" , "linux-kernel" , "linux-pm" , "x86" Cc: "Fenghua Yu" Subject: [PATCH v10 03/14] x86, topology: Don't offline CPU0 if any PIC irq can not be migrated out of it Date: Tue, 13 Nov 2012 11:32:40 -0800 Message-Id: <1352835171-3958-4-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 1.7.2 In-Reply-To: <1352835171-3958-1-git-send-email-fenghua.yu@intel.com> References: <1352835171-3958-1-git-send-email-fenghua.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Fenghua Yu If CONFIG_BOOTPARAM_HOTPLUG_CPU is turned on, CPU0 hotplug feature is enabled by default. If CONFIG_BOOTPARAM_HOTPLUG_CPU is not turned on, CPU0 hotplug feature is not enabled by default. The kernel parameter cpu0_hotplug can enable CPU0 hotplug feature at boot. Currently the feature is supported on Intel platforms only. Signed-off-by: Fenghua Yu --- arch/x86/kernel/topology.c | 50 +++++++++++++++++++++++++++++++++++++------ 1 files changed, 43 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c index 76ee977..0e7b4a7 100644 --- a/arch/x86/kernel/topology.c +++ b/arch/x86/kernel/topology.c @@ -30,23 +30,59 @@ #include #include #include +#include #include static DEFINE_PER_CPU(struct x86_cpu, cpu_devices); #ifdef CONFIG_HOTPLUG_CPU + +#ifdef CONFIG_BOOTPARAM_HOTPLUG_CPU0 +static int cpu0_hotpluggable = 1; +#else +static int cpu0_hotpluggable; +static int __init enable_cpu0_hotplug(char *str) +{ + cpu0_hotpluggable = 1; + return 1; +} + +__setup("cpu0_hotplug", enable_cpu0_hotplug); +#endif + int __ref arch_register_cpu(int num) { + struct cpuinfo_x86 *c = &cpu_data(num); + + /* + * Currently CPU0 is only hotpluggable on Intel platforms. Other + * vendors can add hotplug support later. + */ + if (c->x86_vendor != X86_VENDOR_INTEL) + cpu0_hotpluggable = 0; + /* - * CPU0 cannot be offlined due to several - * restrictions and assumptions in kernel. This basically - * doesn't add a control file, one cannot attempt to offline - * BSP. + * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate + * depends on BSP. PIC interrupts depend on BSP. * - * Also certain PCI quirks require not to enable hotplug control - * for all CPU's. + * If the BSP depencies are under control, one can tell kernel to + * enable BSP hotplug. This basically adds a control file and + * one can attempt to offline BSP. */ - if (num) + if (num == 0 && cpu0_hotpluggable) { + unsigned int irq; + /* + * We won't take down the boot processor on i386 if some + * interrupts only are able to be serviced by the BSP in PIC. + */ + for_each_active_irq(irq) { + if (!IO_APIC_IRQ(irq) && irq_has_action(irq)) { + cpu0_hotpluggable = 0; + break; + } + } + } + if (num || cpu0_hotpluggable) per_cpu(cpu_devices, num).cpu.hotpluggable = 1; return register_cpu(&per_cpu(cpu_devices, num).cpu, num); -- 1.7.2