diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 14 | ||||
| -rw-r--r-- | Documentation/core-api/cpu_hotplug.rst | 13 | ||||
| -rw-r--r-- | arch/x86/Kconfig | 43 | ||||
| -rw-r--r-- | arch/x86/include/asm/cpu.h | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/topology.c | 98 | ||||
| -rw-r--r-- | arch/x86/power/cpu.c | 37 |
6 files changed, 6 insertions, 202 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9e5bab29685f..ccb91a255c6d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -818,20 +818,6 @@ Format: <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] - cpu0_hotplug [X86] Turn on CPU0 hotplug feature when - CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. - Some features depend on CPU0. Known dependencies are: - 1. Resume from suspend/hibernate depends on CPU0. - Suspend/hibernate will fail if CPU0 is offline and you - need to online CPU0 before suspend/hibernate. - 2. PIC interrupts also depend on CPU0. CPU0 can't be - removed if a PIC interrupt is detected. - It's said poweroff/reboot may depend on CPU0 on some - machines although I haven't seen such issues so far - after CPU0 is offline on a few tested machines. - If the dependencies are under your control, you can - turn on cpu0_hotplug. - cpuidle.off=1 [CPU_IDLE] disable the cpuidle sub-system diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst index f75778d37488..e6f5bc39cf5c 100644 --- a/Documentation/core-api/cpu_hotplug.rst +++ b/Documentation/core-api/cpu_hotplug.rst @@ -127,17 +127,8 @@ bring CPU4 back online:: $ echo 1 > /sys/devices/system/cpu/cpu4/online smpboot: Booting Node 0 Processor 4 APIC 0x1 -The CPU is usable again. This should work on all CPUs. CPU0 is often special -and excluded from CPU hotplug. On X86 the kernel option -*CONFIG_BOOTPARAM_HOTPLUG_CPU0* has to be enabled in order to be able to -shutdown CPU0. Alternatively the kernel command option *cpu0_hotplug* can be -used. Some known dependencies of CPU0: - -* Resume from hibernate/suspend. Hibernate/suspend will fail if CPU0 is offline. -* PIC interrupts. CPU0 can't be removed if a PIC interrupt is detected. - -Please let Fenghua Yu <fenghua.yu@intel.com> know if you find any dependencies -on CPU0. +The CPU is usable again. This should work on all CPUs, but CPU0 is often special +and excluded from CPU hotplug. The CPU hotplug coordination ============================ diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 53bab123a8ee..d0191338a102 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2305,49 +2305,6 @@ config HOTPLUG_CPU def_bool y depends on SMP -config BOOTPARAM_HOTPLUG_CPU0 - bool "Set default setting of cpu0_hotpluggable" - depends on HOTPLUG_CPU - help - Set whether default state of cpu0_hotpluggable is on or off. - - Say Y here to enable CPU0 hotplug by default. If this switch - is turned on, there is no need to give cpu0_hotplug kernel - parameter and the CPU0 hotplug feature is enabled by default. - - Please note: there are two known CPU0 dependencies if you want - to enable the CPU0 hotplug feature either by this switch or by - cpu0_hotplug kernel parameter. - - First, resume from hibernate or suspend always starts from CPU0. - So hibernate and suspend are prevented if CPU0 is offline. - - Second dependency is PIC interrupts always go to CPU0. CPU0 can not - offline if any interrupt can not migrate out of CPU0. There may - be other CPU0 dependencies. - - Please make sure the dependencies are under your control before - you enable this feature. - - Say N if you don't want to enable CPU0 hotplug feature by default. - You still can enable the CPU0 hotplug feature at boot by kernel - parameter cpu0_hotplug. - -config DEBUG_HOTPLUG_CPU0 - def_bool n - prompt "Debug CPU0 hotplug" - depends on HOTPLUG_CPU - help - Enabling this option offlines CPU0 (if CPU0 can be offlined) as - soon as possible and boots up userspace with CPU0 offlined. User - can online CPU0 back after boot time. - - To debug CPU0 hotplug, you need to enable CPU0 offline/online - feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during - compilation or giving cpu0_hotplug kernel parameter at boot. - - If unsure, say N. - config COMPAT_VDSO def_bool n prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)" diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index b356464b883b..c854376e1cb9 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -31,9 +31,6 @@ struct x86_cpu { extern int arch_register_cpu(int num); extern void arch_unregister_cpu(int); extern void soft_restart_cpu(void); -#ifdef CONFIG_DEBUG_HOTPLUG_CPU0 -extern int _debug_hotplug_cpu(int cpu, int action); -#endif #endif extern void ap_init_aperfmperf(void); diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c index 1b83377274b8..ca004e2e4469 100644 --- a/arch/x86/kernel/topology.c +++ b/arch/x86/kernel/topology.c @@ -38,102 +38,12 @@ 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 - -#ifdef CONFIG_DEBUG_HOTPLUG_CPU0 -/* - * This function offlines a CPU as early as possible and allows userspace to - * boot up without the CPU. The CPU can be onlined back by user after boot. - * - * This is only called for debugging CPU offline/online feature. - */ -int _debug_hotplug_cpu(int cpu, int action) +int arch_register_cpu(int cpu) { - int ret; - - if (!cpu_is_hotpluggable(cpu)) - return -EINVAL; + struct x86_cpu *xc = per_cpu_ptr(&cpu_devices, cpu); - switch (action) { - case 0: - ret = remove_cpu(cpu); - if (!ret) - pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu); - else - pr_debug("Can't offline CPU%d.\n", cpu); - break; - case 1: - ret = add_cpu(cpu); - if (ret) - pr_debug("Can't online CPU%d.\n", cpu); - - break; - default: - ret = -EINVAL; - } - - return ret; -} - -static int __init debug_hotplug_cpu(void) -{ - _debug_hotplug_cpu(0, 0); - return 0; -} - -late_initcall_sync(debug_hotplug_cpu); -#endif /* CONFIG_DEBUG_HOTPLUG_CPU0 */ - -int 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. - * Xen PV guests don't support CPU0 hotplug at all. - */ - if (c->x86_vendor != X86_VENDOR_INTEL || - cpu_feature_enabled(X86_FEATURE_XENPV)) - cpu0_hotpluggable = 0; - - /* - * Two known BSP/CPU0 dependencies: Resume from suspend/hibernate - * depends on BSP. PIC interrupts depend on BSP. - * - * If the BSP dependencies 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 == 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); + xc->cpu.hotpluggable = cpu > 0; + return register_cpu(&xc->cpu, cpu); } EXPORT_SYMBOL(arch_register_cpu); diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 7a4d5e911415..63230ff8cf4f 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -351,43 +351,6 @@ static int bsp_pm_callback(struct notifier_block *nb, unsigned long action, case PM_HIBERNATION_PREPARE: ret = bsp_check(); break; -#ifdef CONFIG_DEBUG_HOTPLUG_CPU0 - case PM_RESTORE_PREPARE: - /* - * When system resumes from hibernation, online CPU0 because - * 1. it's required for resume and - * 2. the CPU was online before hibernation - */ - if (!cpu_online(0)) - _debug_hotplug_cpu(0, 1); - break; - case PM_POST_RESTORE: - /* - * When a resume really happens, this code won't be called. - * - * This code is called only when user space hibernation software - * prepares for snapshot device during boot time. So we just - * call _debug_hotplug_cpu() to restore to CPU0's state prior to - * preparing the snapshot device. - * - * This works for normal boot case in our CPU0 hotplug debug - * mode, i.e. CPU0 is offline and user mode hibernation - * software initializes during boot time. - * - * If CPU0 is online and user application accesses snapshot - * device after boot time, this will offline CPU0 and user may - * see different CPU0 state before and after accessing - * the snapshot device. But hopefully this is not a case when - * user debugging CPU0 hotplug. Even if users hit this case, - * they can easily online CPU0 back. - * - * To simplify this debug code, we only consider normal boot - * case. Otherwise we need to remember CPU0's state and restore - * to that state and resolve racy conditions etc. - */ - _debug_hotplug_cpu(0, 0); - break; -#endif default: break; } |