diff options
| -rw-r--r-- | Documentation/cpu-hotplug.txt | 24 | ||||
| -rw-r--r-- | Documentation/kernel-parameters.txt | 14 | ||||
| -rw-r--r-- | arch/x86/Kconfig | 44 | ||||
| -rw-r--r-- | arch/x86/include/asm/cpu.h | 4 | ||||
| -rw-r--r-- | arch/x86/include/asm/smp.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/apic/io_apic.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/mtrr/main.c | 9 | ||||
| -rw-r--r-- | arch/x86/kernel/head_32.S | 13 | ||||
| -rw-r--r-- | arch/x86/kernel/head_64.S | 16 | ||||
| -rw-r--r-- | arch/x86/kernel/i387.c | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 149 | ||||
| -rw-r--r-- | arch/x86/kernel/topology.c | 101 | ||||
| -rw-r--r-- | arch/x86/power/cpu.c | 82 | ||||
| -rw-r--r-- | kernel/cpu.c | 5 |
15 files changed, 436 insertions, 41 deletions
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index 66ef8f35613d..9f401350f502 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -207,6 +207,30 @@ by making it not-removable. In such cases you will also notice that the online file is missing under cpu0. +Q: Is CPU0 removable on X86? +A: Yes. If kernel is compiled with CONFIG_BOOTPARAM_HOTPLUG_CPU0=y, CPU0 is +removable by default. Otherwise, CPU0 is also removable by kernel option +cpu0_hotplug. + +But some features depend on CPU0. Two known dependencies are: + +1. Resume from hibernate/suspend depends on CPU0. Hibernate/suspend will fail if +CPU0 is offline and you need to online CPU0 before hibernate/suspend can +continue. +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 any poweroff/reboot failure so far after CPU0 is offline on a few tested +machines. + +Please let me know if you know or see any other dependencies of CPU0. + +If the dependencies are under your control, you can turn on CPU0 hotplug feature +either by CONFIG_BOOTPARAM_HOTPLUG_CPU0 or by kernel parameter cpu0_hotplug. + +--Fenghua Yu <fenghua.yu@intel.com> + Q: How do i find out if a particular CPU is not removable? A: Depending on the implementation, some architectures may show this by the absence of the "online" file. This is done if it can be determined ahead of diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 03d1251a915e..5190f1706414 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1984,6 +1984,20 @@ bytes respectively. Such letter suffixes can also be entirely omitted. nox2apic [X86-64,APIC] Do not enable x2APIC mode. + 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. + nptcg= [IA-64] Override max number of concurrent global TLB purges which is reported from either PAL_VM_SUMMARY or SAL PALO. diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 6c304438b503..2d643255c40d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1698,6 +1698,50 @@ config HOTPLUG_CPU automatically on SMP systems. ) Say N if you want to disable CPU hotplug. +config BOOTPARAM_HOTPLUG_CPU0 + bool "Set default setting of cpu0_hotpluggable" + default n + depends on HOTPLUG_CPU && EXPERIMENTAL + ---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 && EXPERIMENTAL + ---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 y prompt "Compat VDSO support" diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index 4564c8e28a33..5f9a1243190e 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -28,6 +28,10 @@ struct x86_cpu { #ifdef CONFIG_HOTPLUG_CPU extern int arch_register_cpu(int num); extern void arch_unregister_cpu(int); +extern void __cpuinit start_cpu0(void); +#ifdef CONFIG_DEBUG_HOTPLUG_CPU0 +extern int _debug_hotplug_cpu(int cpu, int action); +#endif #endif DECLARE_PER_CPU(int, cpu_state); diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index 4f19a1526037..b073aaea747c 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -166,6 +166,7 @@ void native_send_call_func_ipi(const struct cpumask *mask); void native_send_call_func_single_ipi(int cpu); void x86_idle_thread_init(unsigned int cpu, struct task_struct *idle); +void smp_store_boot_cpu_info(void); void smp_store_cpu_info(int id); #define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu) diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 1817fa911024..f78fc2b4deb0 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2199,9 +2199,11 @@ static int ioapic_retrigger_irq(struct irq_data *data) { struct irq_cfg *cfg = data->chip_data; unsigned long flags; + int cpu; raw_spin_lock_irqsave(&vector_lock, flags); - apic->send_IPI_mask(cpumask_of(cpumask_first(cfg->domain)), cfg->vector); + cpu = cpumask_first_and(cfg->domain, cpu_online_mask); + apic->send_IPI_mask(cpumask_of(cpu), cfg->vector); raw_spin_unlock_irqrestore(&vector_lock, flags); return 1; diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 7505f7b13e71..ca165ac6793b 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1237,7 +1237,7 @@ void __cpuinit cpu_init(void) oist = &per_cpu(orig_ist, cpu); #ifdef CONFIG_NUMA - if (cpu != 0 && this_cpu_read(numa_node) == 0 && + if (this_cpu_read(numa_node) == 0 && early_cpu_to_node(cpu) != NUMA_NO_NODE) set_numa_node(early_cpu_to_node(cpu)); #endif @@ -1269,8 +1269,7 @@ void __cpuinit cpu_init(void) barrier(); x86_configure_nx(); - if (cpu != 0) - enable_x2apic(); + enable_x2apic(); /* * set up and load the per-CPU TSS diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c index 6b96110bb0c3..e4c1a4184531 100644 --- a/arch/x86/kernel/cpu/mtrr/main.c +++ b/arch/x86/kernel/cpu/mtrr/main.c @@ -695,11 +695,16 @@ void mtrr_ap_init(void) } /** - * Save current fixed-range MTRR state of the BSP + * Save current fixed-range MTRR state of the first cpu in cpu_online_mask. */ void mtrr_save_state(void) { - smp_call_function_single(0, mtrr_save_fixed_ranges, NULL, 1); + int first_cpu; + + get_online_cpus(); + first_cpu = cpumask_first(cpu_online_mask); + smp_call_function_single(first_cpu, mtrr_save_fixed_ranges, NULL, 1); + put_online_cpus(); } void set_mtrr_aps_delayed_init(void) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 4dac2f68ed4a..8e7f6556028f 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -266,6 +266,19 @@ num_subarch_entries = (. - subarch_entries) / 4 jmp default_entry #endif /* CONFIG_PARAVIRT */ +#ifdef CONFIG_HOTPLUG_CPU +/* + * Boot CPU0 entry point. It's called from play_dead(). Everything has been set + * up already except stack. We just set up stack here. Then call + * start_secondary(). + */ +ENTRY(start_cpu0) + movl stack_start, %ecx + movl %ecx, %esp + jmp *(initial_code) +ENDPROC(start_cpu0) +#endif + /* * Non-boot CPU entry point; entered from trampoline.S * We can't lgdt here, because lgdt itself uses a data segment, but diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 94bf9cc2c7ee..980053c4b9cc 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -252,6 +252,22 @@ ENTRY(secondary_startup_64) pushq %rax # target address in negative space lretq +#ifdef CONFIG_HOTPLUG_CPU +/* + * Boot CPU0 entry point. It's called from play_dead(). Everything has been set + * up already except stack. We just set up stack here. Then call + * start_secondary(). + */ +ENTRY(start_cpu0) + movq stack_start(%rip),%rsp + movq initial_code(%rip),%rax + pushq $0 # fake return address to stop unwinder + pushq $__KERNEL_CS # set correct cs + pushq %rax # target address in negative space + lretq +ENDPROC(start_cpu0) +#endif + /* SMP bootup changes these two */ __REFDATA .align 8 diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 675a05012449..245a71db401a 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -175,7 +175,11 @@ void __cpuinit fpu_init(void) cr0 |= X86_CR0_EM; write_cr0(cr0); - if (!smp_processor_id()) + /* + * init_thread_xstate is only called once to avoid overriding + * xstate_size during boot time or during CPU hotplug. + */ + if (xstate_size == 0) init_thread_xstate(); mxcsr_feature_mask_init(); diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index f3e2ec878b8c..c635663b20d9 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -127,8 +127,8 @@ EXPORT_PER_CPU_SYMBOL(cpu_info); atomic_t init_deasserted; /* - * Report back to the Boot Processor. - * Running on AP. + * Report back to the Boot Processor during boot time or to the caller processor + * during CPU online. */ static void __cpuinit smp_callin(void) { @@ -140,15 +140,17 @@ static void __cpuinit smp_callin(void) * we may get here before an INIT-deassert IPI reaches * our local APIC. We have to wait for the IPI or we'll * lock up on an APIC access. + * + * Since CPU0 is not wakened up by INIT, it doesn't wait for the IPI. */ - if (apic->wait_for_init_deassert) + cpuid = smp_processor_id(); + if (apic->wait_for_init_deassert && cpuid != 0) apic->wait_for_init_deassert(&init_deasserted); /* * (This works even if the APIC is not enabled.) */ phys_id = read_apic_id(); - cpuid = smp_processor_id(); if (cpumask_test_cpu(cpuid, cpu_callin_mask)) { panic("%s: phys CPU#%d, CPU#%d already present??\n", __func__, phys_id, cpuid); @@ -230,6 +232,8 @@ static void __cpuinit smp_callin(void) cpumask_set_cpu(cpuid, cpu_callin_mask); } +static int cpu0_logical_apicid; +static int enable_start_cpu0; /* * Activate a secondary processor. */ @@ -245,6 +249,8 @@ notrace static void __cpuinit start_secondary(void *unused) preempt_disable(); smp_callin(); + enable_start_cpu0 = 0; + #ifdef CONFIG_X86_32 /* switch away from the initial page table */ load_cr3(swapper_pg_dir); @@ -281,19 +287,30 @@ notrace static void __cpuinit start_secondary(void *unused) cpu_idle(); } +void __init smp_store_boot_cpu_info(void) +{ + int id = 0; /* CPU 0 */ + struct cpuinfo_x86 *c = &cpu_data(id); + + *c = boot_cpu_data; + c->cpu_index = id; +} + /* * The bootstrap kernel entry code has set these up. Save them for * a given CPU */ - void __cpuinit smp_store_cpu_info(int id) { struct cpuinfo_x86 *c = &cpu_data(id); *c = boot_cpu_data; c->cpu_index = id; - if (id != 0) - identify_secondary_cpu(c); + /* + * During boot time, CPU0 has this setup already. Save the info when + * bringing up AP or offlined CPU0. + */ + identify_secondary_cpu(c); } static bool __cpuinit @@ -483,7 +500,7 @@ void __inquire_remote_apic(int apicid) * won't ... remember to clear down the APIC, etc later. */ int __cpuinit -wakeup_secondary_cpu_via_nmi(int logical_apicid, unsigned long start_eip) +wakeup_secondary_cpu_via_nmi(int apicid, unsigned long start_eip) { unsigned long send_status, accept_status = 0; int maxlvt; @@ -491,7 +508,7 @@ wakeup_secondary_cpu_via_nmi(int logical_apicid, unsigned long start_eip) /* Target chip */ /* Boot on the stack */ /* Kick the second */ - apic_icr_write(APIC_DM_NMI | apic->dest_logical, logical_apicid); + apic_icr_write(APIC_DM_NMI | apic->dest_logical, apicid); pr_debug("Waiting for send to finish...\n"); send_status = safe_apic_wait_icr_idle(); @@ -651,6 +668,63 @@ static void __cpuinit announce_cpu(int cpu, int apicid) node, cpu, apicid); } +static int wakeup_cpu0_nmi(unsigned int cmd, struct pt_regs *regs) +{ + int cpu; + + cpu = smp_processor_id(); + if (cpu == 0 && !cpu_online(cpu) && enable_start_cpu0) + return NMI_HANDLED; + + return NMI_DONE; +} + +/* + * Wake up AP by INIT, INIT, STARTUP sequence. + * + * Instead of waiting for STARTUP after INITs, BSP will execute the BIOS + * boot-strap code which is not a desired behavior for waking up BSP. To + * void the boot-strap code, wake up CPU0 by NMI instead. + * + * This works to wake up soft offlined CPU0 only. If CPU0 is hard offlined + * (i.e. physically hot removed and then hot added), NMI won't wake it up. + * We'll change this code in the future to wake up hard offlined CPU0 if + * real platform and request are available. + */ +static int __cpuinit +wakeup_cpu_via_init_nmi(int cpu, unsigned long start_ip, int apicid, + int *cpu0_nmi_registered) +{ + int id; + int boot_error; + + /* + * Wake up AP by INIT, INIT, STARTUP sequence. + */ + if (cpu) + return wakeup_secondary_cpu_via_init(apicid, start_ip); + + /* + * Wake up BSP by nmi. + * + * Register a NMI handler to help wake up CPU0. + */ + boot_error = register_nmi_handler(NMI_LOCAL, + wakeup_cpu0_nmi, 0, "wake_cpu0"); + + if (!boot_error) { + enable_start_cpu0 = 1; + *cpu0_nmi_registered = 1; + if (apic->dest_logical == APIC_DEST_LOGICAL) + id = cpu0_logical_apicid; + else + id = apicid; + boot_error = wakeup_secondary_cpu_via_nmi(id, start_ip); + } + + return boot_error; +} + /* * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad * (ie clustered apic addressing mode), this is a LOGICAL apic ID. @@ -666,6 +740,7 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle) unsigned long boot_error = 0; int timeout; + int cpu0_nmi_registered = 0; /* Just in case we booted with a single CPU. */ alternatives_enable_smp(); @@ -713,13 +788,16 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle) } /* - * Kick the secondary CPU. Use the method in the APIC driver - * if it's defined - or use an INIT boot APIC message otherwise: + * Wake up a CPU in difference cases: + * - Use the method in the APIC driver if it's defined + * Otherwise, + * - Use an INIT boot APIC message for APs or NMI for BSP. */ if (apic->wakeup_secondary_cpu) boot_error = apic->wakeup_secondary_cpu(apicid, start_ip); else - boot_error = wakeup_secondary_cpu_via_init(apicid, start_ip); + boot_error = wakeup_cpu_via_init_nmi(cpu, start_ip, apicid, + &cpu0_nmi_registered); if (!boot_error) { /* @@ -784,6 +862,13 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle) */ smpboot_restore_warm_reset_vector(); } + /* + * Clean up the nmi handler. Do this after the callin and callout sync + * to avoid impact of possible long unregister time. + */ + if (cpu0_nmi_registered) + unregister_nmi_handler(NMI_LOCAL, "wake_cpu0"); + return boot_error; } @@ -797,7 +882,7 @@ int __cpuinit native_cpu_up(unsigned int cpu, struct task_struct *tidle) pr_debug("++++++++++++++++++++=_---CPU UP %u\n", cpu); - if (apicid == BAD_APICID || apicid == boot_cpu_physical_apicid || + if (apicid == BAD_APICID || !physid_isset(apicid, phys_cpu_present_map) || !apic->apic_id_valid(apicid)) { pr_err("%s: bad cpu %d\n", __func__, cpu); @@ -995,7 +1080,7 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) /* * Setup boot CPU information */ - smp_store_cpu_info(0); /* Final full version of the data */ + smp_store_boot_cpu_info(); /* Final full version of the data */ cpumask_copy(cpu_callin_mask, cpumask_of(0)); mb(); @@ -1031,6 +1116,11 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) */ setup_local_APIC(); + if (x2apic_mode) + cpu0_logical_apicid = apic_read(APIC_LDR); + else + cpu0_logical_apicid = GET_APIC_LOGICAL_ID(apic_read(APIC_LDR)); + /* * Enable IO APIC before setting up error vector */ @@ -1219,19 +1309,6 @@ void cpu_disable_common(void) int native_cpu_disable(void) { - int cpu = smp_processor_id(); - - /* - * Perhaps use cpufreq to drop frequency, but that could go - * into generic code. - * - * We won't take down the boot processor on i386 due to some - * interrupts only being able to be serviced by the BSP. - * Especially so if we're not using an IOAPIC -zwane - */ - if (cpu == 0) - return -EBUSY; - clear_local_APIC(); cpu_disable_common(); @@ -1271,6 +1348,14 @@ void play_dead_common(void) local_irq_disable(); } +static bool wakeup_cpu0(void) +{ + if (smp_processor_id() == 0 && enable_start_cpu0) + return true; + + return false; +} + /* * We need to flush the caches before going to sleep, lest we have * dirty data in our caches when we come back up. @@ -1334,6 +1419,11 @@ static inline void mwait_play_dead(void) __monitor(mwait_ptr, 0, 0); mb(); __mwait(eax, 0); + /* + * If NMI wants to wake up CPU0, start CPU0. + */ + if (wakeup_cpu0()) + start_cpu0(); } } @@ -1344,6 +1434,11 @@ static inline void hlt_play_dead(void) while (1) { native_halt(); + /* + * If NMI wants to wake up CPU0, start CPU0. + */ + if (wakeup_cpu0()) + start_cpu0(); } } diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c index 76ee97709a00..6e60b5fe2244 100644 --- a/arch/x86/kernel/topology.c +++ b/arch/x86/kernel/topology.c @@ -30,23 +30,110 @@ #include <linux/mmzone.h> #include <linux/init.h> #include <linux/smp.h> +#include <linux/irq.h> #include <asm/cpu.h> 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 __ref _debug_hotplug_cpu(int cpu, int action) +{ + struct device *dev = get_cpu_device(cpu); + int ret; + + if (!cpu_is_hotpluggable(cpu)) + return -EINVAL; + + cpu_hotplug_driver_lock(); + + switch (action) { + case 0: + ret = cpu_down(cpu); + if (!ret) { + pr_info("CPU %u is now offline\n", cpu); + kobject_uevent(&dev->kobj, KOBJ_OFFLINE); + } else + pr_debug("Can't offline CPU%d.\n", cpu); + break; + case 1: + ret = cpu_up(cpu); + if (!ret) + kobject_uevent(&dev->kobj, KOBJ_ONLINE); + else + pr_debug("Can't online CPU%d.\n", cpu); + break; + default: + ret = -EINVAL; + } + + cpu_hotplug_driver_unlock(); + + 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 __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); diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 218cdb16163c..120cee1c3f8d 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -21,6 +21,7 @@ #include <asm/suspend.h> #include <asm/debugreg.h> #include <asm/fpu-internal.h> /* pcntxt_mask */ +#include <asm/cpu.h> #ifdef CONFIG_X86_32 static struct saved_context saved_context; @@ -237,3 +238,84 @@ void restore_processor_state(void) #ifdef CONFIG_X86_32 EXPORT_SYMBOL(restore_processor_state); #endif + +/* + * When bsp_check() is called in hibernate and suspend, cpu hotplug + * is disabled already. So it's unnessary to handle race condition between + * cpumask query and cpu hotplug. + */ +static int bsp_check(void) +{ + if (cpumask_first(cpu_online_mask) != 0) { + pr_warn("CPU0 is offline.\n"); + return -ENODEV; + } + + return 0; +} + +static int bsp_pm_callback(struct notifier_block *nb, unsigned long action, + void *ptr) +{ + int ret = 0; + + switch (action) { + case PM_SUSPEND_PREPARE: + 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; + } + return notifier_from_errno(ret); +} + +static int __init bsp_pm_check_init(void) +{ + /* + * Set this bsp_pm_callback as lower priority than + * cpu_hotplug_pm_callback. So cpu_hotplug_pm_callback will be called + * earlier to disable cpu hotplug before bsp online check. + */ + pm_notifier(bsp_pm_callback, -INT_MAX); + return 0; +} + +core_initcall(bsp_pm_check_init); diff --git a/kernel/cpu.c b/kernel/cpu.c index f45657f1eb8e..3046a503242c 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -603,6 +603,11 @@ cpu_hotplug_pm_callback(struct notifier_block *nb, static int __init cpu_hotplug_pm_sync_init(void) { + /* + * cpu_hotplug_pm_callback has higher priority than x86 + * bsp_pm_callback which depends on cpu_hotplug_pm_callback + * to disable cpu hotplug to avoid cpu hotplug race. + */ pm_notifier(cpu_hotplug_pm_callback, 0); return 0; } |