@@ -150,6 +150,13 @@ config NR_CPUS
depends on SMP
default "4"
+config HOTPLUG_CPU
+ bool "Support for hot-pluggable CPUs"
+ depends on SMP && HOTPLUG
+ help
+ Say Y here to experiment with turning CPUs off and on. CPUs
+ can be controlled through /sys/devices/system/cpu.
+
source kernel/Kconfig.preempt
config HZ
@@ -4,6 +4,7 @@
#include <asm-generic/irq.h>
extern void (*handle_arch_irq)(struct pt_regs *);
+extern void migrate_irqs(void);
extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
#endif
@@ -67,6 +67,11 @@ extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
struct device_node;
+extern int __cpu_disable(void);
+
+extern void __cpu_die(unsigned int cpu);
+extern void cpu_die(void);
+
struct smp_operations {
const char *name;
/*
@@ -85,6 +90,11 @@ struct smp_operations {
* Performs post-boot cleanup
*/
void (*cpu_postboot)(void);
+#ifdef CONFIG_HOTPLUG_CPU
+ int (*cpu_disable)(unsigned int cpu);
+ void (*cpu_die)(unsigned int cpu);
+ int (*cpu_kill)(unsigned int cpu);
+#endif
};
extern const struct smp_operations smp_spin_table_ops;
@@ -22,7 +22,7 @@
extern unsigned long __cpu_setup(void);
-struct cpu_info __initdata cpu_table[] = {
+struct cpu_info __cpuinitdata cpu_table[] = {
{
.cpu_id_val = 0x000f0000,
.cpu_id_mask = 0x000f0000,
@@ -81,3 +81,64 @@ void __init init_IRQ(void)
if (!handle_arch_irq)
panic("No interrupt controller found.");
}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static bool migrate_one_irq(struct irq_desc *desc)
+{
+ struct irq_data *d = irq_desc_get_irq_data(desc);
+ const struct cpumask *affinity = d->affinity;
+ struct irq_chip *c;
+ bool ret = false;
+
+ /*
+ * If this is a per-CPU interrupt, or the affinity does not
+ * include this CPU, then we have nothing to do.
+ */
+ if (irqd_is_per_cpu(d) || !cpumask_test_cpu(smp_processor_id(), affinity))
+ return false;
+
+ if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids) {
+ affinity = cpu_online_mask;
+ ret = true;
+ }
+
+ c = irq_data_get_irq_chip(d);
+ if (!c->irq_set_affinity)
+ pr_debug("IRQ%u: unable to set affinity\n", d->irq);
+ else if (c->irq_set_affinity(d, affinity, true) == IRQ_SET_MASK_OK && ret)
+ cpumask_copy(d->affinity, affinity);
+
+ return ret;
+}
+
+/*
+ * The current CPU has been marked offline. Migrate IRQs off this CPU.
+ * If the affinity settings do not allow other CPUs, force them onto any
+ * available CPU.
+ *
+ * Note: we must iterate over all IRQs, whether they have an attached
+ * action structure or not, as we need to get chained interrupts too.
+ */
+void migrate_irqs(void)
+{
+ unsigned int i;
+ struct irq_desc *desc;
+ unsigned long flags;
+
+ local_irq_save(flags);
+
+ for_each_irq_desc(i, desc) {
+ bool affinity_broken;
+
+ raw_spin_lock(&desc->lock);
+ affinity_broken = migrate_one_irq(desc);
+ raw_spin_unlock(&desc->lock);
+
+ if (affinity_broken)
+ pr_warn_ratelimited("IRQ%u no longer affine to CPU%u\n",
+ i, smp_processor_id());
+ }
+
+ local_irq_restore(flags);
+}
+#endif /* CONFIG_HOTPLUG_CPU */
@@ -102,6 +102,13 @@ void arch_cpu_idle(void)
local_irq_enable();
}
+#ifdef CONFIG_HOTPLUG_CPU
+void arch_cpu_idle_dead(void)
+{
+ cpu_die();
+}
+#endif
+
void machine_shutdown(void)
{
#ifdef CONFIG_SMP
@@ -167,6 +167,117 @@ asmlinkage void __cpuinit secondary_start_kernel(void)
cpu_startup_entry(CPUHP_ONLINE);
}
+#ifdef CONFIG_HOTPLUG_CPU
+static int __cpuinit op_cpu_kill(unsigned int cpu)
+{
+ if (smp_ops[cpu]->cpu_kill)
+ return smp_ops[cpu]->cpu_kill(cpu);
+ return 1;
+}
+
+static int __cpuinit op_cpu_disable(unsigned int cpu)
+{
+ /* CPU0 may not have smp_ops */
+ if (!smp_ops[cpu])
+ return -EPERM;
+
+ if (smp_ops[cpu]->cpu_disable)
+ return smp_ops[cpu]->cpu_disable(cpu);
+
+ return 0;
+}
+
+/*
+ * __cpu_disable runs on the processor to be shutdown.
+ */
+int __cpuinit __cpu_disable(void)
+{
+ unsigned int cpu = smp_processor_id();
+ int ret;
+
+ ret = op_cpu_disable(cpu);
+ if (ret)
+ return ret;
+
+ /*
+ * Take this CPU offline. Once we clear this, we can't return,
+ * and we must not schedule until we're ready to give up the cpu.
+ */
+ set_cpu_online(cpu, false);
+
+ /*
+ * OK - migrate IRQs away from this CPU
+ */
+ migrate_irqs();
+
+ /*
+ * Remove this CPU from the vm mask set of all processes.
+ */
+ clear_tasks_mm_cpumask(cpu);
+
+ return 0;
+}
+
+static DECLARE_COMPLETION(cpu_died);
+
+/*
+ * called on the thread which is asking for a CPU to be shutdown -
+ * waits until shutdown has completed, or it is timed out.
+ */
+void __cpuinit __cpu_die(unsigned int cpu)
+{
+ if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) {
+ pr_err("CPU%u: cpu didn't die\n", cpu);
+ return;
+ }
+ pr_notice("CPU%u: shutdown\n", cpu);
+
+ if (!op_cpu_kill(cpu))
+ pr_warn("CPU%u: unable to kill\n", cpu);
+}
+
+/*
+ * Called from the idle thread for the CPU which has been shutdown.
+ *
+ * Note that we disable IRQs here, but do not re-enable them
+ * before returning to the caller. This is also the behaviour
+ * of the other hotplug-cpu capable cores, so presumably coming
+ * out of idle fixes this.
+ */
+void __ref cpu_die(void)
+{
+ unsigned int cpu = smp_processor_id();
+
+ idle_task_exit();
+
+ local_irq_disable();
+ mb();
+
+ /* Tell __cpu_die() that this CPU is now safe to dispose of */
+ RCU_NONIDLE(complete(&cpu_died));
+
+ /*
+ * actual CPU shutdown procedure is at least platform (if not
+ * CPU) specific.
+ */
+ if (smp_ops[cpu]->cpu_die)
+ smp_ops[cpu]->cpu_die(cpu);
+
+ /*
+ * Do not return to the idle loop - jump back to the secondary
+ * cpu initialisation. There's some initialisation which needs
+ * to be repeated to undo the effects of taking the CPU offline.
+ */
+ __asm__("mov sp, %0\n"
+ " mov x29, #0\n"
+ " b secondary_start_kernel"
+ :
+ : "r" (task_stack_page(current) + THREAD_START_SP));
+}
+#endif
+
+
+
void __init smp_cpus_done(unsigned int max_cpus)
{
unsigned long bogosum = loops_per_jiffy * num_online_cpus();
This patch adds the basic infrastructure necessary to support CPU_HOTPLUG on arm64, based on the arm implementation. Actual hotplug support will depend on an implementation's smp_operations (e.g. PSCI). Signed-off-by: Mark Rutland <mark.rutland@arm.com> --- arch/arm64/Kconfig | 7 +++ arch/arm64/include/asm/irq.h | 1 + arch/arm64/include/asm/smp.h | 10 ++++ arch/arm64/kernel/cputable.c | 2 +- arch/arm64/kernel/irq.c | 61 +++++++++++++++++++++++ arch/arm64/kernel/process.c | 7 +++ arch/arm64/kernel/smp.c | 111 ++++++++++++++++++++++++++++++++++++++++++ 7 files changed, 198 insertions(+), 1 deletion(-)