#include <linux/notifier.h> #include <xen/xenbus.h> #include <asm/xen/hypervisor.h> #include <asm/cpu.h> static void enable_hotplug_cpu(int cpu) { if (!cpu_present(cpu)) arch_register_cpu(cpu); cpu_set(cpu, cpu_present_map); } static void disable_hotplug_cpu(int cpu) { if (cpu_present(cpu)) arch_unregister_cpu(cpu); cpu_clear(cpu, cpu_present_map); } static void vcpu_hotplug(unsigned int cpu) { int err; char dir[32], state[32]; if (!cpu_possible(cpu)) return; sprintf(dir, "cpu/%u", cpu); err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state); if (err != 1) { printk(KERN_ERR "XENBUS: Unable to read cpu state\n"); return; } if (strcmp(state, "online") == 0) { enable_hotplug_cpu(cpu); } else if (strcmp(state, "offline") == 0) { (void)cpu_down(cpu); disable_hotplug_cpu(cpu); } else { printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu); } } static void handle_vcpu_hotplug_event(struct xenbus_watch *watch, const char **vec, unsigned int len) { unsigned int cpu; char *cpustr; const char *node = vec[XS_WATCH_PATH]; cpustr = strstr(node, "cpu/"); if (cpustr != NULL) { sscanf(cpustr, "cpu/%u", &cpu); vcpu_hotplug(cpu); } } static int setup_cpu_watcher(struct notifier_block *notifier, unsigned long event, void *data) { static struct xenbus_watch cpu_watch = { .node = "cpu", .callback = handle_vcpu_hotplug_event}; (void)register_xenbus_watch(&cpu_watch); return NOTIFY_DONE; } static int __init setup_vcpu_hotplug_event(void) { static struct notifier_block xsn_cpu = { .notifier_call = setup_cpu_watcher }; if (!xen_pv_domain()) return -ENODEV; register_xenstore_notifier(&xsn_cpu); return 0; } arch_initcall(setup_vcpu_hotplug_event);