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#include <linux/notifier.h>
#include <xen/xenbus.h>
#include <asm-x86/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 (!is_running_on_xen())
return -ENODEV;
register_xenstore_notifier(&xsn_cpu);
return 0;
}
arch_initcall(setup_vcpu_hotplug_event);
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