xen: implement CPU hotplugging
Note the changes from 2.6.18-xen CPU hotplugging:
A vcpu_down request from the remote admin via Xenbus both hotunplugs the
CPU, and disables it by removing it from the cpu_present map, and removing
its entry in /sys.
A vcpu_up request from the remote admin only re-enables the CPU, and does
not immediately bring the CPU up. A udev event is emitted, which can be
caught by the user if he wishes to automatically re-up CPUs when available,
or implement a more complex policy.
Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index baca7f2..be5cbb2 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -11,8 +11,6 @@
* useful topology information for the kernel to make use of. As a
* result, all CPUs are treated as if they're single-core and
* single-threaded.
- *
- * This does not handle HOTPLUG_CPU yet.
*/
#include <linux/sched.h>
#include <linux/err.h>
@@ -61,11 +59,12 @@
return IRQ_HANDLED;
}
-static __cpuinit void cpu_bringup_and_idle(void)
+static __cpuinit void cpu_bringup(void)
{
int cpu = smp_processor_id();
cpu_init();
+ touch_softlockup_watchdog();
preempt_disable();
xen_enable_sysenter();
@@ -86,6 +85,11 @@
local_irq_enable();
wmb(); /* make sure everything is out */
+}
+
+static __cpuinit void cpu_bringup_and_idle(void)
+{
+ cpu_bringup();
cpu_idle();
}
@@ -209,8 +213,6 @@
cpu_set(cpu, cpu_present_map);
}
-
- //init_xenbus_allowed_cpumask();
}
static __cpuinit int
@@ -278,12 +280,6 @@
struct task_struct *idle = idle_task(cpu);
int rc;
-#if 0
- rc = cpu_up_check(cpu);
- if (rc)
- return rc;
-#endif
-
#ifdef CONFIG_X86_64
/* Allocate node local memory for AP pdas */
WARN_ON(cpu == 0);
@@ -336,6 +332,42 @@
{
}
+int xen_cpu_disable(void)
+{
+ unsigned int cpu = smp_processor_id();
+ if (cpu == 0)
+ return -EBUSY;
+
+ cpu_disable_common();
+
+ load_cr3(swapper_pg_dir);
+ return 0;
+}
+
+void xen_cpu_die(unsigned int cpu)
+{
+ while (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpu, NULL)) {
+ current->state = TASK_UNINTERRUPTIBLE;
+ schedule_timeout(HZ/10);
+ }
+ unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
+ unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
+ unbind_from_irqhandler(per_cpu(debug_irq, cpu), NULL);
+ unbind_from_irqhandler(per_cpu(callfuncsingle_irq, cpu), NULL);
+ xen_uninit_lock_cpu(cpu);
+ xen_teardown_timer(cpu);
+
+ if (num_online_cpus() == 1)
+ alternatives_smp_switch(0);
+}
+
+void xen_play_dead(void)
+{
+ play_dead_common();
+ HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
+ cpu_bringup();
+}
+
static void stop_self(void *v)
{
int cpu = smp_processor_id();
@@ -419,9 +451,13 @@
static const struct smp_ops xen_smp_ops __initdata = {
.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
.smp_prepare_cpus = xen_smp_prepare_cpus,
- .cpu_up = xen_cpu_up,
.smp_cpus_done = xen_smp_cpus_done,
+ .cpu_up = xen_cpu_up,
+ .cpu_die = xen_cpu_die,
+ .cpu_disable = xen_cpu_disable,
+ .play_dead = xen_play_dead,
+
.smp_send_stop = xen_smp_send_stop,
.smp_send_reschedule = xen_smp_send_reschedule,
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index d072823..dd71e3a 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -357,6 +357,11 @@
printk("cpu %d spinlock event irq %d\n", cpu, irq);
}
+void xen_uninit_lock_cpu(int cpu)
+{
+ unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
+}
+
void __init xen_init_spinlocks(void)
{
pv_lock_ops.spin_is_locked = xen_spin_is_locked;
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 20182d9..004ba86 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -450,6 +450,14 @@
setup_runstate_info(cpu);
}
+void xen_teardown_timer(int cpu)
+{
+ struct clock_event_device *evt;
+ BUG_ON(cpu == 0);
+ evt = &per_cpu(xen_clock_events, cpu);
+ unbind_from_irqhandler(evt->irq, NULL);
+}
+
void xen_setup_cpu_clockevents(void)
{
BUG_ON(preemptible());
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 1e8bfda..8dbd97f 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -34,6 +34,7 @@
void xen_init_irq_ops(void);
void xen_setup_timer(int cpu);
+void xen_teardown_timer(int cpu);
cycle_t xen_clocksource_read(void);
void xen_setup_cpu_clockevents(void);
unsigned long xen_tsc_khz(void);
@@ -50,11 +51,16 @@
void __init xen_setup_vcpu_info_placement(void);
+void xen_play_dead(void);
+void xen_cpu_die(unsigned int cpu);
+int xen_cpu_disable(void);
+
#ifdef CONFIG_SMP
void xen_smp_init(void);
void __init xen_init_spinlocks(void);
__cpuinit void xen_init_lock_cpu(int cpu);
+void xen_uninit_lock_cpu(int cpu);
extern cpumask_t xen_cpu_initialized_map;
#else
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index 363286c..f62d8df 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -1,4 +1,4 @@
-obj-y += grant-table.o features.o events.o manage.o
+obj-y += grant-table.o features.o events.o manage.o cpu_hotplug.o
obj-y += xenbus/
obj-$(CONFIG_XEN_XENCOMM) += xencomm.o
obj-$(CONFIG_XEN_BALLOON) += balloon.o
diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
new file mode 100644
index 0000000..1bc0035
--- /dev/null
+++ b/drivers/xen/cpu_hotplug.c
@@ -0,0 +1,90 @@
+#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);
+
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index b6c2b8f..c3290bc 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -360,6 +360,10 @@
per_cpu(virq_to_irq, cpu_from_evtchn(evtchn))
[index_from_irq(irq)] = -1;
break;
+ case IRQT_IPI:
+ per_cpu(ipi_to_irq, cpu_from_evtchn(evtchn))
+ [index_from_irq(irq)] = -1;
+ break;
default:
break;
}