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>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 20182d9072c4..004ba86326ae 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -450,6 +450,14 @@ void xen_setup_timer(int cpu)
         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());