HOTPLUG: Add CPU_DYING notifier

KVM wants a notification when a cpu is about to die, so it can disable
hardware extensions, but at a time when user processes cannot be scheduled
on the cpu, so it doesn't try to use virtualization extensions after they
have been disabled.

This adds a CPU_DYING notification.  The notification is called in atomic
context on the doomed cpu.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 9431101bf876..576f2bb34cc8 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -196,6 +196,8 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
 #define CPU_DEAD                0x0007 /* CPU (unsigned)v dead */
 #define CPU_LOCK_ACQUIRE        0x0008 /* Acquire all hotcpu locks */
 #define CPU_LOCK_RELEASE        0x0009 /* Release all hotcpu locks */
+#define CPU_DYING               0x000A /* CPU (unsigned)v not running any task,
+                                        * not handling interrupts, soon dead */
 
 /* Used for CPU hotplug events occuring while tasks are frozen due to a suspend
  * operation in progress
@@ -208,6 +210,7 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
 #define CPU_DOWN_PREPARE_FROZEN (CPU_DOWN_PREPARE | CPU_TASKS_FROZEN)
 #define CPU_DOWN_FAILED_FROZEN  (CPU_DOWN_FAILED | CPU_TASKS_FROZEN)
 #define CPU_DEAD_FROZEN         (CPU_DEAD | CPU_TASKS_FROZEN)
+#define CPU_DYING_FROZEN        (CPU_DYING | CPU_TASKS_FROZEN)
 
 #endif /* __KERNEL__ */
 #endif /* _LINUX_NOTIFIER_H */