KVM: x86: Introduce a workqueue to deliver PIT timer interrupts

We really want to "kvm_set_irq" during the hrtimer callback,
but that is risky because that is during interrupt context.
Instead, offload the work to a workqueue, which is a bit safer
and should provide most of the same functionality.

Signed-off-by: Chris Lalancette <clalance@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/i8254.h

@@ -27,7 +27,7 @@ struct kvm_kpit_state {
 	u32    speaker_data_on;
 	struct mutex lock;
 	struct kvm_pit *pit;
-	raw_spinlock_t inject_lock;
+	spinlock_t inject_lock;
 	unsigned long irq_ack;
 	struct kvm_irq_ack_notifier irq_ack_notifier;
 };
@@ -40,6 +40,8 @@ struct kvm_pit {
 	struct kvm_kpit_state pit_state;
 	int irq_source_id;
 	struct kvm_irq_mask_notifier mask_notifier;
+	struct workqueue_struct *wq;
+	struct work_struct expired;
 };
 
 #define KVM_PIT_BASE_ADDRESS	    0x40