Xen: make events.c portable for ia64/xen support

Remove x86 dependency in drivers/xen/events.c for ia64/xen support
introducing include/asm/xen/events.h.
Introduce xen_irqs_disabled() to hide regs->flags
Introduce xen_do_IRQ() to hide regs->orig_ax.
make enum ipi_vector definition arch specific. ia64/xen needs four vectors.
Add one rmb() because on ia64 xchg() isn't barrier.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/asm-x86/xen/events.h b/include/asm-x86/xen/events.h
new file mode 100644
index 0000000..596312a
--- /dev/null
+++ b/include/asm-x86/xen/events.h
@@ -0,0 +1,22 @@
+#ifndef __XEN_EVENTS_H
+#define __XEN_EVENTS_H
+
+enum ipi_vector {
+	XEN_RESCHEDULE_VECTOR,
+	XEN_CALL_FUNCTION_VECTOR,
+
+	XEN_NR_IPIS,
+};
+
+static inline int xen_irqs_disabled(struct pt_regs *regs)
+{
+	return raw_irqs_disabled_flags(regs->flags);
+}
+
+static inline void xen_do_IRQ(int irq, struct pt_regs *regs)
+{
+	regs->orig_ax = ~irq;
+	do_IRQ(regs);
+}
+
+#endif /* __XEN_EVENTS_H */