[PATCH] x86, uv: Fix uv with destroy_irq()

[Yinghai Lu <yinghai@kernel.org>]

Russ found that:

| There is a regression that is causing a NULL pointer dereference
| in free_irte when shutting down xpc.  git bisect narrowed it down
| to git commit d585d060b42bd36f6f0b23ff327d3b91f80c7139, which
| changed free_irte().  Reverse applying the patch fixes the problem.

and he bisected to

| commit d585d060b42bd36f6f0b23ff327d3b91f80c7139
| Author: Thomas Gleixner <tglx@linutronix.de>
|Date:   Sun Oct 10 12:34:27 2010 +0200
|
|   intr_remap: Simplify the code further
|
|   Having irq_2_iommu in struct irq_cfg allows further simplifications.

We need to use irq_mapped() for every irq instead of intr_remapping_enabled
overall

Reported-by: Russ Anderson <rja@sgi.com>
Bisected-by: Russ Anderson <rja@sgi.com>
Tested-by: Russ Anderson <rja@sgi.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/kernel/apic/io_apic.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/arch/x86/kernel/apic/io_apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c
+++ linux-2.6/arch/x86/kernel/apic/io_apic.c
@@ -3109,7 +3109,7 @@ void destroy_irq(unsigned int irq)
 
 	irq_set_status_flags(irq, IRQ_NOREQUEST|IRQ_NOPROBE);
 
-	if (intr_remapping_enabled)
+	if (irq_remapped(get_irq_chip_data(irq)))
 		free_irte(irq);
 	raw_spin_lock_irqsave(&vector_lock, flags);
 	__clear_irq_vector(irq, cfg);