xen: fix memory access violation bug when CONFIG_HAVE_SPARSE_IRQ is enabled

When sparse IRQs are enabled, it is not safe to assume an IRQ descriptor
exists for every possible IRQ.  This patch causes init_evtchn_cpu_bindings
to skip initialisation of IRQ descriptors which don't exist.

Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 56ace47f24d6..e6d47e8ca1ac 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -141,6 +141,8 @@ static void init_evtchn_cpu_bindings(void)
         /* By default all event channels notify CPU#0. */
         for (i = 0; i < nr_irqs; i++) {
                 struct irq_desc *desc = irq_to_desc(i);
+                if (!desc)
+                        continue;
                 desc->affinity = cpumask_of_cpu(0);
         }
 #endif