xen: Fix find_unbound_irq in presence of ioapic irqs.

Don't break the assumption that the first 16 irqs are ISA irqs;
make sure that the irq is actually free before using it.

Use dynamic_irq_init_keep_chip_data instead of
dynamic_irq_init so that chip_data is not NULL (a NULL chip_data breaks
setup_vector_irq).

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 7c64473c9f3f..b5a254e9aebe 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -340,9 +340,18 @@ static int find_unbound_irq(void)
         int irq;
         struct irq_desc *desc;
 
-        for (irq = 0; irq < nr_irqs; irq++)
+        for (irq = 0; irq < nr_irqs; irq++) {
+                desc = irq_to_desc(irq);
+                /* only 0->15 have init'd desc; handle irq > 16 */
+                if (desc == NULL)
+                        break;
+                if (desc->chip == &no_irq_chip)
+                        break;
+                if (desc->chip != &xen_dynamic_chip)
+                        continue;
                 if (irq_info[irq].type == IRQT_UNBOUND)
                         break;
+        }
 
         if (irq == nr_irqs)
                 panic("No available IRQ to bind to: increase nr_irqs!\n");
@@ -351,7 +360,7 @@ static int find_unbound_irq(void)
         if (WARN_ON(desc == NULL))
                 return -1;
 
-        dynamic_irq_init(irq);
+        dynamic_irq_init_keep_chip_data(irq);
 
         return irq;
 }