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-rw-r--r--drivers/xen/events.c21
1 files changed, 15 insertions, 6 deletions
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 65f8637d13cf..74681478100a 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -170,6 +170,9 @@ static struct irq_info *info_for_irq(unsigned irq)
static unsigned int evtchn_from_irq(unsigned irq)
{
+ if (unlikely(WARN(irq < 0 || irq >= nr_irqs, "Invalid irq %d!\n", irq)))
+ return 0;
+
return info_for_irq(irq)->evtchn;
}
@@ -405,15 +408,21 @@ static int find_unbound_irq(void)
{
struct irq_data *data;
int irq, res;
- int start = get_nr_hw_irqs();
+ int bottom = get_nr_hw_irqs();
+ int top = nr_irqs-1;
- if (start == nr_irqs)
+ if (bottom == nr_irqs)
goto no_irqs;
- /* nr_irqs is a magic value. Must not use it.*/
- for (irq = nr_irqs-1; irq > start; irq--) {
+ /* This loop starts from the top of IRQ space and goes down.
+ * We need this b/c if we have a PCI device in a Xen PV guest
+ * we do not have an IO-APIC (though the backend might have them)
+ * mapped in. To not have a collision of physical IRQs with the Xen
+ * event channels start at the top of the IRQ space for virtual IRQs.
+ */
+ for (irq = top; irq > bottom; irq--) {
data = irq_get_irq_data(irq);
- /* only 0->15 have init'd desc; handle irq > 16 */
+ /* only 15->0 have init'd desc; handle irq > 16 */
if (!data)
break;
if (data->chip == &no_irq_chip)
@@ -424,7 +433,7 @@ static int find_unbound_irq(void)
return irq;
}
- if (irq == start)
+ if (irq == bottom)
goto no_irqs;
res = irq_alloc_desc_at(irq, -1);