Log error code of EVTCHNOP_bind_pirq failure

Ease debugging of PCI passthrough problems.

patches.xen/irq-bind-debug-log.patch

@@ -0,0 +1,13 @@
+diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
+index 524c221..acb29f4 100644
+--- a/drivers/xen/events/events_base.c
++++ b/drivers/xen/events/events_base.c
+@@ -519,7 +519,7 @@ static unsigned int __startup_pirq(unsigned int irq)
+ 					BIND_PIRQ__WILL_SHARE : 0;
+ 	rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_pirq, &bind_pirq);
+ 	if (rc != 0) {
+-		pr_warn("Failed to obtain physical IRQ %d\n", irq);
++		pr_warn("Failed to obtain physical IRQ %d (error %d)\n", irq, rc);
+ 		return 0;
+ 	}
+ 	evtchn = bind_pirq.port;

series.conf

@@ -4,6 +4,7 @@ patches.xen/0001-Revert-xen-xenbus-Avoid-synchronous-wait-on-XenBus-s.patch
 patches.xen/0001-xen-fix-deadlock-on-proc-xen-xenbus-access.patch
 patches.xen/xen-netfront-detach-crash.patch
 patches.xen/0001-mce-hide-EBUSY-initialization-error-on-Xen.patch
+patches.xen/irq-bind-debug-log.patch
 
 # Additional features
 #patches.xen/pvops-0100-usb-xen-pvusb-driver.patch