[RFC PATCH V5 11/14] xen: introduce xen_event_channel_query_extended_abis

[Wei Liu <wei.liu2@citrix.com>]

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 drivers/xen/events.c |   37 +++++++++++++++++++++++++++++++++++++
 include/xen/events.h |    3 +++
 2 files changed, 40 insertions(+)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index ee33421..270821d 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -2109,6 +2109,43 @@ void xen_callback_vector(void)
 void xen_callback_vector(void) {}
 #endif
 
+/*
+ * This function returns the extended AIBs a guest can use.
+ * When
+ *  1) hypervisor doesn't support extended ABIs (EVTCHNOP_* not implemented)
+ *  2) hypervisor supports extended ABIs but this guest cannot use them
+ * it returns EVTCHN_EXTENDED_NONE
+ * otherwise it returns a or'ed bitmap of enabled ABIs
+ */
+uint64_t xen_event_channel_query_extended_abis(void)
+{
+	struct evtchn_query_extended_abis query;
+	int rc;
+
+	memset(&query, 0, sizeof(query));
+
+	rc = HYPERVISOR_event_channel_op(EVTCHNOP_query_extended_abis, &query);
+
+	if (rc < 0) {
+		printk(KERN_INFO
+		       "Hypervisor does not support extended event channel ABIs.");
+		return EVTCHN_EXTENDED_NONE;
+	}
+
+	printk(KERN_INFO "Hypervisor supports extended event channel ABIs.\n");
+
+	printk(KERN_INFO
+	       "Extended event channel AIBs enabled for this guest:\n");
+	if (query.abis == EVTCHN_EXTENDED_NONE /* 0 */)
+		printk(KERN_INFO "  None (disabled by host administrator)\n");
+	else {
+		if (query.abis & EVTCHN_EXTENDED_L3)
+			printk(KERN_INFO "  3-level event channel ABI\n");
+	}
+
+	return query.abis;
+}
+
 const struct evtchn_ops evtchn_l2_ops = {
 	.unmask = __unmask_local_port_l2,
 	.debug_interrupt = xen_debug_interrupt_l2,
diff --git a/include/xen/events.h b/include/xen/events.h
index 24cf421..49d54ac 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -114,4 +114,7 @@ void xen_init_IRQ(void);
 extern unsigned int xen_nr_event_channels;
 extern uint64_t xen_evtchn_extended;
 
+/* Query hypervisor for supported / enabled extended event channel ABIs. */
+uint64_t xen_event_channel_query_extended_abis(void);
+
 #endif	/* _XEN_EVENTS_H */
-- 
1.7.10.4