[PATCH 3/7] hyper-v: use fast hypercall for HVCALL_SIGNAL_EVENT

[Vitaly Kuznetsov <vkuznets@redhat.com>]

We need to pass only 8 bytes of input for HvSignalEvent which makes it a
perfect fit for fast hypercall. hv_input_signal_event_buffer is not needed
any more and hv_input_signal_event is converted to union for convenience.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/channel_mgmt.c | 15 +++++----------
 drivers/hv/connection.c   |  3 ++-
 include/linux/hyperv.h    | 19 ++++++++-----------
 3 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 735f936..6cfa297 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -804,20 +804,15 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 	/*
 	 * Setup state for signalling the host.
 	 */
-	newchannel->sig_event = (struct hv_input_signal_event *)
-				(ALIGN((unsigned long)
-				&newchannel->sig_buf,
-				HV_HYPERCALL_PARAM_ALIGN));
-
-	newchannel->sig_event->connectionid.asu32 = 0;
-	newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
-	newchannel->sig_event->flag_number = 0;
-	newchannel->sig_event->rsvdz = 0;
+	newchannel->sig_event.connectionid.asu32 = 0;
+	newchannel->sig_event.connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
+	newchannel->sig_event.flag_number = 0;
+	newchannel->sig_event.rsvdz = 0;
 
 	if (vmbus_proto_version != VERSION_WS2008) {
 		newchannel->is_dedicated_interrupt =
 				(offer->is_dedicated_interrupt != 0);
-		newchannel->sig_event->connectionid.u.id =
+		newchannel->sig_event.connectionid.u.id =
 				offer->connection_id;
 	}
 
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index cf77c7f..545f2a4 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -405,6 +405,7 @@ void vmbus_set_event(struct vmbus_channel *channel)
 	if (!channel->is_dedicated_interrupt)
 		vmbus_send_interrupt(child_relid);
 
-	hv_do_hypercall(HVCALL_SIGNAL_EVENT, channel->sig_event, NULL);
+	hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT,
+			      channel->sig_event.as_uint64);
 }
 EXPORT_SYMBOL_GPL(vmbus_set_event);
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 677f084..5d6777c 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -678,15 +678,13 @@ union hv_connection_id {
 };
 
 /* Definition of the hv_signal_event hypercall input structure. */
-struct hv_input_signal_event {
-	union hv_connection_id connectionid;
-	u16 flag_number;
-	u16 rsvdz;
-};
-
-struct hv_input_signal_event_buffer {
-	u64 align8;
-	struct hv_input_signal_event event;
+union hv_input_signal_event {
+	u64 as_uint64;
+	struct {
+		union hv_connection_id connectionid;
+		u16 flag_number;
+		u16 rsvdz;
+	};
 };
 
 enum hv_numa_policy {
@@ -771,8 +769,7 @@ struct vmbus_channel {
 	} callback_mode;
 
 	bool is_dedicated_interrupt;
-	struct hv_input_signal_event_buffer sig_buf;
-	struct hv_input_signal_event *sig_event;
+	union hv_input_signal_event sig_event;
 
 	/*
 	 * Starting with win8, this field will be used to specify
-- 
2.9.3