Drivers: hv: Add state to manage incoming channel interrupt load

Add state to bind a channel to a specific VCPU. This will help us better
distribute incoming interrupt load.
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: NHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/channel.c

@@ -181,7 +181,7 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
 	open_msg->ringbuffer_gpadlhandle = newchannel->ringbuffer_gpadlhandle;
 	open_msg->downstream_ringbuffer_pageoffset = send_ringbuffer_size >>
 						  PAGE_SHIFT;
-	open_msg->server_contextarea_gpadlhandle = 0;
+	open_msg->target_vp = newchannel->target_vp;
 
 	if (userdatalen > MAX_USER_DEFINED_BYTES) {
 		err = -EINVAL;

drivers/hv/channel_mgmt.c

@@ -302,6 +302,8 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 				offer->connection_id;
 	}
 
+	newchannel->target_vp = 0;
+
 	memcpy(&newchannel->offermsg, offer,
 	       sizeof(struct vmbus_channel_offer_channel));
 	newchannel->monitor_grp = (u8)offer->monitorid / 32;

include/linux/hyperv.h

@@ -732,8 +732,15 @@ struct vmbus_channel_open_channel {
 	/* GPADL for the channel's ring buffer. */
 	u32 ringbuffer_gpadlhandle;
 
-	/* GPADL for the channel's server context save area. */
-	u32 server_contextarea_gpadlhandle;
+	/*
+	 * Starting with win8, this field will be used to specify
+	 * the target virtual processor on which to deliver the interrupt for
+	 * the host to guest communication.
+	 * Prior to win8, incoming channel interrupts would only
+	 * be delivered on cpu 0. Setting this value to 0 would
+	 * preserve the earlier behavior.
+	 */
+	u32 target_vp;
 
 	/*
 	* The upstream ring buffer begins at offset zero in the memory
@@ -971,6 +978,16 @@ struct vmbus_channel {
 	bool is_dedicated_interrupt;
 	struct hv_input_signal_event_buffer sig_buf;
 	struct hv_input_signal_event *sig_event;
+
+	/*
+	 * Starting with win8, this field will be used to specify
+	 * the target virtual processor on which to deliver the interrupt for
+	 * the host to guest communication.
+	 * Prior to win8, incoming channel interrupts would only
+	 * be delivered on cpu 0. Setting this value to 0 would
+	 * preserve the earlier behavior.
+	 */
+	u32 target_vp;
 };
 
 static inline void set_channel_read_state(struct vmbus_channel *c, bool state)