Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state

Implement the protocol for tearing down the monitor state established with
the host.

Signed-off-by: K. Y. Srinivasan <[e-mail]>
Tested-by: Vitaly Kuznetsov <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/hv/channel_mgmt.c

···
 }
 
 /*
+ * vmbus_unload_response - Handler for the unload response.
+ */
+static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
+{
+	/*
+	 * This is a global event; just wakeup the waiting thread.
+	 * Once we successfully unload, we can cleanup the monitor state.
+	 */
+	complete(&vmbus_connection.unload_event);
+}
+
+void vmbus_initiate_unload(void)
+{
+	struct vmbus_channel_message_header hdr;
+
+	init_completion(&vmbus_connection.unload_event);
+	memset(&hdr, 0, sizeof(struct vmbus_channel_message_header));
+	hdr.msgtype = CHANNELMSG_UNLOAD;
+	vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header));
+
+	wait_for_completion(&vmbus_connection.unload_event);
+}
+
+/*
  * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
  *
  */
···
 	{CHANNELMSG_INITIATE_CONTACT,		0, NULL},
 	{CHANNELMSG_VERSION_RESPONSE,		1, vmbus_onversion_response},
 	{CHANNELMSG_UNLOAD,			0, NULL},
+	{CHANNELMSG_UNLOAD_RESPONSE,		1, vmbus_unload_response},
 };
 
 /*

drivers/hv/connection.c

···
 
 void vmbus_disconnect(void)
 {
+	/*
+	 * First send the unload request to the host.
+	 */
+	vmbus_initiate_unload();
+
 	if (vmbus_connection.work_queue) {
 		drain_workqueue(vmbus_connection.work_queue);
 		destroy_workqueue(vmbus_connection.work_queue);

drivers/hv/hyperv_vmbus.h

···
 
 	atomic_t next_gpadl_handle;
 
+	struct completion  unload_event;
 	/*
 	 * Represents channel interrupts. Each bit position represents a
 	 * channel.  When a channel sends an interrupt via VMBUS, it finds its
···
 int hv_fcopy_init(struct hv_util_service *);
 void hv_fcopy_deinit(void);
 void hv_fcopy_onchannelcallback(void *);
+void vmbus_initiate_unload(void);
 
 static inline void hv_poll_channel(struct vmbus_channel *channel,
 				   void (*cb)(void *))

drivers/hv/vmbus_drv.c

···
 
 	vmbus_connection.conn_state = DISCONNECTED;
 	hv_synic_clockevents_cleanup();
+	vmbus_disconnect();
 	hv_remove_vmbus_irq();
 	vmbus_free_channels();
 	if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
···
 		smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);
 	acpi_bus_unregister_driver(&vmbus_acpi_driver);
 	hv_cpu_hotplug_quirk(false);
-	vmbus_disconnect();
 }
 
 

include/linux/hyperv.h

···
 	CHANNELMSG_INITIATE_CONTACT		= 14,
 	CHANNELMSG_VERSION_RESPONSE		= 15,
 	CHANNELMSG_UNLOAD			= 16,
+	CHANNELMSG_UNLOAD_RESPONSE		= 17,
 	CHANNELMSG_COUNT
 };