1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 7d3bccb3b2a..40956d1c660 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -62,6 +62,14 @@ struct hv_device_info {
         struct hv_dev_port_info outbound;
 };
 
+static int vmbus_exists(void)
+{
+        if (hv_acpi_dev == NULL)
+                return -ENODEV;
+
+        return 0;
+}
+
 
 static void get_channel_info(struct hv_device *device,
                              struct hv_device_info *info)
@@ -590,6 +598,10 @@ int __vmbus_driver_register(struct hv_driver *hv_driver, struct module *owner, c
 
         pr_info("registering driver %s\n", hv_driver->name);
 
+        ret = vmbus_exists();
+        if (ret < 0)
+                return ret;
+
         hv_driver->driver.name = hv_driver->name;
         hv_driver->driver.owner = owner;
         hv_driver->driver.mod_name = mod_name;
@@ -614,6 +626,9 @@ void vmbus_driver_unregister(struct hv_driver *hv_driver)
 {
         pr_info("unregistering driver %s\n", hv_driver->name);
 
+        if (!vmbus_exists())
+                return;
+
         driver_unregister(&hv_driver->driver);
 
 }
@@ -776,6 +791,7 @@ static int __init hv_acpi_init(void)
 
 cleanup:
         acpi_bus_unregister_driver(&vmbus_acpi_driver);
+        hv_acpi_dev = NULL;
         return ret;
 }