@@ -0,0 +1,21 @@
+What:           /sys/kernel/debug/hyperv/<UUID>/fuzz_test_state
+Date:           August 2019
+KernelVersion:  5.3
+Contact:        Branden Bonaby <brandonbonaby94@gmail.com>
+Description:    Fuzz testing status of a vmbus device, whether its in an ON
+                state or a OFF state
+Users:          Debugging tools
+
+What:           /sys/kernel/debug/hyperv/<UUID>/delay/fuzz_test_buffer_interrupt_delay
+Date:           August 2019
+KernelVersion:  5.3
+Contact:        Branden Bonaby <brandonbonaby94@gmail.com>
+Description:    Fuzz testing buffer delay value between 0 - 1000
+Users:          Debugging tools
+
+What:           /sys/kernel/debug/hyperv/<UUID>/delay/fuzz_test_message_delay
+Date:           August 2019
+KernelVersion:  5.3
+Contact:        Branden Bonaby <brandonbonaby94@gmail.com>
+Description:    Fuzz testing message delay value between 0 - 1000
+Users:          Debugging tools

@@ -7460,6 +7460,7 @@ F:	include/uapi/linux/hyperv.h
 F:	include/asm-generic/mshyperv.h
 F:	tools/hv/
 F:	Documentation/ABI/stable/sysfs-bus-vmbus
+F:	Documentation/ABI/testing/debugfs-hyperv
 
 HYPERBUS SUPPORT
 M:	Vignesh Raghavendra <vigneshr@ti.com>

@@ -919,6 +919,10 @@ static void vmbus_device_release(struct device *device)
 	struct hv_device *hv_dev = device_to_hv_device(device);
 	struct vmbus_channel *channel = hv_dev->channel;
 
+#ifdef CONFIG_HYPERV_TESTING
+	hv_debug_rm_dev_dir(hv_dev);
+#endif /* CONFIG_HYPERV_TESTING */
+
 	mutex_lock(&vmbus_connection.channel_mutex);
 	hv_process_channel_removal(channel);
 	mutex_unlock(&vmbus_connection.channel_mutex);

@@ -1727,6 +1731,9 @@ int vmbus_device_register(struct hv_device *child_device_obj)
 		pr_err("Unable to register primary channeln");
 		goto err_kset_unregister;
 	}
+#ifdef CONFIG_HYPERV_TESTING
+	hv_debug_add_dev_dir(child_device_obj);
+#endif /* CONFIG_HYPERV_TESTING */
 
 	return 0;
 

@@ -2086,6 +2093,159 @@ static void hv_crash_handler(struct pt_regs *regs)
 	hyperv_cleanup();
 };
 
+#ifdef CONFIG_HYPERV_TESTING
+
+struct dentry *hv_root;
+
+static int hv_debugfs_delay_get(void *data, u64 *val)
+{
+	*val = *(u32 *)data;
+	return 0;
+}
+
+static int hv_debugfs_delay_set(void *data, u64 val)
+{
+	if (val >= 1 && val <= 1000)
+		*(u32 *)data = val;
+	/*Best to not use else statement here since we want
+	 * the delay to remain the same if val > 1000
+	 */
+	else if (val <= 0)
+		*(u32 *)data = 0;
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(hv_debugfs_delay_fops, hv_debugfs_delay_get,
+			 hv_debugfs_delay_set, "%llu\n");
+
+/* Setup delay files to store test values */
+int hv_debug_delay_files(struct hv_device *dev, struct dentry *root)
+{
+	struct vmbus_channel *channel = dev->channel;
+	char *buffer = "fuzz_test_buffer_interrupt_delay";
+	char *message = "fuzz_test_message_delay";
+	int *buffer_val = &channel->fuzz_testing_interrupt_delay;
+	int *message_val = &channel->fuzz_testing_message_delay;
+	struct dentry *buffer_file, *message_file;
+
+	buffer_file = debugfs_create_file(buffer, 0644, root,
+					  buffer_val,
+					  &hv_debugfs_delay_fops);
+	if (IS_ERR(buffer_file)) {
+		pr_debug("debugfs_hyperv: file %s not created\n", buffer);
+		return PTR_ERR(buffer_file);
+	}
+
+	message_file = debugfs_create_file(message, 0644, root,
+					   message_val,
+					   &hv_debugfs_delay_fops);
+	if (IS_ERR(message_file)) {
+		pr_debug("debugfs_hyperv: file %s not created\n", message);
+		return PTR_ERR(message_file);
+	}
+
+	return 0;
+}
+
+/* Setup test state value for vmbus device */
+int hv_debug_set_test_state(struct hv_device *dev, struct dentry *root)
+{
+	struct vmbus_channel *channel = dev->channel;
+	bool *state = &channel->fuzz_testing_state;
+	char *status = "fuzz_test_state";
+	struct dentry *test_state;
+
+	test_state = debugfs_create_bool(status, 0644, root, state);
+	if (IS_ERR(test_state)) {
+		pr_debug("debugfs_hyperv: file %s not created\n", status);
+		return PTR_ERR(test_state);
+	}
+
+	return 0;
+}
+
+/* Bind hv device to a dentry for debugfs */
+void hv_debug_set_dir_dentry(struct hv_device *dev, struct dentry *root)
+{
+	if (hv_root)
+		dev->debug_dir = root;
+}
+
+/* Create all test dentry's and names for fuzz testing */
+int hv_debug_add_dev_dir(struct hv_device *dev)
+{
+	const char *device = dev_name(&dev->device);
+	char *delay_name = "delay";
+	struct dentry *delay, *dev_root;
+	int ret;
+
+	if (!IS_ERR(hv_root)) {
+		dev_root = debugfs_create_dir(device, hv_root);
+		if (IS_ERR_OR_NULL(dev_root)) {
+			pr_debug("debugfs_hyperv: %s/%s/ not created\n",
+				 TESTING, device);
+			return PTR_ERR(dev_root);
+		}
+
+		hv_debug_set_test_state(dev, dev_root);
+		hv_debug_set_dir_dentry(dev, dev_root);
+		delay = debugfs_create_dir(delay_name, dev_root);
+
+		if (IS_ERR(delay)) {
+			pr_debug("debugfs_hyperv: %s/%s/%s/ not created\n",
+				 TESTING, device, delay_name);
+			return PTR_ERR(delay);
+		}
+		ret = hv_debug_delay_files(dev, delay);
+
+		return ret;
+	}
+	pr_debug("debugfs_hyperv: %s/ not in root debugfs path\n", TESTING);
+	return PTR_ERR(hv_root);
+}
+
+/* Remove dentry associated with released hv device */
+void hv_debug_rm_dev_dir(struct hv_device *dev)
+{
+	if (!IS_ERR(hv_root))
+		debugfs_remove_recursive(dev->debug_dir);
+}
+
+/* Remove all dentrys associated with vmbus testing */
+void hv_debug_rm_all_dir(void)
+{
+	debugfs_remove_recursive(hv_root);
+}
+
+/* Delay buffer/message reads on a vmbus channel */
+void hv_debug_delay_test(struct vmbus_channel *channel, enum delay delay_type)
+{
+	struct vmbus_channel *test_channel =	channel->primary_channel ?
+						channel->primary_channel :
+						channel;
+	bool state = test_channel->fuzz_testing_state;
+
+	if (state) {
+		if (delay_type == 0)
+			udelay(test_channel->fuzz_testing_interrupt_delay);
+		else
+			udelay(test_channel->fuzz_testing_message_delay);
+	}
+}
+
+/* Initialize top dentry for vmbus testing */
+int hv_debug_init(void)
+{
+	hv_root = debugfs_create_dir(TESTING, NULL);
+	if (IS_ERR(hv_root)) {
+		pr_debug("debugfs_hyperv: %s/ not created\n", TESTING);
+		return PTR_ERR(hv_root);
+	}
+
+	return 0;
+}
+#endif /* CONFIG_HYPERV_TESTING */
+
 static int __init hv_acpi_init(void)
 {
 	int ret, t;

@@ -2108,6 +2268,9 @@ static int __init hv_acpi_init(void)
 		ret = -ETIMEDOUT;
 		goto cleanup;
 	}
+#ifdef CONFIG_HYPERV_TESTING
+	hv_debug_init();
+#endif /* CONFIG_HYPERV_TESTING */
 
 	ret = vmbus_bus_init();
 	if (ret)

@@ -2140,6 +2303,10 @@ static void __exit vmbus_exit(void)
 
 		tasklet_kill(&hv_cpu->msg_dpc);
 	}
+#ifdef CONFIG_HYPERV_TESTING
+	hv_debug_rm_all_dir();
+#endif /* CONFIG_HYPERV_TESTING */
+
 	vmbus_free_channels();
 
 	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {