drivers: hv: vmbus: Introduce latency testing

Introduce user specified latency in the packet reception path
By exposing the test parameters as part of the debugfs channel
attributes. We will control the testing state via these attributes.

Signed-off-by: Branden Bonaby <brandonbonaby94@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

6 files changed, 219 insertions, 0 deletions

diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
index a1eec7177c2d..94daf8240c95 100644
--- a/drivers/hv/Makefile
+++ b/drivers/hv/Makefile
@@ -9,4 +9,5 @@ CFLAGS_hv_balloon.o = -I$(src)
 hv_vmbus-y := vmbus_drv.o \
 		 hv.o connection.o channel.o \
 		 channel_mgmt.o ring_buffer.o hv_trace.o
+hv_vmbus-$(CONFIG_HYPERV_TESTING)	+= hv_debugfs.o
 hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_fcopy.o hv_utils_transport.o
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 0475be4356dd..e947c39d4cc7 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -363,6 +363,7 @@ void vmbus_on_event(unsigned long data)
 
 	trace_vmbus_on_event(channel);
 
+	hv_debug_delay_test(channel, INTERRUPT_DELAY);
 	do {
 		void (*callback_fn)(void *);
 
diff --git a/drivers/hv/hv_debugfs.c b/drivers/hv/hv_debugfs.c
new file mode 100644
index 000000000000..8a2878573582
--- /dev/null
+++ b/drivers/hv/hv_debugfs.c
@@ -0,0 +1,178 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Authors:
+ *   Branden Bonaby <brandonbonaby94@gmail.com>
+ */
+
+#include <linux/hyperv.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+
+#include "hyperv_vmbus.h"
+
+struct dentry *hv_debug_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 > 1000)
+		return -EINVAL;
+	*(u32 *)data = val;
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(hv_debugfs_delay_fops, hv_debugfs_delay_get,
+			 hv_debugfs_delay_set, "%llu\n");
+
+static int hv_debugfs_state_get(void *data, u64 *val)
+{
+	*val = *(bool *)data;
+	return 0;
+}
+
+static int hv_debugfs_state_set(void *data, u64 val)
+{
+	if (val == 1)
+		*(bool *)data = true;
+	else if (val == 0)
+		*(bool *)data = false;
+	else
+		return -EINVAL;
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(hv_debugfs_state_fops, hv_debugfs_state_get,
+			 hv_debugfs_state_set, "%llu\n");
+
+/* Setup delay files to store test values */
+static 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 */
+static 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_file(status, 0644, root,
+					 state,
+					 &hv_debugfs_state_fops);
+	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 */
+static void hv_debug_set_dir_dentry(struct hv_device *dev, struct dentry *root)
+{
+	if (hv_debug_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_debug_root)) {
+		dev_root = debugfs_create_dir(device, hv_debug_root);
+		if (IS_ERR(dev_root)) {
+			pr_debug("debugfs_hyperv: hyperv/%s/ not created\n",
+				 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: hyperv/%s/%s/ not created\n",
+				 device, delay_name);
+			return PTR_ERR(delay);
+		}
+		ret = hv_debug_delay_files(dev, delay);
+
+		return ret;
+	}
+	pr_debug("debugfs_hyperv: hyperv/ not in root debugfs path\n");
+	return PTR_ERR(hv_debug_root);
+}
+
+/* Remove dentry associated with released hv device */
+void hv_debug_rm_dev_dir(struct hv_device *dev)
+{
+	if (!IS_ERR(hv_debug_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_debug_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_debug_root = debugfs_create_dir("hyperv", NULL);
+	if (IS_ERR(hv_debug_root)) {
+		pr_debug("debugfs_hyperv: hyperv/ not created\n");
+		return PTR_ERR(hv_debug_root);
+	}
+	return 0;
+}
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index af9379a3bf89..20edcfd3b96c 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -385,4 +385,35 @@ enum hvutil_device_state {
 	HVUTIL_DEVICE_DYING,     /* driver unload is in progress */
 };
 
+enum delay {
+	INTERRUPT_DELAY = 0,
+	MESSAGE_DELAY   = 1,
+};
+
+#ifdef CONFIG_HYPERV_TESTING
+
+int hv_debug_add_dev_dir(struct hv_device *dev);
+void hv_debug_rm_dev_dir(struct hv_device *dev);
+void hv_debug_rm_all_dir(void);
+int hv_debug_init(void);
+void hv_debug_delay_test(struct vmbus_channel *channel, enum delay delay_type);
+
+#else /* CONFIG_HYPERV_TESTING */
+
+static inline void hv_debug_rm_dev_dir(struct hv_device *dev) {};
+static inline void hv_debug_rm_all_dir(void) {};
+static inline void hv_debug_delay_test(struct vmbus_channel *channel,
+				       enum delay delay_type) {};
+static inline int hv_debug_init(void)
+{
+	return -1;
+}
+
+static inline int hv_debug_add_dev_dir(struct hv_device *dev)
+{
+	return -1;
+}
+
+#endif /* CONFIG_HYPERV_TESTING */
+
 #endif /* _HYPERV_VMBUS_H */
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 9a03b163cbbd..356e22159e83 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -396,6 +396,7 @@ struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
 	struct hv_ring_buffer_info *rbi = &channel->inbound;
 	struct vmpacket_descriptor *desc;
 
+	hv_debug_delay_test(channel, MESSAGE_DELAY);
 	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
 		return NULL;
 
@@ -421,6 +422,7 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
 	u32 packetlen = desc->len8 << 3;
 	u32 dsize = rbi->ring_datasize;
 
+	hv_debug_delay_test(channel, MESSAGE_DELAY);
 	/* bump offset to next potential packet */
 	rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
 	if (rbi->priv_read_index >= dsize)
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 0ac874faf720..125991820278 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -960,6 +960,8 @@ 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;
 
+	hv_debug_rm_dev_dir(hv_dev);
+
 	mutex_lock(&vmbus_connection.channel_mutex);
 	hv_process_channel_removal(channel);
 	mutex_unlock(&vmbus_connection.channel_mutex);
@@ -1814,6 +1816,7 @@ int vmbus_device_register(struct hv_device *child_device_obj)
 		pr_err("Unable to register primary channeln");
 		goto err_kset_unregister;
 	}
+	hv_debug_add_dev_dir(child_device_obj);
 
 	return 0;
 
@@ -2374,6 +2377,7 @@ static int __init hv_acpi_init(void)
 		ret = -ETIMEDOUT;
 		goto cleanup;
 	}
+	hv_debug_init();
 
 	ret = vmbus_bus_init();
 	if (ret)
@@ -2410,6 +2414,8 @@ static void __exit vmbus_exit(void)
 
 		tasklet_kill(&hv_cpu->msg_dpc);
 	}
+	hv_debug_rm_all_dir();
+
 	vmbus_free_channels();
 
 	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {