Commit d765edbb authored by Stephen Hemminger's avatar Stephen Hemminger Committed by Greg Kroah-Hartman
Browse files

vmbus: add driver_override support 

Add support for overriding the default driver for a VMBus device
in the same way that it can be done for PCI devices. This patch
adds the /sys/bus/vmbus/devices/.../driver_override file
and the logic for matching.

This is used by driverctl tool to do driver override.
https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.com%2Fdriverctl%2Fdriverctl&data=02%7C01%7Ckys%40microsoft.com%7C42e803feb2c544ef6ea908d5fd538878%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636693457619960040&sdata=kEyYHRIjNZCk%2B37moCSqbrZL426YccNQrsWpENcrZdw%3D&reserved=0



Signed-off-by: default avatarStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 83b15fed

Documentation/ABI/testing/sysfs-bus-vmbus

0 → 100644
+21 −0
Original line number Diff line number Diff line 
What:		/sys/bus/vmbus/devices/.../driver_override

Date:		August 2019

Contact:	Stephen Hemminger <sthemmin@microsoft.com>

Description:

		This file allows the driver for a device to be specified which

		will override standard static and dynamic ID matching.  When

		specified, only a driver with a name matching the value written

		to driver_override will have an opportunity to bind to the

		device.  The override is specified by writing a string to the

		driver_override file (echo uio_hv_generic > driver_override) and

		may be cleared with an empty string (echo > driver_override).

		This returns the device to standard matching rules binding.

		Writing to driver_override does not automatically unbind the

		device from its current driver or make any attempt to

		automatically load the specified driver.  If no driver with a

		matching name is currently loaded in the kernel, the device

		will not bind to any driver.  This also allows devices to

		opt-out of driver binding using a driver_override name such as

		"none".  Only a single driver may be specified in the override,

		there is no support for parsing delimiters.

drivers/hv/vmbus_drv.c

+96 −19
Original line number Diff line number Diff line
@@ -498,6 +498,54 @@ static ssize_t device_show(struct device *dev, 
}

static DEVICE_ATTR_RO(device);



static ssize_t driver_override_store(struct device *dev,

				     struct device_attribute *attr,

				     const char *buf, size_t count)

{

	struct hv_device *hv_dev = device_to_hv_device(dev);

	char *driver_override, *old, *cp;



	/* We need to keep extra room for a newline */

	if (count >= (PAGE_SIZE - 1))

		return -EINVAL;



	driver_override = kstrndup(buf, count, GFP_KERNEL);

	if (!driver_override)

		return -ENOMEM;



	cp = strchr(driver_override, '\n');

	if (cp)

		*cp = '\0';



	device_lock(dev);

	old = hv_dev->driver_override;

	if (strlen(driver_override)) {

		hv_dev->driver_override = driver_override;

	} else {

		kfree(driver_override);

		hv_dev->driver_override = NULL;

	}

	device_unlock(dev);



	kfree(old);



	return count;

}



static ssize_t driver_override_show(struct device *dev,

				    struct device_attribute *attr, char *buf)

{

	struct hv_device *hv_dev = device_to_hv_device(dev);

	ssize_t len;



	device_lock(dev);

	len = snprintf(buf, PAGE_SIZE, "%s\n", hv_dev->driver_override);

	device_unlock(dev);



	return len;

}

static DEVICE_ATTR_RW(driver_override);



/* Set up per device attributes in /sys/bus/vmbus/devices/<bus device> */

static struct attribute *vmbus_dev_attrs[] = {

	&dev_attr_id.attr,
@@ -528,6 +576,7 @@ static struct attribute *vmbus_dev_attrs[] = { 
	&dev_attr_channel_vp_mapping.attr,

	&dev_attr_vendor.attr,

	&dev_attr_device.attr,

	&dev_attr_driver_override.attr,

	NULL,

};

ATTRIBUTE_GROUPS(vmbus_dev);
@@ -563,17 +612,26 @@ static inline bool is_null_guid(const uuid_le *guid) 
	return true;

}



/*

 * Return a matching hv_vmbus_device_id pointer.

 * If there is no match, return NULL.

 */

static const struct hv_vmbus_device_id *hv_vmbus_get_id(struct hv_driver *drv,

					const uuid_le *guid)

static const struct hv_vmbus_device_id *

hv_vmbus_dev_match(const struct hv_vmbus_device_id *id, const uuid_le *guid)



{

	if (id == NULL)

		return NULL; /* empty device table */



	for (; !is_null_guid(&id->guid); id++)

		if (!uuid_le_cmp(id->guid, *guid))

			return id;



	return NULL;

}



static const struct hv_vmbus_device_id *

hv_vmbus_dynid_match(struct hv_driver *drv, const uuid_le *guid)

{

	const struct hv_vmbus_device_id *id = NULL;

	struct vmbus_dynid *dynid;



	/* Look at the dynamic ids first, before the static ones */

	spin_lock(&drv->dynids.lock);

	list_for_each_entry(dynid, &drv->dynids.list, node) {

		if (!uuid_le_cmp(dynid->id.guid, *guid)) {
@@ -583,18 +641,37 @@ static const struct hv_vmbus_device_id *hv_vmbus_get_id(struct hv_driver *drv, 
	}

	spin_unlock(&drv->dynids.lock);



	if (id)

	return id;

}



	id = drv->id_table;

	if (id == NULL)

		return NULL; /* empty device table */

static const struct hv_vmbus_device_id vmbus_device_null = {

	.guid = NULL_UUID_LE,

};



	for (; !is_null_guid(&id->guid); id++)

		if (!uuid_le_cmp(id->guid, *guid))

			return id;

/*

 * Return a matching hv_vmbus_device_id pointer.

 * If there is no match, return NULL.

 */

static const struct hv_vmbus_device_id *hv_vmbus_get_id(struct hv_driver *drv,

							struct hv_device *dev)

{

	const uuid_le *guid = &dev->dev_type;

	const struct hv_vmbus_device_id *id;



	/* When driver_override is set, only bind to the matching driver */

	if (dev->driver_override && strcmp(dev->driver_override, drv->name))

		return NULL;



	/* Look at the dynamic ids first, before the static ones */

	id = hv_vmbus_dynid_match(drv, guid);

	if (!id)

		id = hv_vmbus_dev_match(drv->id_table, guid);



	/* driver_override will always match, send a dummy id */

	if (!id && dev->driver_override)

		id = &vmbus_device_null;



	return id;

}



/* vmbus_add_dynid - add a new device ID to this driver and re-probe devices */
@@ -643,7 +720,7 @@ static ssize_t new_id_store(struct device_driver *driver, const char *buf, 
	if (retval)

		return retval;



	if (hv_vmbus_get_id(drv, &guid))

	if (hv_vmbus_dynid_match(drv, &guid))

		return -EEXIST;



	retval = vmbus_add_dynid(drv, &guid);
@@ -708,7 +785,7 @@ static int vmbus_match(struct device *device, struct device_driver *driver) 
	if (is_hvsock_channel(hv_dev->channel))

		return drv->hvsock;



	if (hv_vmbus_get_id(drv, &hv_dev->dev_type))

	if (hv_vmbus_get_id(drv, hv_dev))

		return 1;



	return 0;
@@ -725,7 +802,7 @@ static int vmbus_probe(struct device *child_device) 
	struct hv_device *dev = device_to_hv_device(child_device);

	const struct hv_vmbus_device_id *dev_id;



	dev_id = hv_vmbus_get_id(drv, &dev->dev_type);

	dev_id = hv_vmbus_get_id(drv, dev);

	if (drv->probe) {

		ret = drv->probe(dev, dev_id);

		if (ret != 0)

include/linux/hyperv.h

+1 −0
Original line number Diff line number Diff line
@@ -1125,6 +1125,7 @@ struct hv_device { 
	u16 device_id;



	struct device device;

	char *driver_override; /* Driver name to force a match */



	struct vmbus_channel *channel;

	struct kset	     *channels_kset;

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