Commit 539fec78 authored by Stefano Garzarella's avatar Stefano Garzarella Committed by Michael S. Tsirkin
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vdpa: add driver_override support 



`driver_override` allows to control which of the vDPA bus drivers
binds to a vDPA device.

If `driver_override` is not set, the previous behaviour is followed:
devices use the first vDPA bus driver loaded (unless auto binding
is disabled).

Tested on Fedora 34 with driverctl(8):
  $ modprobe virtio-vdpa
  $ modprobe vhost-vdpa
  $ modprobe vdpa-sim-net

  $ vdpa dev add mgmtdev vdpasim_net name dev1

  # dev1 is attached to the first vDPA bus driver loaded
  $ driverctl -b vdpa list-devices
    dev1 virtio_vdpa

  $ driverctl -b vdpa set-override dev1 vhost_vdpa

  $ driverctl -b vdpa list-devices
    dev1 vhost_vdpa [*]

  Note: driverctl(8) integrates with udev so the binding is
  preserved.

Suggested-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarStefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20211126164753.181829-3-sgarzare@redhat.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 9c25cdeb

Documentation/ABI/testing/sysfs-bus-vdpa

+20 −0
Original line number Diff line number Diff line
@@ -35,3 +35,23 @@ Description: 
		Writing a device name to this file will cause the driver to

		attempt to unbind from the device. This may be useful when

		overriding default bindings.



What:		/sys/bus/vdpa/devices/.../driver_override

Date:		November 2021

Contact:	virtualization@lists.linux-foundation.org

Description:

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

		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 vhost-vdpa > 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/vdpa/vdpa.c

+74 −0
Original line number Diff line number Diff line
@@ -52,8 +52,81 @@ static void vdpa_dev_remove(struct device *d) 
		drv->remove(vdev);

}



static int vdpa_dev_match(struct device *dev, struct device_driver *drv)

{

	struct vdpa_device *vdev = dev_to_vdpa(dev);



	/* Check override first, and if set, only use the named driver */

	if (vdev->driver_override)

		return strcmp(vdev->driver_override, drv->name) == 0;



	/* Currently devices must be supported by all vDPA bus drivers */

	return 1;

}



static ssize_t driver_override_store(struct device *dev,

				     struct device_attribute *attr,

				     const char *buf, size_t count)

{

	struct vdpa_device *vdev = dev_to_vdpa(dev);

	const char *driver_override, *old;

	char *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 = vdev->driver_override;

	if (strlen(driver_override)) {

		vdev->driver_override = driver_override;

	} else {

		kfree(driver_override);

		vdev->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 vdpa_device *vdev = dev_to_vdpa(dev);

	ssize_t len;



	device_lock(dev);

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

	device_unlock(dev);



	return len;

}

static DEVICE_ATTR_RW(driver_override);



static struct attribute *vdpa_dev_attrs[] = {

	&dev_attr_driver_override.attr,

	NULL,

};



static const struct attribute_group vdpa_dev_group = {

	.attrs  = vdpa_dev_attrs,

};

__ATTRIBUTE_GROUPS(vdpa_dev);



static struct bus_type vdpa_bus = {

	.name  = "vdpa",

	.dev_groups = vdpa_dev_groups,

	.match = vdpa_dev_match,

	.probe = vdpa_dev_probe,

	.remove = vdpa_dev_remove,

};
@@ -68,6 +141,7 @@ static void vdpa_release_dev(struct device *d) 


	ida_simple_remove(&vdpa_index_ida, vdev->index);

	mutex_destroy(&vdev->cf_mutex);

	kfree(vdev->driver_override);

	kfree(vdev);

}

include/linux/vdpa.h

+2 −0
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ struct vdpa_mgmt_dev; 
 * struct vdpa_device - representation of a vDPA device

 * @dev: underlying device

 * @dma_dev: the actual device that is performing DMA

 * @driver_override: driver name to force a match

 * @config: the configuration ops for this device.

 * @cf_mutex: Protects get and set access to configuration layout.

 * @index: device index
@@ -76,6 +77,7 @@ struct vdpa_mgmt_dev; 
struct vdpa_device {

	struct device dev;

	struct device *dma_dev;

	const char *driver_override;

	const struct vdpa_config_ops *config;

	struct mutex cf_mutex; /* Protects get/set config */

	unsigned int index;