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.

Stefano Garzarella committed 4 years ago

Commit 539fec71 parent 9c25cde3 files · +96 −0Browse files

Unified · Split

3 files

Documentation/ABI/testing/sysfs-bus-vdpa +20 −0
drivers/vdpa/vdpa.c +74 −0
include/linux/vdpa.h +2 −0

Documentation/ABI/testing/sysfs-bus-vdpa+20−0

@@ -35,3 +35,23 @@ Description: · 34 unmodified lines
35	Writing a device name to this file will cause the driver to	35	Writing a device name to this file will cause the driver to
36	attempt to unbind from the device. This may be useful when	36	attempt to unbind from the device. This may be useful when
37	overriding default bindings.	37	overriding default bindings.
		38
		39	What: /sys/bus/vdpa/devices/.../driver_override
		40	Date: November 2021
		41	Contact: virtualization@lists.linux-foundation.org
		42	Description:
		43	This file allows the driver for a device to be specified.
		44	When specified, only a driver with a name matching the value
		45	written to driver_override will have an opportunity to bind to
		46	the device. The override is specified by writing a string to the
		47	driver_override file (echo vhost-vdpa > driver_override) and may
		48	be cleared with an empty string (echo > driver_override).
		49	This returns the device to standard matching rules binding.
		50	Writing to driver_override does not automatically unbind the
		51	device from its current driver or make any attempt to
		52	automatically load the specified driver. If no driver with a
		53	matching name is currently loaded in the kernel, the device will
		54	not bind to any driver. This also allows devices to opt-out of
		55	driver binding using a driver_override name such as "none".
		56	Only a single driver may be specified in the override, there is
		57	no support for parsing delimiters.

drivers/vdpa/vdpa.c+74−0

@@ -52,8 +52,81 @@ static void vdpa_dev_remove(struct device *d) · 51 unmodified lines
52	drv->remove(vdev);	52	drv->remove(vdev);
53	}	53	}
54		54
		55	static int vdpa_dev_match(struct device dev, struct device_driver drv)
		56	{
		57	struct vdpa_device *vdev = dev_to_vdpa(dev);
		58
		59	/* Check override first, and if set, only use the named driver */
		60	if (vdev->driver_override)
		61	return strcmp(vdev->driver_override, drv->name) == 0;
		62
		63	/* Currently devices must be supported by all vDPA bus drivers */
		64	return 1;
		65	}
		66
		67	static ssize_t driver_override_store(struct device *dev,
		68	struct device_attribute *attr,
		69	const char *buf, size_t count)
		70	{
		71	struct vdpa_device *vdev = dev_to_vdpa(dev);
		72	const char driver_override, old;
		73	char *cp;
		74
		75	/* We need to keep extra room for a newline */
		76	if (count >= (PAGE_SIZE - 1))
		77	return -EINVAL;
		78
		79	driver_override = kstrndup(buf, count, GFP_KERNEL);
		80	if (!driver_override)
		81	return -ENOMEM;
		82
		83	cp = strchr(driver_override, '\n');
		84	if (cp)
		85	*cp = '\0';
		86
		87	device_lock(dev);
		88	old = vdev->driver_override;
		89	if (strlen(driver_override)) {
		90	vdev->driver_override = driver_override;
		91	} else {
		92	kfree(driver_override);
		93	vdev->driver_override = NULL;
		94	}
		95	device_unlock(dev);
		96
		97	kfree(old);
		98
		99	return count;
		100	}
		101
		102	static ssize_t driver_override_show(struct device *dev,
		103	struct device_attribute attr, char buf)
		104	{
		105	struct vdpa_device *vdev = dev_to_vdpa(dev);
		106	ssize_t len;
		107
		108	device_lock(dev);
		109	len = snprintf(buf, PAGE_SIZE, "%s\n", vdev->driver_override);
		110	device_unlock(dev);
		111
		112	return len;
		113	}
		114	static DEVICE_ATTR_RW(driver_override);
		115
		116	static struct attribute *vdpa_dev_attrs[] = {
		117	&dev_attr_driver_override.attr,
		118	NULL,
		119	};
		120
		121	static const struct attribute_group vdpa_dev_group = {
		122	.attrs = vdpa_dev_attrs,
		123	};
		124	__ATTRIBUTE_GROUPS(vdpa_dev);
		125
55	static struct bus_type vdpa_bus = {	126	static struct bus_type vdpa_bus = {
56	.name = "vdpa",	127	.name = "vdpa",
		128	.dev_groups = vdpa_dev_groups,
		129	.match = vdpa_dev_match,
57	.probe = vdpa_dev_probe,	130	.probe = vdpa_dev_probe,
58	.remove = vdpa_dev_remove,	131	.remove = vdpa_dev_remove,
59	};	132	};
@@ -68,6 +141,7 @@ static void vdpa_release_dev(struct device *d) · 8 unmodified lines
68		141
69	ida_simple_remove(&vdpa_index_ida, vdev->index);	142	ida_simple_remove(&vdpa_index_ida, vdev->index);
70	mutex_destroy(&vdev->cf_mutex);	143	mutex_destroy(&vdev->cf_mutex);
		144	kfree(vdev->driver_override);
71	kfree(vdev);	145	kfree(vdev);
72	}	146	}
73		147

include/linux/vdpa.h+2−0

  * 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
 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;

vdpa: add driver_override support

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