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	35	Writing a device name to this file will cause the driver to
36	36	attempt to unbind from the device. This may be useful when
37	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	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	126	static struct bus_type vdpa_bus = {
56	127	.name = "vdpa",
	128	+ .dev_groups = vdpa_dev_groups,
	129	+ .match = vdpa_dev_match,
57	130	.probe = vdpa_dev_probe,
58	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	142	ida_simple_remove(&vdpa_index_ida, vdev->index);
70	143	mutex_destroy(&vdev->cf_mutex);
	144	+ kfree(vdev->driver_override);
71	145	kfree(vdev);
72	146	}
73	147

include/linux/vdpa.h+2−0

@@ -64,6 +64,7 @@ struct vdpa_mgmt_dev; · 63 unmodified lines
64	64	* struct vdpa_device - representation of a vDPA device
65	65	* @dev: underlying device
66	66	* @dma_dev: the actual device that is performing DMA
	67	+ * @driver_override: driver name to force a match
67	68	* @config: the configuration ops for this device.
68	69	* @cf_mutex: Protects get and set access to configuration layout.
69	70	* @index: device index
@@ -76,6 +77,7 @@ struct vdpa_mgmt_dev; · 6 unmodified lines
76	77	struct vdpa_device {
77	78	struct device dev;
78	79	struct device *dma_dev;
	80	+ const char *driver_override;
79	81	const struct vdpa_config_ops *config;
80	82	struct mutex cf_mutex; /* Protects get/set config */
81	83	unsigned int index;

vdpa: add driver_override support

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