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Message-Id: <20211126164753.181829-3-sgarzare@redhat.com>
Date: Fri, 26 Nov 2021 17:47:53 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: virtualization@...ts.linux-foundation.org
Cc: linux-kernel@...r.kernel.org,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Parav Pandit <parav@...dia.com>
Subject: [PATCH v2 2/2] 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: Jason Wang <jasowang@...hat.com>
Acked-by: Jason Wang <jasowang@...hat.com>
Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
---
v2:
- added documentation in Documentation/ABI/testing/sysfs-bus-vdpa
---
include/linux/vdpa.h | 2 +
drivers/vdpa/vdpa.c | 74 ++++++++++++++++++++++++
Documentation/ABI/testing/sysfs-bus-vdpa | 20 +++++++
3 files changed, 96 insertions(+)
diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index c3011ccda430..ae34015b37b7 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -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;
diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 7332a74a4b00..659231bbfee8 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -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);
}
diff --git a/Documentation/ABI/testing/sysfs-bus-vdpa b/Documentation/ABI/testing/sysfs-bus-vdpa
index 4e55761a39df..28a6111202ba 100644
--- a/Documentation/ABI/testing/sysfs-bus-vdpa
+++ b/Documentation/ABI/testing/sysfs-bus-vdpa
@@ -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@...ts.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.
--
2.31.1
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