From 539fec78edb4e084e7c532affc56cc42d4ceea4b Mon Sep 17 00:00:00 2001 From: Stefano Garzarella Date: Fri, 26 Nov 2021 17:47:53 +0100 Subject: [PATCH] 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 Acked-by: Jason Wang Signed-off-by: Stefano Garzarella Link: https://lore.kernel.org/r/20211126164753.181829-3-sgarzare@redhat.com Signed-off-by: Michael S. Tsirkin --- Documentation/ABI/testing/sysfs-bus-vdpa | 20 +++++++ drivers/vdpa/vdpa.c | 74 ++++++++++++++++++++++++ include/linux/vdpa.h | 2 + 3 files changed, 96 insertions(+) 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@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. diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c index 09bbe53c3ac4..59d0b8bbb79c 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/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;