From: k...@linuxonhyperv.com <k...@linuxonhyperv.com> Sent: Friday, August 10, 2018 4:06 PM
> From: Stephen Hemminger <step...@networkplumber.org> > > Add support for overriding the default driver for a VMBus device > in the same way that it can be done for PCI devices. This patch > adds the /sys/bus/vmbus/devices/.../driver_override file > and the logic for matching. > > This is used by driverctl tool to do driver override. > https://gitlab.com/driverctl/driverctl > > Signed-off-by: Stephen Hemminger <sthem...@microsoft.com> > Signed-off-by: K. Y. Srinivasan <k...@microsoft.com> > --- > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c > index b1b548a21f91..e6d8fdac6d8b 100644 > --- a/drivers/hv/vmbus_drv.c > +++ b/drivers/hv/vmbus_drv.c > @@ -498,6 +498,54 @@ static ssize_t device_show(struct device *dev, > } > static DEVICE_ATTR_RO(device); > > +static ssize_t driver_override_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + struct hv_device *hv_dev = device_to_hv_device(dev); > + char *driver_override, *old, *cp; > + > + /* We need to keep extra room for a newline */ > + if (count >= (PAGE_SIZE - 1)) > + return -EINVAL; Does 'count' actually have a relationship to PAGE_SIZE, or is PAGE_SIZE just used as an arbitrary size limit? I'm wondering what happens on ARM64 with a 64K page size, for example. If it's just arbitrary, coding such a constant would be better. > +/* > + * Return a matching hv_vmbus_device_id pointer. > + * If there is no match, return NULL. > + */ > +static const struct hv_vmbus_device_id *hv_vmbus_get_id(struct hv_driver > *drv, > + struct hv_device *dev) > +{ > + const uuid_le *guid = &dev->dev_type; > + const struct hv_vmbus_device_id *id; > > - return NULL; > + /* When driver_override is set, only bind to the matching driver */ > + if (dev->driver_override && strcmp(dev->driver_override, drv->name)) > + return NULL; This function needs to be covered by the device lock, so that dev->driver_override can't be set to NULL and the memory freed during the above 'if' statement. When called from vmbus_probe(), the device lock is held, so it's good. But when called from vmbus_match(), the device lock may not be held: consider the path __driver_attach() -> driver_match_device() -> vmbus_match(). Michael
