On Mon, Apr 26, 2021 at 05:00:04PM -0300, Jason Gunthorpe wrote:
> +/*
> + * mdev drivers can refuse to bind during probe(), in this case we want to fail
> + * the creation of the mdev all the way back to sysfs. This is a weird model
> + * that doesn't fit in the driver core well, nor does it seem to appear any
> + * place else in the kernel, so use a simple hack.
> + */
> +static int mdev_bind_driver(struct mdev_device *mdev)
> +{
> + struct mdev_driver *drv = mdev->type->parent->ops->device_driver;
> + int ret;
> +
> + if (!drv)
> + drv = &vfio_mdev_driver;
> +
> + while (1) {
> + device_lock(&mdev->dev);
> + if (mdev->dev.driver == &drv->driver) {
> + ret = 0;
> + goto out_unlock;
> + }
> + if (mdev->probe_err) {
> + ret = mdev->probe_err;
> + goto out_unlock;
> + }
> + device_unlock(&mdev->dev);
> + ret = device_attach(&mdev->dev);
> + if (ret)
> + return ret;
> + mdev->probe_err = -EINVAL;
> + }
> + return 0;
> +
> +out_unlock:
> + device_unlock(&mdev->dev);
> + return ret;
> +}
> +++ b/drivers/vfio/mdev/mdev_driver.c
> @@ -49,7 +49,7 @@ static int mdev_probe(struct device *dev)
> return ret;
>
> if (drv->probe) {
> - ret = drv->probe(mdev);
> + ret = mdev->probe_err = drv->probe(mdev);
> if (ret)
> mdev_detach_iommu(mdev);
> }
> return 0;
> }
>
> +static int mdev_match(struct device *dev, struct device_driver *drv)
> +{
> + struct mdev_device *mdev = to_mdev_device(dev);
> + struct mdev_driver *target = mdev->type->parent->ops->device_driver;
> +
> + /*
> + * The ops specify the device driver to connect, fall back to the old
> + * shim driver if the driver hasn't been converted.
> + */
> + if (!target)
> + target = &vfio_mdev_driver;
> + return drv == &target->driver;
> +}
I still think this going the wrong way. Why can't we enhance the core
driver code with a version of device_bind_driver() that does call into
->probe? That probably seems like a better model for those existing
direct users of device_bind_driver or device_attach with a pre-set
->drv anyway.
