Hi,

I meet a problem that libvirt handle new mediated devices wrongly.

Command `virsh nodedev-list –cap mdev` return none after I create a mdev, and the root cause I found is:

// kernel code

int mdev_device_create(struct kobject *kobj, struct device *dev, uuid_le uuid)

{

...

ret = device_register(&mdev->dev); // send udev event here --- 1

      if (ret) {

            put_device(&mdev->dev);

            goto create_err;

      }

      ret = mdev_device_create_ops(kobj, mdev);

      if (ret)

            goto create_failed;

ret = mdev_create_sysfs_files(&mdev->dev, type); // create mdev_type symbol link here --- 2

      if (ret) {

            mdev_device_remove_ops(mdev, true);

            goto create_failed;

      }

      mdev->type_kobj = kobj;

      dev_dbg(&mdev->dev, "MDEV: created\n");

...

}

At point 1, kernel send a udev event(add). If libvirt receive this event and handle it before kernel code reach point 2, libvirt

just fail to resolve link such as ‘/sys/devices/pci0000:80/0000:80:02.0/0000:81:00.0/36b79575-ada8-4406-893d-8cfd8d10a984/mdev_type’

because the link haven’t been created yet. Then libvirt thinks this devices doesn’t exsit and stop tracking info of this device.

Finally, command `vish nodedev-list –cap` return nothing though the device exist at host indeed.

To make it easy to reproduce this problem, I just add a `udelay(1)` before point 2 by kprobe.

So I think maybe we should add ‘kobject_uevent(..., KOBJ_ADD)’ after point 2 instead of point 1 ?

Or is there any other method to solve this problem?

Thanks,

Zongyong Wu