On Wed, 3 Mar 2021 11:41:22 -0500 Tony Krowiak akrowiak@linux.ibm.com wrote:
How do you exect userspace to react to this -ENODEV?
The VFIO_DEVICE_RESET ioctl expects a return code. The vfio_ap_mdev_reset_queues() function can return -EIO or -EBUSY, so I would expect userspace to handle -ENODEV similarly to -EIO or any other non-zero return code. I also looked at all of the VFIO_DEVICE_RESET calls from QEMU to see how the return from the ioctl call is handled:
- ap: reports the reset failed along with the rc
And carries on as if nothing happened. There is not much smart userspace can do in such a situation. Therefore the reset really should not fail.
Please note that in this particular case, if the userspace would opt for a retry, we would most likely end up in a retry loop.
- ccw: doesn't check the rc
- pci: kind of hard to follow without digging deep, but definitely
handles non-zero rc.
I think the caller should be notified whether the queues were successfully reset or not, and why; in this case, the answer is there are no devices to reset.
That is the wrong answer. The ioctl is supposed to reset the ap_matrix_mdev device. The ap_matrix_mdev device still exists. Thus returning -ENODEV is bugous.
Regards, Halil