On Wed, Feb 02, 2022 at 04:54:44PM -0700, Alex Williamson wrote:

I think the argument here is that there's no value to validating or
bounds checking the end state, which could be done in the core ioctl
before calling the driver if the first iteration will already fail for
both the end state and the full path validation.

Yes, I had a version like this in an internal draft, it was something
like this:

if (vfio_mig_get_next_state(vdev, set_state.device_state, 
     set_state.device_state) == VFIO_DEVICE_STATE_ERROR)
    return -EINVAL;

Which is fully redundant with the driver, only does half the check and
looks weird.

quoted

Perhaps it is confusing using ERROR to indicate that
vfio_mig_get_next_state() failed. Would you be happier with a -errno
return?

Yes, it's confusing to me that next_state() returns states that don't
become the device_state.  Stuffing the next step back into cur_fsm and
using an errno for a bounds/validity/blocked-arc test would be a better
API.  Thanks,

OK

Jason