Comment 18 for bug 1838575

Hmm, with strace showing almost a hang on a single of those ioctl calls you'D think that is easy to spot :-/

But this isn't as clear as expected:
  sudo trace-cmd record -p function_graph -l vfio_pci_ioctl -O graph-time

Disable all but 1 CPUs to have less concurrency in the trace.
=> Not much better

But it is the handler:
  1276 »···.ioctl»·»···= vfio_pci_ioctl,

There seem to be a lot of calls to vfio_pci_ioctl and not just a few slow ones.
Whatever strace thought, that is not how it looks like.

Starting again with wider traces to check what the entry might be.
sys_splice is high on the radar atm.

As a bonus now the test env broke and can't passthrough anymore.
The emulex firmware breaks and fails.
Maybe abort for now and focus on other things and resetup the testbed another day.