PCI passthrough regression on BSD* guests since 4.13.1

[Samuel Verschelde <samuel.verschelde@xxxxxxxx>]

Hi list.

XCP-ng users have reported a regression with PCI passthrough in XCP-ng 
8.2. We're using Xen 4.13.1 + patches (like Citrix Hypervisor 8.2 does) 
[1].
Symptoms: after a shutdown or reboot of the VM, the passed-through 
device can't be passed-through anymore.
We've build various versions of Xen with select reverted commits for 
users to test, and they helped us identify commit 
6a1036e28240217d1dbfcb096800313a468cdb0e [2] as what caused it.
On IRC, royger confirmed having reproduced the issue.

Best regards,

Samuel Verschelde

[1] 
https://xcp-ng.org/forum/topic/4001/passthough-on-8-2-hangs-on-vm-reboot-and-stops-other-vms-passthough-devices-working 

[2] 
https://github.com/xen-project/xen/commit/6a1036e28240217d1dbfcb096800313a468cdb0e