xl pci-attach silently fails the first time

[Olaf Hering <olaf@aepfle.de>]

I tried to attach a PCI device (IGB Virtual Function) to a HVM guest. 
To actually get it assigned its required to run
pci-attach/pci-detach/pci-attach because it does not show up right away.
Did anyone noticed this bug already, is there a fix? There is no error
reported in dom0 dmesg, xl dmesg or qemu logfiles.

My domU.cfg looks like this:
name="domU"
memory=512
builder="hvm"
vif=['',]
disk=[ 'file:/SLE-12-Server-DVD-x86_64-GM-DVD1.iso,hda:cdrom' ]
serial="pty"

# xl pci-assignable-add 01:10.0
# xl pci-assignable-list
0000:01:10.0
# xl create -f domU.cfg
# xl console domU
## lspci gives just emulated PCI devices
## detach from domU console
# xl pci-attach domU 0000:01:10.0
# xl pci-list domU
Vdev Device
04.0 0000:01:10.0

# xl console domU
## lspci gives just emulated PCI devices
## detach from domU console
# xl pci-detach domU 0000:01:10.0
# xl pci-attach domU 0000:01:10.0
# xl pci-list domU
Vdev Device
04.0 0000:01:10.0
# xl console domU
## lspci shows now also the assigned host device


Olaf