Comment # 6 on bug 1229019 from Jim Niko

I have to add something.

After some search it seems that the Intel I350 T2 NIC card does not use split
IOMMU for each port and create this regression. On previous kernel each port
was assigned in different groups and worked as supposed to be. 

This is the IOMMU group on the 6.4.0-150600.23.17-default kernel:

0b:00.0 Ethernet controller: Intel Corporation I350 Gigabit Network Connection
(rev 01)
        Subsystem: Intel Corporation Ethernet Server Adapter I350-T2
        Kernel driver in use: igb
        Kernel modules: igb
0b:00.1 Ethernet controller: Intel Corporation I350 Gigabit Network Connection
(rev 01)
        Subsystem: Intel Corporation Ethernet Server Adapter I350-T2
        Kernel driver in use: igb
        Kernel modules: igb

Now if I pass through both ports on the same VM it works ok. 

If I try to pass through 1 port it creates the regression.

I hope to be fixed soon this because we have 11 servers which have the same
problem and can not be updated........