One PCI slot does not work in Qubes

[s.w.i.m....@gmail.com]

I have two network cards, both are on PCIx1 slots in a gigabyte H110m-a motherboard. On the top PCIx1 slot this network card works fine using Realtek 8111 nics.

The lower slot does not work in that Qubes sees the nics with lspci, will pass them through to a VM and the VM sees the nics, but no network activity occurs. At first I thought it was a hardware issue because card 2 was using an Intel 82576 nic so I tried with another realtek card and had the same result.

I swapped cards and again, the top PCIx1 slot works with either nic, while nothing works in the second slot.

With other operating systems all pci slots work fine.

Is there some way of diagnosing what is going on here? I kind of think this is a Qubes thing since everything seems to work in other operating systems.

[s.w.i.m....@gmail.com]

Dmseg had errors for the nics which indicated setting pci permissive mode might help.

pciback 0000:0x:00.0: Driver tried to write to a read-only configuration...

Setting permissive mode got rid of the errors but did not actually fix the main issue.

Whenever I attach a computer to these nics they are not getting an ip address from dhcp and cannot communicate upstream. Despite this working fine with one network card, and the motherboard ethernet port.

Is it possible for the one functioning card to block the pci bus for any other devices? I will try replacing that card too, but its a POE network card and id rather not have to lose it.

[s.w.i.m....@gmail.com]

Ok so I have tried all of my network cards individually and the only ones that work are the GA-H110MA onboard motherboard Realtek Nic. And a StarTech ST2000PEXPSE, which is a PoE card with two RTL8111E Nics and a Ti XIO3130 pcie 1.1 control chip.

Not working is
syba SY-PEX24028 with two RTL8111G nics and a Pericon Semi PI7C9X2G 304SLAFDE pci 2.1 chip.

Unknown brand with two intel 82576-2T nics. Unknown pci controller, the heat sink was stuck on there good. Mac addy references Shenzhen Lianrui Electronics so, you know, quality.

All devices work in windows and freebsd11. In Qubes the non working ones cry about pci permissive needing to be set, if set(or not) they will show up in qvm-pci as good. And will passthrough apprantly ok, but will not transmit data over the pci bus. Resulting in anything connected to them not recieving an IP addy(causing them to self assign one) and generally not working.

I wish I had more cards to test to isolate if its the pci controller or the nic chip thats at issue.