xen_pciback: error enabling MSI-X / MSI for guest -- WAS: Re: Kernel panic when passing through 2 identical PCI devices

["J. Roeleveld" <joost@xxxxxxxxxxxx>]

Hi all,

I managed to get past the kernel panic (sort of) by doing the following:

1) Ensure system is fully OFF before booting. A reset/reboot will cause these 
errors.

2) Fix the BIOS config to ensure the PCI-ports are split correctly. If anyone 
has a Supermicro board and gets errors about PCI-slots not getting full speed 
let me know.

Not entirely convinced the 2nd was part of the cause, but that's ok.

I now, however, get a new error message in the Domain0 dmesg:
pciback <pci-address>: xen_map irq failed -28 for <domid> domain
pciback <pci-address>: error enabling MSI-X for guest <domid>: err -28!

For the NVMe devices, I get these twice, with the 2nd time complaining about 
MSI (without the -X)

I feel there is something missing in my kernel-config and/or domain config.
If anyone can point me at what needs to be enabled/disabled or suggestions on 
what I can try?

Many many thanks in advance,

Joost