PCIe passthrough of Intel I226-LM fails to attach in the guest

Hi virtualization mailing list,

I'm scratching my hair atm, I passed through a plain PCIe NIC thats on its
seperate PCIe bus (on-board NIC), so no shared IOMMU with other devices but
I get the following error in the VM also based on FreeBSD:

igc0: Setup of Shared code failed, error -13
igc0: IFDI_ATTACH_PRE failed 6
device_attach: igc0 attach returned 6

Any pointers or ideas?

FYI; I'm also passing 2 virtual functions from a MLX CNX4-LX and those
attach with the mce driver without problem

Regards
Dries

vm config is basic:

uuid="e96341b0-cc3d-11f0-80c6-c87f545c9b33"

loader="uefi"
uefi_vars="yes"

cpu="8"
memory="8G"

disk0_name="disk0"
disk0_dev="sparse-zvol"
disk0_type="virtio-blk"

passthru0="8/0/0" # igc1
passthru1="2/0/2" # mce0
passthru2="2/0/10" # mce1