The pci.conf is introduced to save PCI configurations, such as Number of VFs (Virtual Functions) of a particular PF (Physical Function) on the system. This file has a few purposes:
To persist the PCI configuration, so VFs can be created automatically upon boot.
Since the configuration file is part of the boot_archive, VFs can be used during the boot.
This file is also used by non-IOV system configurations when VFs are used on bare-metal systems. Currently, it contains only VF-related configurations. In the future, more PCI bus specific configuration and even device specific workarounds may make their way to it. Number of VF configurations is saved in "[System_Configuration]" section, which looks like:
[System Configuration] [[path=<pf_device_path>]] num-vf=<num_of_vf>