CONFIG_UML_PCI_OVER_VIRTIO is not available for thedefaultarchitecture x86.
Result is shown for architecture um

Enable PCI over VIRTIO device simulation

modulename: virt-pci.ko

configname: CONFIG_UML_PCI_OVER_VIRTIO

Linux Kernel Configuration
└─>Enable PCI over VIRTIO device simulation
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
source code:
/arch/um/drivers/virt-pci.c