Function cpu_path 

pub fn cpu_path(addr: &PCIAddress, numa: Option<u32>) -> PciPath

Path from CPU memory to the device at addr. With a specific NUMA node, the device is PathType::Phb when it sits on that node and PathType::Sys otherwise; with None (any CPU) it is judged against its own node and so is always PathType::Phb. Bandwidth is the device’s PCIe chain bottleneck.