Fitting Four 32 GB Resizable Bars Behind a PCIe Switch on Linux

A Linux user configured four 32 GB AMD Radeon AI PRO cards behind a PCIe switch to enable peer-to-peer GPU communication, but encountered a BIOS limitation that couldn't map all six GPUs' resizable BARs (Base Address Registers) simultaneously. The Linux kernel's bridge window sizing algorithm also failed to properly allocate the necessary address space in version 7.0, prompting the development of a custom module (gpu-rebar-layout) to manually resize and rescan the PCIe configuration.