When the OpenFirmware loader flattens the firmware device tree into the FDT it hands to the kernel (usefdt=1, i.e. on every real-mode OF system such as pSeries LPARs and QEMU pseries guests), add_node_to_fdt() clamps every property value to 1024 bytes. Any larger property reaches the kernel truncated.
On QEMU pseries the PCI host bridge's "interrupt-map" is 3584 bytes (32 slots x 4 pins x 7 cells), so only the entries for slots 0-8 survive and the entry for slot 9 is cut in the middle. A PCI device in slot 9 or above therefore gets no INTx routing (irq 0), and with INVARIANTS the partial trailing entry trips the "ofw_bus_search_intrmap: truncated map" assertion in ofw_bus_search_intrmap() during PCI attach, panicking the kernel as soon as such a device is present. "ibm,drc-indexes", "ibm,drc-names" and "ibm,drc-power-domains" are cut the same way.
Drop the clamp. fdt_setprop() already reports a property that does not fit into the FDT buffer, so no separate limit is needed.
Fixes: 5ecf8e3852a9