boards/BRINGUP.md A1, FABRIC-3 SXL. It was matched by QEMU's own IDs on
bus 0 alone, so no real board's was found. Now pci_find_class() reads
every bus/slot/function; pci_bar_size() sizes BAR0; the USB Legacy Support
capability hands the controller over from the BIOS, SMIs off; CSZ=1
contexts are placed 64 bytes apart instead of refused. XHCI_QEMU_ARGS
lets QEMU place the controller as real hardware does.
Test first: an NEC controller behind a PCIe root port -- no attach before,
Zuse minted after, on all three ISAs. Standard acceptance unchanged; five
hot-plugged identities attach. Not rehearsable: firmware handoff, CSZ=1.
Still open: only the first controller found is used.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>