Hi,
Guess we can just go with Igor's approach then. "etc/mem64-end" is a pretty bad name to say "please map 64bit pci bars here" though.
reasoning bind was to tell BIOS where RAM ends and let it decide what to do with this information.
But we could do other way around and use "etc/pci-info" that was proposed earlier by Michael, it is already committed into QEMU and provides start/end of 32/64-bit PCI windows in QEMU view. We could use pci-info.w64.start as base for 64-bit bars.
We need only the single value from pci-info, I'd suggest to drop pci-info in favor of a file you can read using romfile_loadint.
cheers, Gerd