Hi,
I think the issue is with legacy guests. E.g. if VCPU claims to support 50 bit of memory do we put high PCI memory at 1 << 50? If yes old guests which expect at most 40 bit will not be able to use it.
Hmm. Sure such guests exist?
I wouldn't be surprised. At least some windows guests crash if you try to tell them your system has too much physical memory (e.g. 2^48).
Ok, so there is not really a way around making the location configurable. The size isn't needed, qemu can handle this on it's own.
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.
cheers, Gerd