question is why is this not needed with legacy bios? Can we emulate their behavior easily?
I think its already there. Notice what Reserved memeory map it used for factory.
224M 76K e820-std on off std
the e820 map.
And for LB
224M 0 LinuxBIOS on off std
The LinuxBIOS map. So you may not have your LB reserved memory map setup. I can't help you much on setting that up since I wasn't even aware we had a reserved memory map but memtest had to get that from somewhere.
-- Richard A. Smith