Hi Julian,
November 9, 2021 6:27 PM, "Julian Stecklina" julian.stecklina@cyberus-technology.de wrote:
This works, but I wonder whether this is the intended way to use Coreboot or whether there is some more elaborate way to do it. Does all of Coreboot have to be mapped at the end of 4G? Or is there any documentation on this?
The normal layout for coreboot on x86 is indeed that it's mapped in its entirety at "below 4GB" because that's how x86 generally works.
The exceptions to that rule are: - emulation/qemu* because, like in your case, hardware is virtual with no/little need for initialization - AMD Zen family, where their coprocessor initializes RAM before x86 even enters the picture
They still map everything to 4GB there because that's the most convenient approach given how everything else on coreboot for x86 works (and on Zen, coreboot is still on that single flash part so why go through the trouble of splitting things up?), but you might be able to take some ideas from those for your own platform.
Is there any particular concern with having coreboot in that memory region on your platform that makes you ask this or is this just some general curiosity?
Regards, Patrick