Hi Julian,

November 9, 2021 6:27 PM, "Julian Stecklina" 
<julian.steckl...@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
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