Re: [coreboot] About Paging, Realmode and what is going on

[Patrick Georgi]

2017-08-02 21:08 GMT+02:00 Zoran Stojsavljevic :
> And my question is: what for? Or I did not get the idea... Who really needs
> to use paging in boot-loaders? Even INTEL, which (on purpose) makes things
> way over-dimensioned and over-complicated, does NOT use paging in UEFI
> BIOSes, so far???

They must for X64 builds. Long Mode _requires_ page tables (even if
it's a single 1TB page to create a 1:1 mapping).

But fear not, UEFI also supported paging for a _really_ long time for
Runtime Services, so everything DXE onward better prepares for being
called by Runtime Services or SMM, even if the spec explicitly says
that it shouldn't happen - it did. Apparently they just couldn't fully
eschew the mantle of superfluous complexity.

Patrick