Patrick Rudolph has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/42982 )
Change subject: Documentation: Add TODOs for secure SMM when using x86_64 ......................................................................
Patch Set 1:
(1 comment)
https://review.coreboot.org/c/coreboot/+/42982/1/Documentation/arch/x86/inde... File Documentation/arch/x86/index.md:
https://review.coreboot.org/c/coreboot/+/42982/1/Documentation/arch/x86/inde... PS1, Line 54: 1. Fine grained page tables for SMM:
Is this not desirable in general for SMM even if the code is running in protected mode?
That depends on your expectations. If you want to keep things simple, then you don't want to use paging at all. In protected mode you don't have to.
As long mode requires page tables you can add additional complexity which might result in a safer execution environment, but more code also means more places for bugs.