[coreboot-gerrit] Change in coreboot[master]: cpu/x86/smm: Add support for long mode

[Patrick Rudolph (Code Review)]

Patrick Rudolph has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/35681 )

Change subject: cpu/x86/smm: Add support for long mode
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Patch Set 5:

(1 comment)

https://review.coreboot.org/c/coreboot/+/35681/5/src/cpu/x86/smm/smmhandler.... 
File src/cpu/x86/smm/smmhandler.S:

https://review.coreboot.org/c/coreboot/+/35681/5/src/cpu/x86/smm/smmhandler.... 
PS5, Line 198: MSR registers
> Why can't that MSR be accessed in 64bit mode?

it can be accessed, but I don't know what happens if you clear the "LME" Long mode enable-bit when running in long mode. Thus the switch back to protected mode.
https://www.amd.com/system/files/TechDocs/24593.pdf doesn't explain this condition.