alt Hacker NewsSMM was originally conceived for power management, as it first appeared in the laptop-oriented 386SL. Then it was used for seamless backwards compatibility e.g. peripheral emulation. Unlike e.g. TPMs or other DRM-ish schemes, IMHO SMM was never hostile from the beginning.
I disagree. If it were not user hostile the days before BIOSes were cryptographically signed the SMM code would have no reason to disallow the kernel modifying or replacing it. Like `insmod` lets root-in-userspace modify kernel-privilege-level code.
In fact the whole situation is very much analogous to Kernel Lockdown, which is controversial.
With signed bootcode you can give a reason for not letting the userspace modify the SMM code. But when all this stuff was designed there were no bootcode signatures.