[emily-c]

I'm not sure why you have legacy in quotes, that is what it is. Modern platforms do not act like a PC AT and there is a ton of cruft to keep those interfaces working which is set up and facilitated by firmware (not so open, at least TianoCore exists regardless of your thoughts on UEFI). Modern x86 systems programming is so much more than these interfaces. I think that it would be beneficial for others to understand how things are actually working on modern platforms.

Regarding your linked post:

For corporate users legacy methods of booting /are/ a security threat. Firmware attacks are a real threat for enterprises. Having IBVs all hand roll things like the S3 boot script or communication with SMM (not using standardized com buffers) is not wise. Secure boot combined with modern security features like using DRTM to remove firmware from the trusted computing base are important and should not be discounted because it's not an 40 year old interface. The PC platform is historically extremely insecure and there is a ton of work still to be done to effectively provide the primitives needed to secure the platform against determined attackers.

If you want to have a USB stack in SMM owning your USB controller to emulate port 60h with IO SMI traps that's fine but it's not a reason to hold the platform back.

[userbinator]

The insecurity is a feature, not a bug.

[veltas]

Usually double-quotes is just pointing out it's as the other person said, not calling it into question which is usually single-quotes.