Another good read and really gives the insight on how much time and effort it takes to make anything happen on bare metal.

@jvns: SPOILERS AHEAD, DO NOT READ FURTHER IF YOU WANT TO GET TO THE HEART OF THIS PROBLEM YOURSELF

As for your problem with the keyboard interrupt firing only once, I think (after a quick glance over the code) that you do not signal "end of interrupt" (EOI) message to the 8259 PIC chip after you have received an interrupt. I faintly recall having this same issue in my ordeals with the PIC chip, if you don't signal EOI, the PIC won't fire the next keyboard interrupt.

Although I think I was working with 8253/8254 PIT (Programmable Interval Timer) chip at the time but I think the same applies to the keyboard interrupt too, it's being handled by the PIC too.

Here's the relevant part from my project: https://github.com/rikusalminen/danjeros/blob/master/src/arc... https://github.com/rikusalminen/danjeros/blob/master/src/arc...

I'm sorry to spoil your "fun" debugging it.

Dealing with any of this is a fun exercise in being close to the metal but unfortunately has no application in modern computers because these days the built-in IO-APIC/LAPIC has replaced the legacy PIC chip.