I'm reading the Intel documentation on control registers, but I'm struggling to understand how CR8 register is used. To quote the docs (2-18 Vol. 3A):
Task Priority Level (bit 3:0 of CR8) — This sets the threshold value corresponding to the highest- priority interrupt to be blocked. A value of 0 means all interrupts are enabled. This field is available in 64- bit mode. A value of 15 means all interrupts will be disabled.
I have 3 quick questions, if you don't mind:
So bits 3 thru 0 of CR8 make up those 16 levels of priority values. But priority of what? A running "thread", I assume, correct?
But what is that priority value in CR8 compared to when an interrupt is received to see if it has to be blocked or not?
When an interrupt is blocked, what does it mean? Is it "delayed" until later time, or is it just discarded, i.e. lost?