How do interrupts in multicore/multicpu machines work?

Question

I recently started diving into low level OS programming. I am (very slowly) currently working through two older books, XINU and Build Your Own 32 Bit OS, as well as some res

Answer 1

In the old days the interrupt went to all processors. In modern times some kinds of hardware can be programmed by an OS to send an interrupt to one particular processor. Of course if you could choose a processor dynamically instead of statically, you wouldn't want to send the interrupt to whichever processor initiated the I/O, you'd want to send it to whichever processor is least burdened at the present time and can most efficiently start the next I/O operation, and/or whichever processor is least burdened at the present time and can most efficiently execute the thread that was waiting for the results.

Answer 2

Looking into the IoConnectInterrupt function you can find the ProcessorEnableMask that will select the cpu's that allowed to run the InterruptService routine (ISR).
Based on this information i can assume that somewhere in the low level (see Adam's post) it's possible to specify where to route the interrupt.

On the side note file operation is not really related to the interrupts and/or dma directly. File operation is file system concept that translated to something low level depend on which bus you filesystem located it might be IDE or SATA disk or it might be even usb storage in this case sector read will be translated to 3 logical operation over usb bus, there will be interrupt served by usb host controller driver, but it's not really related to original file read operation, that was probably split to smaller transaction any way.