MSI(-X) interrupts only fire once on real hardware

[techdude17]

Hi all,

Didn't think I'd have to come back here to ask for help on something like this but have been stumped for a while, and have stumped a few friends

Anyways, on real hardware all of my drivers that use PCI interrupts (in this case, MSI and MSI-X) can receive a total of one interrupt before never getting another one (don't know if this applies to pin interrupts, don't have any hardware that uses it right now).

I immediately guessed it was an acknowledgement problem, but the local APIC gets the acknowledgement for the timer IRQ and everything else just fine. It's just this.

It's not a driver issue I think since multiple drivers failed on real hardware. I've checked my assembly stubs, they contained bugs but I fixed them.

At this point my MSI(-X), I/O APIC, and Local APIC code have been tested to my limit and every emulator I can try on has success. I don't know how to proceed or what to do to even continue. Clearly there's a problem but I have no idea

I'll accept any advice, including even debugging tools

Link to GitHub: https://github.com/sasdallas/Ethereal

[Octocontrabass]

can receive a total of one interrupt before never getting another one

Do the messages use the correct trigger mode? Are you sending an EOI to the local APIC? (Set a breakpoint in your debugger and make sure it actually hits.)

(don't know if this applies to pin interrupts, don't have any hardware that uses it right now)

Have you tried ignoring the MSI/MSI-X capability and falling back to pin interrupts? (Although it looks like you need to rewrite your code for routing pin interrupts first, the Interrupt Line register doesn't do what you seem to think it does.)

the local APIC gets the acknowledgement for the timer IRQ and everything else

Which "everything else" are you talking about here?

I/O APIC

MSI and MSI-X don't use IOAPICs...

I'll accept any advice

Are you sure you have appropriate volatile qualifiers on all pointers to MMIO?