Re: common_interrupt: No irq handler for vector

[Shuah Khan]

On 12/12/20 12:33 PM, Thomas Gleixner wrote:
> On Fri, Dec 11 2020 at 13:41, Shuah Khan wrote:
>
> > I am debugging __common_interrupt: 1.55 No irq handler for vector
> > messages and noticed comments and code don't agree:
>
> I bet that's on an AMD system with broken AGESA BIOS.... Good luck
> debugging it :) BIOS updates are on the way so I'm told.

Interesting. The behavior I am seeing doesn't seem to be consistent
with BIOS problem. I don't see these messages on 5.10-rc7. I started
seeing them on stable releases. It started right around 5.9.9 and
not present on 5.9.7.

I am bisecting to isolate. Same issue on all stables 5.4, 4.19 and
so on. If it is BIOS problem I would expect to see it on 5.10-rc7
and wouldn't have expected to start seeing it 5.9.9.

+ add Greg since I am talking about stable releases.

> > arch/x86/kernel/apic/msi.c: msi_set_affinity() says:
> >
> >
> >    * If the vector is in use then the installed device handler will
> >    * denote it as spurious which is no harm as this is a rare event
> >    * and interrupt handlers have to cope with spurious interrupts
> >    * anyway. If the vector is unused, then it is marked so it won't
> >    * trigger the 'No irq handler for vector' warning in
> >    * common_interrupt().
> >
> > common_interrupt() prints message if vector is unused: VECTOR_UNUSED
> >
> > ack_APIC_irq();
> >
> > if (desc == VECTOR_UNUSED) {
> >       pr_emerg_ratelimited("%s: %d.%u No irq handler for vector\n",
> >                             __func__, smp_processor_id(), vector);
> > }
> >
> > Something wrong here?
>
> No. It's perfectly correct in the MSI code. See further down.
>
> 	if (IS_ERR_OR_NULL(this_cpu_read(vector_irq[cfg->vector])))
> 		this_cpu_write(vector_irq[cfg->vector], VECTOR_RETRIGGERED);

I am asking about inconsistent comments and the actual message as the
comment implies if vector is VECTOR_UNUSED state, this message won't
be triggered in common_interrupt. Based on that my read is the comment
might be wrong if the code is correct as you are saying.

thanks,
-- Shuah