linux-kernel - Re: common_interrupt: No irq handler for vector

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Message-ID: <3630fe3f-0dff-e21e-17a8-ed251df81fbc@linuxfoundation.org>
Date:   Mon, 14 Dec 2020 09:11:57 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: common_interrupt: No irq handler for vector

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