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

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Message-ID: <87im94dsdd.fsf@nanos.tec.linutronix.de>
Date:   Mon, 14 Dec 2020 21:50:38 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Shuah Khan <skhan@...uxfoundation.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     "x86\@kernel.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 Mon, Dec 14 2020 at 21:41, Thomas Gleixner wrote:
> On Mon, Dec 14 2020 at 09:11, Shuah Khan wrote:
>> 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.
>
> What kind of machine?
>
>> 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.
>
> Can you provide some more details, e.g. dmesg please?
>
>>> 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.
>
> The comment says:
>
>   >>    * 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().
>
>   If the vector is unused, then it is _marked_ so ....
>
> It perhaps should explicitely say 'is marked as VECTOR_RETRIGGERED' to make
> it clear.

And it's only marked for this particular case to prevent the message
from being shown. Because the insanities we need to do to migrate
unmaskable (*sigh*) MSI interrupts can trigger that warning which would
be just wrong and confusing. You warning is _not_ coming from a broken
MSI migration attempt, believe me.

Thanks,

        tglx