linux-kernel - Re: [regression] 3.7 ends in APIC panic

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Date:	Mon, 17 Dec 2012 10:34:46 +0100
From:	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>
To:	Borislav Petkov <bp@...en8.de>, Yinghai Lu <yinghai@...nel.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Weidong Han <weidong.han@...el.com>,
	David Woodhouse <David.Woodhouse@...el.com>
Subject: Re: [regression] 3.7 ends in APIC panic

On 12/16/2012 09:39 PM, Borislav Petkov wrote:
> On Sun, Dec 16, 2012 at 08:46:06PM +0100, Bernd Schubert wrote:
>> Hmm, I read it the other way around - x2apic depends on interrupt
>> remapping, but interrupt remapping can be used without x2apic.
>
> Ok, you're right. X2APIC should depend on IRQ_REMAP:
> https://lwn.net/Articles/289881/
>
>> The help text of CONFIG_IRQ_REMAP also says "x2APIC enhancements or to
>> support platforms with CPU's having > 8 bit APIC ID, say Y." I guess
>> may CPU has the latter?
>
> I think it is what Yinghai said - you obviously need x2apic kernel
> support if you have IRQ_REMAP on.
>
>> Can the kernel panic a bit improved to help user to understand what
>> needs to be enabled?
>
> Well, your kernel enables IRQ_REMAP properly:
>
> [    0.031115] Enabled IRQ remapping in x2apic mode
>
> I guess at that stage we could probably check for x2apic support and
> scream loudly if it is not present... IMHO.
>

Hmm, I think that would the wrong place, as the initial 3.7.0 
configuration didn't have IRQ_REMAP enabled. And that was the reason why 
x2apic got disabled during the "make oldconfig" process...

Is this message an indication for missing x2apic?

"smpboot: weird, boot (#255) not listed by the BIOS"


Thanks,
Bernd

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