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

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Message-ID: <50CE24FE.3030409@itwm.fraunhofer.de>
Date:	Sun, 16 Dec 2012 20:46:06 +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 08:13 PM, Borislav Petkov wrote:
> On Sun, Dec 16, 2012 at 07:28:59PM +0100, Bernd Schubert wrote:
>> CONFIG_X86_X2APIC depends on CONFIG_IRQ_REMAP, which I disabled as it
>> is marked as experimental...
> 
> You shouldn't pay too much attention to CONFIG_EXPERIMENTAL because it
> is on its way out from the kernel tree.

I usually don't too much, if I understand what it is about and what are
the consequences.

> 
> But if you don't want to have interrupt remapping on your system,
> you can disable it nevertheless. Wait, you can't: according to
> d0b03bd1c6725a3463290d7f9626e4b583518a5a, you can use x2apic without
> interrupt remapping but interrupt remapping needs to be enabled before
> x2apic.

Hmm, I read it the other way around - x2apic depends on interrupt
remapping, but interrupt remapping can be used without x2apic.

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? Can the kernel panic a bit improved to help user to
understand what needs to be enabled?


Thanks,
Bernd
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