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Date: Sun, 16 Dec 2012 20:46:06 +0100
From: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
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To: Borislav Petkov <bp@alien8.de>, Yinghai Lu <yinghai@kernel.org>,
        Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        Weidong Han <weidong.han@intel.com>,
        David Woodhouse <David.Woodhouse@intel.com>
Subject: Re: [regression] 3.7 ends in APIC panic
References: <50CB3EAB.309@itwm.fraunhofer.de> <CAE9FiQVFSx7sJhYbREk+gfdgxO6uMgHWdDv1tbkU=VXqfH4iAg@mail.gmail.com> <CAE9FiQUyj65jB4bPkJQHGRZEkhOry736g362-m145vNYRRSdAQ@mail.gmail.com> <50CE0C82.20708@itwm.fraunhofer.de> <CAE9FiQUJ-TZCCOki3XfMOgOvOL=TiApJGQdHcHNAPmYKRtVk6A@mail.gmail.com> <50CE12EB.1050804@itwm.fraunhofer.de> <20121216191347.GB14678@liondog.tnic>
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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