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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Paul Menzel <pmenzel@molgen.mpg.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>
Cc:     "x86\@kernel.org" <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, it+linux-x86@molgen.mpg.de
Subject: Re: kernel BUG at arch/x86/kernel/apic/apic.c with Dell server with x2APIC enabled and unset X2APIC
In-Reply-To: <d573ba1c-0dc4-3016-712a-cc23a8a33d42@molgen.mpg.de>
References: <d573ba1c-0dc4-3016-712a-cc23a8a33d42@molgen.mpg.de>
Date:   Fri, 21 Feb 2020 17:27:24 +0100
Message-ID: <87imjzoqhf.fsf@nanos.tec.linutronix.de>
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Sender: linux-kernel-owner@vger.kernel.org
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Paul,

Paul Menzel <pmenzel@molgen.mpg.de> writes:
>
> On the Dell PowerEdge T640/04WYPY, BIOS 2.4.8 11/27/2019, Linux 5.4.14 (and 4.19.57) with
> unset `IRQ_REMAP` and `X86_X2APIC` crashes on start-up, when x2APIC is enabled in the
> firmware.

>     [    3.883893] Switched APIC routing to physical flat.
>     [    3.888904] ------------[ cut here ]------------
>     [    3.893641] kernel BUG at arch/x86/kernel/apic/apic.c:1616!

So the APIC is not registered.
>
> `noapic` and `acpi=off` separately did not work, but `noapic acpi=off` hit the other
> panic.

I have no idea what you are talking about.

Which command line options are set to reproduce the above?

Also please test the latest stable kernels not some random ones.

Thanks,

        tglx