linux-kernel - Re: 4.8.2 not booting in 32-bit VM without I/O-APIC

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Message-ID: <9d85a95e-332c-db85-8e62-2015de8ecb85@oracle.com>
Date:   Thu, 10 Nov 2016 15:21:28 +0100
From:   Michael Thayer <michael.thayer@...cle.com>
To:     tglx@...utronix.de
Cc:     Michal Necasek <michal.necasek@...cle.com>, prarit@...hat.com,
        ville.syrjala@...ux.intel.com, frank.mehnert@...cle.com,
        knut.osmundsen@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: 4.8.2 not booting in 32-bit VM without I/O-APIC

Hello,

On 03.11.2016 21:02, Michal Necasek wrote:
> Sorry for the delay. I can confirm that the problem is fixed in
> 4.9.0-rc3 and prefill_possible_map no longer crashes (as it did in
> 4.9.0-rc2). Thank you!
>
> Just a side question, is the previous fix in commit ff8560512b
> (x86/boot/smp: Don't try to poke disabled/non-existent APIC) actually
> still required or would the no-op APIC driver take care of it?

Sorry for the delay too (holiday-related).  I tested 4.9.0rc4 on a 
32-bit VirtualBox virtual machine without I/O-APIC and can confirm that 
it now boots.  Since I am at it, the OHCI timer wheel-related problems 
are also no longer reproducible.

Regards and thanks,

Michael

>
> Regards, Michal
>
> ----- Original Message ----- From: tglx@...utronix.de To:
> michal.necasek@...cle.com Cc: prarit@...hat.com,
> ville.syrjala@...ux.intel.com, michael.thayer@...cle.com,
> knut.osmundsen@...cle.com, frank.mehnert@...cle.com,
> linux-kernel@...r.kernel.org Sent: Friday, October 28, 2016 9:37:31
> PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
> Subject: Re: 4.8.2 not booting in 32-bit VM without I/O-APIC
>
> On Fri, 28 Oct 2016, Thomas Gleixner wrote:
>
>> On Fri, 28 Oct 2016, Michal Necasek wrote:
>>>
>>> Sorry if I wasn't clear. No, it doesn't work for us. The
>>> ff8560512b8d commit fixes the APIC poking on machines where there
>>> is no local APIC available (and thus fixes the committer's
>>> machine), but it doesn't work in our case, where there is a local
>>> APIC but no I/O APIC, no ACPI MADT, and no MP tables.
>>
>>> In other words, for us boot_cpu_has(X86_FEATURE_APIC) is true but
>>> the APIC has not been set up yet because init_apic_mappings()
>>> hasn't been run.
>
> Right. That mapping setup is an utter trainwreck as we do it from
> multiple places, but there is no reason why we can't move it before
> the call to prefill_possible_map().
>
> Thanks,
>
> tglx
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index
> bbfbca5fea0c..b59fdba3cbdf 100644 --- a/arch/x86/kernel/setup.c +++
> b/arch/x86/kernel/setup.c @@ -1221,11 +1221,13 @@ void __init
> setup_arch(char **cmdline_p) */ get_smp_config();
>
> +	/* Make sure apic is mapped before prefill_possible_map() */ +
> init_apic_mappings(); + prefill_possible_map();
>
> init_cpu_to_node();
>
> -	init_apic_mappings(); io_apic_init_mappings();
>
> kvm_guest_init();
>

-- 
Michael Thayer | VirtualBox engineer
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