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Date: Sat, 29 Oct 2016 12:18:07 +0200
From: Borislav Petkov <bp@alien8.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Necasek <michal.necasek@oracle.com>, prarit@redhat.com,
        ville.syrjala@linux.intel.com, michael.thayer@oracle.com,
        knut.osmundsen@oracle.com, frank.mehnert@oracle.com,
        linux-kernel@vger.kernel.org, wbauer@tmo.at
Subject: Re: 4.8.2 not booting in 32-bit VM without I/O-APIC
Message-ID: <20161029101807.5eqyuka6mjuqd2kw@pd.tnic>
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On Fri, Oct 28, 2016 at 09:34:53PM +0200, Thomas Gleixner wrote:
> 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().

> 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();

FWIW, I got another user's confirmation that this works with his
virtual box:

https://bugzilla.suse.com/show_bug.cgi?id=1006417#c32
https://bugzilla.suse.com/show_bug.cgi?id=1006417#c33

Thanks.

-- 
Regards/Gruss,
    Boris.

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