Re: Make SMP x86-64 kernels boot on more UP systems.

[Andi Kleen <ak@suse.de>]

On Friday 24 February 2006 02:41, Dave Jones wrote:
> Should someone boot an SMP kernel on UP hardware on some systems,
> strange things happen, such as..

Boot logs?
 
> SMP: Allowing 0 CPUs.
> 
> We blow up shortly afterwards.
> 
> Signed-off-by: Dave Jones <davej@redhat.com>
> 
> --- linux-2.6.15.noarch/arch/x86_64/kernel/smpboot.c~	2006-02-20 21:59:56.000000000 -0500
> +++ linux-2.6.15.noarch/arch/x86_64/kernel/smpboot.c	2006-02-20 22:01:57.000000000 -0500
> @@ -975,6 +975,11 @@ __init void prefill_possible_map(void)
>  	if (possible > NR_CPUS) 
>  		possible = NR_CPUS;
>  
> +	if (possible == 0) {	/* Could be SMP kernel on UP hw with broken BIOS */
> +		possible = 1;
> +		printk (KERN_DEBUG "BIOS never enumerated boot CPU, fixing.\n");
> +	}

It's the wrong place to handle this. Better would be in mpparse.c

-Andi
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