BIOS doesn't build MP table for uniprocessor environments

BIOS doesn't build MP table for uniprocessor environments

[Randy Thelen]

Folks --

I noticed (after a long sequence of experimentation) that an smp  
change has been made to the bios to disable the generation of the MP  
table in a uniprocessor environment:

# svn cat svn://kvm.qumranet.com/kvm/tags/public/17/qemu/pc-bios/ 
bios.diff | tail

+#ifdef BX_QEMU
+    if (smp_cpus <= 1)
+        return;
+#endif
+

#

Is there a good rationale for this?

-- Randy

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Re: BIOS doesn't build MP table for uniprocessor environments

[Avi Kivity]

Randy Thelen wrote:
> Folks --
>
> I noticed (after a long sequence of experimentation) that an smp  
> change has been made to the bios to disable the generation of the MP  
> table in a uniprocessor environment:
>
> # svn cat svn://kvm.qumranet.com/kvm/tags/public/17/qemu/pc-bios/ 
> bios.diff | tail
>
> +#ifdef BX_QEMU
> +    if (smp_cpus <= 1)
> +        return;
> +#endif
> +
>
>   

bios.diff is actually the difference between the bochs bios sources at 
some random point in time and the sources Fabrice used to generate 
bios.bin for qemu-0.9.0.  It is not a kvm thing.

I don't know the reason for this particular difference; presumably 
compatibility with something.  You can try asking on qemu-devel, or you 
can try downloading the bochs bios (preferably from around the time 
Fabrice pulled it) and backing out this change.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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