Re: [Xbox-linux] Xbox Linux kernel for 2.6.20.1 working (sort of...)

[Ronald C.F. A. <rc...@cu...>]

On 1 Mar 2007, at 17:31, Luke Yelavich wrote:

> On Thu, Mar 01, 2007 at 08:53:20AM EST, Ronald C.F. Antony wrote:
>> Hi,
>>
>> I have been able to eliminate a lot of potential sources for the
>> unbootable kernel.
>>
>> I have found one culprit however (there may be more, I'm still  
>> testing).
>> The one known problematic kernel option is this one:
>>
>>> CONFIG_X86_UP_APIC:
> <snip>
>
> This option is only needed if the Xbox's CPU supports apic. Have a  
> look
> at /proc/cpuinfo. If apic is not mentioned in the flags, this  
> option can
> remain deselected.
>
> I think that the PIII CPUs don't support this option, unless they are
> used in an SMP configuration.

That may well be true. However, at least according to the make  
menuconfig option help, this should (and likely is in non-XBOX  
configurations) a safe option to select, and the kernel should just  
ignore it at run time when the CPU doesn't support the feature.

Depending on which precise version of the kernel source you have, it  
basically says "when in doubt, select this option" because the kernel  
will just ignore it if the CPU doesn't support the feature and will  
run w/o slowdown if the option is selected.

However, something about the XBOX prevents the system from booting  
when the option is selected. So ideally, either the option should not  
be selectable if the XBOX subarchitecture is selected, or the code  
needs to be fixed somehow, such that the option behaves as benignly  
on an XBOX as it supposedly behaves on other PC platforms.

Unfortunately I know way too little about the linux kernel to attempt  
fixing this.

Ronald