Re: This kernel requires the following features not present on theCPU... (on a VIA C7 CPU)

From: Jan Engelhardt
Date: Fri May 18 2007 - 02:27:34 EST


Hi,


since VIA seems to be one of the quirkier CPUs...

On May 17 2007 21:12, Simon Arlott wrote:
> On 17/05/07 13:27, Claas Langbehn wrote:
>>> Claas Langbehn wrote:

>>>> Would it be possible to override the BIOS settings of cx8 and nx and
>>>> activate it with linux anyway?
>>>> The CPU supports it and I don't see any reason to disable it.
>>
>> Yes, that code is already in the git.newsetup tree.
>
> Is it automatic? I have CONFIG_X86_CMPXCHG=y without cx8 showing in cpuinfo,
> and it appears to work fine.
>
> Will your changes needlessly prevent the kernel running? Would I be right in
> thinking that the kernel is successfully using cmpxchg even though it's
> considered disabled? I realise people compile kernels for the wrong CPU but
> preventing them working when it's been chosen correctly seems wrong.
>
> processor : 0
> vendor_id : CentaurHauls
> cpu family : 6
> model : 10
> model name : VIA Esther processor 1500MHz
> stepping : 9
> cpu MHz : 800.000 (cpufreq)
> cache size : 128 KB
> fdiv_bug : no
> hlt_bug : no
> f00f_bug : no
> coma_bug : no
> fpu : yes
> fpu_exception : yes
> cpuid level : 1
> wp : yes
> flags : fpu vme de pse tsc msr pae mce apic sep mtrr pge cmov pat
> clflush acpi mmx fxsr sse sse2 tm nx pni est tm2 rng rng_en ace ace_en ace2
> ace2_en phe phe_en pmm pmm_en
> bogomips : 1601.18
> clflush size : 64

http://lkml.org/lkml/2007/5/5/134 , shows a Family-6 Model-*9* which
*does* have CX8 (with CONFIG_M586=y, CONFIG_X86_CMPXCHG=y,
CONFIG_X86_CMPXCHG64=y). Just a hint that you do not inadvertently
disable CX there ;-)


Jan
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