[Xenomai-help] XENO_HW_SMI_WORKAROUND safety

[Xenomai-help] XENO_HW_SMI_WORKAROUND safety

[Richard Cochran]

As an x86 dummy, I have a question about XENO_HW_SMI_WORKAROUND and
XENO_HW_SMI_ALL. I remember from the 2009 RTLW, that Thomas Gleixner
said not to disable SMIs or it might melt my cpu.

Is there any risk in enabling the Xenomai options?

Thanks,
Richard

Re: [Xenomai-help] XENO_HW_SMI_WORKAROUND safety

[Gilles Chanteperdrix]

Richard Cochran wrote:
> As an x86 dummy, I have a question about XENO_HW_SMI_WORKAROUND and
> XENO_HW_SMI_ALL. I remember from the 2009 RTLW, that Thomas Gleixner
> said not to disable SMIs or it might melt my cpu.
> 
> Is there any risk in enabling the Xenomai options?

Some people seem to have used it without any problem. The problem
happens if SMIs are used for regulating the cpu fans speed. So far, I
have not seen PCs which do this, but who knows?

You can run a stress test, measuring the CPU temperature, with and
without the SMIs disabled. This way, if the SMIs are involved in
regulating the cpu fan speed, you will know it, and in this case, yes,
you can not disable them.

Note however that the Intel chipsets allow to prevent you from disabling
the SMIs. So, it would be plain silly if your PC manufacturer used the
SMI for regulating the cpu fan speed, and did not prevent you from
disabling them.

-- 
                                                                Gilles.

Re: [Xenomai-help] XENO_HW_SMI_WORKAROUND safety

[Gilles Chanteperdrix]

Gilles Chanteperdrix wrote:
> Richard Cochran wrote:
>> As an x86 dummy, I have a question about XENO_HW_SMI_WORKAROUND and
>> XENO_HW_SMI_ALL. I remember from the 2009 RTLW, that Thomas Gleixner
>> said not to disable SMIs or it might melt my cpu.
>>
>> Is there any risk in enabling the Xenomai options?
> 
> Some people seem to have used it without any problem. The problem
> happens if SMIs are used for regulating the cpu fans speed. So far, I
> have not seen PCs which do this, but who knows?
> 
> You can run a stress test, measuring the CPU temperature, with and
> without the SMIs disabled. This way, if the SMIs are involved in
> regulating the cpu fan speed, you will know it, and in this case, yes,
> you can not disable them.
> 
> Note however that the Intel chipsets allow to prevent you from disabling
> the SMIs. So, it would be plain silly if your PC manufacturer used the
> SMI for regulating the cpu fan speed, and did not prevent you from
> disabling them.

Also note that the chipset allows you to disable the SMI sources
selectively, so, if the cpu fan speed regulation is a fast SMI, you can
disable the others, and keep that one.

So, there are several things to try before giving up on SMIs.

-- 
					    Gilles.