Re: [PATCH] x86, mce: disable MCE if cpu has no MCE banks

[Mike Travis]

Hidetoshi Seto wrote:
> Andi Kleen wrote:
> > Hidetoshi Seto wrote:
> > > Without disabling, what can we do on MCE with no bank?
> > Nothing, but is it really worth adding a special case?
>
> If question were:
>   - is it really worth to support this special environment,
>     "MCE-capable but no MCE banks" ?
> then I'd like to say no.
>
> So I suggested to disable MCE on this uncertain environment.
> Or we will end up adding more codes for special cases...
>
> > > I found that do_machine_check() does nothing if banks==0 ... it is better
> > > to let system to panic with "Machine check from unknown source"?
> > IMHO yes. In this case the system must be very confused and panic is the
> > best you can do. Otherwise it won't do anything interesting anyways.
>
> Agreed, but this is also a special case.
> Not depending on the real number of banks, confused system could fail to
> get the value from memory... Humm, in theory MCE handler must be
> implemented carefully, but I bet the confused value will not be always 0,
> ... is it worth to do?
>
> > > > > Hum, I suppose the line for CPU 0 was slightly different from others,
> > > > > because SHD means "this bank is shared bank and controlled by other".
> > > > > Maybe:
> > > > >  CPU 0 MCA banks CMCI:0 CMCI:1 CMCI:2 CMCI:3 CMCI:5 ... CMCI:21
> > > > >
> > > > > But I agree that we could some work for this messages...
> > > > > Is it better to change the message level to debug from info?
> > > > Can be made INFO yes, but I would prefer not removing them
> > > > from the dmesg for now.
> > > >
> > > > Perhaps they could be also compressed a bit like SRAT.
> > > Like SRAT?  I could not catch the meaning ... For example?
> > See the recent patches from David Rientjes in the same original thread.
>
> I found it, thanks.
>
> So I suppose your idea is like:
>   CPU 0 MCA banks CMCI:{0-3,5-9,12-21} POLL:{4,10,11}
>   CPU 1 MCA banks SHD:{0,1,6-9,12-21} CMCI:{2,3,5} POLL:{4,10,11}
> right?
>
> IMHO the format I suggested is better to read, as far as banks is
> not so big number.
>   CPU 0 MCA banks map : CCCC PCCC CCPP CCCC CCCC CC
>   CPU 1 MCA banks map : ssCC PCss ssPP ssss ssss ss
>
>
> Thanks,
> H.Seto

The problem comes up when you have a whole bunch of cpus, and the lines
become redundant.  Can you compress the lines so that cpus with the
same given mappings are printed on one line?

Thanks,
Mike
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