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

    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 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?


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