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    SubjectRe: [RESEND][PATCH -tip 2/3] x86, mce: Revert "add mce=nopoll option to disable timer polling"
    Andi Kleen wrote:
    > Hidetoshi Seto <> writes:
    >> Disabling only polling but not cmci is pointless setting.
    >> Instead of "mce=nopoll" which tend to be paired with cmci disablement,
    >> it rather make sense to have a "mce=ignore_ce" option that disable
    >> both of polling and cmci at once. A patch for this new implementation
    >> will follow this reverting patch.
    >> OTOH, once booted, we can disable polling by setting check_interval
    >> to 0, but there are no mention about the fact. Later Andi will post
    >> updated documents that can respond this issue.
    > I still think that patch has bad semantics because you leave around
    > the events in the machine check registers and never clear
    > them. Especially with MCA recovery that has very unfortunate side
    > effects -- it means the OVER bit will be set and a in principle
    > recoverable MCA will require a panic. Even without MCA recovery it has
    > similar problems and will lead to confusing log output for non CE
    > MCAs.
    > I think a patch to not log corrected errors would be reasonable,
    > but you still need to clear the events from the machine check
    > banks at least.
    > So I would recommend you add a mce=dont_log_ce or somesuch
    > that just guards the mce_log() call in machine_check_poll()

    I suppose there are two possible situations:

    1) There is a agent checking/clearing corrected errors
    (such as BIOS) other than OS.

    In this case, clearing MSRs by OS is not applicable.
    So ignore_ce is better option here.

    2) There is no agent checking/clearing corrected errors.
    User just want to suppress logs of corrected errors.

    In this case, dont_log_ce would be better option.
    (Or adding filter to mcelog would be another solution)

    I don't mind adding three options (no_cmci/ignore_ce/dont_log_ce)
    at once. I'll rework 3/3 of this series to do so.

    > Also for your use case really the better way would be to use
    > some way to let the firmware communicate that it doesn't want the OS
    > to log.

    Yes. However AFAIK there is no way to do it yet.

    > Also BTW before adding new features like this it would be a good
    > idea to first add the bug fixes I posted two weeks ago.
    > -Andi

    The original of this repost were posted about three weeks ago (Apr.2)...

    I think your patches will go smoothly if my revert patches added before

    BTW, could you give me your Acked-by on this 2/3 too?


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