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    SubjectRe: [PATCH] - x86_64-add-ioapic-nmi-support-fix-3
    John Keller wrote:
    >> [adding Andi Kleen]
    >>
    >> John Keller wrote:
    >>> Place all the IOACPI NMI support code under CONFIG_ACPI
    >>> to clear up build errors with certain configs.
    >>>
    >>> Signed-off-by: John Keller <jpk@sgi.com>
    >>> ---
    >> Is there some architectural reason that IO APIC NMI support should
    >> require ACPI?
    >
    > OK, I guess standing alone this description was a bit misleading.
    > The code referred to here is the new code supporting the ACPI NMI SRC
    > structure that can be specified in the MADT. Without ACPI support this
    > code is not relevant. All the code touched by this patch was introduced
    > by eariler versions of this patchset.
    >
    > This patch makes no changes to the workings of nmi_watchdog.

    OK, thanks for the clarification.

    > John
    >
    >
    >> Is this a new requirement? It seems like a step backwards to me.
    >>
    >>
    >> Documentation/nmi_watchdog.txt doesn't say anything about ACPI being
    >> needed. It does say:
    >>
    >> "For x86-64, the needed APIC is always compiled in, and the NMI watchdog is
    >> always enabled with I/O-APIC mode (nmi_watchdog=1). Currently, local APIC
    >> mode (nmi_watchdog=2) does not work on x86-64.
    >>
    >> Using local APIC (nmi_watchdog=2) needs the first performance register, so
    >> you can't use it for other purposes (such as high precision performance
    >> profiling.) However, at least oprofile and the perfctr driver disable the
    >> local APIC NMI watchdog automatically."


    --
    ~Randy
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