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    SubjectRe: [RFC] perf_events: support for uncore a.k.a. nest units
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    On Thu, 2010-01-21 at 09:47 +0100, stephane eranian wrote:
    > I don't think that is correct. You can be using the uncore PMU on Nehalem
    > without any core PMU event. The only thing to realize is that uncore PMU
    > shares the same interrupt vector as core PMU. You need to configure which
    > core the uncore is going to interrupt on. This is done via a bitmask, so you
    > can interrupt more than one core at a time. Several strategies are possible.

    Ah, sharing the IRQ line is no problem. But from reading I got the
    impression you need to configure an Offcore counter. See 30.6.2.1:

    • EN_PMI_COREn (bit n, n = 0, 3 if four cores are present): When set, processor
    core n is programmed to receive an interrupt signal from any interrupt enabled
    uncore counter. PMI delivery due to an uncore counter overflow is enabled by
    setting IA32_DEBUG_CTL.Offcore_PMI_EN to 1.

    Which seems to indicate a link with the off-core response thing.

    However I would be very glad to be wrong :-)

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