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    Subject[RESEND PATCH V2 4/4] perf/x86: fix: disable userspace RDPMC usage for large PEBS
    Date
    From: Kan Liang <kan.liang@linux.intel.com>

    The userspace RDPMC usage never works for large PEBS since the large
    PEBS is introduced by
    commit b8241d20699e ("perf/x86/intel: Implement batched PEBS interrupt
    handling (large PEBS interrupt threshold)")

    When the PEBS interrupt threshold is larger than one, there is no way to
    get exact auto-reload times and value for userspace RDPMC.

    Disable the userspace RDPMC usage when large PEBS is enabled.

    Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
    ---
    arch/x86/events/core.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
    index acd7ffc..703bd81 100644
    --- a/arch/x86/events/core.c
    +++ b/arch/x86/events/core.c
    @@ -2120,7 +2120,8 @@ static int x86_pmu_event_init(struct perf_event *event)
    event->destroy(event);
    }

    - if (READ_ONCE(x86_pmu.attr_rdpmc))
    + if (READ_ONCE(x86_pmu.attr_rdpmc) &&
    + !(event->hw.flags & PERF_X86_EVENT_FREERUNNING))
    event->hw.flags |= PERF_X86_EVENT_RDPMC_ALLOWED;

    return err;
    --
    2.7.4
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