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Subject[PATCH V3 5/5] 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.

Fixes: b8241d20699e ("perf/x86/intel: Implement batched PEBS interrupt
handling (large PEBS interrupt threshold)")
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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