[PATCH V3 5/5] perf/x86: fix: disable userspace RDPMC usage for large PEBS

From: kan.liang@linux.intel.com
To: peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org
Cc: acme@kernel.org, tglx@linutronix.de, jolsa@redhat.com,
	eranian@google.com, ak@linux.intel.com,
	Kan Liang <kan.liang@linux.intel.com>
Subject: [PATCH V3 5/5] perf/x86: fix: disable userspace RDPMC usage for large PEBS
Date: Mon, 29 Jan 2018 08:29:33 -0800	[thread overview]
Message-ID: <1517243373-355481-6-git-send-email-kan.liang@linux.intel.com> (raw)
In-Reply-To: <1517243373-355481-1-git-send-email-kan.liang@linux.intel.com>

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
