linux-kernel - [PATCH V2 2/3] perf/x86/intel: Set PERF_ATTACH_SCHED

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Date:   Mon, 30 Nov 2020 11:38:41 -0800
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     namhyung@...nel.org, eranian@...gle.com, irogers@...gle.com,
        gmx@...gle.com, acme@...nel.org, jolsa@...hat.com,
        ak@...ux.intel.com, benh@...nel.crashing.org, paulus@...ba.org,
        mpe@...erman.id.au, Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH V2 2/3] perf/x86/intel: Set PERF_ATTACH_SCHED_CB for large PEBS and LBR

From: Kan Liang <kan.liang@...ux.intel.com>

To supply a PID/TID for large PEBS, it requires flushing the PEBS buffer
in a context switch.

For normal LBRs, a context switch can flip the address space and LBR
entries are not tagged with an identifier, we need to wipe the LBR, even
for per-cpu events.

For LBR callstack, save/restore the stack is required during a context
switch.

Set PERF_ATTACH_SCHED_CB for the event with large PEBS & LBR.

Fixes: 9c964efa4330 ("perf/x86/intel: Drain the PEBS buffer during context switches")
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---

Changes since V1
- Set PERF_ATTACH_SCHED_CB for a LBR event as well

 arch/x86/events/intel/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index f1926e9f2143..534e0c84f7f8 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3564,8 +3564,10 @@ static int intel_pmu_hw_config(struct perf_event *event)
 		if (!(event->attr.freq || (event->attr.wakeup_events && !event->attr.watermark))) {
 			event->hw.flags |= PERF_X86_EVENT_AUTO_RELOAD;
 			if (!(event->attr.sample_type &
-			      ~intel_pmu_large_pebs_flags(event)))
+			      ~intel_pmu_large_pebs_flags(event))) {
 				event->hw.flags |= PERF_X86_EVENT_LARGE_PEBS;
+				event->attach_state |= PERF_ATTACH_SCHED_CB;
+			}
 		}
 		if (x86_pmu.pebs_aliases)
 			x86_pmu.pebs_aliases(event);
@@ -3578,6 +3580,7 @@ static int intel_pmu_hw_config(struct perf_event *event)
 		ret = intel_pmu_setup_lbr_filter(event);
 		if (ret)
 			return ret;
+		event->attach_state |= PERF_ATTACH_SCHED_CB;
 
 		/*
 		 * BTS is set up earlier in this path, so don't account twice
-- 
2.17.1