[PATCH 07/14] perf: track number of events that use LBR callstack

[Yan, Zheng]

Later patch will use it to decide if the LBR stack should be saved/restored

Signed-off-by: Yan, Zheng <zheng.z....@intel.com>
---
 arch/x86/kernel/cpu/perf_event_intel_lbr.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c 
b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index bdd8758..2137a9f 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -201,15 +201,27 @@ void intel_pmu_lbr_sched_task(struct perf_event_context 
*ctx, bool sched_in)
                intel_pmu_lbr_reset();
 }
 
+static inline bool branch_user_callstack(unsigned br_sel)
+{
+       return (br_sel & X86_BR_USER) && (br_sel & X86_BR_CALL_STACK);
+}
+
 void intel_pmu_lbr_enable(struct perf_event *event)
 {
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+       struct x86_perf_task_context *task_ctx;
 
        if (!x86_pmu.lbr_nr)
                return;
 
+       cpuc = &__get_cpu_var(cpu_hw_events);
+       task_ctx = event->ctx ? event->ctx->task_ctx_data : NULL;
+
        cpuc->br_sel = event->hw.branch_reg.reg;
 
+       if (branch_user_callstack(cpuc->br_sel))
+               task_ctx->lbr_callstack_users++;
+
        cpuc->lbr_users++;
        if (cpuc->lbr_users == 1)
                perf_sched_cb_enable(event->ctx->pmu);
@@ -217,11 +229,18 @@ void intel_pmu_lbr_enable(struct perf_event *event)
 
 void intel_pmu_lbr_disable(struct perf_event *event)
 {
-       struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+       struct cpu_hw_events *cpuc;
+       struct x86_perf_task_context *task_ctx;
 
        if (!x86_pmu.lbr_nr)
                return;
 
+       cpuc = &__get_cpu_var(cpu_hw_events);
+       task_ctx = event->ctx ? event->ctx->task_ctx_data : NULL;
+
+       if (branch_user_callstack(cpuc->br_sel))
+               task_ctx->lbr_callstack_users--;
+
        cpuc->lbr_users--;
        WARN_ON_ONCE(cpuc->lbr_users < 0);
 
-- 
1.8.4.2

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