[kvm-unit-tests Patch v3 11/11] x86: pmu: Improve branch misses event verification

[Dapeng Mi]

Since IBPB command is already leveraged to force one branch miss
triggering, the lower boundary of branch misses event can be set to 1
instead of 0 on IBPB supported processors. Thus the ambiguity from 0 can
be eliminated.

Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
---
 x86/pmu.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/x86/pmu.c b/x86/pmu.c
index c8d4a0dcd362..d5c3fcfaa84c 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -172,6 +172,16 @@ static void adjust_events_range(struct pmu_event *gp_events, int branch_idx)
 		gp_events[branch_idx].min = PRECISE_LOOP_BRANCHES;
 		gp_events[branch_idx].max = PRECISE_LOOP_BRANCHES;
 	}
+
+	/*
+	 * If HW supports IBPB, one branch miss is forced to trigger by
+	 * IBPB command. Thus overwrite the lower boundary of branch misses
+	 * event to 1.
+	 */
+	if (has_ibpb()) {
+		/* branch misses event */
+		gp_events[branch_idx + 1].min = 1;
+	}
 }
 
 volatile uint64_t irq_received;
-- 
2.34.1