[PATCH v2 4/5] target/ppc: keep ins_cnt/cyc_cnt cleared if MMCR0_FC is set

[Daniel Henrique Barboza <danielhb413@gmail.com>]

pmu_update_summaries() is not considering the case where the PMU can be
turned off (i.e. stop counting all events) if MMCR0_FC is set,
regardless of the other frozen counter bits state. This use case was
covered in the late pmc_get_event(), via the also gone pmc_is_inactive(),
that would return an invalid event if MMCR0_FC was set.

This use case is exercised by the back_to_back_ebbs_test Linux kernel
selftests [1]. As it is today, after enabling EBB exceptions, the test
will report an additional event-based branch being taken and will fail.
Other tests, such as cycles_test.c, will report additional cycles being
calculated in the counters because we're not freezing the PMU quick
enough.

Fix pmu_update_summaries() by keeping env->ins_cnt and env->cyc_cnt
cleared when MMCR0_FC is set.

[1] tools/testing/selftests/powerpc/pmu/ebb/back_to_back_ebbs_test.c

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 target/ppc/power8-pmu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/target/ppc/power8-pmu.c b/target/ppc/power8-pmu.c
index 7fc7d91109..73713ca2a3 100644
--- a/target/ppc/power8-pmu.c
+++ b/target/ppc/power8-pmu.c
@@ -40,6 +40,10 @@ void pmu_update_summaries(CPUPPCState *env)
     int ins_cnt = 0;
     int cyc_cnt = 0;
 
+    if (mmcr0 & MMCR0_FC) {
+        goto hflags_calc;
+    }
+
     if (!(mmcr0 & MMCR0_FC14) && mmcr1 != 0) {
         target_ulong sel;
 
@@ -71,6 +75,7 @@ void pmu_update_summaries(CPUPPCState *env)
     ins_cnt |= !(mmcr0 & MMCR0_FC56) << 5;
     cyc_cnt |= !(mmcr0 & MMCR0_FC56) << 6;
 
+ hflags_calc:
     env->pmc_ins_cnt = ins_cnt;
     env->pmc_cyc_cnt = cyc_cnt;
     env->hflags = deposit32(env->hflags, HFLAGS_INSN_CNT, 1, ins_cnt != 0);
-- 
2.33.1