Re: [kvm-unit-tests patch v6 17/18] x86: pmu: Adjust lower boundary of branch-misses event

Mi, Dapeng
2025-02-18T09:42:40Z

On 2/15/2025 5:09 AM, Sean Christopherson wrote:
> On Sat, Sep 14, 2024, Dapeng Mi wrote:
>> @@ -205,6 +208,17 @@ static void adjust_events_range(struct pmu_event *gp_events,
>> gp_events[branch_idx].min = LOOP_BRANCHES;
>> gp_events[branch_idx].max = LOOP_BRANCHES;
>> }
>> +
>> + /*
>> + * For CPUs without IBPB support, no way to force to trigger a
>> + * branch miss and the measured branch misses is possible to be
>> + * 0. Thus overwrite the lower boundary of branch misses event
>> + * to 0 to avoid false positive.
>> + */
>> + if (!has_ibpb()) {
>> + /* branch misses event */
> This comment is worse than useless, because it necessitates curly braces.

Ah. Yes.

>
>> + gp_events[branch_miss_idx].min = 0;
>> + }
>> }