Re: [tip:perf/core] perf/x86: Add an MSR PMU driver

Andy Lutomirski
2015-08-04T18:01:17Z

On Tue, Aug 4, 2015 at 8:03 AM, Liang, Kan <kan.liang@intel.com> wrote:
>
>> > +
>> > +enum perf_msr_id {
>> > + PERF_MSR_TSC = 0,
>> > + PERF_MSR_APERF = 1,
>> > + PERF_MSR_MPERF = 2,
>> > + PERF_MSR_PPERF = 3,
>> > + PERF_MSR_SMI = 4,
>> > +
>> > + PERF_MSR_EVENT_MAX,
>> > +};
>> > +
>> > +struct perf_msr {
>> > + int id;
>> > + u64 msr;
>> > +};
>> > +
>> > +static struct perf_msr msr[] = {
>> > + { PERF_MSR_TSC, 0 },
>> > + { PERF_MSR_APERF, MSR_IA32_APERF },
>> > + { PERF_MSR_MPERF, MSR_IA32_MPERF },
>> > + { PERF_MSR_PPERF, MSR_PPERF },
>> > + { PERF_MSR_SMI, MSR_SMI_COUNT }, };
>>
>> I think this could be easier to work with if it were [PERF_MSR_TSC] = {...},
>> etc. No big deal, though, until the list gets long. However, it might make
>> fixing the apparent issue below easier...
>>
>> > +static int msr_event_init(struct perf_event *event) {
>> > + u64 cfg = event->attr.config;
>>
>> ...
>>
>> > + event->hw.event_base = msr[cfg].msr;
>>
>> Shouldn't this verify that the fancy enumeration code actually believes that
>> msr[cfg] exists on this system? Otherwise we might have a very short wait
>> until the perf fuzzer oopses this thing :)
>>
>
> I think we already did the check before using msr[cfg].

Where? All I see is:

+ if (cfg >= PERF_MSR_EVENT_MAX)
+ return -EINVAL;

--Andy