linux-kernel - Re: [kvm-unit-tests Patch v3 03/11] x86: pmu: Add asserts to warn inconsistent fixed events and counters

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Date: Thu, 28 Mar 2024 17:29:37 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Jim Mattson <jmattson@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, Zhenyu Wang <zhenyuw@...ux.intel.com>,
 Zhang Xiong <xiong.y.zhang@...el.com>, Mingwei Zhang <mizhang@...gle.com>,
 Like Xu <like.xu.linux@...il.com>, Jinrong Liang <cloudliang@...cent.com>,
 Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [kvm-unit-tests Patch v3 03/11] x86: pmu: Add asserts to warn
 inconsistent fixed events and counters


On 3/27/2024 9:11 PM, Jim Mattson wrote:
> On Tue, Jan 2, 2024 at 7:09 PM Dapeng Mi <dapeng1.mi@...ux.intel.com> wrote:
>> Current PMU code deosn't check whether PMU fixed counter number is
>> larger than pre-defined fixed events. If so, it would cause memory
>> access out of range.
>>
>> So add assert to warn this invalid case.
>>
>> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
>> ---
>>   x86/pmu.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/x86/pmu.c b/x86/pmu.c
>> index a13b8a8398c6..a42fff8d8b36 100644
>> --- a/x86/pmu.c
>> +++ b/x86/pmu.c
>> @@ -111,8 +111,12 @@ static struct pmu_event* get_counter_event(pmu_counter_t *cnt)
>>                  for (i = 0; i < gp_events_size; i++)
>>                          if (gp_events[i].unit_sel == (cnt->config & 0xffff))
>>                                  return &gp_events[i];
>> -       } else
>> -               return &fixed_events[cnt->ctr - MSR_CORE_PERF_FIXED_CTR0];
>> +       } else {
>> +               int idx = cnt->ctr - MSR_CORE_PERF_FIXED_CTR0;
>> +
>> +               assert(idx < ARRAY_SIZE(fixed_events));
>> +               return &fixed_events[idx];
>> +       }
>>
>>          return (void*)0;
>>   }
>> @@ -245,6 +249,7 @@ static void check_fixed_counters(void)
>>          };
>>          int i;
>>
>> +       assert(pmu.nr_fixed_counters <= ARRAY_SIZE(fixed_events));
>>          for (i = 0; i < pmu.nr_fixed_counters; i++) {
>>                  cnt.ctr = fixed_events[i].unit_sel;
>>                  measure_one(&cnt);
>> @@ -266,6 +271,7 @@ static void check_counters_many(void)
>>                          gp_events[i % gp_events_size].unit_sel;
>>                  n++;
>>          }
>> +       assert(pmu.nr_fixed_counters <= ARRAY_SIZE(fixed_events));
> Can we assert this just once, in main()?
sure. would do.
>
>>          for (i = 0; i < pmu.nr_fixed_counters; i++) {
>>                  cnt[n].ctr = fixed_events[i].unit_sel;
>>                  cnt[n].config = EVNTSEL_OS | EVNTSEL_USR;
>> --
>> 2.34.1
>>