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: Wed, 27 Mar 2024 14:43:54 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Mingwei Zhang <mizhang@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>, Jim Mattson <jmattson@...gle.com>,
 kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Zhenyu Wang <zhenyuw@...ux.intel.com>, Zhang Xiong
 <xiong.y.zhang@...el.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 1:30 PM, Mingwei Zhang wrote:
> On Wed, Jan 03, 2024, Dapeng Mi 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>
> Reviewed-by: Mingwei Zhang <mizhang@...gle.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;
> maybe unsigned int is better?

Make sense. Thanks for review.

>> +
>> +		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));
>>   	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
>>