Re: [kvm-unit-tests PATCH v4 07/12] arm: pmu: Basic event counter Tests

[Eric Auger]

Hi Zenghui,

On 9/19/22 16:30, Zenghui Yu wrote:
> Hi Eric,
>
> A few comments when looking through the PMU test code (2 years after
> the series was merged).

Thank you for reviewing even after this time! Do you want to address the
issues yourself and send a patch series or do you prefer I proceed?

Thanks

Eric
> On 2020/4/3 15:13, Eric Auger wrote:
>> Adds the following tests:
>> - event-counter-config: test event counter configuration
>> - basic-event-count:
>>   - programs counters #0 and #1 to count 2 required events
>>   (resp. CPU_CYCLES and INST_RETIRED). Counter #0 is preset
>>   to a value close enough to the 32b
>>   overflow limit so that we check the overflow bit is set
>>   after the execution of the asm loop.
>> - mem-access: counts MEM_ACCESS event on counters #0 and #1
>>   with and without 32-bit overflow.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> Reviewed-by: Andre Przywara <andre.przywara@arm.com>
>
> [...]
>
>> diff --git a/arm/pmu.c b/arm/pmu.c
>> index 8c49e50..45dccf7 100644
>> --- a/arm/pmu.c
>> +++ b/arm/pmu.c
>> @@ -38,6 +43,7 @@
>>  #define SW_INCR            0x0
>>  #define INST_RETIRED        0x8
>>  #define CPU_CYCLES        0x11
>> +#define MEM_ACCESS        0x13
>>  #define INST_PREC        0x1B
>
> The spec spells event 0x001B as INST_SPEC.
>
>>  #define STALL_FRONTEND        0x23
>>  #define STALL_BACKEND        0x24
>
> [...]
>
>> @@ -175,6 +188,11 @@ static inline void precise_instrs_loop(int loop,
>> uint32_t pmcr)
>>  }
>>  
>>  #define PMCEID1_EL0 sys_reg(3, 3, 9, 12, 7)
>> +#define PMCNTENSET_EL0 sys_reg(3, 3, 9, 12, 1)
>> +#define PMCNTENCLR_EL0 sys_reg(3, 3, 9, 12, 2)
>> +
>> +#define PMEVTYPER_EXCLUDE_EL1 BIT(31)
>
> Unused macro.
>
>> +#define PMEVTYPER_EXCLUDE_EL0 BIT(30)
>>  
>>  static bool is_event_supported(uint32_t n, bool warn)
>>  {
>> @@ -228,6 +246,224 @@ static void test_event_introspection(void)
>>      report(required_events, "Check required events are implemented");
>>  }
>>  
>> +/*
>> + * Extra instructions inserted by the compiler would be difficult to
>> compensate
>> + * for, so hand assemble everything between, and including, the PMCR
>> accesses
>> + * to start and stop counting. isb instructions are inserted to make
>> sure
>> + * pmccntr read after this function returns the exact instructions
>> executed
>> + * in the controlled block. Loads @loop times the data at @address
>> into x9.
>> + */
>> +static void mem_access_loop(void *addr, int loop, uint32_t pmcr)
>> +{
>> +asm volatile(
>> +    "       msr     pmcr_el0, %[pmcr]\n"
>> +    "       isb\n"
>> +    "       mov     x10, %[loop]\n"
>> +    "1:     sub     x10, x10, #1\n"
>> +    "       ldr    x9, [%[addr]]\n"
>> +    "       cmp     x10, #0x0\n"
>> +    "       b.gt    1b\n"
>> +    "       msr     pmcr_el0, xzr\n"
>> +    "       isb\n"
>> +    :
>> +    : [addr] "r" (addr), [pmcr] "r" (pmcr), [loop] "r" (loop)
>> +    : "x9", "x10", "cc");
>> +}
>> +
>> +static void pmu_reset(void)
>> +{
>> +    /* reset all counters, counting disabled at PMCR level*/
>> +    set_pmcr(pmu.pmcr_ro | PMU_PMCR_LC | PMU_PMCR_C | PMU_PMCR_P);
>> +    /* Disable all counters */
>> +    write_sysreg_s(ALL_SET, PMCNTENCLR_EL0);
>> +    /* clear overflow reg */
>> +    write_sysreg(ALL_SET, pmovsclr_el0);
>> +    /* disable overflow interrupts on all counters */
>> +    write_sysreg(ALL_SET, pmintenclr_el1);
>> +    isb();
>> +}
>> +
>> +static void test_event_counter_config(void)
>> +{
>> +    int i;
>> +
>> +    if (!pmu.nb_implemented_counters) {
>> +        report_skip("No event counter, skip ...");
>> +        return;
>> +    }
>> +
>> +    pmu_reset();
>> +
>> +    /*
>> +     * Test setting through PMESELR/PMXEVTYPER and PMEVTYPERn read,
>
> s/PMESELR/PMSELR/ ?
>
>> +     * select counter 0
>> +     */
>> +    write_sysreg(1, PMSELR_EL0);
>> +    /* program this counter to count unsupported event */
>> +    write_sysreg(0xEA, PMXEVTYPER_EL0);
>> +    write_sysreg(0xdeadbeef, PMXEVCNTR_EL0);
>> +    report((read_regn_el0(pmevtyper, 1) & 0xFFF) == 0xEA,
>> +        "PMESELR/PMXEVTYPER/PMEVTYPERn");
>
> Ditto
>
>> +    report((read_regn_el0(pmevcntr, 1) == 0xdeadbeef),
>> +        "PMESELR/PMXEVCNTR/PMEVCNTRn");
>
> Ditto
>
>> +
>> +    /* try to configure an unsupported event within the range [0x0,
>> 0x3F] */
>> +    for (i = 0; i <= 0x3F; i++) {
>> +        if (!is_event_supported(i, false))
>> +            break;
>> +    }
>> +    if (i > 0x3F) {
>> +        report_skip("pmevtyper: all events within [0x0, 0x3F] are
>> supported");
>> +        return;
>> +    }
>> +
>> +    /* select counter 0 */
>> +    write_sysreg(0, PMSELR_EL0);
>> +    /* program this counter to count unsupported event */
>
> We get the unsupported event number *i* but don't program it into
> PMXEVTYPER_EL0 (or PMEVTYPER0_EL0). Is it intentional?
>
>> +    write_sysreg(i, PMXEVCNTR_EL0);
>> +    /* read the counter value */
>> +    read_sysreg(PMXEVCNTR_EL0);
>> +    report(read_sysreg(PMXEVCNTR_EL0) == i,
>> +        "read of a counter programmed with unsupported event");
>> +
>> +}
>
> [...]
>
>> +
>> +static void test_mem_access(void)
>> +{
>> +    void *addr = malloc(PAGE_SIZE);
>
> *addr* isn't freed at the end of test_mem_access(). The same in
> test_chain_promotion() and test_overflow_interrupt().
>
> Zenghui
>