On Wed, Nov 30, 2016 at 11:16:41PM -0600, Wei Huang wrote:
> From: Christopher Covington <c...@codeaurora.org>
> 
> Ensure that reads of the PMCCNTR_EL0 are monotonically increasing,
> even for the smallest delta of two subsequent reads.
> 
> Signed-off-by: Christopher Covington <c...@codeaurora.org>
> Signed-off-by: Wei Huang <w...@redhat.com>
> Reviewed-by: Andrew Jones <drjo...@redhat.com>
> ---
>  arm/pmu.c | 94 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 94 insertions(+)
> 
> diff --git a/arm/pmu.c b/arm/pmu.c
> index 1fe2b1a..3566a27 100644
> --- a/arm/pmu.c
> +++ b/arm/pmu.c
> @@ -16,6 +16,9 @@
>  #include "asm/barrier.h"
>  #include "asm/processor.h"
>  
> +#define PMU_PMCR_E         (1 << 0)
> +#define PMU_PMCR_C         (1 << 2)
> +#define PMU_PMCR_LC        (1 << 6)
>  #define PMU_PMCR_N_SHIFT   11
>  #define PMU_PMCR_N_MASK    0x1f
>  #define PMU_PMCR_ID_SHIFT  16
> @@ -23,10 +26,57 @@
>  #define PMU_PMCR_IMP_SHIFT 24
>  #define PMU_PMCR_IMP_MASK  0xff
>  
> +#define ID_DFR0_PERFMON_SHIFT 24
> +#define ID_DFR0_PERFMON_MASK  0xf
> +
> +#define PMU_CYCLE_IDX         31
> +
> +#define NR_SAMPLES 10
> +
> +static unsigned int pmu_version;
>  #if defined(__arm__)
>  DEFINE_GET_SYSREG32(pmcr, 0, c9, c12, 0)
> +DEFINE_SET_SYSREG32(pmcr, 0, c9, c12, 0)
> +DEFINE_GET_SYSREG32(id_dfr0, 0, c0, c1, 2)
> +DEFINE_SET_SYSREG32(pmselr, 0, c9, c12, 5)
> +DEFINE_SET_SYSREG32(pmxevtyper, 0, c9, c13, 1)
> +DEFINE_GET_SYSREG32(pmccntr32, 0, c9, c13, 0)
> +DEFINE_SET_SYSREG32(pmccntr32, 0, c9, c13, 0)
> +DEFINE_GET_SYSREG64(pmccntr64, 0, c9)
> +DEFINE_SET_SYSREG64(pmccntr64, 0, c9)
> +DEFINE_SET_SYSREG32(pmcntenset, 0, c9, c12, 1)

Seeing how we get lots of redundant looking lines, I think instead
of defining DEFINE_SET/GET_SYSREG32/64, we should instead have

DEFINE_SYSREG32/64      ... creates both get_<reg> and set_<reg>
DEFINE_SYSREG32/64_RO   ... creates just get_<reg>

> +
> +static inline uint64_t get_pmccntr(void)
> +{
> +     if (pmu_version == 0x3)
> +             return get_pmccntr64();
> +     else
> +             return get_pmccntr32();
> +}
> +
> +static inline void set_pmccntr(uint64_t value)
> +{
> +     if (pmu_version == 0x3)
> +             set_pmccntr64(value);
> +     else
> +             set_pmccntr32(value & 0xffffffff);
> +}

So the two accessors above are exceptional, which is why we don't
use SYSREG for them. These can have uint64_t for there external
interface. We can't require 'unsigned long' or 'unsigned long long'

> +
> +/* PMCCFILTR is an obsolete name for PMXEVTYPER31 in ARMv7 */
> +static inline void set_pmccfiltr(uint32_t value)
> +{
> +     set_pmselr(PMU_CYCLE_IDX);
> +     set_pmxevtyper(value);
> +     isb();
> +}
>  #elif defined(__aarch64__)
>  DEFINE_GET_SYSREG32(pmcr, el0)
> +DEFINE_SET_SYSREG32(pmcr, el0)
> +DEFINE_GET_SYSREG32(id_dfr0, el1)
> +DEFINE_GET_SYSREG64(pmccntr, el0);
> +DEFINE_SET_SYSREG64(pmccntr, el0);
> +DEFINE_SET_SYSREG32(pmcntenset, el0);
> +DEFINE_SET_SYSREG32(pmccfiltr, el0);
>  #endif
>  
>  /*
> @@ -52,11 +102,55 @@ static bool check_pmcr(void)
>       return ((pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK) != 0;
>  }
>  
> +/*
> + * Ensure that the cycle counter progresses between back-to-back reads.
> + */
> +static bool check_cycles_increase(void)
> +{
> +     bool success = true;
> +
> +     /* init before event access, this test only cares about cycle count */
> +     set_pmcntenset(1 << PMU_CYCLE_IDX);
> +     set_pmccfiltr(0); /* count cycles in EL0, EL1, but not EL2 */
> +     set_pmccntr(0);
> +
> +     set_pmcr(get_pmcr() | PMU_PMCR_LC | PMU_PMCR_C | PMU_PMCR_E);
> +
> +     for (int i = 0; i < NR_SAMPLES; i++) {
> +             uint64_t a, b;
> +
> +             a = get_pmccntr();
> +             b = get_pmccntr();
> +
> +             if (a >= b) {
> +                     printf("Read %"PRId64" then %"PRId64".\n", a, b);
> +                     success = false;
> +                     break;
> +             }
> +     }
> +
> +     set_pmcr(get_pmcr() & ~PMU_PMCR_E);
> +
> +     return success;
> +}
> +
> +void pmu_init(void)
> +{
> +     uint32_t dfr0;
> +
> +     /* probe pmu version */
> +     dfr0 = get_id_dfr0();
> +     pmu_version = (dfr0 >> ID_DFR0_PERFMON_SHIFT) & ID_DFR0_PERFMON_MASK;
> +     report_info("PMU version: %d", pmu_version);
> +}
> +
>  int main(void)
>  {
>       report_prefix_push("pmu");
>  
> +     pmu_init();
>       report("Control register", check_pmcr());
> +     report("Monotonically increasing cycle count", check_cycles_increase());
>  
>       return report_summary();
>  }
> -- 
> 1.8.3.1
> 
>

drew 
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