Hi,
On 01/12/16 05:16, Wei Huang wrote:
> From: Christopher Covington <cov@xxxxxxxxxxxxxx>
>
> Ensure that reads of the PMCCNTR_EL0 are monotonically increasing,
> even for the smallest delta of two subsequent reads.
>
> Signed-off-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
> Signed-off-by: Wei Huang <wei@xxxxxxxxxx>
> Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> 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)
> +
> +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);
> +}
> +
> +/* 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);
Why do we need this? Shouldn't PMU_PMCR_C below take care of that?
> +
> + 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)
Mmh, this function doesn't really initialize anything, does it?
Should it be named pmu_available() or pmu_version() or the like?
And should we bail out early here (or rather at the caller) if this
register reports that no PMU is available? For instance by making it
return a boolean?
> +{
> + 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());
I wonder if we should skip this test if check_pmcr() has returned false
before? We let it return a boolean, so it seems quite natural to use
this information here.
This would avoid a lot of false FAILs due to the PMU not being available
(because QEMU is too old, for instance).
Cheers,
Andre.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
