| Message ID | 1444662470-13045-3-git-send-email-cov@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Oct 12, 2015 at 11:07:49AM -0400, Christopher Covington wrote: > 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@codeaurora.org> > --- > arm/pmu.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 54 insertions(+) > > diff --git a/arm/pmu.c b/arm/pmu.c > index 42d0ee1..ae81970 100644 > --- a/arm/pmu.c > +++ b/arm/pmu.c > @@ -14,6 +14,8 @@ > */ > #include "libcflat.h" > > +#define NR_SAMPLES 10 > + > #if defined(__arm__) > static inline uint32_t get_pmcr(void) > { > @@ -22,6 +24,19 @@ static inline uint32_t get_pmcr(void) > asm volatile("mrc p15, 0, %0, c9, c12, 0" : "=r" (ret)); > return ret; > } > + > +static inline void set_pmcr(uint32_t pmcr) > +{ > + asm volatile("mcr p15, 0, %0, c9, c12, 0" : : "r" (pmcr)); > +} > + > +static inline unsigned long get_pmccntr(void) > +{ > + unsigned long cycles; > + > + asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (cycles)); > + return cycles; This is a 64-bit register, even for arm, but I guess there's no need to access more than 32-bits using mrrc? > +} > #elif defined(__aarch64__) > static inline uint32_t get_pmcr(void) > { > @@ -30,6 +45,19 @@ static inline uint32_t get_pmcr(void) > asm volatile("mrs %0, pmcr_el0" : "=r" (ret)); > return ret; > } > + > +static inline void set_pmcr(uint32_t pmcr) > +{ > + asm volatile("msr pmcr_el0, %0" : : "r" (pmcr)); > +} > + > +static inline unsigned long get_pmccntr(void) > +{ > + unsigned long cycles; > + > + asm volatile("mrs %0, pmccntr_el0" : "=r" (cycles)); > + return cycles; > +} > #endif > > struct pmu_data { > @@ -72,11 +100,37 @@ static bool check_pmcr(void) > return pmu.implementer != 0; > } > > +/* > + * Ensure that the cycle counter progresses between back-to-back reads. > + */ > +static bool check_cycles_increase(void) > +{ > + struct pmu_data pmu; > + > + pmu.enable = 1; > + set_pmcr(pmu.pmcr_el0); You need to zero pmu out first, it's just random stack junk except for 'enable' definitely being 1 at this point. > + > + for (int i = 0; i < NR_SAMPLES; i++) { > + unsigned long a, b; > + > + a = get_pmccntr(); > + b = get_pmccntr(); > + > + if (a >= b) { > + printf("Read %ld then %ld.\n", a, b); > + return false; > + } > + } > + > + return true; > +} > + > int main(void) > { > report_prefix_push("pmu"); > > report("Control register", check_pmcr()); > + report("Monotonically increasing cycle count", check_cycles_increase()); > > return report_summary(); > } > -- > Qualcomm Innovation Center, Inc. > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arm/pmu.c b/arm/pmu.c index 42d0ee1..ae81970 100644 --- a/arm/pmu.c +++ b/arm/pmu.c @@ -14,6 +14,8 @@ */ #include "libcflat.h" +#define NR_SAMPLES 10 + #if defined(__arm__) static inline uint32_t get_pmcr(void) { @@ -22,6 +24,19 @@ static inline uint32_t get_pmcr(void) asm volatile("mrc p15, 0, %0, c9, c12, 0" : "=r" (ret)); return ret; } + +static inline void set_pmcr(uint32_t pmcr) +{ + asm volatile("mcr p15, 0, %0, c9, c12, 0" : : "r" (pmcr)); +} + +static inline unsigned long get_pmccntr(void) +{ + unsigned long cycles; + + asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (cycles)); + return cycles; +} #elif defined(__aarch64__) static inline uint32_t get_pmcr(void) { @@ -30,6 +45,19 @@ static inline uint32_t get_pmcr(void) asm volatile("mrs %0, pmcr_el0" : "=r" (ret)); return ret; } + +static inline void set_pmcr(uint32_t pmcr) +{ + asm volatile("msr pmcr_el0, %0" : : "r" (pmcr)); +} + +static inline unsigned long get_pmccntr(void) +{ + unsigned long cycles; + + asm volatile("mrs %0, pmccntr_el0" : "=r" (cycles)); + return cycles; +} #endif struct pmu_data { @@ -72,11 +100,37 @@ static bool check_pmcr(void) return pmu.implementer != 0; } +/* + * Ensure that the cycle counter progresses between back-to-back reads. + */ +static bool check_cycles_increase(void) +{ + struct pmu_data pmu; + + pmu.enable = 1; + set_pmcr(pmu.pmcr_el0); + + for (int i = 0; i < NR_SAMPLES; i++) { + unsigned long a, b; + + a = get_pmccntr(); + b = get_pmccntr(); + + if (a >= b) { + printf("Read %ld then %ld.\n", a, b); + return false; + } + } + + return true; +} + int main(void) { report_prefix_push("pmu"); report("Control register", check_pmcr()); + report("Monotonically increasing cycle count", check_cycles_increase()); return report_summary(); }
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@codeaurora.org> --- arm/pmu.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+)