On 10/26/2015 11:58 AM, Andrew Jones wrote: > On Mon, Oct 26, 2015 at 11:38:49AM -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@xxxxxxxxxxxxxx> >> --- >> arm/pmu.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 60 insertions(+) >> >> diff --git a/arm/pmu.c b/arm/pmu.c >> index 42d0ee1..c44d708 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 +24,25 @@ 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)); >> +} >> + >> +/* >> + * While PMCCNTR can be accessed as a 64 bit coprocessor register, returning 64 >> + * bits doesn't seem worth the trouble when differential usage of the result is >> + * expected (with differences that can easily fit in 32 bits). So just return >> + * the lower 32 bits of the cycle count in AArch32. >> + */ >> +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 +51,19 @@ 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 +106,37 @@ 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 = { {0} }; > > One set of {} is enough, and looks better. As I tried to mention in the cover letter, that can trigger a spurious GCC warning (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119). But if you don't mind, I don't mind. > Otherwise > Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx> Thanks! Christopher Covington -- 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@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html