From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Huang Subject: [kvm-unit-tests PATCH v8 2/3] arm: pmu: Check cycle count increases Date: Tue, 8 Nov 2016 12:17:14 -0600 Message-ID: <1478629035-12938-3-git-send-email-wei@redhat.com> References: <1478629035-12938-1-git-send-email-wei@redhat.com> Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, shannon.zhao@linaro.org, alistair.francis@xilinx.com, croberts@codeaurora.org, alindsay@codeaurora.org, drjones@redhat.com To: cov@codeaurora.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43470 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932287AbcKHSRX (ORCPT ); Tue, 8 Nov 2016 13:17:23 -0500 In-Reply-To: <1478629035-12938-1-git-send-email-wei@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: From: Christopher Covington Ensure that reads of the PMCCNTR_EL0 are monotonically increasing, even for the smallest delta of two subsequent reads. Signed-off-by: Christopher Covington Signed-off-by: Wei Huang --- arm/pmu.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) diff --git a/arm/pmu.c b/arm/pmu.c index 0b29088..d5e3ac3 100644 --- a/arm/pmu.c +++ b/arm/pmu.c @@ -14,6 +14,7 @@ */ #include "libcflat.h" +#define PMU_PMCR_E (1 << 0) #define PMU_PMCR_N_SHIFT 11 #define PMU_PMCR_N_MASK 0x1f #define PMU_PMCR_ID_SHIFT 16 @@ -21,6 +22,10 @@ #define PMU_PMCR_IMP_SHIFT 24 #define PMU_PMCR_IMP_MASK 0xff +#define PMU_CYCLE_IDX 31 + +#define NR_SAMPLES 10 + #if defined(__arm__) static inline uint32_t pmcr_read(void) { @@ -29,6 +34,47 @@ static inline uint32_t pmcr_read(void) asm volatile("mrc p15, 0, %0, c9, c12, 0" : "=r" (ret)); return ret; } + +static inline void pmcr_write(uint32_t value) +{ + asm volatile("mcr p15, 0, %0, c9, c12, 0" : : "r" (value)); +} + +static inline void pmselr_write(uint32_t value) +{ + asm volatile("mcr p15, 0, %0, c9, c12, 5" : : "r" (value)); +} + +static inline void pmxevtyper_write(uint32_t value) +{ + asm volatile("mcr p15, 0, %0, c9, c13, 1" : : "r" (value)); +} + +/* + * 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 uint32_t pmccntr_read(void) +{ + uint32_t cycles; + + asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (cycles)); + return cycles; +} + +static inline void pmcntenset_write(uint32_t value) +{ + asm volatile("mcr p15, 0, %0, c9, c12, 1" : : "r" (value)); +} + +/* PMCCFILTR is an obsolete name for PMXEVTYPER31 in ARMv7 */ +static inline void pmccfiltr_write(uint32_t value) +{ + pmselr_write(PMU_CYCLE_IDX); + pmxevtyper_write(value); +} #elif defined(__aarch64__) static inline uint32_t pmcr_read(void) { @@ -37,6 +83,29 @@ static inline uint32_t pmcr_read(void) asm volatile("mrs %0, pmcr_el0" : "=r" (ret)); return ret; } + +static inline void pmcr_write(uint32_t value) +{ + asm volatile("msr pmcr_el0, %0" : : "r" (value)); +} + +static inline uint32_t pmccntr_read(void) +{ + uint32_t cycles; + + asm volatile("mrs %0, pmccntr_el0" : "=r" (cycles)); + return cycles; +} + +static inline void pmcntenset_write(uint32_t value) +{ + asm volatile("msr pmcntenset_el0, %0" : : "r" (value)); +} + +static inline void pmccfiltr_write(uint32_t value) +{ + asm volatile("msr pmccfiltr_el0, %0" : : "r" (value)); +} #endif /* @@ -63,11 +132,40 @@ 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) +{ + pmcr_write(pmcr_read() | PMU_PMCR_E); + + for (int i = 0; i < NR_SAMPLES; i++) { + unsigned long a, b; + + a = pmccntr_read(); + b = pmccntr_read(); + + if (a >= b) { + printf("Read %ld then %ld.\n", a, b); + return false; + } + } + + pmcr_write(pmcr_read() & ~PMU_PMCR_E); + + return true; +} + int main(void) { report_prefix_push("pmu"); + /* init for PMU event access, right now only care about cycle count */ + pmcntenset_write(1 << PMU_CYCLE_IDX); + pmccfiltr_write(0); /* count cycles in EL0, EL1, but not EL2 */ + report("Control register", check_pmcr()); + report("Monotonically increasing cycle count", check_cycles_increase()); return report_summary(); } -- 1.8.3.1