From 4e7beb0cc0f3fb05f1c055113debaa0c7d34fc89 Mon Sep 17 00:00:00 2001 From: Aaron Lindsay OS Date: Fri, 1 Feb 2019 14:55:45 +0000 Subject: [PATCH] target/arm: Add a timer to predict PMU counter overflow Make PMU overflow interrupts more accurate by using a timer to predict when they will overflow rather than waiting for an event to occur which allows us to otherwise check them. Signed-off-by: Aaron Lindsay Reviewed-by: Richard Henderson Message-id: 20190124162401.5111-3-aaron@os.amperecomputing.com Signed-off-by: Peter Maydell --- target/arm/cpu.c | 12 ++++++++ target/arm/cpu.h | 10 +++++++ target/arm/helper.c | 72 +++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 92 insertions(+), 2 deletions(-) diff --git a/target/arm/cpu.c b/target/arm/cpu.c index d6da3f4fed..8a9cd0900d 100644 --- a/target/arm/cpu.c +++ b/target/arm/cpu.c @@ -836,6 +836,13 @@ static void arm_cpu_finalizefn(Object *obj) QLIST_REMOVE(hook, node); g_free(hook); } +#ifndef CONFIG_USER_ONLY + if (cpu->pmu_timer) { + timer_del(cpu->pmu_timer); + timer_deinit(cpu->pmu_timer); + timer_free(cpu->pmu_timer); + } +#endif } static void arm_cpu_realizefn(DeviceState *dev, Error **errp) @@ -1045,6 +1052,11 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp) arm_register_pre_el_change_hook(cpu, &pmu_pre_el_change, 0); arm_register_el_change_hook(cpu, &pmu_post_el_change, 0); } + +#ifndef CONFIG_USER_ONLY + cpu->pmu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, arm_pmu_timer_cb, + cpu); +#endif } else { cpu->id_aa64dfr0 &= ~0xf00; cpu->pmceid0 = 0; diff --git a/target/arm/cpu.h b/target/arm/cpu.h index b8161cb6d7..63934a200a 100644 --- a/target/arm/cpu.h +++ b/target/arm/cpu.h @@ -746,6 +746,11 @@ struct ARMCPU { /* Timers used by the generic (architected) timer */ QEMUTimer *gt_timer[NUM_GTIMERS]; + /* + * Timer used by the PMU. Its state is restored after migration by + * pmu_op_finish() - it does not need other handling during migration + */ + QEMUTimer *pmu_timer; /* GPIO outputs for generic timer */ qemu_irq gt_timer_outputs[NUM_GTIMERS]; /* GPIO output for GICv3 maintenance interrupt signal */ @@ -1005,6 +1010,11 @@ void pmccntr_op_finish(CPUARMState *env); void pmu_op_start(CPUARMState *env); void pmu_op_finish(CPUARMState *env); +/* + * Called when a PMU counter is due to overflow + */ +void arm_pmu_timer_cb(void *opaque); + /** * Functions to register as EL change hooks for PMU mode filtering */ diff --git a/target/arm/helper.c b/target/arm/helper.c index c27e349dd0..e6f69180ba 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -1021,6 +1021,13 @@ typedef struct pm_event { * counters hold a difference from the return value from this function */ uint64_t (*get_count)(CPUARMState *); + /* + * Return how many nanoseconds it will take (at a minimum) for count events + * to occur. A negative value indicates the counter will never overflow, or + * that the counter has otherwise arranged for the overflow bit to be set + * and the PMU interrupt to be raised on overflow. + */ + int64_t (*ns_per_count)(uint64_t); } pm_event; static bool event_always_supported(CPUARMState *env) @@ -1037,6 +1044,11 @@ static uint64_t swinc_get_count(CPUARMState *env) return 0; } +static int64_t swinc_ns_per(uint64_t ignored) +{ + return -1; +} + /* * Return the underlying cycle count for the PMU cycle counters. If we're in * usermode, simply return 0. @@ -1052,6 +1064,11 @@ static uint64_t cycles_get_count(CPUARMState *env) } #ifndef CONFIG_USER_ONLY +static int64_t cycles_ns_per(uint64_t cycles) +{ + return (ARM_CPU_FREQ / NANOSECONDS_PER_SECOND) * cycles; +} + static bool instructions_supported(CPUARMState *env) { return use_icount == 1 /* Precise instruction counting */; @@ -1061,21 +1078,29 @@ static uint64_t instructions_get_count(CPUARMState *env) { return (uint64_t)cpu_get_icount_raw(); } + +static int64_t instructions_ns_per(uint64_t icount) +{ + return cpu_icount_to_ns((int64_t)icount); +} #endif static const pm_event pm_events[] = { { .number = 0x000, /* SW_INCR */ .supported = event_always_supported, .get_count = swinc_get_count, + .ns_per_count = swinc_ns_per, }, #ifndef CONFIG_USER_ONLY { .number = 0x008, /* INST_RETIRED, Instruction architecturally executed */ .supported = instructions_supported, .get_count = instructions_get_count, + .ns_per_count = instructions_ns_per, }, { .number = 0x011, /* CPU_CYCLES, Cycle */ .supported = event_always_supported, .get_count = cycles_get_count, + .ns_per_count = cycles_ns_per, } #endif }; @@ -1340,13 +1365,27 @@ void pmccntr_op_start(CPUARMState *env) void pmccntr_op_finish(CPUARMState *env) { if (pmu_counter_enabled(env, 31)) { - uint64_t prev_cycles = env->cp15.c15_ccnt_delta; +#ifndef CONFIG_USER_ONLY + /* Calculate when the counter will next overflow */ + uint64_t remaining_cycles = -env->cp15.c15_ccnt; + if (!(env->cp15.c9_pmcr & PMCRLC)) { + remaining_cycles = (uint32_t)remaining_cycles; + } + int64_t overflow_in = cycles_ns_per(remaining_cycles); + if (overflow_in > 0) { + int64_t overflow_at = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + + overflow_in; + ARMCPU *cpu = arm_env_get_cpu(env); + timer_mod_anticipate_ns(cpu->pmu_timer, overflow_at); + } +#endif + + uint64_t prev_cycles = env->cp15.c15_ccnt_delta; if (env->cp15.c9_pmcr & PMCRD) { /* Increment once every 64 processor clock cycles */ prev_cycles /= 64; } - env->cp15.c15_ccnt_delta = prev_cycles - env->cp15.c15_ccnt; } } @@ -1376,6 +1415,21 @@ static void pmevcntr_op_start(CPUARMState *env, uint8_t counter) static void pmevcntr_op_finish(CPUARMState *env, uint8_t counter) { if (pmu_counter_enabled(env, counter)) { +#ifndef CONFIG_USER_ONLY + uint16_t event = env->cp15.c14_pmevtyper[counter] & PMXEVTYPER_EVTCOUNT; + uint16_t event_idx = supported_event_map[event]; + uint64_t delta = UINT32_MAX - + (uint32_t)env->cp15.c14_pmevcntr[counter] + 1; + int64_t overflow_in = pm_events[event_idx].ns_per_count(delta); + + if (overflow_in > 0) { + int64_t overflow_at = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + + overflow_in; + ARMCPU *cpu = arm_env_get_cpu(env); + timer_mod_anticipate_ns(cpu->pmu_timer, overflow_at); + } +#endif + env->cp15.c14_pmevcntr_delta[counter] -= env->cp15.c14_pmevcntr[counter]; } @@ -1409,6 +1463,20 @@ void pmu_post_el_change(ARMCPU *cpu, void *ignored) pmu_op_finish(&cpu->env); } +void arm_pmu_timer_cb(void *opaque) +{ + ARMCPU *cpu = opaque; + + /* + * Update all the counter values based on the current underlying counts, + * triggering interrupts to be raised, if necessary. pmu_op_finish() also + * has the effect of setting the cpu->pmu_timer to the next earliest time a + * counter may expire. + */ + pmu_op_start(&cpu->env); + pmu_op_finish(&cpu->env); +} + static void pmcr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value) {