pmccntr_read and pmccntr_write contained duplicate code that was already being handled by pmccntr_sync. Consolidate the duplicated code into two functions: pmccntr_op_start and pmccntr_op_finish. Add a companion to c15_ccnt in CPUARMState so that we can simultaneously save both the architectural register value and the last underlying cycle count - this ensure time isn't lost and will also allow us to access the 'old' architectural register value in order to detect overflows in later patches.
Signed-off-by: Aaron Lindsay <alind...@codeaurora.org> --- target/arm/cpu.h | 28 ++++++++++----- target/arm/helper.c | 100 ++++++++++++++++++++++++++++------------------------ 2 files changed, 73 insertions(+), 55 deletions(-) diff --git a/target/arm/cpu.h b/target/arm/cpu.h index 19a0c03..04041db 100644 --- a/target/arm/cpu.h +++ b/target/arm/cpu.h @@ -454,10 +454,20 @@ typedef struct CPUARMState { uint64_t oslsr_el1; /* OS Lock Status */ uint64_t mdcr_el2; uint64_t mdcr_el3; - /* If the counter is enabled, this stores the last time the counter - * was reset. Otherwise it stores the counter value + /* Stores the architectural value of the counter *the last time it was + * updated* by pmccntr_op_start. Accesses should always be surrounded + * by pmccntr_op_start/pmccntr_op_finish to guarantee the latest + * architecturally-corect value is being read/set. */ uint64_t c15_ccnt; + /* Stores the delta between the architectural value and the underlying + * cycle count during normal operation. It is used to update c15_ccnt + * to be the correct architectural value before accesses. During + * accesses, c15_ccnt_delta contains the underlying count being used + * for the access, after which it reverts to the delta value in + * pmccntr_op_finish. + */ + uint64_t c15_ccnt_delta; uint64_t pmccfiltr_el0; /* Performance Monitor Filter Register */ uint64_t vpidr_el2; /* Virtualization Processor ID Register */ uint64_t vmpidr_el2; /* Virtualization Multiprocessor ID Register */ @@ -890,15 +900,17 @@ int cpu_arm_signal_handler(int host_signum, void *pinfo, void *puc); /** - * pmccntr_sync + * pmccntr_op_start/finish * @env: CPUARMState * - * Synchronises the counter in the PMCCNTR. This must always be called twice, - * once before any action that might affect the timer and again afterwards. - * The function is used to swap the state of the register if required. - * This only happens when not in user mode (!CONFIG_USER_ONLY) + * Convert the counter in the PMCCNTR between its delta form (the typical mode + * when it's enabled) and the guest-visible value. These two calls must always + * surround any action which might affect the counter, and the return value + * from pmccntr_op_start must be supplied as the second argument to + * pmccntr_op_finish. */ -void pmccntr_sync(CPUARMState *env); +void pmccntr_op_start(CPUARMState *env); +void pmccntr_op_finish(CPUARMState *env); /* SCTLR bit meanings. Several bits have been reused in newer * versions of the architecture; in that case we define constants diff --git a/target/arm/helper.c b/target/arm/helper.c index 83ea8f4..f6269a2 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -1000,28 +1000,53 @@ static inline bool arm_ccnt_enabled(CPUARMState *env) return true; } - -void pmccntr_sync(CPUARMState *env) +/* + * Ensure c15_ccnt is the guest-visible count so that operations such as + * enabling/disabling the counter or filtering, modifying the count itself, + * etc. can be done logically. This is essentially a no-op if the counter is + * not enabled at the time of the call. + */ +void pmccntr_op_start(CPUARMState *env) { - uint64_t temp_ticks; - - temp_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), + uint64_t cycles = 0; + cycles = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), ARM_CPU_FREQ, NANOSECONDS_PER_SECOND); - if (env->cp15.c9_pmcr & PMCRD) { - /* Increment once every 64 processor clock cycles */ - temp_ticks /= 64; - } - if (arm_ccnt_enabled(env)) { - env->cp15.c15_ccnt = temp_ticks - env->cp15.c15_ccnt; + uint64_t eff_cycles = cycles; + if (env->cp15.c9_pmcr & PMCRD) { + /* Increment once every 64 processor clock cycles */ + eff_cycles /= 64; + } + + env->cp15.c15_ccnt = eff_cycles - env->cp15.c15_ccnt_delta; + } + env->cp15.c15_ccnt_delta = cycles; +} + +/* + * If PMCCNTR is enabled, recalculate the delta between the clock and the + * guest-visible count. A call to pmccntr_op_finish should follow every call to + * pmccntr_op_start. + */ +void pmccntr_op_finish(CPUARMState *env) +{ + if (arm_ccnt_enabled(env)) { + 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; } } static void pmcr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value) { - pmccntr_sync(env); + pmccntr_op_start(env); if (value & PMCRC) { /* The counter has been reset */ @@ -1032,26 +1057,16 @@ static void pmcr_write(CPUARMState *env, const ARMCPRegInfo *ri, env->cp15.c9_pmcr &= ~0x39; env->cp15.c9_pmcr |= (value & 0x39); - pmccntr_sync(env); + pmccntr_op_finish(env); } static uint64_t pmccntr_read(CPUARMState *env, const ARMCPRegInfo *ri) { - uint64_t total_ticks; - - if (!arm_ccnt_enabled(env)) { - /* Counter is disabled, do not change value */ - return env->cp15.c15_ccnt; - } - - total_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), - ARM_CPU_FREQ, NANOSECONDS_PER_SECOND); - - if (env->cp15.c9_pmcr & PMCRD) { - /* Increment once every 64 processor clock cycles */ - total_ticks /= 64; - } - return total_ticks - env->cp15.c15_ccnt; + uint64_t ret; + pmccntr_op_start(env); + ret = env->cp15.c15_ccnt; + pmccntr_op_finish(env); + return ret; } static void pmselr_write(CPUARMState *env, const ARMCPRegInfo *ri, @@ -1068,22 +1083,9 @@ static void pmselr_write(CPUARMState *env, const ARMCPRegInfo *ri, static void pmccntr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value) { - uint64_t total_ticks; - - if (!arm_ccnt_enabled(env)) { - /* Counter is disabled, set the absolute value */ - env->cp15.c15_ccnt = value; - return; - } - - total_ticks = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), - ARM_CPU_FREQ, NANOSECONDS_PER_SECOND); - - if (env->cp15.c9_pmcr & PMCRD) { - /* Increment once every 64 processor clock cycles */ - total_ticks /= 64; - } - env->cp15.c15_ccnt = total_ticks - value; + pmccntr_op_start(env); + env->cp15.c15_ccnt = value; + pmccntr_op_finish(env); } static void pmccntr_write32(CPUARMState *env, const ARMCPRegInfo *ri, @@ -1096,7 +1098,11 @@ static void pmccntr_write32(CPUARMState *env, const ARMCPRegInfo *ri, #else /* CONFIG_USER_ONLY */ -void pmccntr_sync(CPUARMState *env) +void pmccntr_op_start(CPUARMState *env) +{ +} + +void pmccntr_op_finish(CPUARMState *env) { } @@ -1105,9 +1111,9 @@ void pmccntr_sync(CPUARMState *env) static void pmccfiltr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value) { - pmccntr_sync(env); + pmccntr_op_start(env); env->cp15.pmccfiltr_el0 = value & 0x7E000000; - pmccntr_sync(env); + pmccntr_op_finish(env); } static void pmcntenset_write(CPUARMState *env, const ARMCPRegInfo *ri, -- Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.