On Thu, Nov 25, 2021 at 12:08:12PM -0300, Daniel Henrique Barboza wrote: 65;6601;1c> The PowerISA v3.1 defines that if the proper bits are set (MMCR0_PMC1CE > for PMC1 and MMCR0_PMCjCE for the remaining PMCs), counter negative > conditions are enabled. This means that if the counter value overflows > (i.e. exceeds 0x80000000) a performance monitor alert will occur. This alert > can trigger an event-based exception (to be implemented in the next patches) > if the MMCR0_EBE bit is set. > > For now, overflowing the counter when the PMC is counting cycles will > just trigger a performance monitor alert. This is done by starting the > overflow timer to expire in the moment the overflow would be occuring. The > timer will call fire_PMC_interrupt() (via cpu_ppc_pmu_timer_cb) which will > trigger the PMU alert and, if the conditions are met, an EBB exception. > > Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au> A couple of minor nits noted below, though. > --- > target/ppc/cpu.h | 2 ++ > target/ppc/power8-pmu.c | 80 +++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 82 insertions(+) > > diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h > index 9c732953f0..9b41b022e2 100644 > --- a/target/ppc/cpu.h > +++ b/target/ppc/cpu.h > @@ -364,6 +364,8 @@ typedef enum { > #define MMCR0_PMCC PPC_BITMASK(44, 45) /* PMC Control */ > #define MMCR0_FC14 PPC_BIT(58) /* PMC Freeze Counters 1-4 bit */ > #define MMCR0_FC56 PPC_BIT(59) /* PMC Freeze Counters 5-6 bit */ > +#define MMCR0_PMC1CE PPC_BIT(48) /* MMCR0 PMC1 Condition Enabled */ > +#define MMCR0_PMCjCE PPC_BIT(49) /* MMCR0 PMCj Condition Enabled */ > /* MMCR0 userspace r/w mask */ > #define MMCR0_UREG_MASK (MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE) > /* MMCR2 userspace r/w mask */ > diff --git a/target/ppc/power8-pmu.c b/target/ppc/power8-pmu.c > index acdaee7459..01e0b9b8fc 100644 > --- a/target/ppc/power8-pmu.c > +++ b/target/ppc/power8-pmu.c > @@ -23,6 +23,8 @@ > > #if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) > > +#define PMC_COUNTER_NEGATIVE_VAL 0x80000000UL > + > static bool pmc_is_inactive(CPUPPCState *env, int sprn) > { > if (env->spr[SPR_POWER_MMCR0] & MMCR0_FC) { > @@ -36,6 +38,15 @@ static bool pmc_is_inactive(CPUPPCState *env, int sprn) > return env->spr[SPR_POWER_MMCR0] & MMCR0_FC56; > } > > +static bool pmc_has_overflow_enabled(CPUPPCState *env, int sprn) > +{ > + if (sprn == SPR_POWER_PMC1) { > + return env->spr[SPR_POWER_MMCR0] & MMCR0_PMC1CE; > + } > + > + return env->spr[SPR_POWER_MMCR0] & MMCR0_PMCjCE; > +} > + > /* > * For PMCs 1-4, IBM POWER chips has support for an implementation > * dependent event, 0x1E, that enables cycle counting. The Linux kernel > @@ -123,6 +134,70 @@ static void pmu_update_cycles(CPUPPCState *env) > env->pmu_base_time = now; > } > > +/* > + * Helper function to retrieve the cycle overflow timer of the > + * 'sprn' counter. Given that PMC5 doesn't have a timer, the > + * amount of timers is less than the total counters and the PMC6 > + * timer is the last of the array. > + */ > +static QEMUTimer *get_cyc_overflow_timer(CPUPPCState *env, int sprn) > +{ > + if (sprn == SPR_POWER_PMC5) { > + return NULL; Given that the entries in the pmu_cyc_overflow_timers are just pointers, it would probably be slightly cheaper in terms of both time and space to just have an always-NULL entry for PMC5, rather than having to special case it. > + } > + > + if (sprn == SPR_POWER_PMC6) { > + return env->pmu_cyc_overflow_timers[PMU_TIMERS_NUM - 1]; > + } > + > + return env->pmu_cyc_overflow_timers[sprn - SPR_POWER_PMC1]; > +} > + > +static void pmc_update_overflow_timer(CPUPPCState *env, int sprn) > +{ > + QEMUTimer *pmc_overflow_timer; > + int64_t timeout; > + > + /* PMC5 does not have an overflow timer */ > + if (sprn == SPR_POWER_PMC5) { > + return; Since you've already handled the PMC5 case in get_cyc_overflow_timer(), you could replace this handling with just an if (!pmc_overflow_timer) {return;} > + } > + > + pmc_overflow_timer = get_cyc_overflow_timer(env, sprn); > + > + if (pmc_get_event(env, sprn) != PMU_EVENT_CYCLES || > + !pmc_has_overflow_enabled(env, sprn)) { > + /* Overflow timer is not needed for this counter */ > + timer_del(pmc_overflow_timer); > + return; > + } > + > + if (env->spr[sprn] >= PMC_COUNTER_NEGATIVE_VAL) { > + timeout = 0; > + } else { > + timeout = PMC_COUNTER_NEGATIVE_VAL - env->spr[sprn]; > + } > + > + /* > + * Use timer_mod_anticipate() because an overflow timer might > + * be already running for this PMC. > + */ > + timer_mod_anticipate(pmc_overflow_timer, env->pmu_base_time + timeout); > +} > + > +static void pmu_update_overflow_timers(CPUPPCState *env) > +{ > + int sprn; > + > + /* > + * Scroll through all PMCs and start counter overflow timers for > + * PM_CYC events, if needed. > + */ > + for (sprn = SPR_POWER_PMC1; sprn <= SPR_POWER_PMC6; sprn++) { > + pmc_update_overflow_timer(env, sprn); > + } > +} > + > void helper_store_mmcr0(CPUPPCState *env, target_ulong value) > { > target_ulong curr_value = env->spr[SPR_POWER_MMCR0]; > @@ -143,6 +218,9 @@ void helper_store_mmcr0(CPUPPCState *env, target_ulong > value) > (curr_FC != new_FC)) { > hreg_compute_hflags(env); > } > + > + /* Update cycle overflow timers with the current MMCR0 state */ > + pmu_update_overflow_timers(env); > } > > void helper_store_mmcr1(CPUPPCState *env, uint64_t value) > @@ -164,6 +242,8 @@ void helper_store_pmc(CPUPPCState *env, uint32_t sprn, > uint64_t value) > pmu_update_cycles(env); > > env->spr[sprn] = value; > + > + pmc_update_overflow_timer(env, sprn); > } > > static void fire_PMC_interrupt(PowerPCCPU *cpu) -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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