On Thu, Nov 25, 2021 at 12:08:13PM -0300, Daniel Henrique Barboza wrote: > The PMU is already counting cycles by calculating time elapsed in > nanoseconds. Counting instructions is a different matter and requires > another approach. > > This patch adds the capability of counting completed instructions > (Perf event PM_INST_CMPL) by counting the amount of instructions > translated in each translation block right before exiting it. > > A new pmu_count_insns() helper in translation.c was added to do that. > After verifying that the PMU is running (MMCR0_FC bit not set), call > helper_insns_inc(). This new helper from power8-pmu.c will add the > instructions to the relevant counters. It'll also be responsible for > triggering counter negative overflows as it is already being done with > cycles. > > Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com> > --- > target/ppc/cpu.h | 1 + > target/ppc/helper.h | 1 + > target/ppc/helper_regs.c | 4 +++ > target/ppc/power8-pmu-regs.c.inc | 6 +++++ > target/ppc/power8-pmu.c | 38 ++++++++++++++++++++++++++ > target/ppc/translate.c | 46 ++++++++++++++++++++++++++++++++ > 6 files changed, 96 insertions(+) > > diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h > index 9b41b022e2..38cd2b5c43 100644 > --- a/target/ppc/cpu.h > +++ b/target/ppc/cpu.h > @@ -656,6 +656,7 @@ enum { > HFLAGS_PR = 14, /* MSR_PR */ > HFLAGS_PMCC0 = 15, /* MMCR0 PMCC bit 0 */ > HFLAGS_PMCC1 = 16, /* MMCR0 PMCC bit 1 */ > + HFLAGS_MMCR0FC = 17, /* MMCR0 FC bit */
Now that the event stuff is a bit more refined, you could narrow this down to specifically marking if any counters are actively counting instructions (not frozen by MMCR0[FC] and not frozen by MMCR0[FC14|FC56] *and* have the right event selected). Since I suspect the instruction counting instrumentation could be quite expensive (helper call on every tb), that might be worthwhile. > HFLAGS_VSX = 23, /* MSR_VSX if cpu has VSX */ > HFLAGS_VR = 25, /* MSR_VR if cpu has VRE */ > > diff --git a/target/ppc/helper.h b/target/ppc/helper.h > index 94b4690375..d8a23e054a 100644 > --- a/target/ppc/helper.h > +++ b/target/ppc/helper.h > @@ -24,6 +24,7 @@ DEF_HELPER_2(store_mmcr0, void, env, tl) > DEF_HELPER_2(store_mmcr1, void, env, tl) > DEF_HELPER_3(store_pmc, void, env, i32, i64) > DEF_HELPER_2(read_pmc, tl, env, i32) > +DEF_HELPER_2(insns_inc, void, env, i32) > #endif > DEF_HELPER_1(check_tlb_flush_local, void, env) > DEF_HELPER_1(check_tlb_flush_global, void, env) > diff --git a/target/ppc/helper_regs.c b/target/ppc/helper_regs.c > index 99562edd57..875c2fdfc6 100644 > --- a/target/ppc/helper_regs.c > +++ b/target/ppc/helper_regs.c > @@ -115,6 +115,10 @@ static uint32_t hreg_compute_hflags_value(CPUPPCState > *env) > if (env->spr[SPR_POWER_MMCR0] & MMCR0_PMCC1) { > hflags |= 1 << HFLAGS_PMCC1; > } > + if (env->spr[SPR_POWER_MMCR0] & MMCR0_FC) { > + hflags |= 1 << HFLAGS_MMCR0FC; > + } > + > > #ifndef CONFIG_USER_ONLY > if (!env->has_hv_mode || (msr & (1ull << MSR_HV))) { > diff --git a/target/ppc/power8-pmu-regs.c.inc > b/target/ppc/power8-pmu-regs.c.inc > index 25b13ad564..580e4e41b2 100644 > --- a/target/ppc/power8-pmu-regs.c.inc > +++ b/target/ppc/power8-pmu-regs.c.inc > @@ -113,6 +113,12 @@ static void write_MMCR0_common(DisasContext *ctx, TCGv > val) > */ > gen_icount_io_start(ctx); > gen_helper_store_mmcr0(cpu_env, val); > + > + /* > + * End the translation block because MMCR0 writes can change > + * ctx->pmu_frozen. > + */ > + ctx->base.is_jmp = DISAS_EXIT_UPDATE; > } > > void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn) > diff --git a/target/ppc/power8-pmu.c b/target/ppc/power8-pmu.c > index 01e0b9b8fc..59d0def79d 100644 > --- a/target/ppc/power8-pmu.c > +++ b/target/ppc/power8-pmu.c > @@ -112,6 +112,30 @@ static PMUEventType pmc_get_event(CPUPPCState *env, int > sprn) > return evt_type; > } > > +static bool pmu_increment_insns(CPUPPCState *env, uint32_t num_insns) > +{ > + bool overflow_triggered = false; > + int sprn; > + > + /* PMC6 never counts instructions */ > + for (sprn = SPR_POWER_PMC1; sprn <= SPR_POWER_PMC5; sprn++) { > + if (pmc_get_event(env, sprn) != PMU_EVENT_INSTRUCTIONS) { > + continue; > + } > + > + env->spr[sprn] += num_insns; > + > + if (env->spr[sprn] >= PMC_COUNTER_NEGATIVE_VAL && > + pmc_has_overflow_enabled(env, sprn)) { > + > + overflow_triggered = true; > + env->spr[sprn] = PMC_COUNTER_NEGATIVE_VAL; Does the hardware PMU actually guarantee that the event will happen exactly on the overflow? Or could you count a few into the negative zone before the event is delivered? > + } > + } > + > + return overflow_triggered; > +} > + > static void pmu_update_cycles(CPUPPCState *env) > { > uint64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); > @@ -258,6 +282,20 @@ static void fire_PMC_interrupt(PowerPCCPU *cpu) > return; > } > > +/* This helper assumes that the PMC is running. */ > +void helper_insns_inc(CPUPPCState *env, uint32_t num_insns) > +{ > + bool overflow_triggered; > + PowerPCCPU *cpu; > + > + overflow_triggered = pmu_increment_insns(env, num_insns); > + > + if (overflow_triggered) { > + cpu = env_archcpu(env); > + fire_PMC_interrupt(cpu); > + } > +} > + > static void cpu_ppc_pmu_timer_cb(void *opaque) > { > PowerPCCPU *cpu = opaque; > diff --git a/target/ppc/translate.c b/target/ppc/translate.c > index 9960df6e18..ccc83d0603 100644 > --- a/target/ppc/translate.c > +++ b/target/ppc/translate.c > @@ -177,6 +177,7 @@ struct DisasContext { > bool hr; > bool mmcr0_pmcc0; > bool mmcr0_pmcc1; > + bool pmu_frozen; > ppc_spr_t *spr_cb; /* Needed to check rights for mfspr/mtspr */ > int singlestep_enabled; > uint32_t flags; > @@ -4170,6 +4171,31 @@ static inline void gen_update_cfar(DisasContext *ctx, > target_ulong nip) > #endif > } > > +#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) Should this actually be !CONFIG_USER_ONLY? IIUC there are circumstances where userspace could access the PMU, including instruction counting. > +static void pmu_count_insns(DisasContext *ctx) > +{ > + /* Do not bother calling the helper if the PMU is frozen */ > + if (ctx->pmu_frozen) { > + return; > + } > + > + /* > + * The PMU insns_inc() helper stops the internal PMU timer if a > + * counter overflows happens. In that case, if the guest is > + * running with icount and we do not handle it beforehand, > + * the helper can trigger a 'bad icount read'. > + */ > + gen_icount_io_start(ctx); > + > + gen_helper_insns_inc(cpu_env, tcg_constant_i32(ctx->base.num_insns)); > +} > +#else > +static void pmu_count_insns(DisasContext *ctx) > +{ > + return; > +} > +#endif > + > static inline bool use_goto_tb(DisasContext *ctx, target_ulong dest) > { > return translator_use_goto_tb(&ctx->base, dest); > @@ -4180,6 +4206,14 @@ static void gen_lookup_and_goto_ptr(DisasContext *ctx) > if (unlikely(ctx->singlestep_enabled)) { > gen_debug_exception(ctx); > } else { > + /* > + * tcg_gen_lookup_and_goto_ptr will exit the TB if > + * CF_NO_GOTO_PTR is set. Count insns now. > + */ > + if (ctx->base.tb->flags & CF_NO_GOTO_PTR) { > + pmu_count_insns(ctx); > + } > + > tcg_gen_lookup_and_goto_ptr(); > } > } > @@ -4191,6 +4225,7 @@ static void gen_goto_tb(DisasContext *ctx, int n, > target_ulong dest) > dest = (uint32_t) dest; > } > if (use_goto_tb(ctx, dest)) { > + pmu_count_insns(ctx); > tcg_gen_goto_tb(n); > tcg_gen_movi_tl(cpu_nip, dest & ~3); > tcg_gen_exit_tb(ctx->base.tb, n); > @@ -8458,6 +8493,7 @@ static void ppc_tr_init_disas_context(DisasContextBase > *dcbase, CPUState *cs) > ctx->hr = (hflags >> HFLAGS_HR) & 1; > ctx->mmcr0_pmcc0 = (hflags >> HFLAGS_PMCC0) & 1; > ctx->mmcr0_pmcc1 = (hflags >> HFLAGS_PMCC1) & 1; > + ctx->pmu_frozen = (hflags >> HFLAGS_MMCR0FC) & 1; > > ctx->singlestep_enabled = 0; > if ((hflags >> HFLAGS_SE) & 1) { > @@ -8564,6 +8600,7 @@ static void ppc_tr_tb_stop(DisasContextBase *dcbase, > CPUState *cs) > switch (is_jmp) { > case DISAS_TOO_MANY: > if (use_goto_tb(ctx, nip)) { > + pmu_count_insns(ctx); > tcg_gen_goto_tb(0); > gen_update_nip(ctx, nip); > tcg_gen_exit_tb(ctx->base.tb, 0); > @@ -8574,6 +8611,14 @@ static void ppc_tr_tb_stop(DisasContextBase *dcbase, > CPUState *cs) > gen_update_nip(ctx, nip); > /* fall through */ > case DISAS_CHAIN: > + /* > + * tcg_gen_lookup_and_goto_ptr will exit the TB if > + * CF_NO_GOTO_PTR is set. Count insns now. > + */ > + if (ctx->base.tb->flags & CF_NO_GOTO_PTR) { > + pmu_count_insns(ctx); > + } > + > tcg_gen_lookup_and_goto_ptr(); > break; > > @@ -8581,6 +8626,7 @@ static void ppc_tr_tb_stop(DisasContextBase *dcbase, > CPUState *cs) > gen_update_nip(ctx, nip); > /* fall through */ > case DISAS_EXIT: > + pmu_count_insns(ctx); > tcg_gen_exit_tb(NULL, 0); > break; > -- 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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