Re: [PATCH v8 02/10] target/ppc: PMU basic cycle count for pseries TCG

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Nov 25, 2021 at 12:08:09PM -0300, Daniel Henrique Barboza wrote:
> This patch adds the barebones of the PMU logic by enabling cycle
> counting. The overall logic goes as follows:
> 
> - MMCR0 reg initial value is set to 0x80000000 (MMCR0_FC set) to avoid
> having to spin the PMU right at system init;
> 
> - to retrieve the events that are being profiled, pmc_get_event() will
> check the current MMCR0 and MMCR1 value and return the appropriate
> PMUEventType. For PMCs 1-4, event 0x2 is the implementation dependent
> value of PMU_EVENT_INSTRUCTIONS and event 0x1E is the implementation
> dependent value of PMU_EVENT_CYCLES. These events are supported by IBM
> Power chips since Power8, at least, and the Linux Perf driver makes use
> of these events until kernel v5.15. For PMC1, event 0xF0 is the
> architected PowerISA event for cycles. Event 0xFE is the architected
> PowerISA event for instructions;
> 
> - if the counter is frozen, either via the global MMCR0_FC bit or its
> individual frozen counter bit, PMU_EVENT_INACTIVE is returned;
> 
> - pmu_update_cycles() will go through each counter and update the
> values of all PMCs that are counting cycles. This function will be
> called every time a MMCR0 update is done to keep counters values
> up to date. Upcoming patches will use this function to allow the
> counters to be properly updated during read/write of the PMCs
> and MMCR1 writes.
> 
> Given that the base CPU frequency is fixed at 1Ghz for both powernv and
> pseries clock, cycle calculation assumes that 1 nanosecond equals 1 CPU
> cycle. Cycle value is then calculated by adding the elapsed time, in
> nanoseconds, of the last cycle update done via pmu_update_cycles().
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  target/ppc/cpu.h                 |  20 +++++
>  target/ppc/cpu_init.c            |   6 +-
>  target/ppc/helper.h              |   1 +
>  target/ppc/power8-pmu-regs.c.inc |  23 +++++-
>  target/ppc/power8-pmu.c          | 122 +++++++++++++++++++++++++++++++
>  target/ppc/spr_tcg.h             |   1 +
>  6 files changed, 169 insertions(+), 4 deletions(-)
> 
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index 2ad47b06d0..9c732953f0 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -361,6 +361,9 @@ typedef enum {
>  #define MMCR0_FCECE  PPC_BIT(38)         /* FC on Enabled Cond or Event */
>  #define MMCR0_PMCC0  PPC_BIT(44)         /* PMC Control bit 0 */
>  #define MMCR0_PMCC1  PPC_BIT(45)         /* PMC Control bit 1 */
> +#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 */
>  /* MMCR0 userspace r/w mask */
>  #define MMCR0_UREG_MASK (MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE)
>  /* MMCR2 userspace r/w mask */
> @@ -373,6 +376,17 @@ typedef enum {
>  #define MMCR2_UREG_MASK (MMCR2_FC1P0 | MMCR2_FC2P0 | MMCR2_FC3P0 | \
>                           MMCR2_FC4P0 | MMCR2_FC5P0 | MMCR2_FC6P0)
>  
> +#define MMCR1_EVT_SIZE 8
> +/* extract64() does a right shift before extracting */
> +#define MMCR1_PMC1SEL_START 32
> +#define MMCR1_PMC1EVT_EXTR (64 - MMCR1_PMC1SEL_START - MMCR1_EVT_SIZE)
> +#define MMCR1_PMC2SEL_START 40
> +#define MMCR1_PMC2EVT_EXTR (64 - MMCR1_PMC2SEL_START - MMCR1_EVT_SIZE)
> +#define MMCR1_PMC3SEL_START 48
> +#define MMCR1_PMC3EVT_EXTR (64 - MMCR1_PMC3SEL_START - MMCR1_EVT_SIZE)
> +#define MMCR1_PMC4SEL_START 56
> +#define MMCR1_PMC4EVT_EXTR (64 - MMCR1_PMC4SEL_START - MMCR1_EVT_SIZE)
> +
>  /* LPCR bits */
>  #define LPCR_VPM0         PPC_BIT(0)
>  #define LPCR_VPM1         PPC_BIT(1)
> @@ -1207,6 +1221,12 @@ struct CPUPPCState {
>       * when counting cycles.
>       */
>      QEMUTimer *pmu_cyc_overflow_timers[PMU_TIMERS_NUM];
> +
> +    /*
> +     * PMU base time value used by the PMU to calculate
> +     * running cycles.
> +     */
> +    uint64_t pmu_base_time;
>  };
>  
>  #define SET_FIT_PERIOD(a_, b_, c_, d_)          \
> diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
> index 9610e65c76..e0b6fe4057 100644
> --- a/target/ppc/cpu_init.c
> +++ b/target/ppc/cpu_init.c
> @@ -6821,8 +6821,8 @@ static void register_book3s_pmu_sup_sprs(CPUPPCState *env)
>  {
>      spr_register_kvm(env, SPR_POWER_MMCR0, "MMCR0",
>                       SPR_NOACCESS, SPR_NOACCESS,
> -                     &spr_read_generic, &spr_write_generic,
> -                     KVM_REG_PPC_MMCR0, 0x00000000);
> +                     &spr_read_generic, &spr_write_MMCR0,
> +                     KVM_REG_PPC_MMCR0, 0x80000000);
>      spr_register_kvm(env, SPR_POWER_MMCR1, "MMCR1",
>                       SPR_NOACCESS, SPR_NOACCESS,
>                       &spr_read_generic, &spr_write_generic,
> @@ -6870,7 +6870,7 @@ static void register_book3s_pmu_user_sprs(CPUPPCState *env)
>      spr_register(env, SPR_POWER_UMMCR0, "UMMCR0",
>                   &spr_read_MMCR0_ureg, &spr_write_MMCR0_ureg,
>                   &spr_read_ureg, &spr_write_ureg,
> -                 0x00000000);
> +                 0x80000000);
>      spr_register(env, SPR_POWER_UMMCR1, "UMMCR1",
>                   &spr_read_ureg, SPR_NOACCESS,
>                   &spr_read_ureg, &spr_write_ureg,
> diff --git a/target/ppc/helper.h b/target/ppc/helper.h
> index 627811cefc..ea60a7493c 100644
> --- a/target/ppc/helper.h
> +++ b/target/ppc/helper.h
> @@ -20,6 +20,7 @@ DEF_HELPER_1(rfscv, void, env)
>  DEF_HELPER_1(hrfid, void, env)
>  DEF_HELPER_2(store_lpcr, void, env, tl)
>  DEF_HELPER_2(store_pcr, void, env, tl)
> +DEF_HELPER_2(store_mmcr0, void, env, tl)
>  #endif
>  DEF_HELPER_1(check_tlb_flush_local, void, env)
>  DEF_HELPER_1(check_tlb_flush_global, void, env)
> diff --git a/target/ppc/power8-pmu-regs.c.inc b/target/ppc/power8-pmu-regs.c.inc
> index 7391851238..fbb8977641 100644
> --- a/target/ppc/power8-pmu-regs.c.inc
> +++ b/target/ppc/power8-pmu-regs.c.inc
> @@ -104,6 +104,17 @@ void spr_read_MMCR0_ureg(DisasContext *ctx, int gprn, int sprn)
>      tcg_temp_free(t0);
>  }
>  
> +static void write_MMCR0_common(DisasContext *ctx, TCGv val)
> +{
> +    /*
> +     * helper_store_mmcr0 will make clock based operations that
> +     * will cause 'bad icount read' errors if we do not execute
> +     * gen_icount_io_start() beforehand.
> +     */
> +    gen_icount_io_start(ctx);
> +    gen_helper_store_mmcr0(cpu_env, val);
> +}
> +
>  void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn)
>  {
>      TCGv masked_gprn;
> @@ -119,7 +130,7 @@ void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn)
>       */
>      masked_gprn = masked_gprn_for_spr_write(gprn, SPR_POWER_MMCR0,
>                                              MMCR0_UREG_MASK);
> -    gen_store_spr(SPR_POWER_MMCR0, masked_gprn);
> +    write_MMCR0_common(ctx, masked_gprn);
>  
>      tcg_temp_free(masked_gprn);
>  }
> @@ -219,6 +230,11 @@ void spr_write_PMC56_ureg(DisasContext *ctx, int sprn, int gprn)
>      /* The remaining steps are similar to PMCs 1-4 userspace write */
>      spr_write_PMC14_ureg(ctx, sprn, gprn);
>  }
> +
> +void spr_write_MMCR0(DisasContext *ctx, int sprn, int gprn)
> +{
> +    write_MMCR0_common(ctx, cpu_gpr[gprn]);
> +}
>  #else
>  void spr_read_MMCR0_ureg(DisasContext *ctx, int gprn, int sprn)
>  {
> @@ -259,4 +275,9 @@ void spr_write_PMC56_ureg(DisasContext *ctx, int sprn, int gprn)
>  {
>      spr_noaccess(ctx, gprn, sprn);
>  }
> +
> +void spr_write_MMCR0(DisasContext *ctx, int sprn, int gprn)
> +{
> +    spr_write_generic(ctx, sprn, gprn);
> +}
>  #endif /* defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) */
> diff --git a/target/ppc/power8-pmu.c b/target/ppc/power8-pmu.c
> index e66c152eb5..47932ded4f 100644
> --- a/target/ppc/power8-pmu.c
> +++ b/target/ppc/power8-pmu.c
> @@ -23,6 +23,128 @@
>  
>  #if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
>  
> +static bool pmc_is_inactive(CPUPPCState *env, int sprn)
> +{
> +    if (env->spr[SPR_POWER_MMCR0] & MMCR0_FC) {
> +        return true;
> +    }
> +
> +    if (sprn < SPR_POWER_PMC5) {
> +        return env->spr[SPR_POWER_MMCR0] & MMCR0_FC14;
> +    }
> +
> +    return env->spr[SPR_POWER_MMCR0] & MMCR0_FC56;
> +}
> +
> +/*
> + * For PMCs 1-4, IBM POWER chips has support for an implementation
> + * dependent event, 0x1E, that enables cycle counting. The Linux kernel
> + * makes extensive use of 0x1E, so let's also support it.
> + *
> + * Likewise, event 0x2 is an implementation-dependent event that IBM
> + * POWER chips implement (at least since POWER8) that is equivalent to
> + * PM_INST_CMPL. Let's support this event on PMCs 1-4 as well.
> + */
> +static PMUEventType pmc_get_event(CPUPPCState *env, int sprn)
> +{
> +    uint8_t mmcr1_evt_extr[] = { MMCR1_PMC1EVT_EXTR, MMCR1_PMC2EVT_EXTR,
> +                                 MMCR1_PMC3EVT_EXTR, MMCR1_PMC4EVT_EXTR };
> +    PMUEventType evt_type = PMU_EVENT_INVALID;
> +    uint8_t pmcsel;
> +    int i;
> +
> +    if (pmc_is_inactive(env, sprn)) {
> +        return PMU_EVENT_INACTIVE;
> +    }
> +
> +    if (sprn == SPR_POWER_PMC5) {
> +        return PMU_EVENT_INSTRUCTIONS;
> +    }
> +
> +    if (sprn == SPR_POWER_PMC6) {
> +        return PMU_EVENT_CYCLES;
> +    }
> +
> +    i = sprn - SPR_POWER_PMC1;
> +    pmcsel = extract64(env->spr[SPR_POWER_MMCR1], mmcr1_evt_extr[i],
> +                       MMCR1_EVT_SIZE);
> +
> +    switch (pmcsel) {
> +    case 0x2:
> +        evt_type = PMU_EVENT_INSTRUCTIONS;
> +        break;
> +    case 0x1E:
> +        evt_type = PMU_EVENT_CYCLES;
> +        break;
> +    case 0xF0:
> +        /*
> +         * PMC1SEL = 0xF0 is the architected PowerISA v3.1
> +         * event that counts cycles using PMC1.
> +         */
> +        if (sprn == SPR_POWER_PMC1) {
> +            evt_type = PMU_EVENT_CYCLES;
> +        }
> +        break;
> +    case 0xFE:
> +        /*
> +         * PMC1SEL = 0xFE is the architected PowerISA v3.1
> +         * event to sample instructions using PMC1.
> +         */
> +        if (sprn == SPR_POWER_PMC1) {
> +            evt_type = PMU_EVENT_INSTRUCTIONS;
> +        }
> +        break;
> +    default:
> +        break;
> +    }
> +
> +    return evt_type;
> +}
> +
> +static void pmu_update_cycles(CPUPPCState *env)
> +{
> +    uint64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> +    uint64_t time_delta = now - env->pmu_base_time;
> +    int sprn;
> +
> +    for (sprn = SPR_POWER_PMC1; sprn <= SPR_POWER_PMC6; sprn++) {
> +        if (pmc_get_event(env, sprn) != PMU_EVENT_CYCLES) {
> +            continue;
> +        }
> +
> +        /*
> +         * The pseries and powernv clock runs at 1Ghz, meaning
> +         * that 1 nanosec equals 1 cycle.
> +         */
> +        env->spr[sprn] += time_delta;
> +    }
> +
> +    /* Update base_time for future calculations */
> +    env->pmu_base_time = now;
> +}
> +
> +void helper_store_mmcr0(CPUPPCState *env, target_ulong value)
> +{
> +    target_ulong curr_value = env->spr[SPR_POWER_MMCR0];
> +    bool curr_FC = curr_value & MMCR0_FC;
> +    bool new_FC = value & MMCR0_FC;
> +
> +    pmu_update_cycles(env);
> +
> +    env->spr[SPR_POWER_MMCR0] = value;
> +
> +    /*
> +     * MMCR0 writes can change HFLAGS_PMCCCLEAR and HFLAGS_MMCR0FC.
> +     * hreg_compute_hflags() does too much stuff to be called
> +     * needlessly, so check beforehand if we really need a hflags
> +     * update.
> +     */
> +    if (((curr_value & MMCR0_PMCC) != (value & MMCR0_PMCC)) ||
> +        (curr_FC != new_FC)) {
> +        hreg_compute_hflags(env);
> +    }
> +}
> +
>  static void fire_PMC_interrupt(PowerPCCPU *cpu)
>  {
>      CPUPPCState *env = &cpu->env;
> diff --git a/target/ppc/spr_tcg.h b/target/ppc/spr_tcg.h
> index 520f1ef233..eb1d0c2bf0 100644
> --- a/target/ppc/spr_tcg.h
> +++ b/target/ppc/spr_tcg.h
> @@ -25,6 +25,7 @@
>  void spr_noaccess(DisasContext *ctx, int gprn, int sprn);
>  void spr_read_generic(DisasContext *ctx, int gprn, int sprn);
>  void spr_write_generic(DisasContext *ctx, int sprn, int gprn);
> +void spr_write_MMCR0(DisasContext *ctx, int sprn, int gprn);
>  void spr_read_xer(DisasContext *ctx, int gprn, int sprn);
>  void spr_write_xer(DisasContext *ctx, int sprn, int gprn);
>  void spr_read_lr(DisasContext *ctx, int gprn, int sprn);

-- 
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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