Re: [PATCH v4 5/5] target/riscv: Implement privilege mode filtering for cycle/instret

[Atish Kumar Patra]

On Tue, Jan 23, 2024 at 4:15 PM Atish Kumar Patra <atishp@rivosinc.com> wrote:

On Sun, Jan 21, 2024 at 9:04 PM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Tue, Jan 9, 2024 at 10:29 AM Atish Patra <atishp@rivosinc.com> wrote:
> >
> > Privilege mode filtering can also be emulated for cycle/instret by
> > tracking host_ticks/icount during each privilege mode switch. This
> > patch implements that for both cycle/instret and mhpmcounters. The
> > first one requires Smcntrpmf while the other one requires Sscofpmf
> > to be enabled.
> >
> > The cycle/instret are still computed using host ticks when icount
> > is not enabled. Otherwise, they are computed using raw icount which
> > is more accurate in icount mode.
> >
> > Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> > Signed-off-by: Atish Patra <atishp@rivosinc.com>
> > ---
> >  target/riscv/cpu.h        | 11 +++++
> >  target/riscv/cpu_helper.c |  9 +++-
> >  target/riscv/csr.c        | 95 ++++++++++++++++++++++++++++++---------
> >  target/riscv/pmu.c        | 43 ++++++++++++++++++
> >  target/riscv/pmu.h        |  2 +
> >  5 files changed, 136 insertions(+), 24 deletions(-)
> >
> > diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> > index 34617c4c4bab..40d10726155b 100644
> > --- a/target/riscv/cpu.h
> > +++ b/target/riscv/cpu.h
> > @@ -136,6 +136,15 @@ typedef struct PMUCTRState {
> >      target_ulong irq_overflow_left;
> >  } PMUCTRState;
> >
> > +typedef struct PMUFixedCtrState {
> > +        /* Track cycle and icount for each privilege mode */
> > +        uint64_t counter[4];
> > +        uint64_t counter_prev[4];
>
> Are these two used?
>

Yes. That's where it tracks the current/previous value cycle/instret.
riscv_pmu_icount_update_priv/riscv_pmu_cycle_update_priv

The priv mode based filtering is enabled in riscv_pmu_ctr_get_fixed_counters_val
using "counter" afterwards.

Did I misunderstand your question ?

ping ?

 

> Alistair
>
> > +        /* Track cycle and icount for each privilege mode when V = 1*/
> > +        uint64_t counter_virt[2];
> > +        uint64_t counter_virt_prev[2];
> > +} PMUFixedCtrState;
> > +
> >  struct CPUArchState {
> >      target_ulong gpr[32];
> >      target_ulong gprh[32]; /* 64 top bits of the 128-bit registers */
> > @@ -334,6 +343,8 @@ struct CPUArchState {
> >      /* PMU event selector configured values for RV32 */
> >      target_ulong mhpmeventh_val[RV_MAX_MHPMEVENTS];
> >
> > +    PMUFixedCtrState pmu_fixed_ctrs[2];
> > +
> >      target_ulong sscratch;
> >      target_ulong mscratch;
> >
> > diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> > index e7e23b34f455..3dddb1b433e8 100644
> > --- a/target/riscv/cpu_helper.c
> > +++ b/target/riscv/cpu_helper.c
> > @@ -715,8 +715,13 @@ void riscv_cpu_set_mode(CPURISCVState *env, target_ulong newpriv)
> >  {
> >      g_assert(newpriv <= PRV_M && newpriv != PRV_RESERVED);
> >
> > -    if (icount_enabled() && newpriv != env->priv) {
> > -        riscv_itrigger_update_priv(env);
> > +    if (newpriv != env->priv) {
> > +        if (icount_enabled()) {
> > +            riscv_itrigger_update_priv(env);
> > +            riscv_pmu_icount_update_priv(env, newpriv);
> > +        } else {
> > +            riscv_pmu_cycle_update_priv(env, newpriv);
> > +        }
> >      }
> >      /* tlb_flush is unnecessary as mode is contained in mmu_idx */
> >      env->priv = newpriv;
> > diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> > index 3bd4aa22374f..307d052021c5 100644
> > --- a/target/riscv/csr.c
> > +++ b/target/riscv/csr.c
> > @@ -782,32 +782,16 @@ static int write_vcsr(CPURISCVState *env, int csrno, target_ulong val)
> >      return RISCV_EXCP_NONE;
> >  }
> >
> > +#if defined(CONFIG_USER_ONLY)
> >  /* User Timers and Counters */
> >  static target_ulong get_ticks(bool shift)
> >  {
> > -    int64_t val;
> > -    target_ulong result;
> > -
> > -#if !defined(CONFIG_USER_ONLY)
> > -    if (icount_enabled()) {
> > -        val = icount_get();
> > -    } else {
> > -        val = cpu_get_host_ticks();
> > -    }
> > -#else
> > -    val = cpu_get_host_ticks();
> > -#endif
> > -
> > -    if (shift) {
> > -        result = val >> 32;
> > -    } else {
> > -        result = val;
> > -    }
> > +    int64_t val = cpu_get_host_ticks();
> > +    target_ulong result = shift ? val >> 32 : val;
> >
> >      return result;
> >  }
> >
> > -#if defined(CONFIG_USER_ONLY)
> >  static RISCVException read_time(CPURISCVState *env, int csrno,
> >                                  target_ulong *val)
> >  {
> > @@ -932,6 +916,70 @@ static int write_mhpmeventh(CPURISCVState *env, int csrno, target_ulong val)
> >      return RISCV_EXCP_NONE;
> >  }
> >
> > +static target_ulong riscv_pmu_ctr_get_fixed_counters_val(CPURISCVState *env,
> > +                                                         int counter_idx,
> > +                                                         bool upper_half)
> > +{
> > +    uint64_t curr_val = 0;
> > +    target_ulong result = 0;
> > +    uint64_t *counter_arr = icount_enabled() ? env->pmu_fixed_ctrs[1].counter :
> > +                            env->pmu_fixed_ctrs[0].counter;
> > +    uint64_t *counter_arr_virt = icount_enabled() ?
> > +                                 env->pmu_fixed_ctrs[1].counter_virt :
> > +                                 env->pmu_fixed_ctrs[0].counter_virt;
> > +    uint64_t cfg_val = 0;
> > +
> > +    if (counter_idx == 0) {
> > +        cfg_val = upper_half ? ((uint64_t)env->mcyclecfgh << 32) :
> > +                  env->mcyclecfg;
> > +    } else if (counter_idx == 2) {
> > +        cfg_val = upper_half ? ((uint64_t)env->minstretcfgh << 32) :
> > +                  env->minstretcfg;
> > +    } else {
> > +        cfg_val = upper_half ?
> > +                  ((uint64_t)env->mhpmeventh_val[counter_idx] << 32) :
> > +                  env->mhpmevent_val[counter_idx];
> > +    }
> > +
> > +    if (!cfg_val) {
> > +        if (icount_enabled()) {
> > +            curr_val = icount_get_raw();
> > +        } else {
> > +            curr_val = cpu_get_host_ticks();
> > +        }
> > +        goto done;
> > +    }
> > +
> > +    if (!(cfg_val & MCYCLECFG_BIT_MINH)) {
> > +        curr_val += counter_arr[PRV_M];
> > +    }
> > +
> > +    if (!(cfg_val & MCYCLECFG_BIT_SINH)) {
> > +        curr_val += counter_arr[PRV_S];
> > +    }
> > +
> > +    if (!(cfg_val & MCYCLECFG_BIT_UINH)) {
> > +        curr_val += counter_arr[PRV_U];
> > +    }
> > +
> > +    if (!(cfg_val & MCYCLECFG_BIT_VSINH)) {
> > +        curr_val += counter_arr_virt[PRV_S];
> > +    }
> > +
> > +    if (!(cfg_val & MCYCLECFG_BIT_VUINH)) {
> > +        curr_val += counter_arr_virt[PRV_U];
> > +    }
> > +
> > +done:
> > +    if (riscv_cpu_mxl(env) == MXL_RV32) {
> > +        result = upper_half ? curr_val >> 32 : curr_val;
> > +    } else {
> > +        result = curr_val;
> > +    }
> > +
> > +    return result;
> > +}
> > +
> >  static int write_mhpmcounter(CPURISCVState *env, int csrno, target_ulong val)
> >  {
> >      int ctr_idx = csrno - CSR_MCYCLE;
> > @@ -941,7 +989,8 @@ static int write_mhpmcounter(CPURISCVState *env, int csrno, target_ulong val)
> >      counter->mhpmcounter_val = val;
> >      if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> >          riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> > -        counter->mhpmcounter_prev = get_ticks(false);
> > +        counter->mhpmcounter_prev = riscv_pmu_ctr_get_fixed_counters_val(env,
> > +                                                                ctr_idx, false);
> >          if (ctr_idx > 2) {
> >              if (riscv_cpu_mxl(env) == MXL_RV32) {
> >                  mhpmctr_val = mhpmctr_val |
> > @@ -968,7 +1017,8 @@ static int write_mhpmcounterh(CPURISCVState *env, int csrno, target_ulong val)
> >      mhpmctr_val = mhpmctr_val | (mhpmctrh_val << 32);
> >      if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> >          riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> > -        counter->mhpmcounterh_prev = get_ticks(true);
> > +        counter->mhpmcounterh_prev = riscv_pmu_ctr_get_fixed_counters_val(env,
> > +                                                                 ctr_idx, true);
> >          if (ctr_idx > 2) {
> >              riscv_pmu_setup_timer(env, mhpmctr_val, ctr_idx);
> >          }
> > @@ -1009,7 +1059,8 @@ static RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val,
> >       */
> >      if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> >          riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> > -        *val = get_ticks(upper_half) - ctr_prev + ctr_val;
> > +        *val = riscv_pmu_ctr_get_fixed_counters_val(env, ctr_idx, upper_half) -
> > +                                                    ctr_prev + ctr_val;
> >      } else {
> >          *val = ctr_val;
> >      }
> > diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
> > index 0e7d58b8a5c2..8b6cc4c6bb4d 100644
> > --- a/target/riscv/pmu.c
> > +++ b/target/riscv/pmu.c
> > @@ -19,6 +19,7 @@
> >  #include "qemu/osdep.h"
> >  #include "qemu/log.h"
> >  #include "qemu/error-report.h"
> > +#include "qemu/timer.h"
> >  #include "cpu.h"
> >  #include "pmu.h"
> >  #include "sysemu/cpu-timers.h"
> > @@ -176,6 +177,48 @@ static int riscv_pmu_incr_ctr_rv64(RISCVCPU *cpu, uint32_t ctr_idx)
> >      return 0;
> >  }
> >
> > +void riscv_pmu_icount_update_priv(CPURISCVState *env, target_ulong newpriv)
> > +{
> > +    uint64_t delta;
> > +    uint64_t *counter_arr;
> > +    uint64_t *counter_arr_prev;
> > +    uint64_t current_icount = icount_get_raw();
> > +
> > +    if (env->virt_enabled) {
> > +        counter_arr = env->pmu_fixed_ctrs[1].counter_virt;
> > +        counter_arr_prev = env->pmu_fixed_ctrs[1].counter_virt_prev;
> > +    } else {
> > +        counter_arr = env->pmu_fixed_ctrs[1].counter;
> > +        counter_arr_prev = env->pmu_fixed_ctrs[1].counter_prev;
> > +    }
> > +
> > +    counter_arr_prev[newpriv] = current_icount;
> > +    delta = current_icount - counter_arr_prev[env->priv];
> > +
> > +    counter_arr[env->priv] += delta;
> > +}
> > +
> > +void riscv_pmu_cycle_update_priv(CPURISCVState *env, target_ulong newpriv)
> > +{
> > +    uint64_t delta;
> > +    uint64_t *counter_arr;
> > +    uint64_t *counter_arr_prev;
> > +    uint64_t current_host_ticks = cpu_get_host_ticks();
> > +
> > +    if (env->virt_enabled) {
> > +        counter_arr = env->pmu_fixed_ctrs[0].counter_virt;
> > +        counter_arr_prev = env->pmu_fixed_ctrs[0].counter_virt_prev;
> > +    } else {
> > +        counter_arr = env->pmu_fixed_ctrs[0].counter;
> > +        counter_arr_prev = env->pmu_fixed_ctrs[0].counter_prev;
> > +    }
> > +
> > +    counter_arr_prev[newpriv] = current_host_ticks;
> > +    delta = current_host_ticks - counter_arr_prev[env->priv];
> > +
> > +    counter_arr[env->priv] += delta;
> > +}
> > +
> >  int riscv_pmu_incr_ctr(RISCVCPU *cpu, enum riscv_pmu_event_idx event_idx)
> >  {
> >      uint32_t ctr_idx;
> > diff --git a/target/riscv/pmu.h b/target/riscv/pmu.h
> > index 505fc850d38e..50de6031a730 100644
> > --- a/target/riscv/pmu.h
> > +++ b/target/riscv/pmu.h
> > @@ -31,3 +31,5 @@ int riscv_pmu_incr_ctr(RISCVCPU *cpu, enum riscv_pmu_event_idx event_idx);
> >  void riscv_pmu_generate_fdt_node(void *fdt, uint32_t cmask, char *pmu_name);
> >  int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t value,
> >                            uint32_t ctr_idx);
> > +void riscv_pmu_icount_update_priv(CPURISCVState *env, target_ulong newpriv);
> > +void riscv_pmu_cycle_update_priv(CPURISCVState *env, target_ulong newpriv);
> > --
> > 2.34.1
> >
> >