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Re: [PATCH v2 07/13] target/riscv: Add counter delegation/configuration


From: Alistair Francis
Subject: Re: [PATCH v2 07/13] target/riscv: Add counter delegation/configuration support
Date: Tue, 6 Aug 2024 11:21:18 +1000

On Wed, Jul 24, 2024 at 9:32 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> From: Kaiwen Xue <kaiwenx@rivosinc.com>
>
> The Smcdeleg/Ssccfg adds the support for counter delegation via
> S*indcsr and Ssccfg.
>
> It also adds a new shadow CSR scountinhibit and menvcfg enable bit (CDE)
> to enable this extension and scountovf virtualization.
>
> Signed-off-by: Kaiwen Xue <kaiwenx@rivosinc.com>
> Co-developed-by: Atish Patra <atishp@rivosinc.com>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
>  target/riscv/csr.c | 302 
> ++++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 290 insertions(+), 12 deletions(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index da27ba1b7580..2369a746a285 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -366,6 +366,21 @@ static RISCVException aia_smode32(CPURISCVState *env, 
> int csrno)
>      return smode32(env, csrno);
>  }
>
> +static RISCVException scountinhibit_pred(CPURISCVState *env, int csrno)
> +{
> +    RISCVCPU *cpu = env_archcpu(env);
> +
> +    if (!cpu->cfg.ext_ssccfg || !cpu->cfg.ext_smcdeleg) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    if (env->virt_enabled) {
> +        return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> +    }
> +
> +    return smode(env, csrno);
> +}
> +
>  static bool csrind_extensions_present(CPURISCVState *env)
>  {
>      return riscv_cpu_cfg(env)->ext_smcsrind || 
> riscv_cpu_cfg(env)->ext_sscsrind;
> @@ -1190,10 +1205,9 @@ done:
>      return result;
>  }
>
> -static RISCVException write_mhpmcounter(CPURISCVState *env, int csrno,
> -                                        target_ulong val)
> +static RISCVException riscv_pmu_write_ctr(CPURISCVState *env, target_ulong 
> val,
> +                                          uint32_t ctr_idx)
>  {
> -    int ctr_idx = csrno - CSR_MCYCLE;
>      PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
>      uint64_t mhpmctr_val = val;
>
> @@ -1218,10 +1232,9 @@ static RISCVException write_mhpmcounter(CPURISCVState 
> *env, int csrno,
>      return RISCV_EXCP_NONE;
>  }
>
> -static RISCVException write_mhpmcounterh(CPURISCVState *env, int csrno,
> -                                         target_ulong val)
> +static RISCVException riscv_pmu_write_ctrh(CPURISCVState *env, target_ulong 
> val,
> +                                          uint32_t ctr_idx)
>  {
> -    int ctr_idx = csrno - CSR_MCYCLEH;
>      PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
>      uint64_t mhpmctr_val = counter->mhpmcounter_val;
>      uint64_t mhpmctrh_val = val;
> @@ -1243,6 +1256,20 @@ static RISCVException write_mhpmcounterh(CPURISCVState 
> *env, int csrno,
>      return RISCV_EXCP_NONE;
>  }
>
> +static int write_mhpmcounter(CPURISCVState *env, int csrno, target_ulong val)
> +{
> +    int ctr_idx = csrno - CSR_MCYCLE;
> +
> +    return riscv_pmu_write_ctr(env, val, ctr_idx);
> +}
> +
> +static int write_mhpmcounterh(CPURISCVState *env, int csrno, target_ulong 
> val)
> +{
> +    int ctr_idx = csrno - CSR_MCYCLEH;
> +
> +    return riscv_pmu_write_ctrh(env, val, ctr_idx);
> +}
> +
>  RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val,
>                                           bool upper_half, uint32_t ctr_idx)
>  {
> @@ -1308,6 +1335,167 @@ static RISCVException read_hpmcounterh(CPURISCVState 
> *env, int csrno,
>      return riscv_pmu_read_ctr(env, val, true, ctr_index);
>  }
>
> +static int rmw_cd_mhpmcounter(CPURISCVState *env, int ctr_idx,
> +                              target_ulong *val, target_ulong new_val,
> +                              target_ulong wr_mask)
> +{
> +    if (wr_mask != 0 && wr_mask != -1) {
> +        return -EINVAL;
> +    }
> +
> +    if (!wr_mask && val) {
> +        riscv_pmu_read_ctr(env, val, false, ctr_idx);
> +    } else if (wr_mask) {
> +        riscv_pmu_write_ctr(env, new_val, ctr_idx);
> +    } else {
> +        return -EINVAL;
> +    }
> +
> +    return 0;
> +}
> +
> +static int rmw_cd_mhpmcounterh(CPURISCVState *env, int ctr_idx,
> +                               target_ulong *val, target_ulong new_val,
> +                               target_ulong wr_mask)
> +{
> +    if (wr_mask != 0 && wr_mask != -1) {
> +        return -EINVAL;
> +    }
> +
> +    if (!wr_mask && val) {
> +        riscv_pmu_read_ctr(env, val, true, ctr_idx);

riscv_pmu_write_ctrh?

Alistair

> +    } else if (wr_mask) {
> +        riscv_pmu_write_ctrh(env, new_val, ctr_idx);
> +    } else {
> +        return -EINVAL;
> +    }
> +
> +    return 0;
> +}
> +
> +static int rmw_cd_mhpmevent(CPURISCVState *env, int evt_index,
> +                            target_ulong *val, target_ulong new_val,
> +                            target_ulong wr_mask)
> +{
> +    uint64_t mhpmevt_val = new_val;
> +
> +    if (wr_mask != 0 && wr_mask != -1) {
> +        return -EINVAL;
> +    }
> +
> +    if (!wr_mask && val) {
> +        *val = env->mhpmevent_val[evt_index];
> +        if (riscv_cpu_cfg(env)->ext_sscofpmf) {
> +            *val &= ~MHPMEVENT_BIT_MINH;
> +        }
> +    } else if (wr_mask) {
> +        wr_mask &= ~MHPMEVENT_BIT_MINH;
> +        mhpmevt_val = (new_val & wr_mask) |
> +                      (env->mhpmevent_val[evt_index] & ~wr_mask);
> +        if (riscv_cpu_mxl(env) == MXL_RV32) {
> +            mhpmevt_val = mhpmevt_val |
> +                          ((uint64_t)env->mhpmeventh_val[evt_index] << 32);
> +        }
> +        env->mhpmevent_val[evt_index] = mhpmevt_val;
> +        riscv_pmu_update_event_map(env, mhpmevt_val, evt_index);
> +    } else {
> +        return -EINVAL;
> +    }
> +
> +    return 0;
> +}
> +
> +static int rmw_cd_mhpmeventh(CPURISCVState *env, int evt_index,
> +                             target_ulong *val, target_ulong new_val,
> +                             target_ulong wr_mask)
> +{
> +    uint64_t mhpmevth_val;
> +    uint64_t mhpmevt_val = env->mhpmevent_val[evt_index];
> +
> +    if (wr_mask != 0 && wr_mask != -1) {
> +        return -EINVAL;
> +    }
> +
> +    if (!wr_mask && val) {
> +        *val = env->mhpmeventh_val[evt_index];
> +        if (riscv_cpu_cfg(env)->ext_sscofpmf) {
> +            *val &= ~MHPMEVENTH_BIT_MINH;
> +        }
> +    } else if (wr_mask) {
> +        wr_mask &= ~MHPMEVENTH_BIT_MINH;
> +        env->mhpmeventh_val[evt_index] =
> +            (new_val & wr_mask) | (env->mhpmeventh_val[evt_index] & 
> ~wr_mask);
> +        mhpmevth_val = env->mhpmeventh_val[evt_index];
> +        mhpmevt_val = mhpmevt_val | (mhpmevth_val << 32);
> +        riscv_pmu_update_event_map(env, mhpmevt_val, evt_index);
> +    } else {
> +        return -EINVAL;
> +    }
> +
> +    return 0;
> +}
> +
> +static int rmw_cd_ctr_cfg(CPURISCVState *env, int cfg_index, target_ulong 
> *val,
> +                            target_ulong new_val, target_ulong wr_mask)
> +{
> +    switch (cfg_index) {
> +    case 0:             /* CYCLECFG */
> +        if (wr_mask) {
> +            wr_mask &= ~MCYCLECFG_BIT_MINH;
> +            env->mcyclecfg = (new_val & wr_mask) | (env->mcyclecfg & 
> ~wr_mask);
> +        } else {
> +            *val = env->mcyclecfg &= ~MHPMEVENTH_BIT_MINH;
> +        }
> +        break;
> +    case 2:             /* INSTRETCFG */
> +        if (wr_mask) {
> +            wr_mask &= ~MINSTRETCFG_BIT_MINH;
> +            env->minstretcfg = (new_val & wr_mask) |
> +                               (env->minstretcfg & ~wr_mask);
> +        } else {
> +            *val = env->minstretcfg &= ~MHPMEVENTH_BIT_MINH;
> +        }
> +        break;
> +    default:
> +        return -EINVAL;
> +    }
> +    return 0;
> +}
> +
> +static int rmw_cd_ctr_cfgh(CPURISCVState *env, int cfg_index, target_ulong 
> *val,
> +                            target_ulong new_val, target_ulong wr_mask)
> +{
> +
> +    if (riscv_cpu_mxl(env) != MXL_RV32) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    switch (cfg_index) {
> +    case 0:         /* CYCLECFGH */
> +        if (wr_mask) {
> +            wr_mask &= ~MCYCLECFGH_BIT_MINH;
> +            env->mcyclecfgh = (new_val & wr_mask) |
> +                              (env->mcyclecfgh & ~wr_mask);
> +        } else {
> +            *val = env->mcyclecfgh;
> +        }
> +        break;
> +    case 2:          /* INSTRETCFGH */
> +        if (wr_mask) {
> +            wr_mask &= ~MINSTRETCFGH_BIT_MINH;
> +            env->minstretcfgh = (new_val & wr_mask) |
> +                                (env->minstretcfgh & ~wr_mask);
> +        } else {
> +            *val = env->minstretcfgh;
> +        }
> +        break;
> +    default:
> +        return -EINVAL;
> +    }
> +    return 0;
> +}
> +
> +
>  static RISCVException read_scountovf(CPURISCVState *env, int csrno,
>                                       target_ulong *val)
>  {
> @@ -1317,6 +1505,14 @@ static RISCVException read_scountovf(CPURISCVState 
> *env, int csrno,
>      target_ulong *mhpm_evt_val;
>      uint64_t of_bit_mask;
>
> +    /* Virtualize scountovf for counter delegation */
> +    if (riscv_cpu_cfg(env)->ext_sscofpmf &&
> +        riscv_cpu_cfg(env)->ext_ssccfg &&
> +        get_field(env->menvcfg, MENVCFG_CDE) &&
> +        env->virt_enabled) {
> +        return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> +    }
> +
>      if (riscv_cpu_mxl(env) == MXL_RV32) {
>          mhpm_evt_val = env->mhpmeventh_val;
>          of_bit_mask = MHPMEVENTH_BIT_OF;
> @@ -2254,11 +2450,70 @@ static int rmw_xireg_cd(CPURISCVState *env, int csrno,
>                          target_ulong isel, target_ulong *val,
>                          target_ulong new_val, target_ulong wr_mask)
>  {
> -    if (!riscv_cpu_cfg(env)->ext_smcdeleg) {
> +    int ret = -EINVAL;
> +    int ctr_index = isel - ISELECT_CD_FIRST;
> +    int isel_hpm_start = ISELECT_CD_FIRST + 3;
> +
> +    if (!riscv_cpu_cfg(env)->ext_smcdeleg || 
> !riscv_cpu_cfg(env)->ext_ssccfg) {
>          return RISCV_EXCP_ILLEGAL_INST;
>      }
> -    /* TODO: Implement the functionality later */
> -    return RISCV_EXCP_NONE;
> +
> +    /* Invalid siselect value for reserved */
> +    if (ctr_index == 1) {
> +        goto done;
> +    }
> +
> +    /* sireg4 and sireg5 provides access RV32 only CSRs */
> +    if (((csrno == CSR_SIREG5) || (csrno == CSR_SIREG4)) &&
> +        (riscv_cpu_mxl(env) != MXL_RV32)) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    /* Check Sscofpmf dependancy */
> +    if (!riscv_cpu_cfg(env)->ext_sscofpmf && csrno == CSR_SIREG5 &&
> +        (isel_hpm_start <= isel && isel <= ISELECT_CD_LAST)) {
> +        goto done;
> +    }
> +
> +    /* Check smcntrpmf dependancy */
> +    if (!riscv_cpu_cfg(env)->ext_smcntrpmf &&
> +        (csrno == CSR_SIREG2 || csrno == CSR_SIREG5) &&
> +        (ISELECT_CD_FIRST <= isel && isel < isel_hpm_start)) {
> +        goto done;
> +    }
> +
> +    if (!get_field(env->mcounteren, BIT(ctr_index)) ||
> +        !get_field(env->menvcfg, MENVCFG_CDE)) {
> +        goto done;
> +    }
> +
> +    switch (csrno) {
> +    case CSR_SIREG:
> +        ret = rmw_cd_mhpmcounter(env, ctr_index, val, new_val, wr_mask);
> +        break;
> +    case CSR_SIREG4:
> +        ret = rmw_cd_mhpmcounterh(env, ctr_index, val, new_val, wr_mask);
> +        break;
> +    case CSR_SIREG2:
> +        if (ctr_index <= 2) {
> +            ret = rmw_cd_ctr_cfg(env, ctr_index, val, new_val, wr_mask);
> +        } else {
> +            ret = rmw_cd_mhpmevent(env, ctr_index, val, new_val, wr_mask);
> +        }
> +        break;
> +    case CSR_SIREG5:
> +        if (ctr_index <= 2) {
> +            ret = rmw_cd_ctr_cfgh(env, ctr_index, val, new_val, wr_mask);
> +        } else {
> +            ret = rmw_cd_mhpmeventh(env, ctr_index, val, new_val, wr_mask);
> +        }
> +        break;
> +    default:
> +        goto done;
> +    }
> +
> +done:
> +    return ret;
>  }
>
>  /*
> @@ -2540,6 +2795,21 @@ static RISCVException 
> write_mcountinhibit(CPURISCVState *env, int csrno,
>      return RISCV_EXCP_NONE;
>  }
>
> +static RISCVException read_scountinhibit(CPURISCVState *env, int csrno,
> +                                         target_ulong *val)
> +{
> +    /* S-mode can only access the bits delegated by M-mode */
> +    *val = env->mcountinhibit & env->mcounteren;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_scountinhibit(CPURISCVState *env, int csrno,
> +                                          target_ulong val)
> +{
> +    write_mcountinhibit(env, csrno, val & env->mcounteren);
> +    return RISCV_EXCP_NONE;
> +}
> +
>  static RISCVException read_mcounteren(CPURISCVState *env, int csrno,
>                                        target_ulong *val)
>  {
> @@ -2642,12 +2912,14 @@ static RISCVException write_menvcfg(CPURISCVState 
> *env, int csrno,
>                                      target_ulong val)
>  {
>      const RISCVCPUConfig *cfg = riscv_cpu_cfg(env);
> -    uint64_t mask = MENVCFG_FIOM | MENVCFG_CBIE | MENVCFG_CBCFE | 
> MENVCFG_CBZE;
> +    uint64_t mask = MENVCFG_FIOM | MENVCFG_CBIE | MENVCFG_CBCFE |
> +                    MENVCFG_CBZE | MENVCFG_CDE;
>
>      if (riscv_cpu_mxl(env) == MXL_RV64) {
>          mask |= (cfg->ext_svpbmt ? MENVCFG_PBMTE : 0) |
>                  (cfg->ext_sstc ? MENVCFG_STCE : 0) |
> -                (cfg->ext_svadu ? MENVCFG_ADUE : 0);
> +                (cfg->ext_svadu ? MENVCFG_ADUE : 0) |
> +                (cfg->ext_smcdeleg ? MENVCFG_CDE : 0);
>      }
>      env->menvcfg = (env->menvcfg & ~mask) | (val & mask);
>
> @@ -2667,7 +2939,8 @@ static RISCVException write_menvcfgh(CPURISCVState 
> *env, int csrno,
>      const RISCVCPUConfig *cfg = riscv_cpu_cfg(env);
>      uint64_t mask = (cfg->ext_svpbmt ? MENVCFG_PBMTE : 0) |
>                      (cfg->ext_sstc ? MENVCFG_STCE : 0) |
> -                    (cfg->ext_svadu ? MENVCFG_ADUE : 0);
> +                    (cfg->ext_svadu ? MENVCFG_ADUE : 0) |
> +                    (cfg->ext_smcdeleg ? MENVCFG_CDE : 0);
>      uint64_t valh = (uint64_t)val << 32;
>
>      env->menvcfg = (env->menvcfg & ~mask) | (valh & mask);
> @@ -5417,6 +5690,11 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>                          write_sstateen_1_3,
>                          .min_priv_ver = PRIV_VERSION_1_12_0 },
>
> +    /* Supervisor Counter Delegation */
> +    [CSR_SCOUNTINHIBIT] = {"scountinhibit", scountinhibit_pred,
> +                            read_scountinhibit, write_scountinhibit,
> +                           .min_priv_ver = PRIV_VERSION_1_12_0 },
> +
>      /* Supervisor Trap Setup */
>      [CSR_SSTATUS]    = { "sstatus",    smode, read_sstatus,    write_sstatus,
>                           NULL,                read_sstatus_i128              
> },
>
> --
> 2.34.1
>
>



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