Re: [PATCH v4 4/5] target/riscv: Add cycle & instret privilege mode filtering support

[Alistair Francis]

On Tue, Jan 9, 2024 at 10:29 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> From: Kaiwen Xue <kaiwenx@rivosinc.com>
>
> QEMU only calculates dummy cycles and instructions, so there is no
> actual means to stop the icount in QEMU. Hence this patch merely adds
> the functionality of accessing the cfg registers, and cause no actual
> effects on the counting of cycle and instret counters.
>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> Signed-off-by: Kaiwen Xue <kaiwenx@rivosinc.com>

Acked-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/csr.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 80 insertions(+)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 283468bbc652..3bd4aa22374f 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -233,6 +233,24 @@ static RISCVException sscofpmf_32(CPURISCVState *env, 
> int csrno)
>      return sscofpmf(env, csrno);
>  }
>
> +static RISCVException smcntrpmf(CPURISCVState *env, int csrno)
> +{
> +    if (!riscv_cpu_cfg(env)->ext_smcntrpmf) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException smcntrpmf_32(CPURISCVState *env, int csrno)
> +{
> +    if (riscv_cpu_mxl(env) != MXL_RV32) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    return smcntrpmf(env, csrno);
> +}
> +
>  static RISCVException any(CPURISCVState *env, int csrno)
>  {
>      return RISCV_EXCP_NONE;
> @@ -818,6 +836,54 @@ static int read_hpmcounterh(CPURISCVState *env, int 
> csrno, target_ulong *val)
>
>  #else /* CONFIG_USER_ONLY */
>
> +static int read_mcyclecfg(CPURISCVState *env, int csrno, target_ulong *val)
> +{
> +    *val = env->mcyclecfg;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int write_mcyclecfg(CPURISCVState *env, int csrno, target_ulong val)
> +{
> +    env->mcyclecfg = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int read_mcyclecfgh(CPURISCVState *env, int csrno, target_ulong *val)
> +{
> +    *val = env->mcyclecfgh;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int write_mcyclecfgh(CPURISCVState *env, int csrno, target_ulong val)
> +{
> +    env->mcyclecfgh = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int read_minstretcfg(CPURISCVState *env, int csrno, target_ulong *val)
> +{
> +    *val = env->minstretcfg;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int write_minstretcfg(CPURISCVState *env, int csrno, target_ulong val)
> +{
> +    env->minstretcfg = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int read_minstretcfgh(CPURISCVState *env, int csrno, target_ulong 
> *val)
> +{
> +    *val = env->minstretcfgh;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int write_minstretcfgh(CPURISCVState *env, int csrno, target_ulong 
> val)
> +{
> +    env->minstretcfgh = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
>  static int read_mhpmevent(CPURISCVState *env, int csrno, target_ulong *val)
>  {
>      int evt_index = csrno - CSR_MCOUNTINHIBIT;
> @@ -4922,6 +4988,13 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>                               write_mcountinhibit,
>                               .min_priv_ver = PRIV_VERSION_1_11_0       },
>
> +    [CSR_MCYCLECFG]      = { "mcyclecfg",   smcntrpmf, read_mcyclecfg,
> +                             write_mcyclecfg,
> +                             .min_priv_ver = PRIV_VERSION_1_12_0       },
> +    [CSR_MINSTRETCFG]    = { "minstretcfg", smcntrpmf, read_minstretcfg,
> +                             write_minstretcfg,
> +                             .min_priv_ver = PRIV_VERSION_1_12_0       },
> +
>      [CSR_MHPMEVENT3]     = { "mhpmevent3",     any,    read_mhpmevent,
>                               write_mhpmevent                           },
>      [CSR_MHPMEVENT4]     = { "mhpmevent4",     any,    read_mhpmevent,
> @@ -4981,6 +5054,13 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>      [CSR_MHPMEVENT31]    = { "mhpmevent31",    any,    read_mhpmevent,
>                               write_mhpmevent                           },
>
> +    [CSR_MCYCLECFGH]     = { "mcyclecfgh",   smcntrpmf_32, read_mcyclecfgh,
> +                             write_mcyclecfgh,
> +                             .min_priv_ver = PRIV_VERSION_1_12_0        },
> +    [CSR_MINSTRETCFGH]   = { "minstretcfgh", smcntrpmf_32, read_minstretcfgh,
> +                             write_minstretcfgh,
> +                             .min_priv_ver = PRIV_VERSION_1_12_0        },
> +
>      [CSR_MHPMEVENT3H]    = { "mhpmevent3h",    sscofpmf_32,  read_mhpmeventh,
>                               write_mhpmeventh,
>                               .min_priv_ver = PRIV_VERSION_1_12_0        },
> --
> 2.34.1
>
>