Re: [PATCH v7 05/11] target/riscv: Add cycle & instret privilege mode filtering support

[Alistair Francis]

On Thu, Jun 27, 2024 at 10:00 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>
> ---
>  target/riscv/csr.c | 88 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 88 insertions(+)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 3ad851707e5c..665c534db1a0 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -236,6 +236,24 @@ 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;
> @@ -830,6 +848,62 @@ static RISCVException read_hpmcounterh(CPURISCVState 
> *env, int csrno,
>
>  #else /* CONFIG_USER_ONLY */
>
> +static RISCVException read_mcyclecfg(CPURISCVState *env, int csrno,
> +                                     target_ulong *val)
> +{
> +    *val = env->mcyclecfg;

We don't do a good job of this in other places, but we should check
for RVU and RVS to determine if the bits can actually be set.

This is especially important for Hypervisor support (VS/VU-modes), as
that is often not supported so we should report that here

Alistair

> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_mcyclecfg(CPURISCVState *env, int csrno,
> +                                      target_ulong val)
> +{
> +    env->mcyclecfg = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_mcyclecfgh(CPURISCVState *env, int csrno,
> +                                      target_ulong *val)
> +{
> +    *val = env->mcyclecfgh;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_mcyclecfgh(CPURISCVState *env, int csrno,
> +                                       target_ulong val)
> +{
> +    env->mcyclecfgh = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_minstretcfg(CPURISCVState *env, int csrno,
> +                                       target_ulong *val)
> +{
> +    *val = env->minstretcfg;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_minstretcfg(CPURISCVState *env, int csrno,
> +                                        target_ulong val)
> +{
> +    env->minstretcfg = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_minstretcfgh(CPURISCVState *env, int csrno,
> +                                        target_ulong *val)
> +{
> +    *val = env->minstretcfgh;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_minstretcfgh(CPURISCVState *env, int csrno,
> +                                         target_ulong val)
> +{
> +    env->minstretcfgh = val;
> +    return RISCV_EXCP_NONE;
> +}
> +
>  static RISCVException read_mhpmevent(CPURISCVState *env, int csrno,
>                                       target_ulong *val)
>  {
> @@ -5051,6 +5125,13 @@ 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,
> @@ -5110,6 +5191,13 @@ 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
>
>