Re: [PATCH 3/3] target/riscv: Add cycle & instret privilege mode filtering support

[Weiwei Li <liweiwei@iscas.ac.cn>]

On 2023/7/19 06:47, Kaiwen Xue wrote:
> 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.
Maybe you can record/accumulate them when privilege mode changes/switchs.
>
> Signed-off-by: Kaiwen Xue <kaiwenx@andrew.cmu.edu>
> Signed-off-by: Kaiwen Xue <kaiwenx@rivosinc.com>
> ---
>   target/riscv/csr.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 73 insertions(+)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index ea7585329e..b1d5e85a79 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -218,6 +218,17 @@ static RISCVException sscofpmf(CPURISCVState *env, int csrno)
>       return RISCV_EXCP_NONE;
>   }
>   
> +static RISCVException smcntrpmf(CPURISCVState *env, int csrno)
> +{
> +    RISCVCPU *cpu = env_archcpu(env);
> +
> +    if (!cpu->cfg.ext_smcntrpmf) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
>   static RISCVException any(CPURISCVState *env, int csrno)
>   {
>       return RISCV_EXCP_NONE;
> @@ -800,6 +811,54 @@ 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;
> @@ -4506,6 +4565,13 @@ 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,
> @@ -4565,6 +4631,13 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>       [CSR_MHPMEVENT31]    = { "mhpmevent31",    any,    read_mhpmevent,
>                                write_mhpmevent                           },
>   
> +    [CSR_MCYCLECFGH]     = { "mcyclecfgh",   smcntrpmf, read_mcyclecfgh,
> +                             write_mcyclecfgh,
> +                             .min_priv_ver = PRIV_VERSION_1_12_0        },
> +    [CSR_MINSTRETCFGH]   = { "minstretcfgh", smcntrpmf, read_minstretcfgh,
> +                             write_minstretcfgh,
> +                             .min_priv_ver = PRIV_VERSION_1_12_0        },

This two CSRs are RV32-only, they cannot directly share the same 
predicate as MCYCLECFG/MINSTRETCFG.

Regards,

Weiwei Li

> +
>       [CSR_MHPMEVENT3H]    = { "mhpmevent3h",    sscofpmf,  read_mhpmeventh,
>                                write_mhpmeventh,
>                                .min_priv_ver = PRIV_VERSION_1_12_0        },