Re: [PATCH v12 3/7] target/riscv: Add helper functions to calculate current number of masked bits for pointer masking

[Daniel Henrique Barboza]

On 12/5/24 8:23 AM, baturo.alexey@gmail.com wrote:
> From: Alexey Baturo <baturo.alexey@gmail.com>
>
> Signed-off-by: Alexey Baturo <baturo.alexey@gmail.com>
> ---
>   target/riscv/cpu.h        |  5 +++
>   target/riscv/cpu_helper.c | 74 +++++++++++++++++++++++++++++++++++++++
>   2 files changed, 79 insertions(+)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 417ff45544..74d7076f5a 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -768,8 +768,13 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
>   
>   bool riscv_cpu_is_32bit(RISCVCPU *cpu);
>   
> +bool riscv_cpu_virt_mem_enabled(CPURISCVState *env);
> +RISCVPmPmm riscv_pm_get_pmm(CPURISCVState *env);
> +int riscv_pm_get_pmlen(RISCVPmPmm pmm);
> +
>   RISCVException riscv_csrr(CPURISCVState *env, int csrno,
>                             target_ulong *ret_value);
> +
>   RISCVException riscv_csrrw(CPURISCVState *env, int csrno,
>                              target_ulong *ret_value,
>                              target_ulong new_value, target_ulong write_mask);
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index dba04851d5..2558f869f2 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -214,6 +214,80 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
>       *pflags = flags;
>   }
>   
> +RISCVPmPmm riscv_pm_get_pmm(CPURISCVState *env)
> +{
> +    RISCVPmPmm pmm = PMM_FIELD_DISABLED;
> +#ifndef CONFIG_USER_ONLY
> +    if (get_field(env->mstatus, MSTATUS_MPRV) &&
> +        get_field(env->mstatus, MSTATUS_MXR)) {
> +        return pmm;
> +    }
> +    int priv_mode = cpu_address_mode(env);
> +    /* Get current PMM field */
> +    switch (priv_mode) {
> +    case PRV_M:
> +        if (riscv_cpu_cfg(env)->ext_smmpm) {
> +            pmm = get_field(env->mseccfg, MSECCFG_PMM);
> +        }
> +        break;
> +    case PRV_S:
> +        if (riscv_cpu_cfg(env)->ext_smnpm) {
> +            if (get_field(env->mstatus, MSTATUS_MPV)) {
> +                pmm = get_field(env->henvcfg, HENVCFG_PMM);
> +            } else {
> +                pmm = get_field(env->menvcfg, MENVCFG_PMM);
> +            }
> +        }
> +        break;
> +    case PRV_U:
> +        if (riscv_has_ext(env, RVS)) {
> +            if (riscv_cpu_cfg(env)->ext_ssnpm) {
> +                pmm = get_field(env->senvcfg, SENVCFG_PMM);
> +            }
> +        } else {
> +            if (riscv_cpu_cfg(env)->ext_smnpm) {
> +                pmm = get_field(env->menvcfg, MENVCFG_PMM);
> +            }
> +        }
> +        break;
> +    default:
> +        g_assert_not_reached();
> +    }
> +#endif
> +    return pmm;
> +}
> +
> +bool riscv_cpu_virt_mem_enabled(CPURISCVState *env)
> +{
> +    bool virt_mem_en = false;
> +#ifndef CONFIG_USER_ONLY
> +    int satp_mode = 0;
> +    int priv_mode = cpu_address_mode(env);
> +    if (riscv_cpu_mxl(env) == MXL_RV32) {
> +        satp_mode = get_field(env->satp, SATP32_MODE);
> +    } else {
> +        satp_mode = get_field(env->satp, SATP64_MODE);
> +    }
> +    virt_mem_en = ((satp_mode != VM_1_10_MBARE) && (priv_mode != PRV_M));
> +#endif
> +    return virt_mem_en;
> +}
> +
> +int riscv_pm_get_pmlen(RISCVPmPmm pmm)
> +{
> +    switch (pmm) {
> +    case PMM_FIELD_DISABLED:
> +        return 0;
> +    case PMM_FIELD_PMLEN7:
> +        return 7;
> +    case PMM_FIELD_PMLEN16:
> +        return 16;
> +    default:
> +        g_assert_not_reached();
> +    }
> +    return -1;

You don't need a 'return -1' here since all possible return values are already
covered in the 'switch' and the default label is using g_assert_not_reached(),
i.e. you'll never return -1. The compiler will be fine with it - we use this
kind of pattern all the time (cpu_get_fcfien() does this in this same file).

You can remove the -1 return and even turn the helper to uint32_t. That way
the caller knows that there's no need to handle negative values.


Thanks,

Daniel


> +}
> +
>   #ifndef CONFIG_USER_ONLY
>   
>   /*