Re: [RFC v1 6/8] target/riscv: Add functions to calculate current N masked bits for pointer masking

[Alistair Francis]

On Sat, Sep 9, 2023 at 5:37 AM Alexey Baturo <baturo.alexey@gmail.com> wrote:
>
> Signed-off-by: Alexey Baturo <baturo.alexey@gmail.com>
> ---
>  target/riscv/cpu.h        |  6 ++--
>  target/riscv/cpu_helper.c | 58 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 62 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 17d0088cb4..c87c4f26a2 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -91,11 +91,9 @@ typedef enum {
>  /* Enum holds maximum for N bits to be ignored depending on privilege level 
> */
>  typedef enum {
>      PM_BARE_N_BITS = 16,
> -    PM_SV32_N_BITS = 0,
>      PM_SV39_N_BITS = 25,
>      PM_SV48_N_BITS = 16,
>      PM_SV57_N_BITS = 7,
> -    PM_SV64_N_BITS = 0,
>  } RISCVZjpmMaxNBits;

Didn't you just add this? Why remove parts from it

Alistair

>
>  #define MMU_USER_IDX 3
> @@ -633,6 +631,10 @@ static inline uint32_t vext_get_vlmax(RISCVCPU *cpu, 
> target_ulong vtype)
>  void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
>                            uint64_t *cs_base, uint32_t *pflags);
>
> +void riscv_cpu_update_mask(CPURISCVState *env);
> +RISCVZjpmMaxNBits riscv_cpu_pm_get_n_bits(int satp_mode, int priv_mode);
> +bool riscv_cpu_pm_check_applicable(CPURISCVState *env, int priv_mode);
> +
>  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 b3871b0a28..6e68b2fc27 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -144,6 +144,64 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
>      *pflags = flags;
>  }
>
> +/*
> + * Curernt Zjpm v0.6.1 spec doesn't strictly specify the exact value of N 
> bits.
> + * It allows it to be dependent on both translation mode and priv level.
> + * For now let's ignore priv mode and always return max available value.
> + */
> +RISCVZjpmMaxNBits riscv_cpu_pm_get_n_bits(int satp_mode, int priv_mode)
> +{
> +    switch (satp_mode) {
> +    case VM_1_10_MBARE:
> +        return PM_BARE_N_BITS;
> +    case VM_1_10_SV39:
> +        return PM_SV39_N_BITS;
> +    case VM_1_10_SV48:
> +        return PM_SV48_N_BITS;
> +    case VM_1_10_SV57:
> +        return PM_SV57_N_BITS;
> +    default:
> +        g_assert_not_reached();
> +    }
> +}
> +
> +/* For current priv level check if pointer masking should be applied */
> +bool riscv_cpu_pm_check_applicable(CPURISCVState *env, int priv_mode)
> +{
> +    /* checks if appropriate extension is present and enable bit is set */
> +    switch (priv_mode) {
> +    case PRV_M:
> +        return riscv_cpu_cfg(env)->ext_smmjpm && env->mseccfg & 
> MSECCFG_MPMEN;
> +    case PRV_S:
> +        return riscv_cpu_cfg(env)->ext_smnjpm && env->menvcfg & 
> MENVCFG_SPMEN;
> +    case PRV_U:
> +        return riscv_cpu_cfg(env)->ext_ssnjpm && env->senvcfg & 
> SENVCFG_UPMEN;
> +    default:
> +        g_assert_not_reached();
> +    }
> +    g_assert_not_reached();
> +    return false;
> +}
> +
> +void riscv_cpu_update_mask(CPURISCVState *env)
> +{
> +#ifndef CONFIG_USER_ONLY
> +    int priv_mode = cpu_address_mode(env);
> +    int satp_mode = 0;
> +    if (riscv_cpu_mxl(env) == MXL_RV32) {
> +        satp_mode = get_field(env->satp, SATP32_MODE);
> +    } else {
> +        satp_mode = get_field(env->satp, SATP64_MODE);
> +    }
> +    RISCVZjpmMaxNBits n_bits = riscv_cpu_pm_get_n_bits(satp_mode, priv_mode);
> +    /* in bare mode address is not sign extended */
> +    env->pm_signext = (satp_mode != VM_1_10_MBARE);
> +    /* if pointer masking is applicable set env variable */
> +    bool applicable = riscv_cpu_pm_check_applicable(env, priv_mode);
> +    env->pm_n_bits = applicable ? n_bits : 0;
> +#endif
> +}
> +
>  #ifndef CONFIG_USER_ONLY
>
>  /*
> --
> 2.34.1
>
>