Re: [PATCH v10 3/7] [RISCV_PM] Support CSRs required for RISC-V PM extension except for the h-mode

[Alistair Francis <alistair23@gmail.com>]

On Mon, Aug 30, 2021 at 3:54 AM Alexey Baturo <baturo.alexey@gmail.com> wrote:
>
> Signed-off-by: Alexey Baturo <space.monkey.delivers@gmail.com>
> ---
>  target/riscv/cpu.c |   6 +
>  target/riscv/cpu.h |  11 ++
>  target/riscv/csr.c | 276 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 293 insertions(+)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 991a6bb760..4178eecbec 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -553,6 +553,12 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
>              }
>              set_vext_version(env, vext_version);
>          }
> +        if (cpu->cfg.ext_j) {
> +#ifndef CONFIG_USER_ONLY
> +            /* mmte is supposed to have pm.current hardwired to 1 */
> +            env->mmte |= (PM_EXT_INITIAL | MMTE_M_PM_CURRENT);

This should probably be in the reset function instead.

> +#endif
> +        }
>
>          set_misa(env, target_misa);
>      }
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 451a1637a1..94e680cbd0 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -238,6 +238,17 @@ struct CPURISCVState {
>
>      /* True if in debugger mode.  */
>      bool debugger;
> +
> +    /*
> +     * CSRs for PointerMasking extension
> +     */
> +    target_ulong mmte;
> +    target_ulong mpmmask;
> +    target_ulong mpmbase;
> +    target_ulong spmmask;
> +    target_ulong spmbase;
> +    target_ulong upmmask;
> +    target_ulong upmbase;
>  #endif
>
>      float_status fp_status;
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 9a4ed18ac5..42a0867e5d 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -192,6 +192,16 @@ static RISCVException hmode32(CPURISCVState *env, int csrno)
>
>  }
>
> +/* Checks if PointerMasking registers could be accessed */
> +static RISCVException pointer_masking(CPURISCVState *env, int csrno)
> +{
> +    /* Check if j-ext is present */
> +    if (riscv_has_ext(env, RVJ)) {
> +        return RISCV_EXCP_NONE;
> +    }
> +    return RISCV_EXCP_ILLEGAL_INST;
> +}
> +
>  static RISCVException pmp(CPURISCVState *env, int csrno)
>  {
>      if (riscv_feature(env, RISCV_FEATURE_PMP)) {
> @@ -1404,6 +1414,259 @@ static RISCVException write_pmpaddr(CPURISCVState *env, int csrno,
>      return RISCV_EXCP_NONE;
>  }
>
> +/*
> + * Functions to access Pointer Masking feature registers
> + * We have to check if current priv lvl could modify
> + * csr in given mode
> + */
> +static bool check_pm_current_disabled(CPURISCVState *env, int csrno)
> +{
> +    int csr_priv = get_field(csrno, 0x300);

Can you add a newline between declarations and code?

> +    /*
> +     * If priv lvls differ that means we're accessing csr from higher priv lvl,
> +     * so allow the access
> +     */
> +    if (env->priv != csr_priv) {
> +        return false;
> +    }
> +    int cur_bit_pos;

Can you keep all of the declarations at the start of blocks please.

> +    switch (env->priv) {
> +    case PRV_M:
> +        cur_bit_pos = M_PM_CURRENT;
> +        break;
> +    case PRV_S:
> +        cur_bit_pos = S_PM_CURRENT;
> +        break;
> +    case PRV_U:
> +        cur_bit_pos = U_PM_CURRENT;
> +        break;
> +    default:
> +        g_assert_not_reached();
> +    }
> +    int pm_current = get_field(env->mmte, cur_bit_pos);
> +    /* It's same priv lvl, so we allow to modify csr only if pm.current==1 */
> +    return !pm_current;
> +}
> +
> +static RISCVException read_mmte(CPURISCVState *env, int csrno,
> +                                target_ulong *val)
> +{
> +    *val = env->mmte & MMTE_MASK;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_mmte(CPURISCVState *env, int csrno,
> +                                 target_ulong val)
> +{
> +    uint64_t mstatus;
> +    target_ulong wpri_val = val & MMTE_MASK;
> +    if (val != wpri_val) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "MMTE: WPRI violation written 0x%lx vs expected 0x%lx\n",
> +                      val, wpri_val);
> +    }
> +    /* for machine mode pm.current is hardwired to 1 */
> +    wpri_val |= MMTE_M_PM_CURRENT;
> +
> +    /* hardwiring pm.instruction bit to 0, since it's not supported yet */
> +    wpri_val &= ~(MMTE_M_PM_INSN | MMTE_S_PM_INSN | MMTE_U_PM_INSN);
> +    env->mmte = wpri_val | PM_EXT_DIRTY;
> +
> +    /* Set XS and SD bits, since PM CSRs are dirty */
> +    mstatus = env->mstatus | MSTATUS_XS;
> +    write_mstatus(env, csrno, mstatus);
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_smte(CPURISCVState *env, int csrno,
> +                                target_ulong *val)
> +{
> +    *val = env->mmte & SMTE_MASK;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_smte(CPURISCVState *env, int csrno,
> +                                 target_ulong val)
> +{
> +    target_ulong wpri_val = val & SMTE_MASK;
> +    if (val != wpri_val) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "SMTE: WPRI violation written 0x%lx vs expected 0x%lx\n",
> +                      val, wpri_val);
> +    }
> +
> +    /* if pm.current==0 we can't modify current PM CSRs */
> +    if (check_pm_current_disabled(env, csrno)) {
> +        return RISCV_EXCP_NONE;
> +    }
> +
> +    target_ulong new_val = wpri_val | (env->mmte & ~SMTE_MASK);
> +    write_mmte(env, csrno, new_val);

You don't really need the new_val variable here.

> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_umte(CPURISCVState *env, int csrno,
> +                                target_ulong *val)
> +{
> +    *val = env->mmte & UMTE_MASK;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_umte(CPURISCVState *env, int csrno,
> +                                 target_ulong val)
> +{
> +    target_ulong wpri_val = val & UMTE_MASK;
> +    if (val != wpri_val) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "UMTE: WPRI violation written 0x%lx vs expected 0x%lx\n",
> +                      val, wpri_val);
> +    }
> +
> +    if (check_pm_current_disabled(env, csrno)) {
> +        return RISCV_EXCP_NONE;
> +    }
> +
> +    target_ulong new_val = wpri_val | (env->mmte & ~UMTE_MASK);
> +    write_mmte(env, csrno, new_val);

Same here

> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_mpmmask(CPURISCVState *env, int csrno,
> +                                   target_ulong *val)
> +{
> +    *val = env->mpmmask;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_mpmmask(CPURISCVState *env, int csrno,
> +                                    target_ulong val)
> +{
> +    uint64_t mstatus;
> +    env->mpmmask = val;
> +    env->mmte |= PM_EXT_DIRTY;
> +
> +    /* Set XS and SD bits, since PM CSRs are dirty */
> +    mstatus = env->mstatus | MSTATUS_XS;
> +    write_mstatus(env, csrno, mstatus);
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_spmmask(CPURISCVState *env, int csrno,
> +                                   target_ulong *val)
> +{
> +    *val = env->spmmask;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_spmmask(CPURISCVState *env, int csrno,
> +                                    target_ulong val)
> +{
> +    uint64_t mstatus;
> +    /* if pm.current==0 we can't modify current PM CSRs */
> +    if (check_pm_current_disabled(env, csrno)) {
> +        return RISCV_EXCP_NONE;
> +    }
> +    env->spmmask = val;
> +    env->mmte |= PM_EXT_DIRTY;
> +
> +    /* Set XS and SD bits, since PM CSRs are dirty */
> +    mstatus = env->mstatus | MSTATUS_XS;
> +    write_mstatus(env, csrno, mstatus);
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_upmmask(CPURISCVState *env, int csrno,
> +                                   target_ulong *val)
> +{
> +    *val = env->upmmask;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_upmmask(CPURISCVState *env, int csrno,
> +                                    target_ulong val)
> +{
> +    uint64_t mstatus;
> +    /* if pm.current==0 we can't modify current PM CSRs */
> +    if (check_pm_current_disabled(env, csrno)) {
> +        return RISCV_EXCP_NONE;
> +    }
> +    env->upmmask = val;
> +    env->mmte |= PM_EXT_DIRTY;
> +
> +    /* Set XS and SD bits, since PM CSRs are dirty */
> +    mstatus = env->mstatus | MSTATUS_XS;
> +    write_mstatus(env, csrno, mstatus);
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_mpmbase(CPURISCVState *env, int csrno,
> +                                   target_ulong *val)
> +{
> +    *val = env->mpmbase;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_mpmbase(CPURISCVState *env, int csrno,
> +                                    target_ulong val)
> +{
> +    uint64_t mstatus;
> +    env->mpmbase = val;
> +    env->mmte |= PM_EXT_DIRTY;
> +
> +    /* Set XS and SD bits, since PM CSRs are dirty */
> +    mstatus = env->mstatus | MSTATUS_XS;
> +    write_mstatus(env, csrno, mstatus);
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_spmbase(CPURISCVState *env, int csrno,
> +                                   target_ulong *val)
> +{
> +    *val = env->spmbase;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_spmbase(CPURISCVState *env, int csrno,
> +                                    target_ulong val)
> +{
> +    uint64_t mstatus;
> +    /* if pm.current==0 we can't modify current PM CSRs */
> +    if (check_pm_current_disabled(env, csrno)) {
> +        return RISCV_EXCP_NONE;
> +    }
> +    env->spmbase = val;
> +    env->mmte |= PM_EXT_DIRTY;
> +
> +    /* Set XS and SD bits, since PM CSRs are dirty */
> +    mstatus = env->mstatus | MSTATUS_XS;
> +    write_mstatus(env, csrno, mstatus);
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_upmbase(CPURISCVState *env, int csrno,
> +                                   target_ulong *val)
> +{
> +    *val = env->upmbase;
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_upmbase(CPURISCVState *env, int csrno,
> +                                    target_ulong val)
> +{
> +    uint64_t mstatus;
> +    /* if pm.current==0 we can't modify current PM CSRs */
> +    if (check_pm_current_disabled(env, csrno)) {
> +        return RISCV_EXCP_NONE;
> +    }
> +    env->upmbase = val;
> +    env->mmte |= PM_EXT_DIRTY;
> +
> +    /* Set XS and SD bits, since PM CSRs are dirty */
> +    mstatus = env->mstatus | MSTATUS_XS;
> +    write_mstatus(env, csrno, mstatus);
> +    return RISCV_EXCP_NONE;
> +}
> +
>  #endif
>
>  /*
> @@ -1636,6 +1899,19 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>      [CSR_PMPADDR14] =  { "pmpaddr14", pmp, read_pmpaddr, write_pmpaddr },
>      [CSR_PMPADDR15] =  { "pmpaddr15", pmp, read_pmpaddr, write_pmpaddr },
>
> +    /* User Pointer Masking */
> +    [CSR_UMTE]    =    { "umte",    pointer_masking, read_umte,    write_umte    },
> +    [CSR_UPMMASK] =    { "upmmask", pointer_masking, read_upmmask, write_upmmask },
> +    [CSR_UPMBASE] =    { "upmbase", pointer_masking, read_upmbase, write_upmbase },
> +    /* Machine Pointer Masking */
> +    [CSR_MMTE]    =    { "mmte",    pointer_masking, read_mmte,    write_mmte    },
> +    [CSR_MPMMASK] =    { "mpmmask", pointer_masking, read_mpmmask, write_mpmmask },
> +    [CSR_MPMBASE] =    { "mpmbase", pointer_masking, read_mpmbase, write_mpmbase },
> +    /* Supervisor Pointer Masking */
> +    [CSR_SMTE]    =    { "smte",    pointer_masking, read_smte,    write_smte    },
> +    [CSR_SPMMASK] =    { "spmmask", pointer_masking, read_spmmask, write_spmmask },
> +    [CSR_SPMBASE] =    { "spmbase", pointer_masking, read_spmbase, write_spmbase },
> +

Looks good! Just a few style nits and then this should be good to go.

Alistair

>      /* Performance Counters */
>      [CSR_HPMCOUNTER3]    = { "hpmcounter3",    ctr,    read_zero },
>      [CSR_HPMCOUNTER4]    = { "hpmcounter4",    ctr,    read_zero },
> --
> 2.20.1
>
>