Re: [PATCH v2 3/6] target/riscv: Add support for Control Transfer Records extension CSRs.

[Jason Chien <jason.chien@sifive.com>]

Hi Rajnesh,

On 2024/6/19 下午 11:27, Rajnesh Kanwal wrote:
> This commit adds support for [m|s|vs]ctrcontrol, sctrstatus and
> sctrdepth CSRs handling.
>
> Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
> ---
>   target/riscv/cpu.h     |   5 ++
>   target/riscv/cpu_cfg.h |   2 +
>   target/riscv/csr.c     | 128 +++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 135 insertions(+)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index a185e2d494..3d4d5172b8 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -263,6 +263,11 @@ struct CPUArchState {
>       target_ulong mcause;
>       target_ulong mtval;  /* since: priv-1.10.0 */
>   
> +    uint64_t mctrctl;
> +    uint32_t sctrdepth;
> +    uint32_t sctrstatus;
> +    uint64_t vsctrctl;
> +
>       /* Machine and Supervisor interrupt priorities */
>       uint8_t miprio[64];
>       uint8_t siprio[64];
> diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
> index d9354dc80a..d329a65811 100644
> --- a/target/riscv/cpu_cfg.h
> +++ b/target/riscv/cpu_cfg.h
> @@ -123,6 +123,8 @@ struct RISCVCPUConfig {
>       bool ext_zvfhmin;
>       bool ext_smaia;
>       bool ext_ssaia;
> +    bool ext_smctr;
> +    bool ext_ssctr;
>       bool ext_sscofpmf;
>       bool ext_smepmp;
>       bool rvv_ta_all_1s;
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 2f92e4b717..0b5bf4d050 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -621,6 +621,48 @@ static RISCVException pointer_masking(CPURISCVState *env, int csrno)
>       return RISCV_EXCP_ILLEGAL_INST;
>   }
>   
> +/*
> + * M-mode:
> + * Without ext_smctr raise illegal inst excep.
> + * Otherwise everything is accessible to m-mode.
> + *
> + * S-mode:
> + * Without ext_ssctr or mstateen.ctr raise illegal inst excep.
> + * Otherwise everything other than mctrctl is accessible.
> + *
> + * VS-mode:
> + * Without ext_ssctr or mstateen.ctr raise illegal inst excep.
> + * Without hstateen.ctr raise virtual illegal inst excep.
> + * Otherwise allow sctrctl (vsctrctl), sctrstatus, 0x200-0x2ff entry range.
> + * Always raise illegal instruction exception for sctrdepth.
> + */
> +static RISCVException ctr_mmode(CPURISCVState *env, int csrno)
> +{
> +    /* Check if smctr-ext is present */
> +    if (riscv_cpu_cfg(env)->ext_smctr) {
> +        return RISCV_EXCP_NONE;
> +    }
> +
> +    return RISCV_EXCP_ILLEGAL_INST;
> +}
> +
> +static RISCVException ctr_smode(CPURISCVState *env, int csrno)
> +{
> +    const RISCVCPUConfig *cfg = riscv_cpu_cfg(env);
> +
> +    if (!cfg->ext_smctr && !cfg->ext_ssctr) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    RISCVException ret = smstateen_acc_ok(env, 0, SMSTATEEN0_CTR);
> +    if (ret == RISCV_EXCP_NONE && csrno == CSR_SCTRDEPTH &&
> +        env->virt_enabled) {
> +        return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> +    }
> +
> +    return ret;
> +}
> +
>   static RISCVException aia_hmode(CPURISCVState *env, int csrno)
>   {
>       int ret;
> @@ -3835,6 +3877,86 @@ static RISCVException write_satp(CPURISCVState *env, int csrno,
>       return RISCV_EXCP_NONE;
>   }
>   
> +static RISCVException rmw_sctrdepth(CPURISCVState *env, int csrno,
> +                                    target_ulong *ret_val,
> +                                    target_ulong new_val, target_ulong wr_mask)
> +{
> +    uint64_t mask = wr_mask & SCTRDEPTH_MASK;
> +
> +    if (ret_val) {
> +        *ret_val = env->sctrdepth;
> +    }
> +
> +    env->sctrdepth = (env->sctrdepth & ~mask) | (new_val & mask);
> +
> +    /* Correct depth. */
> +    if (wr_mask & SCTRDEPTH_MASK) {

We can use the variable "mask" here.

if (mask) {}

> +        uint64_t depth = get_field(env->sctrdepth, SCTRDEPTH_MASK);
> +
> +        if (depth > SCTRDEPTH_MAX) {
> +            depth = SCTRDEPTH_MAX;
> +            env->sctrdepth = set_field(env->sctrdepth, SCTRDEPTH_MASK, depth);
> +        }
> +
> +        /* Update sctrstatus.WRPTR with a legal value */
> +        depth = 16 << depth;
> +        env->sctrstatus =
> +            env->sctrstatus & (~SCTRSTATUS_WRPTR_MASK | (depth - 1));
> +    }
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException rmw_sctrstatus(CPURISCVState *env, int csrno,
> +                                     target_ulong *ret_val,
> +                                     target_ulong new_val, target_ulong wr_mask)
> +{
> +    uint32_t depth = 16 << get_field(env->sctrdepth, SCTRDEPTH_MASK);
> +    uint32_t mask = wr_mask & SCTRSTATUS_MASK;
> +
> +    if (ret_val) {
> +        *ret_val = env->sctrstatus;
> +    }
> +
> +    env->sctrstatus = (env->sctrstatus & ~mask) | (new_val & mask);
> +
> +    /* Update sctrstatus.WRPTR with a legal value */
> +    env->sctrstatus = env->sctrstatus & (~SCTRSTATUS_WRPTR_MASK | (depth - 1));
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException rmw_xctrctl(CPURISCVState *env, int csrno,
> +                                    target_ulong *ret_val,
> +                                    target_ulong new_val, target_ulong wr_mask)
> +{
> +    uint64_t csr_mask, mask = wr_mask;
> +    uint64_t *ctl_ptr = &env->mctrctl;
> +
> +    if (csrno == CSR_MCTRCTL) {
> +        csr_mask = MCTRCTL_MASK;
> +    } else if (csrno == CSR_SCTRCTL && !env->virt_enabled) {
> +        csr_mask = SCTRCTL_MASK;
> +    } else {
> +        /*
> +         * This is for csrno == CSR_SCTRCTL and env->virt_enabled == true
> +         * or csrno == CSR_VSCTRCTL.
> +         */
> +        csr_mask = VSCTRCTL_MASK;
> +        ctl_ptr = &env->vsctrctl;
> +    }
> +
> +    mask &= csr_mask;
> +
> +    if (ret_val) {
> +        *ret_val = *ctl_ptr & csr_mask;
> +    }
> +
> +    *ctl_ptr = (*ctl_ptr & ~mask) | (new_val & mask);
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
>   static RISCVException read_vstopi(CPURISCVState *env, int csrno,
>                                     target_ulong *val)
>   {
> @@ -5771,6 +5893,12 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>       [CSR_SPMBASE] =    { "spmbase", pointer_masking, read_spmbase,
>                            write_spmbase                                      },
>   
> +    [CSR_MCTRCTL]    = { "mctrctl",    ctr_mmode,  NULL, NULL, rmw_xctrctl },
> +    [CSR_SCTRCTL]    = { "sctrctl",    ctr_smode,  NULL, NULL, rmw_xctrctl },
> +    [CSR_VSCTRCTL]   = { "vsctrctl",   ctr_smode,  NULL, NULL, rmw_xctrctl },
> +    [CSR_SCTRDEPTH]  = { "sctrdepth",  ctr_smode,  NULL, NULL, rmw_sctrdepth },
> +    [CSR_SCTRSTATUS] = { "sctrstatus", ctr_smode,  NULL, NULL, rmw_sctrstatus },
Would you mind aligning the right curly bracket like other CSR entries?
> +
>       /* Performance Counters */
>       [CSR_HPMCOUNTER3]    = { "hpmcounter3",    ctr,    read_hpmcounter },
>       [CSR_HPMCOUNTER4]    = { "hpmcounter4",    ctr,    read_hpmcounter },