Re: [PATCH 2/3] target/riscv: Enforce WARL behavior for scounteren/hcounteren

[Alistair Francis]

On Tue, Apr 30, 2024 at 5:29 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> scounteren/hcountern are also WARL registers similar to mcountern.
> Only set the bits for the available counters during the write to
> preserve the WARL behavior.
>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/csr.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 68ca31aff47d..a01911541d67 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -2843,7 +2843,11 @@ static RISCVException read_scounteren(CPURISCVState 
> *env, int csrno,
>  static RISCVException write_scounteren(CPURISCVState *env, int csrno,
>                                         target_ulong val)
>  {
> -    env->scounteren = val;
> +    RISCVCPU *cpu = env_archcpu(env);
> +
> +    /* WARL register - disable unavailable counters */
> +    env->scounteren = val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | 
> COUNTEREN_TM |
> +                             COUNTEREN_IR);
>      return RISCV_EXCP_NONE;
>  }
>
> @@ -3475,7 +3479,11 @@ static RISCVException read_hcounteren(CPURISCVState 
> *env, int csrno,
>  static RISCVException write_hcounteren(CPURISCVState *env, int csrno,
>                                         target_ulong val)
>  {
> -    env->hcounteren = val;
> +    RISCVCPU *cpu = env_archcpu(env);
> +
> +    /* WARL register - disable unavailable counters */
> +    env->hcounteren = val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | 
> COUNTEREN_TM |
> +                             COUNTEREN_IR);
>      return RISCV_EXCP_NONE;
>  }
>
>
> --
> 2.34.1
>
>