Re: [PATCH v3 5/6] target/riscv: Gate hardware A/D PTE bit updating

[Alistair Francis <alistair23@gmail.com>]

On Sat, Feb 3, 2024 at 1:22 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> From: Andrew Jones <ajones@ventanamicro.com>
>
> Gate hardware A/D PTE bit updating on {m,h}envcfg.ADUE and only
> enable menvcfg.ADUE on reset if svade has not been selected. Now
> that we also consider svade, we have four possible configurations:
>
>  1) !svade && !svadu
>     use hardware updating and there's no way to disable it
>     (the default, which maintains past behavior. Maintaining
>      the default, even with !svadu is a change that fixes [1])
>
>  2) !svade && svadu
>     use hardware updating, but also provide {m,h}envcfg.ADUE,
>     allowing software to switch to exception mode
>     (being able to switch is a change which fixes [1])
>
>  3) svade && !svadu
>     use exception mode and there's no way to switch to hardware
>     updating
>     (this behavior change fixes [2])
>
>  4) svade && svadu
>     use exception mode, but also provide {m,h}envcfg.ADUE,
>     allowing software to switch to hardware updating
>     (this behavior change fixes [2])
>
> Fixes: 0af3f115e68e ("target/riscv: Add *envcfg.HADE related check in address translation") [1]
> Fixes: 48531f5adb2a ("target/riscv: implement svade") [2]
> Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> Signed-off-by: Andrew Jones <ajones@ventanamicro.com>

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

Alistair

> ---
>  target/riscv/cpu.c         |  3 ++-
>  target/riscv/cpu_helper.c  | 19 +++++++++++++++----
>  target/riscv/tcg/tcg-cpu.c | 15 +++++----------
>  3 files changed, 22 insertions(+), 15 deletions(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 9045f87481..50ac7845a8 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -960,7 +960,8 @@ static void riscv_cpu_reset_hold(Object *obj)
>      env->two_stage_lookup = false;
>
>      env->menvcfg = (cpu->cfg.ext_svpbmt ? MENVCFG_PBMTE : 0) |
> -                   (cpu->cfg.ext_svadu ? MENVCFG_ADUE : 0);
> +                   (!cpu->cfg.ext_svade && cpu->cfg.ext_svadu ?
> +                    MENVCFG_ADUE : 0);
>      env->henvcfg = 0;
>
>      /* Initialized default priorities of local interrupts. */
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index 8da9104da4..3a440833f8 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -907,7 +907,9 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
>      }
>
>      bool pbmte = env->menvcfg & MENVCFG_PBMTE;
> -    bool adue = env->menvcfg & MENVCFG_ADUE;
> +    bool svade = riscv_cpu_cfg(env)->ext_svade;
> +    bool svadu = riscv_cpu_cfg(env)->ext_svadu;
> +    bool adue = svadu ? env->menvcfg & MENVCFG_ADUE : !svade;
>
>      if (first_stage && two_stage && env->virt_enabled) {
>          pbmte = pbmte && (env->henvcfg & HENVCFG_PBMTE);
> @@ -1082,9 +1084,18 @@ restart:
>          return TRANSLATE_FAIL;
>      }
>
> -    /* If necessary, set accessed and dirty bits. */
> -    target_ulong updated_pte = pte | PTE_A |
> -                (access_type == MMU_DATA_STORE ? PTE_D : 0);
> +    target_ulong updated_pte = pte;
> +
> +    /*
> +     * If ADUE is enabled, set accessed and dirty bits.
> +     * Otherwise raise an exception if necessary.
> +     */
> +    if (adue) {
> +        updated_pte |= PTE_A | (access_type == MMU_DATA_STORE ? PTE_D : 0);
> +    } else if (!(pte & PTE_A) ||
> +               (access_type == MMU_DATA_STORE && !(pte & PTE_D))) {
> +        return TRANSLATE_FAIL;
> +    }
>
>      /* Page table updates need to be atomic with MTTCG enabled */
>      if (updated_pte != pte && !is_debug) {
> diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
> index 673097c6e4..43c32b4a15 100644
> --- a/target/riscv/tcg/tcg-cpu.c
> +++ b/target/riscv/tcg/tcg-cpu.c
> @@ -196,17 +196,14 @@ static bool cpu_cfg_offset_is_named_feat(uint32_t ext_offset)
>
>  static void riscv_cpu_enable_named_feat(RISCVCPU *cpu, uint32_t feat_offset)
>  {
> -    switch (feat_offset) {
> -    case CPU_CFG_OFFSET(ext_zic64b):
> +     /*
> +      * All other named features are already enabled
> +      * in riscv_tcg_cpu_instance_init().
> +      */
> +    if (feat_offset == CPU_CFG_OFFSET(ext_zic64b)) {
>          cpu->cfg.cbom_blocksize = 64;
>          cpu->cfg.cbop_blocksize = 64;
>          cpu->cfg.cboz_blocksize = 64;
> -        break;
> -    case CPU_CFG_OFFSET(ext_svade):
> -        cpu->cfg.ext_svadu = false;
> -        break;
> -    default:
> -        g_assert_not_reached();
>      }
>  }
>
> @@ -348,8 +345,6 @@ static void riscv_cpu_update_named_features(RISCVCPU *cpu)
>      cpu->cfg.ext_zic64b = cpu->cfg.cbom_blocksize == 64 &&
>                            cpu->cfg.cbop_blocksize == 64 &&
>                            cpu->cfg.cboz_blocksize == 64;
> -
> -    cpu->cfg.ext_svade = !cpu->cfg.ext_svadu;
>  }
>
>  static void riscv_cpu_validate_g(RISCVCPU *cpu)
> --
> 2.43.0
>
>