Re: [PATCH for-8.2 v2 6/7] target/riscv: add 'max' CPU type

[Alistair Francis]

On Thu, Jul 13, 2023 at 7:00 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> The 'max' CPU type is used by tooling to determine what's the most
> capable CPU a current QEMU version implements. Other archs such as ARM
> implements this type. Let's add it to RISC-V.
>
> What we consider "most capable CPU" in this context are related to
> ratified, non-vendor extensions. This means that we want the 'max' CPU
> to enable all (possible) ratified extensions by default. The reasoning
> behind this design is (1) vendor extensions can conflict with each other
> and we won't play favorities deciding which one is default or not and
> (2) non-ratified extensions are always prone to changes, not being
> stable enough to be enabled by default.
>
> All this said, we're still not able to enable all ratified extensions
> due to conflicts between them. Zfinx and all its dependencies aren't
> enabled because of a conflict with RVF. zce, zcmp and zcmt are also
> disabled due to RVD conflicts. When running with 64 bits we're also
> disabling zcf.
>
> MISA bits RVG, RVJ and RVV are also being set manually since they're
> default disabled.
>
> This is the resulting 'riscv,isa' DT for this new CPU:
>
> rv64imafdcvh_zicbom_zicboz_zicsr_zifencei_zihintpause_zawrs_zfa_
> zfh_zfhmin_zca_zcb_zcd_zba_zbb_zbc_zbkb_zbkc_zbkx_zbs_zk_zkn_zknd_
> zkne_zknh_zkr_zks_zksed_zksh_zkt_zve32f_zve64f_zve64d_
> smstateen_sscofpmf_sstc_svadu_svinval_svnapot_svpbmt
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu-qom.h |  1 +
>  target/riscv/cpu.c     | 53 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 54 insertions(+)
>
> diff --git a/target/riscv/cpu-qom.h b/target/riscv/cpu-qom.h
> index 04af50983e..f3fbe37a2c 100644
> --- a/target/riscv/cpu-qom.h
> +++ b/target/riscv/cpu-qom.h
> @@ -30,6 +30,7 @@
>  #define CPU_RESOLVING_TYPE TYPE_RISCV_CPU
>
>  #define TYPE_RISCV_CPU_ANY              RISCV_CPU_TYPE_NAME("any")
> +#define TYPE_RISCV_CPU_MAX              RISCV_CPU_TYPE_NAME("max")

>From memory the "any" CPU was supposed to do this, so we might want to remove 
>it

Alistair

>  #define TYPE_RISCV_CPU_BASE32           RISCV_CPU_TYPE_NAME("rv32")
>  #define TYPE_RISCV_CPU_BASE64           RISCV_CPU_TYPE_NAME("rv64")
>  #define TYPE_RISCV_CPU_BASE128          RISCV_CPU_TYPE_NAME("x-rv128")
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index b61465c8c4..5172566cda 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -248,6 +248,7 @@ static const char * const riscv_intr_names[] = {
>  };
>
>  static void riscv_cpu_add_user_properties(Object *obj);
> +static void riscv_init_max_cpu_extensions(Object *obj);
>
>  const char *riscv_cpu_get_trap_name(target_ulong cause, bool async)
>  {
> @@ -374,6 +375,25 @@ static void riscv_any_cpu_init(Object *obj)
>      cpu->cfg.pmp = true;
>  }
>
> +static void riscv_max_cpu_init(Object *obj)
> +{
> +    RISCVCPU *cpu = RISCV_CPU(obj);
> +    CPURISCVState *env = &cpu->env;
> +    RISCVMXL mlx = MXL_RV64;
> +
> +#ifdef TARGET_RISCV32
> +    mlx = MXL_RV32;
> +#endif
> +    set_misa(env, mlx, 0);
> +    riscv_cpu_add_user_properties(obj);
> +    riscv_init_max_cpu_extensions(obj);
> +    env->priv_ver = PRIV_VERSION_LATEST;
> +#ifndef CONFIG_USER_ONLY
> +    set_satp_mode_max_supported(RISCV_CPU(obj), mlx == MXL_RV32 ?
> +                                VM_1_10_SV32 : VM_1_10_SV57);
> +#endif
> +}
> +
>  #if defined(TARGET_RISCV64)
>  static void rv64_base_cpu_init(Object *obj)
>  {
> @@ -1934,6 +1954,38 @@ static void riscv_cpu_add_user_properties(Object *obj)
>      ADD_CPU_PROPERTIES_ARRAY(dev, riscv_cpu_experimental_exts);
>  }
>
> +/*
> + * The 'max' type CPU will have all possible ratified
> + * non-vendor extensions enabled.
> + */
> +static void riscv_init_max_cpu_extensions(Object *obj)
> +{
> +    RISCVCPU *cpu = RISCV_CPU(obj);
> +    CPURISCVState *env = &cpu->env;
> +    Property *prop;
> +
> +    /* Enable RVG, RVJ and RVV that are disabled by default */
> +    set_misa(env, env->misa_mxl, env->misa_ext | RVG | RVJ | RVV);
> +
> +    for (prop = riscv_cpu_extensions; prop && prop->name; prop++) {
> +        object_property_set_bool(obj, prop->name, true, NULL);
> +    }
> +
> +    /* Zfinx is not compatible with F. Disable it */
> +    object_property_set_bool(obj, "zfinx", false, NULL);
> +    object_property_set_bool(obj, "zdinx", false, NULL);
> +    object_property_set_bool(obj, "zhinx", false, NULL);
> +    object_property_set_bool(obj, "zhinxmin", false, NULL);
> +
> +    object_property_set_bool(obj, "zce", false, NULL);
> +    object_property_set_bool(obj, "zcmp", false, NULL);
> +    object_property_set_bool(obj, "zcmt", false, NULL);
> +
> +    if (env->misa_mxl != MXL_RV32) {
> +        object_property_set_bool(obj, "zcf", false, NULL);
> +    }
> +}
> +
>  static Property riscv_cpu_properties[] = {
>      DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),
>
> @@ -2272,6 +2324,7 @@ static const TypeInfo riscv_cpu_type_infos[] = {
>          .abstract = true,
>      },
>      DEFINE_DYNAMIC_CPU(TYPE_RISCV_CPU_ANY,      riscv_any_cpu_init),
> +    DEFINE_DYNAMIC_CPU(TYPE_RISCV_CPU_MAX,      riscv_max_cpu_init),
>  #if defined(CONFIG_KVM)
>      DEFINE_CPU(TYPE_RISCV_CPU_HOST,             riscv_host_cpu_init),
>  #endif
> --
> 2.41.0
>
>