Re: [PATCH v13 10/26] target/riscv/tcg: add user flag for profile support

[Alistair Francis]

On Tue, Dec 19, 2023 at 12:09 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> The TCG emulation implements all the extensions described in the
> RVA22U64 profile, both mandatory and optional. The mandatory extensions
> will be enabled via the profile flag. We'll leave the optional
> extensions to be enabled by hand.
>
> Given that this is the first profile we're implementing in TCG we'll
> need some ground work first:
>
> - all profiles declared in riscv_profiles[] will be exposed to users.
> TCG is the main accelerator we're considering when adding profile
> support in QEMU, so for now it's safe to assume that all profiles in
> riscv_profiles[] will be relevant to TCG;
>
> - we'll not support user profile settings for vendor CPUs. The flags
> will still be exposed but users won't be able to change them;
>
> - profile support, albeit available for all non-vendor CPUs, will be
> based on top of the new 'rv64i' CPU. Setting a profile to 'true' means
> enable all mandatory extensions of this profile, setting it to 'false'
> will disable all mandatory profile extensions of the CPU, which will
> obliterate preset defaults. This is not a problem for a bare CPU like
> rv64i but it can allow for silly scenarios when using other CPUs. E.g.
> an user can do "-cpu rv64,rva22u64=false" and have a bunch of default
> rv64 extensions disabled. The recommended way of using profiles is the
> rv64i CPU, but users are free to experiment.
>
> For now we'll handle multi-letter extensions only. MISA extensions need
> additional steps that we'll take care later. At this point we can boot a
> Linux buildroot using rva22u64 using the following options:
>
> -cpu rv64i,rva22u64=true,sv39=true,g=true,c=true,s=true
>
> Note that being an usermode/application profile we still need to
> explicitly set 's=true' to enable Supervisor mode to boot Linux.
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

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

Alistair

> ---
>  target/riscv/tcg/tcg-cpu.c | 80 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 80 insertions(+)
>
> diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
> index 3319ba8e4e..83d4dd00cf 100644
> --- a/target/riscv/tcg/tcg-cpu.c
> +++ b/target/riscv/tcg/tcg-cpu.c
> @@ -127,6 +127,19 @@ static bool cpu_cfg_offset_is_named_feat(uint32_t 
> ext_offset)
>      return false;
>  }
>
> +static void riscv_cpu_enable_named_feat(RISCVCPU *cpu, uint32_t feat_offset)
> +{
> +    switch (feat_offset) {
> +    case CPU_CFG_OFFSET(zic64b):
> +        cpu->cfg.cbom_blocksize = 64;
> +        cpu->cfg.cbop_blocksize = 64;
> +        cpu->cfg.cboz_blocksize = 64;
> +        break;
> +    default:
> +        g_assert_not_reached();
> +    }
> +}
> +
>  static void cpu_bump_multi_ext_priv_ver(CPURISCVState *env,
>                                          uint32_t ext_offset)
>  {
> @@ -885,6 +898,71 @@ static void riscv_cpu_add_misa_properties(Object 
> *cpu_obj)
>      }
>  }
>
> +static void cpu_set_profile(Object *obj, Visitor *v, const char *name,
> +                            void *opaque, Error **errp)
> +{
> +    RISCVCPUProfile *profile = opaque;
> +    RISCVCPU *cpu = RISCV_CPU(obj);
> +    bool value;
> +    int i, ext_offset;
> +
> +    if (riscv_cpu_is_vendor(obj)) {
> +        error_setg(errp, "Profile %s is not available for vendor CPUs",
> +                   profile->name);
> +        return;
> +    }
> +
> +    if (cpu->env.misa_mxl != MXL_RV64) {
> +        error_setg(errp, "Profile %s only available for 64 bit CPUs",
> +                   profile->name);
> +        return;
> +    }
> +
> +    if (!visit_type_bool(v, name, &value, errp)) {
> +        return;
> +    }
> +
> +    profile->user_set = true;
> +    profile->enabled = value;
> +
> +    for (i = 0; profile->ext_offsets[i] != RISCV_PROFILE_EXT_LIST_END; i++) {
> +        ext_offset = profile->ext_offsets[i];
> +
> +        if (profile->enabled) {
> +            if (cpu_cfg_offset_is_named_feat(ext_offset)) {
> +                riscv_cpu_enable_named_feat(cpu, ext_offset);
> +            }
> +
> +            cpu_bump_multi_ext_priv_ver(&cpu->env, ext_offset);
> +        }
> +
> +        g_hash_table_insert(multi_ext_user_opts,
> +                            GUINT_TO_POINTER(ext_offset),
> +                            (gpointer)profile->enabled);
> +        isa_ext_update_enabled(cpu, ext_offset, profile->enabled);
> +    }
> +}
> +
> +static void cpu_get_profile(Object *obj, Visitor *v, const char *name,
> +                            void *opaque, Error **errp)
> +{
> +    RISCVCPUProfile *profile = opaque;
> +    bool value = profile->enabled;
> +
> +    visit_type_bool(v, name, &value, errp);
> +}
> +
> +static void riscv_cpu_add_profiles(Object *cpu_obj)
> +{
> +    for (int i = 0; riscv_profiles[i] != NULL; i++) {
> +        const RISCVCPUProfile *profile = riscv_profiles[i];
> +
> +        object_property_add(cpu_obj, profile->name, "bool",
> +                            cpu_get_profile, cpu_set_profile,
> +                            NULL, (void *)profile);
> +    }
> +}
> +
>  static bool cpu_ext_is_deprecated(const char *ext_name)
>  {
>      return isupper(ext_name[0]);
> @@ -1012,6 +1090,8 @@ static void riscv_cpu_add_user_properties(Object *obj)
>
>      riscv_cpu_add_multiext_prop_array(obj, riscv_cpu_deprecated_exts);
>
> +    riscv_cpu_add_profiles(obj);
> +
>      for (Property *prop = riscv_cpu_options; prop && prop->name; prop++) {
>          qdev_property_add_static(DEVICE(obj), prop);
>      }
> --
> 2.43.0
>
>