Re: [PATCH 3/6] target/riscv: add remaining named features

[Alistair Francis]

On Fri, Jan 26, 2024 at 5:54 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> The RVA22U64 and RVA22S64 profiles mandates certain extensions that,
> until now, we were implying that they were available.
>
> We can't do this anymore since named features also has a riscv,isa
> entry.  Let's add them to riscv_cpu_named_features[].
>
> They will also need to be explicitly enabled in both profile
> descriptions. TCG will enable the named features it already implements,
> other accelerators are free to handle it as they like.
>
> After this patch, here's the riscv,isa from a buildroot using the
> 'rva22s64' CPU:
>
>  # cat /proc/device-tree/cpus/cpu@0/riscv,isa
> rv64imafdc_zic64b_zicbom_zicbop_zicboz_ziccamoa_ziccif_zicclsm_ziccrse_
> zicntr_zicsr_zifencei_zihintpause_zihpm_za64rs_zfhmin_zca_zcd_zba_zbb_
> zbs_zkt_sscounterenw_sstvala_sstvecd_svade_svinval_svpbmt#
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c         | 41 +++++++++++++++++++++++++++++---------
>  target/riscv/cpu_cfg.h     |  9 +++++++++
>  target/riscv/tcg/tcg-cpu.c | 19 +++++++++++++++++-
>  3 files changed, 59 insertions(+), 10 deletions(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 28d3cfa8ce..1ecd8a57ed 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -101,6 +101,10 @@ const RISCVIsaExtData isa_edata_arr[] = {
>      ISA_EXT_DATA_ENTRY(zicbom, PRIV_VERSION_1_12_0, ext_zicbom),
>      ISA_EXT_DATA_ENTRY(zicbop, PRIV_VERSION_1_12_0, ext_zicbop),
>      ISA_EXT_DATA_ENTRY(zicboz, PRIV_VERSION_1_12_0, ext_zicboz),
> +    ISA_EXT_DATA_ENTRY(ziccamoa, PRIV_VERSION_1_11_0, ext_ziccamoa),
> +    ISA_EXT_DATA_ENTRY(ziccif, PRIV_VERSION_1_11_0, ext_ziccif),
> +    ISA_EXT_DATA_ENTRY(zicclsm, PRIV_VERSION_1_11_0, ext_zicclsm),
> +    ISA_EXT_DATA_ENTRY(ziccrse, PRIV_VERSION_1_11_0, ext_ziccrse),
>      ISA_EXT_DATA_ENTRY(zicond, PRIV_VERSION_1_12_0, ext_zicond),
>      ISA_EXT_DATA_ENTRY(zicntr, PRIV_VERSION_1_12_0, ext_zicntr),
>      ISA_EXT_DATA_ENTRY(zicsr, PRIV_VERSION_1_10_0, ext_zicsr),
> @@ -109,6 +113,7 @@ const RISCVIsaExtData isa_edata_arr[] = {
>      ISA_EXT_DATA_ENTRY(zihintpause, PRIV_VERSION_1_10_0, ext_zihintpause),
>      ISA_EXT_DATA_ENTRY(zihpm, PRIV_VERSION_1_12_0, ext_zihpm),
>      ISA_EXT_DATA_ENTRY(zmmul, PRIV_VERSION_1_12_0, ext_zmmul),
> +    ISA_EXT_DATA_ENTRY(za64rs, PRIV_VERSION_1_12_0, ext_za64rs),
>      ISA_EXT_DATA_ENTRY(zacas, PRIV_VERSION_1_12_0, ext_zacas),
>      ISA_EXT_DATA_ENTRY(zawrs, PRIV_VERSION_1_12_0, ext_zawrs),
>      ISA_EXT_DATA_ENTRY(zfa, PRIV_VERSION_1_12_0, ext_zfa),
> @@ -170,8 +175,12 @@ const RISCVIsaExtData isa_edata_arr[] = {
>      ISA_EXT_DATA_ENTRY(smepmp, PRIV_VERSION_1_12_0, ext_smepmp),
>      ISA_EXT_DATA_ENTRY(smstateen, PRIV_VERSION_1_12_0, ext_smstateen),
>      ISA_EXT_DATA_ENTRY(ssaia, PRIV_VERSION_1_12_0, ext_ssaia),
> +    ISA_EXT_DATA_ENTRY(ssccptr, PRIV_VERSION_1_11_0, ext_ssccptr),
>      ISA_EXT_DATA_ENTRY(sscofpmf, PRIV_VERSION_1_12_0, ext_sscofpmf),
> +    ISA_EXT_DATA_ENTRY(sscounterenw, PRIV_VERSION_1_12_0, ext_sscounterenw),
>      ISA_EXT_DATA_ENTRY(sstc, PRIV_VERSION_1_12_0, ext_sstc),
> +    ISA_EXT_DATA_ENTRY(sstvala, PRIV_VERSION_1_12_0, ext_sstvala),
> +    ISA_EXT_DATA_ENTRY(sstvecd, PRIV_VERSION_1_12_0, ext_sstvecd),
>      ISA_EXT_DATA_ENTRY(svade, PRIV_VERSION_1_11_0, ext_svade),
>      ISA_EXT_DATA_ENTRY(svadu, PRIV_VERSION_1_12_0, ext_svadu),
>      ISA_EXT_DATA_ENTRY(svinval, PRIV_VERSION_1_12_0, ext_svinval),
> @@ -1523,6 +1532,22 @@ const RISCVCPUMultiExtConfig 
> riscv_cpu_named_features[] = {
>      MULTI_EXT_CFG_BOOL("svade", ext_svade, true),
>      MULTI_EXT_CFG_BOOL("zic64b", ext_zic64b, true),
>
> +    /*
> +     * cache-related extensions that are always enabled
> +     * since QEMU RISC-V does not have a cache model.
> +     */
> +    MULTI_EXT_CFG_BOOL("za64rs", ext_za64rs, true),
> +    MULTI_EXT_CFG_BOOL("ziccif", ext_ziccif, true),
> +    MULTI_EXT_CFG_BOOL("ziccrse", ext_ziccrse, true),
> +    MULTI_EXT_CFG_BOOL("ziccamoa", ext_ziccamoa, true),
> +    MULTI_EXT_CFG_BOOL("zicclsm", ext_zicclsm, true),
> +    MULTI_EXT_CFG_BOOL("ssccptr", ext_ssccptr, true),
> +
> +    /* Other named features that QEMU TCG always implements */
> +    MULTI_EXT_CFG_BOOL("sstvecd", ext_sstvecd, true),
> +    MULTI_EXT_CFG_BOOL("sstvala", ext_sstvala, true),
> +    MULTI_EXT_CFG_BOOL("sscounterenw", ext_sscounterenw, true),
> +
>      DEFINE_PROP_END_OF_LIST(),
>  };
>
> @@ -2116,13 +2141,8 @@ static const PropertyInfo prop_marchid = {
>  };
>
>  /*
> - * RVA22U64 defines some 'named features' or 'synthetic extensions'
> - * that are cache related: Za64rs, Zic64b, Ziccif, Ziccrse, Ziccamoa
> - * and Zicclsm. We do not implement caching in QEMU so we'll consider
> - * all these named features as always enabled.
> - *
> - * There's no riscv,isa update for them (nor for zic64b, despite it
> - * having a cfg offset) at this moment.
> + * RVA22U64 defines some cache related extensions: Za64rs,
> + * Ziccif, Ziccrse, Ziccamoa and Zicclsm.
>   */
>  static RISCVCPUProfile RVA22U64 = {
>      .parent = NULL,
> @@ -2139,7 +2159,9 @@ static RISCVCPUProfile RVA22U64 = {
>          CPU_CFG_OFFSET(ext_zicbop), CPU_CFG_OFFSET(ext_zicboz),
>
>          /* mandatory named features for this profile */
> -        CPU_CFG_OFFSET(ext_zic64b),
> +        CPU_CFG_OFFSET(ext_za64rs), CPU_CFG_OFFSET(ext_zic64b),
> +        CPU_CFG_OFFSET(ext_ziccif), CPU_CFG_OFFSET(ext_ziccrse),
> +        CPU_CFG_OFFSET(ext_ziccamoa), CPU_CFG_OFFSET(ext_zicclsm),
>
>          RISCV_PROFILE_EXT_LIST_END
>      }
> @@ -2170,7 +2192,8 @@ static RISCVCPUProfile RVA22S64 = {
>          CPU_CFG_OFFSET(ext_svinval),
>
>          /* rva22s64 named features */
> -        CPU_CFG_OFFSET(ext_svade),
> +        CPU_CFG_OFFSET(ext_sstvecd), CPU_CFG_OFFSET(ext_sstvala),
> +        CPU_CFG_OFFSET(ext_sscounterenw), CPU_CFG_OFFSET(ext_svade),
>
>          RISCV_PROFILE_EXT_LIST_END
>      }
> diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
> index 698f926ab1..f79fc3dfd1 100644
> --- a/target/riscv/cpu_cfg.h
> +++ b/target/riscv/cpu_cfg.h
> @@ -125,6 +125,15 @@ struct RISCVCPUConfig {
>      /* Named features  */
>      bool ext_svade;
>      bool ext_zic64b;
> +    bool ext_za64rs;
> +    bool ext_ziccif;
> +    bool ext_ziccrse;
> +    bool ext_ziccamoa;
> +    bool ext_zicclsm;
> +    bool ext_ssccptr;
> +    bool ext_sstvecd;
> +    bool ext_sstvala;
> +    bool ext_sscounterenw;

Overall this and the previous patch look fine.

One thing though, why store this information? I feel it could be
confusing having these variables. If a developer sets them to false
nothing actually happens, which is a little misleading

Alistair

>
>      /* Vendor-specific custom extensions */
>      bool ext_xtheadba;
> diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
> index 90861cc065..6d5028cf84 100644
> --- a/target/riscv/tcg/tcg-cpu.c
> +++ b/target/riscv/tcg/tcg-cpu.c
> @@ -206,7 +206,8 @@ static void riscv_cpu_enable_named_feat(RISCVCPU *cpu, 
> uint32_t feat_offset)
>          cpu->cfg.ext_svadu = false;
>          break;
>      default:
> -        g_assert_not_reached();
> +        /* Named feature already enabled in riscv_tcg_cpu_instance_init */
> +        return;
>      }
>  }
>
> @@ -1342,6 +1343,20 @@ static bool riscv_cpu_has_max_extensions(Object 
> *cpu_obj)
>      return object_dynamic_cast(cpu_obj, TYPE_RISCV_CPU_MAX) != NULL;
>  }
>
> +/* Named features that TCG always implements */
> +static void riscv_tcg_cpu_enable_named_feats(RISCVCPU *cpu)
> +{
> +    cpu->cfg.ext_za64rs = true;
> +    cpu->cfg.ext_ziccif = true;
> +    cpu->cfg.ext_ziccrse = true;
> +    cpu->cfg.ext_ziccamoa = true;
> +    cpu->cfg.ext_zicclsm = true;
> +    cpu->cfg.ext_ssccptr = true;
> +    cpu->cfg.ext_sstvecd = true;
> +    cpu->cfg.ext_sstvala = true;
> +    cpu->cfg.ext_sscounterenw = true;
> +}
> +
>  static void riscv_tcg_cpu_instance_init(CPUState *cs)
>  {
>      RISCVCPU *cpu = RISCV_CPU(cs);
> @@ -1354,6 +1369,8 @@ static void riscv_tcg_cpu_instance_init(CPUState *cs)
>      if (riscv_cpu_has_max_extensions(obj)) {
>          riscv_init_max_cpu_extensions(obj);
>      }
> +
> +    riscv_tcg_cpu_enable_named_feats(cpu);
>  }
>
>  static void riscv_tcg_cpu_init_ops(AccelCPUClass *accel_cpu, CPUClass *cc)
> --
> 2.43.0
>
>