[PATCH 4/4] lib: sbi: detect extensions from menvcfg

[Anup Patel]

On Thu, Sep 7, 2023 at 2:57 PM Yong-Xuan Wang <yongxuan.wang at sifive.com> wrote:
>
> Currently "Boot HART ISA Extensions" only shows extensions which can be
> detected by test and set their CSRs. We can expand this functionality to
> detect additional extensions from menvcfg that do not introduce new CSRs
> but are controlled through menvcfg settings.

To detect extensions this way, we have to write the CSR and some of the
CSR fields can have side effects. For example, the MML bit is a sticky bit
and enables ePMP mode.

Instead, I suggest detecting extensions from the ISA string provided in the
DT. We have already done this for Smepmp extension so it should be easy
to extend.

Regards,
Anup

>
> Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
> ---
>  include/sbi/sbi_hart.h |  8 +++++++
>  lib/sbi/sbi_hart.c     | 49 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 57 insertions(+)
>
> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> index e60f415..a0e5f58 100644
> --- a/include/sbi/sbi_hart.h
> +++ b/include/sbi/sbi_hart.h
> @@ -42,6 +42,14 @@ enum sbi_hart_extensions {
>         SBI_HART_EXT_ZIHPM,
>         /** Hart has Smcntrpmf extension */
>         SBI_HART_EXT_SMCNTRPMF,
> +       /** Hart has Smcntrpmf extension */
> +       SBI_HART_EXT_ZICBOZ,
> +       /** Hart has Smcntrpmf extension */
> +       SBI_HART_EXT_ZICBOM,
> +       /** Hart has Smcntrpmf extension */
> +       SBI_HART_EXT_SVPBMT,
> +       /** Hart has Svadu extension */
> +       SBI_HART_EXT_SVADU,
>
>         /** Maximum index of Hart extension */
>         SBI_HART_EXT_MAX,
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index b7ca0e6..9a0572e 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -604,6 +604,18 @@ static inline char *sbi_hart_extension_id2string(int ext)
>         case SBI_HART_EXT_SMCNTRPMF:
>                 estr = "smcntrpmf";
>                 break;
> +       case SBI_HART_EXT_ZICBOZ:
> +               estr = "zicboz";
> +               break;
> +       case SBI_HART_EXT_ZICBOM:
> +               estr = "zicbom";
> +               break;
> +       case SBI_HART_EXT_SVPBMT:
> +               estr = "svpbmt";
> +               break;
> +       case SBI_HART_EXT_SVADU:
> +               estr = "svadu";
> +               break;
>         default:
>                 break;
>         }
> @@ -875,6 +887,43 @@ __pmp_skip:
>                 __sbi_hart_update_extension(hfeatures,
>                                         SBI_HART_EXT_ZIHPM, true);
>
> +       if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_12) {
> +               unsigned long orig_menvcfg_val, menvcfg_val;
> +
> +               orig_menvcfg_val = csr_read(CSR_MENVCFG);
> +               csr_write(CSR_MENVCFG, ~0);
> +               menvcfg_val = csr_read(CSR_MENVCFG);
> +
> +#if __riscv_xlen == 32
> +               orig_menvcfg_val |= ((uint64_t)csr_read(CSR_MENVCFGH)) << 32;
> +               csr_write(CSR_MENVCFGH, ~0);
> +               menvcfg_val |= ((uint64_t)csr_read(CSR_MENVCFGH)) << 32;
> +#endif
> +
> +#define __check_ext_menvcfg(__bit, __ext)                              \
> +               if (menvcfg_val & (__bit))                              \
> +                       __sbi_hart_update_extension(hfeatures,          \
> +                                                   __ext, true);       \
> +
> +               /* If the extension is not implemented, the related fields in
> +                * menvcfg are read-only zero.
> +                */
> +               __check_ext_menvcfg(ENVCFG_CBZE, SBI_HART_EXT_ZICBOZ);
> +               __check_ext_menvcfg(ENVCFG_CBCFE |
> +                                   (ENVCFG_CBIE_INV << ENVCFG_CBIE_SHIFT),
> +                                   SBI_HART_EXT_ZICBOM);
> +               __check_ext_menvcfg(ENVCFG_PBMTE, SBI_HART_EXT_SVPBMT);
> +               __check_ext_menvcfg(ENVCFG_HADE, SBI_HART_EXT_SVADU);
> +
> +#undef __check_ext_menvcfg
> +
> +               csr_write(CSR_MENVCFG, orig_menvcfg_val);
> +#if __riscv_xlen == 32
> +               csr_write(CSR_MENVCFGH, orig_menvcfg_val >> 32);
> +#endif
> +
> +       }
> +
>         /* Mark hart feature detection done */
>         hfeatures->detected = true;
>
> --
> 2.17.1
>
>
> --
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