[PATCH v5 2/4] lib: sbi: add zicfilp/zicfiss and elp cfi state reflect back in status

[Atish Kumar Patra]

On Sat, Sep 14, 2024 at 10:04 AM Samuel Holland
<samuel.holland at sifive.com> wrote:
>
> On 2024-09-10 11:35 AM, Deepak Gupta wrote:
> > This patch adds support to check for zicfilp / zicfiss extension.
> >
> > zicfilp record status of hart's ELP state in *status csr. Missing landing pad
> > sets MPELP in mstatus. When SBI is redirecting back to S/VS/HS, SPELP is
> > set in sstatus/vsstatus.
> >
> > Signed-off-by: Deepak Gupta <debug at rivosinc.com>
> > ---
> >  include/sbi/sbi_hart.h |  3 +++
> >  lib/sbi/sbi_hart.c     |  2 ++
> >  lib/sbi/sbi_trap.c     | 20 ++++++++++++++++++++
> >  3 files changed, 25 insertions(+)
> >
> > diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> > index 81ec061..2aa6867 100644
> > --- a/include/sbi/sbi_hart.h
> > +++ b/include/sbi/sbi_hart.h
> > @@ -67,6 +67,9 @@ enum sbi_hart_extensions {
> >       SBI_HART_EXT_SVADE,
> >       /** Hart has Svadu extension */
> >       SBI_HART_EXT_SVADU,
> > +     /** HART has zicfiss & zicfilp extension */
> > +     SBI_HART_EXT_ZICFILP,
> > +     SBI_HART_EXT_ZICFISS,
> >

nit: Just to follow the convention above, let's split the comment
into individual extensions.

However, I am not sure if those comments provide any additional info
as most of the comments above the extension have the exact same extension
name in lowercase which is not that useful.

> >       /** Maximum index of Hart extension */
> >       SBI_HART_EXT_MAX,
> > diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> > index c366701..e1bc346 100644
> > --- a/lib/sbi/sbi_hart.c
> > +++ b/lib/sbi/sbi_hart.c
> > @@ -680,6 +680,8 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
> >       __SBI_HART_EXT_DATA(ssccfg, SBI_HART_EXT_SSCCFG),
> >       __SBI_HART_EXT_DATA(svade, SBI_HART_EXT_SVADE),
> >       __SBI_HART_EXT_DATA(svadu, SBI_HART_EXT_SVADU),
> > +     __SBI_HART_EXT_DATA(zicfilp, SBI_HART_EXT_ZICFILP),
> > +     __SBI_HART_EXT_DATA(zicfiss, SBI_HART_EXT_ZICFISS),
> >  };
> >
> >  _Static_assert(SBI_HART_EXT_MAX == array_size(sbi_hart_ext),
> > diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c
> > index b4f3a17..e2502f2 100644
> > --- a/lib/sbi/sbi_trap.c
> > +++ b/lib/sbi/sbi_trap.c
> > @@ -103,6 +103,7 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
> >                     const struct sbi_trap_info *trap)
> >  {
> >       ulong hstatus, vsstatus, prev_mode;
> > +     bool elp = false;
> >  #if __riscv_xlen == 32
> >       bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? true : false;
> >  #else
> > @@ -116,6 +117,17 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
> >       if (prev_mode != PRV_S && prev_mode != PRV_U)
> >               return SBI_ENOTSUPP;
> >
> > +     /* If extension has support for CFI, clear MPELP because redirecting to VS or (H)S */
>
> Did you mean "If hart has support for CFI" here?
>
> > +     if (sbi_hart_has_extension(sbi_scratch_thishart_ptr(), SBI_HART_EXT_ZICFILP)) {
> > +#if __riscv_xlen == 32
> > +             elp = regs->mstatusH & MSTATUSH_MPELP;
> > +             regs->mstatusH &= ~MSTATUSH_MPELP;
> > +#else
> > +             elp = regs->mstatus & MSTATUS_MPELP;
> > +             regs->mstatus &= ~MSTATUS_MPELP;
> > +#endif
> > +     }
> > +
> >       /* If exceptions came from VS/VU-mode, redirect to VS-mode if
> >        * delegated in hedeleg
> >        */
> > @@ -169,6 +181,10 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
> >               /* Get VS-mode SSTATUS CSR */
> >               vsstatus = csr_read(CSR_VSSTATUS);
> >
> > +             /*if elp was set, set it back in vsstatus */
>
> Missing space before "if". With this fixed:
>
> Reviewed-by: Samuel Holland <samuel.holland at sifive.com>
>
> > +             if (elp)
> > +                     vsstatus |= MSTATUS_SPELP;
> > +
> >               /* Set SPP for VS-mode */
> >               vsstatus &= ~SSTATUS_SPP;
> >               if (prev_mode == PRV_S)
> > @@ -209,6 +225,10 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
> >
> >               /* Clear SIE for S-mode */
> >               regs->mstatus &= ~MSTATUS_SIE;
> > +
> > +             /* if elp was set, set it back in mstatus */
> > +             if (elp)
> > +                     regs->mstatus |= MSTATUS_SPELP;
> >       }
> >
> >       return 0;
>

With Samuel's suggestion fixed,

Reviewed-by: Atish Patra <atishp at rivosinc.com>