Re: [PATCH v2 1/1] target/riscv: Add Zihintpause support

[Dao Lu]

Hi Alistair,

Thanks for the response. I don't think I can find any comments
on this patch though, could you help point me to them?

Thanks,
Dao

On Tue, Jun 7, 2022 at 4:04 PM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Wed, Jun 8, 2022 at 8:59 AM Dao Lu <daolu@rivosinc.com> wrote:
> >
> > Ping
>
> The latest version of this patch on the mailing list has comments that
> need to be addressed
>
> Alistair
>
> >
> > On Tue, May 24, 2022 at 1:36 PM Dao Lu <daolu@rivosinc.com> wrote:
> > >
> > > Tested-by: Heiko Stuebner <heiko@sntech.de>
> > > Signed-off-by: Dao Lu <daolu@rivosinc.com>
> > > ---
> > >  target/riscv/cpu.c                      |  2 ++
> > >  target/riscv/cpu.h                      |  1 +
> > >  target/riscv/insn32.decode              |  7 ++++++-
> > >  target/riscv/insn_trans/trans_rvi.c.inc | 18 ++++++++++++++++++
> > >  4 files changed, 27 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> > > index ccacdee215..183fb37fdf 100644
> > > --- a/target/riscv/cpu.c
> > > +++ b/target/riscv/cpu.c
> > > @@ -825,6 +825,7 @@ static Property riscv_cpu_properties[] = {
> > >      DEFINE_PROP_BOOL("Counters", RISCVCPU, cfg.ext_counters, true),
> > >      DEFINE_PROP_BOOL("Zifencei", RISCVCPU, cfg.ext_ifencei, true),
> > >      DEFINE_PROP_BOOL("Zicsr", RISCVCPU, cfg.ext_icsr, true),
> > > +    DEFINE_PROP_BOOL("Zihintpause", RISCVCPU, cfg.ext_zihintpause, true),
> > >      DEFINE_PROP_BOOL("Zfh", RISCVCPU, cfg.ext_zfh, false),
> > >      DEFINE_PROP_BOOL("Zfhmin", RISCVCPU, cfg.ext_zfhmin, false),
> > >      DEFINE_PROP_BOOL("Zve32f", RISCVCPU, cfg.ext_zve32f, false),
> > > @@ -996,6 +997,7 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char 
> > > **isa_str, int max_str_len)
> > >       *    extensions by an underscore.
> > >       */
> > >      struct isa_ext_data isa_edata_arr[] = {
> > > +        ISA_EDATA_ENTRY(zihintpause, ext_zihintpause),
> > >          ISA_EDATA_ENTRY(zfh, ext_zfh),
> > >          ISA_EDATA_ENTRY(zfhmin, ext_zfhmin),
> > >          ISA_EDATA_ENTRY(zfinx, ext_zfinx),
> > > diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> > > index fe6c9a2c92..e466a04a59 100644
> > > --- a/target/riscv/cpu.h
> > > +++ b/target/riscv/cpu.h
> > > @@ -394,6 +394,7 @@ struct RISCVCPUConfig {
> > >      bool ext_counters;
> > >      bool ext_ifencei;
> > >      bool ext_icsr;
> > > +    bool ext_zihintpause;
> > >      bool ext_svinval;
> > >      bool ext_svnapot;
> > >      bool ext_svpbmt;
> > > diff --git a/target/riscv/insn32.decode b/target/riscv/insn32.decode
> > > index 4033565393..595fdcdad8 100644
> > > --- a/target/riscv/insn32.decode
> > > +++ b/target/riscv/insn32.decode
> > > @@ -149,7 +149,12 @@ srl      0000000 .....    ..... 101 ..... 0110011 @r
> > >  sra      0100000 .....    ..... 101 ..... 0110011 @r
> > >  or       0000000 .....    ..... 110 ..... 0110011 @r
> > >  and      0000000 .....    ..... 111 ..... 0110011 @r
> > > -fence    ---- pred:4 succ:4 ----- 000 ----- 0001111
> > > +
> > > +{
> > > +  pause  0000 0001   0000   00000 000 00000 0001111
> > > +  fence  ---- pred:4 succ:4 ----- 000 ----- 0001111
> > > +}
> > > +
> > >  fence_i  ---- ----   ----   ----- 001 ----- 0001111
> > >  csrrw    ............     ..... 001 ..... 1110011 @csr
> > >  csrrs    ............     ..... 010 ..... 1110011 @csr
> > > diff --git a/target/riscv/insn_trans/trans_rvi.c.inc 
> > > b/target/riscv/insn_trans/trans_rvi.c.inc
> > > index f1342f30f8..ca75e05f4b 100644
> > > --- a/target/riscv/insn_trans/trans_rvi.c.inc
> > > +++ b/target/riscv/insn_trans/trans_rvi.c.inc
> > > @@ -796,6 +796,24 @@ static bool trans_srad(DisasContext *ctx, arg_srad 
> > > *a)
> > >      return gen_shift(ctx, a, EXT_SIGN, tcg_gen_sar_tl, NULL);
> > >  }
> > >
> > > +static bool trans_pause(DisasContext *ctx, arg_pause *a)
> > > +{
> > > +    if (!ctx->cfg_ptr->ext_zihintpause) {
> > > +        return false;
> > > +    }
> > > +
> > > +    /*
> > > +     * PAUSE is a no-op in QEMU,
> > > +     * however we need to clear the reservation,
> > > +     * end the TB and return to main loop
> > > +     */
> > > +    tcg_gen_movi_tl(load_res, -1);
> > > +    gen_set_pc_imm(ctx, ctx->pc_succ_insn);
> > > +    tcg_gen_exit_tb(NULL, 0);
> > > +    ctx->base.is_jmp = DISAS_NORETURN;
> > > +
> > > +    return true;
> > > +}
> > >
> > >  static bool trans_fence(DisasContext *ctx, arg_fence *a)
> > >  {
> > > --
> > > 2.30.1 (Apple Git-130)
> > >
> >