Re: [PATCH] target/sparc: fake UltraSPARC T1 PCR and PIC registers

[Artyom Tarasenko <atar4qemu@gmail.com>]

On Sun, Feb 2, 2025 at 10:47 PM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 1/31/25 13:44, Artyom Tarasenko wrote:
> > fake access to
> > PCR Performance Control Register
> > and
> > PIC Performance Instrumentation Counter.
> >
> > Ignore writes in privileged mode, and return 0 on reads.
> >
> > This allows booting Tribblix, MilaX and v9os under Niagara target.
> >
> > Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
> > ---
> >   target/sparc/insns.decode |  7 ++++++-
> >   target/sparc/translate.c  | 20 ++++++++++++++++++++
> >   2 files changed, 26 insertions(+), 1 deletion(-)
> >
> > diff --git a/target/sparc/insns.decode b/target/sparc/insns.decode
> > index 989c20b44a..504147563c 100644
> > --- a/target/sparc/insns.decode
> > +++ b/target/sparc/insns.decode
> > @@ -96,7 +96,10 @@ CALL    01 i:s30
> >       RDTICK          10 rd:5  101000 00100 0 0000000000000
> >       RDPC            10 rd:5  101000 00101 0 0000000000000
> >       RDFPRS          10 rd:5  101000 00110 0 0000000000000
> > -    RDASR17         10 rd:5  101000 10001 0 0000000000000
> > +    {
> > +      RDASR17       10 rd:5  101000 10001 0 0000000000000
> > +      RDPIC         10 rd:5  101000 10001 0 0000000000000
> > +    }
> >       RDGSR           10 rd:5  101000 10011 0 0000000000000
> >       RDSOFTINT       10 rd:5  101000 10110 0 0000000000000
> >       RDTICK_CMPR     10 rd:5  101000 10111 0 0000000000000
> > @@ -114,6 +117,8 @@ CALL    01 i:s30
> >       WRCCR           10 00010 110000 ..... . .............  @n_r_ri
> >       WRASI           10 00011 110000 ..... . .............  @n_r_ri
> >       WRFPRS          10 00110 110000 ..... . .............  @n_r_ri
> > +    WRPCR           10 10000 110000 01000 0 0000000000000
> > +    WRPIC           10 10001 110000 01000 0 0000000000000
> >       {
> >         WRGSR         10 10011 110000 ..... . .............  @n_r_ri
> >         WRPOWERDOWN   10 10011 110000 ..... . .............  @n_r_ri
> > diff --git a/target/sparc/translate.c b/target/sparc/translate.c
> > index 7e5c7351cb..285c9b0a59 100644
> > --- a/target/sparc/translate.c
> > +++ b/target/sparc/translate.c
> > @@ -2882,6 +2882,15 @@ static TCGv do_rd_leon3_config(DisasContext *dc, TCGv dst)
> >
> >   TRANS(RDASR17, ASR17, do_rd_special, true, a->rd, do_rd_leon3_config)
> >
> > +static TCGv do_rdpic(DisasContext *dc, TCGv dst)
> > +{
> > +    tcg_gen_movi_tl(dst, 0UL);
> > +    return dst;
> > +}
>
> return tcg_constant_tl(0);
>
> > +
> > +TRANS(RDPIC, HYPV, do_rd_special, true, a->rd, do_rdpic)
>
> Surely reads are not allowed in user mode.

Thanks Richard, addressed it in v2.