Re: [PATCH v2 1/3] target/riscv: Do not allow MXL_RV32 for TARGET_RISCV64

[LIU Zhiwei]

On 2023/10/17 11:32, Alistair Francis wrote:
> On Tue, Oct 17, 2023 at 12:14 PM LIU Zhiwei
> <zhiwei_liu@linux.alibaba.com> wrote:
> > On 2023/10/16 9:51, Alistair Francis wrote:
> > > On Sun, Oct 15, 2023 at 4:05 AM Daniel Henrique Barboza
> > > <dbarboza@ventanamicro.com> wrote:
> > > > On 10/14/23 00:35, Akihiko Odaki wrote:
> > > > > TARGET_RISCV64 does not have riscv-32bit-cpu.xml so it shouldn't accept
> > > > > MXL_RV32.
> > > > >
> > > > > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> > > > > ---
> > > > Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> > > >
> > > >
> > > > >     target/riscv/tcg/tcg-cpu.c | 3 ++-
> > > > >     1 file changed, 2 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
> > > > > index a28918ab30..e0cbc56320 100644
> > > > > --- a/target/riscv/tcg/tcg-cpu.c
> > > > > +++ b/target/riscv/tcg/tcg-cpu.c
> > > > > @@ -161,10 +161,11 @@ static void riscv_cpu_validate_misa_mxl(RISCVCPU *cpu, 
> > > > > Error **errp)
> > > > >         case MXL_RV128:
> > > > >             cc->gdb_core_xml_file = "riscv-64bit-cpu.xml";
> > > > >             break;
> > > > > -#endif
> > > > > +#elif defined(TARGET_RISCV32)
> > > > >         case MXL_RV32:
> > > > >             cc->gdb_core_xml_file = "riscv-32bit-cpu.xml";
> > > > >             break;
> > > > > +#endif
> > > This isn't the right fix. The idea is that riscv64-softmmu can run
> > > 32-bit CPUs, so we instead should include riscv-32bit-cpu.xml
> > Agree. I'd like to go on the work. The question is that we don't have
> > 64-bit OpenSBI which supports booting 32-bit Linux.
> > So even we have implemented the SXLEN 32bit, we may not have the
> > software to test it.
> Ah! So I was first talking around just a full 32-bit CPU.
>
> So for example:
>      qemu-system-riscv64 -machine opentitan
>
> So we are using qemu-system-riscv64 to run a 32-bit only CPU.

Yes, if the 32-bit only cpu only has M mode, it can work now.

I have tried this for Xuantie E series cpu, for example the e902,  in 
the wild tree.

> Then we can think about SXLEN

Agree, maybe we can expose these cpus now.

Thanks,
Zhiwei

> > Do you support the SXL upstreaming with no testing?
> No, it should be tested
>
> Alistair
>
> > Thanks,
> > Zhiwei
> >
> > > Alistair
> > >
> > > > >         default:
> > > > >             g_assert_not_reached();
> > > > >         }