Re: [kvm-unit-tests PATCH] riscv: lib: sbi_shutdown add exit code.

[Andrew Jones <andrew.jones@linux.dev>]

On Mon, Jun 23, 2025 at 03:46:31PM -0700, Jesse Taube wrote:
> On Mon, Jun 23, 2025 at 10:01 AM Andrew Jones <andrew.jones@linux.dev> wrote:
> >
> > On Fri, Jun 20, 2025 at 08:50:51AM -0700, Jesse Taube wrote:
> > > When exiting it may be useful for the sbi implementation to know the
> > > exit code.
> > > Add exit code to sbi_shutdown, and use it in exit().
> > >
> > > Signed-off-by: Jesse Taube <jesse@rivosinc.com>
> > > ---
> > >  lib/riscv/asm/sbi.h | 2 +-
> > >  lib/riscv/io.c      | 2 +-
> > >  lib/riscv/sbi.c     | 4 ++--
> > >  3 files changed, 4 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/lib/riscv/asm/sbi.h b/lib/riscv/asm/sbi.h
> > > index a5738a5c..de11c109 100644
> > > --- a/lib/riscv/asm/sbi.h
> > > +++ b/lib/riscv/asm/sbi.h
> > > @@ -250,7 +250,7 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
> > >                       unsigned long arg3, unsigned long arg4,
> > >                       unsigned long arg5);
> > >
> > > -void sbi_shutdown(void);
> > > +void sbi_shutdown(unsigned int code);
> > >  struct sbiret sbi_hart_start(unsigned long hartid, unsigned long entry, unsigned long sp);
> > >  struct sbiret sbi_hart_stop(void);
> > >  struct sbiret sbi_hart_get_status(unsigned long hartid);
> > > diff --git a/lib/riscv/io.c b/lib/riscv/io.c
> > > index fb40adb7..02231268 100644
> > > --- a/lib/riscv/io.c
> > > +++ b/lib/riscv/io.c
> > > @@ -150,7 +150,7 @@ void halt(int code);
> > >  void exit(int code)
> > >  {
> > >       printf("\nEXIT: STATUS=%d\n", ((code) << 1) | 1);
> > > -     sbi_shutdown();
> > > +     sbi_shutdown(code & 1);
> > >       halt(code);
> > >       __builtin_unreachable();
> > >  }
> > > diff --git a/lib/riscv/sbi.c b/lib/riscv/sbi.c
> > > index 2959378f..9dd11e9d 100644
> > > --- a/lib/riscv/sbi.c
> > > +++ b/lib/riscv/sbi.c
> > > @@ -107,9 +107,9 @@ struct sbiret sbi_sse_inject(unsigned long event_id, unsigned long hart_id)
> > >       return sbi_ecall(SBI_EXT_SSE, SBI_EXT_SSE_INJECT, event_id, hart_id, 0, 0, 0, 0);
> > >  }
> > >
> > > -void sbi_shutdown(void)
> > > +void sbi_shutdown(unsigned int code)
> > >  {
> > > -     sbi_ecall(SBI_EXT_SRST, 0, 0, 0, 0, 0, 0, 0);
> > > +     sbi_ecall(SBI_EXT_SRST, 0, 0, code, 0, 0, 0, 0);
> >
> > We can't do this because a kvm-unit-tests exit code is not an
> > SRST::reset_reason[1]. This could result in the SBI implementation
> > returning an error, or doing something else, rather than shutting
> > down.
> 
> Yes that's why there is:
> +sbi_shutdown(code & 1);

Ah, I overlooked that.

> Admittedly it should probably be:
> +sbi_shutdown(!!code);

Indeed, it would only work now because bit 0 is set in the abort
exit code.

> 
> >
> > If this is a custom kvm-unit-tests-specific SBI implementation, then
> > we could pass in a reset_reason in the 0xE0000000 - 0xEFFFFFFF range.
> 
> That still doesn't guarantee it to succeed.
> In the exit function we can add a fallback like `sbi_shutdown(0);`,
> but reason code 1 (System failure) should always work.
> If anyone wants to use it for SBI specific codes, that's fine,
> but I only added it for the No reason and System failure exit codes.

Yup, I see now that the intention is just to say success/failure, not
pass down the actual exit code. The commit message says exit code,
though, which is why I didn't read the patch closely.

Please send a v2 with the !! change and a change to the commit message.

Thanks,
drew

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