Re: [PATCH v6] target/riscv/kvm/kvm-cpu.c: kvm_riscv_handle_sbi() fail with vendor-specific SBI

[Aleksei Filippov]

On 25.04.2024 12:21, Andrew Jones wrote:
> On Mon, Apr 22, 2024 at 02:31:36PM +0200, Andrew Jones wrote:
> > On Mon, Apr 22, 2024 at 02:42:54PM +0300, Alexei Filippov wrote:
> > > kvm_riscv_handle_sbi() may return not supported return code to not
> > > trigger qemu abort with vendor-specific sbi.
> > >
> > > Add new error path to provide proper error in case of
> > > qemu_chr_fe_read_all() may not return sizeof(ch).
> >
> > I think something more along the lines of what I wrote in my previous
> > reply will help clarify this more. Here's what I wrote
> >
> > """
> > Exactly zero just means we failed to read input, which can happen, so
> > telling the SBI caller we failed to read, but telling the caller of this
> > function that we successfully emulated the SBI call, is correct. However,
> > anything else, other than sizeof(ch), means something unexpected happened,
> > so we should indeed return an error from this function.
> > """
> >
> > Thanks,
> > drew
> >
> > > Added SBI related return code's defines.
> > >
> > > Signed-off-by: Alexei Filippov <alexei.filippov@syntacore.com>
> > > ---
> > > Changes since v4-5:
> > >                 -Added new error path in case of qemu_chr_fe_read_all() may not
> > >                 return sizeof(ch).
> > >                 -Added more comments in commit message.
> > >   target/riscv/kvm/kvm-cpu.c         | 10 ++++++----
> > >   target/riscv/sbi_ecall_interface.h | 12 ++++++++++++
> > >   2 files changed, 18 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
> > > index f9dbc18a76..5bb7b74d03 100644
> > > --- a/target/riscv/kvm/kvm-cpu.c
> > > +++ b/target/riscv/kvm/kvm-cpu.c
> > > @@ -1173,16 +1173,18 @@ static int kvm_riscv_handle_sbi(CPUState *cs, struct 
> > > kvm_run *run)
> > >           ret = qemu_chr_fe_read_all(serial_hd(0)->be, &ch, sizeof(ch));
> > >           if (ret == sizeof(ch)) {
> > >               run->riscv_sbi.ret[0] = ch;
> > > +            ret = 0;
> > > +        } else if (ret == 0) {
> > > +            run->riscv_sbi.ret[0] = SBI_ERR_FAILURE;
>
> I'd prefer we still explicitly assign ret[0] to -1 here since that's what
> the spec explicitly says.
>
> Thanks,
> drew

Can you please explain it a little bit more, cz I believe SBI_ERR_FAILURE is -1 
anyway. Defines was added at first place just to came along with Linux kernel 
SBI related defines.
--
Sincerely,
Aleksei Filippov

> > >           } else {
> > > -            run->riscv_sbi.ret[0] = -1;
> > > +            ret = -1;
> > >           }
> > > -        ret = 0;
> > >           break;
> > >       default:
> > >           qemu_log_mask(LOG_UNIMP,
> > > -                      "%s: un-handled SBI EXIT, specific reasons is %lu\n",
> > > +                      "%s: Unhandled SBI exit with extension-id %lu\n"
> > >                         __func__, run->riscv_sbi.extension_id);
> > > -        ret = -1;
> > > +        run->riscv_sbi.ret[0] = SBI_ERR_NOT_SUPPORTED;
> > >           break;
> > >       }
> > >       return ret;
> > > diff --git a/target/riscv/sbi_ecall_interface.h 
> > > b/target/riscv/sbi_ecall_interface.h
> > > index 43899d08f6..a2e21d9b8c 100644
> > > --- a/target/riscv/sbi_ecall_interface.h
> > > +++ b/target/riscv/sbi_ecall_interface.h
> > > @@ -69,4 +69,16 @@
> > >   #define SBI_EXT_VENDOR_END              0x09FFFFFF
> > >   /* clang-format on */
> > >   
> > > +/* SBI return error codes */
> > > +#define SBI_SUCCESS                  0
> > > +#define SBI_ERR_FAILURE             -1
> > > +#define SBI_ERR_NOT_SUPPORTED       -2
> > > +#define SBI_ERR_INVALID_PARAM       -3
> > > +#define SBI_ERR_DENIED              -4
> > > +#define SBI_ERR_INVALID_ADDRESS     -5
> > > +#define SBI_ERR_ALREADY_AVAILABLE   -6
> > > +#define SBI_ERR_ALREADY_STARTED     -7
> > > +#define SBI_ERR_ALREADY_STOPPED     -8
> > > +#define SBI_ERR_NO_SHMEM            -9
> > > +
> > >   #endif
> > > --
> > > 2.34.1