Re: [PATCH v9] target/riscv/kvm/kvm-cpu.c: kvm_riscv_handle_sbi() fail with vendor-specific SBI

[Andrew Jones <ajones@ventanamicro.com>]

On Wed, Sep 18, 2024 at 04:37:12PM GMT, Aleksei Filippov wrote:
> 
> 
> On 17.09.2024 16:10, Andrew Jones wrote:
> > On Tue, Sep 17, 2024 at 02:29:41PM GMT, Andrew Jones wrote:
> > > On Tue, Sep 17, 2024 at 02:54:33PM GMT, 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), because 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 return an error.
> > > > 
> > > > Added SBI related return code's defines.
> > > > 
> > > > Signed-off-by: Alexei Filippov <alexei.filippov@syntacore.com>
> > > > Fixes: 4eb47125 ("target/riscv: Handle KVM_EXIT_RISCV_SBI exit")
> > > 
> > > Fixes tag goes above s-o-b and 8 hex digits is a bit small. Most
> > > commit references in QEMU are using 10 or 12 digits.
> > > 
> > > > ---
> > > >   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 f6e3156b8d..9f2ca67c9f 100644
> > > > --- a/target/riscv/kvm/kvm-cpu.c
> > > > +++ b/target/riscv/kvm/kvm-cpu.c
> > > > @@ -1517,19 +1517,21 @@ 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;
> > > > -        } else {
> > > > +            ret = 0;
> > > > +        } else if (ret == 0) {
> > > >               run->riscv_sbi.ret[0] = -1;
> > > > +        } else {
> > > > +            ret = -1;
> > > >           }
> > > > -        ret = 0;
> > > 
> > > Looks good!
> > > 
> > > >           break;
> > > >       case SBI_EXT_DBCN:
> > > >           kvm_riscv_handle_sbi_dbcn(cs, run);
> > > >           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;
> > > 
> > > This, along with the addition of the SBI_* defines below, should be a
> > > separate patch. If we were just naming the -1, then I wouldn't mind it
> > > slipping in with the same patch, but this is changing behavior since
> > > SBI_ERR_NOT_SUPPORTED is -2. I agree with the change, though, it just
> > > needs to be a separate patch. And the separate patch should have the
> > > same Fixes tag.
> > > 
> > 
> > Actually it's even more of a difference than s/-1/-2/ since we're no long
> > aborting the SBI call, but returning non-supported instead.
> 
> I agreed, I'll split commits, but do you want me to resend patch as 2 patch
> series or 2 separate patches?

Either way is fine by me.

Thanks,
drew