On Fri, May 03, 2024 at 01:39:32PM GMT, Aleksei Filippov wrote:
>
>
> 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.filip...@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.
Legacy SBI calls like SBI_EXT_0_1_CONSOLE_GETCHAR don't return a struct
sbiret, they only return a function-specific long. The spec says for
Getchar that it returns "...the byte on success, or -1 for failure."
So we should explicitly set failure to -1, especially since
SBI_ERR_FAILURE isn't defined for legacy SBI calls.
Thanks,
drew
> --
> 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
> > > >
