Re: [PATCH v4] target/riscv/kvm/kvm-cpu.c: kvm_riscv_handle_sbi() fail with vendor-specific SBI

[Alistair Francis]

On Sat, Apr 13, 2024 at 9:26 PM Alexei Filippov
<alexei.filippov@syntacore.com> wrote:
>
> kvm_riscv_handle_sbi() may return not supported return code to not trigger
> qemu abort with vendor-specific sbi.
>
> 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")
> ---
>
> Changes since v3:
>         -Clear Reviewed-by tags
>  target/riscv/kvm/kvm-cpu.c         | 13 +++++--------
>  target/riscv/sbi_ecall_interface.h | 12 ++++++++++++
>  2 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
> index 6a6c6cae80..844942d9ba 100644
> --- a/target/riscv/kvm/kvm-cpu.c
> +++ b/target/riscv/kvm/kvm-cpu.c
> @@ -1392,7 +1392,6 @@ bool kvm_arch_stop_on_emulation_error(CPUState *cs)
>
>  static int kvm_riscv_handle_sbi(CPUState *cs, struct kvm_run *run)
>  {
> -    int ret = 0;
>      unsigned char ch;
>      switch (run->riscv_sbi.extension_id) {
>      case SBI_EXT_0_1_CONSOLE_PUTCHAR:
> @@ -1400,22 +1399,20 @@ static int kvm_riscv_handle_sbi(CPUState *cs, struct 
> kvm_run *run)
>          qemu_chr_fe_write(serial_hd(0)->be, &ch, sizeof(ch));
>          break;
>      case SBI_EXT_0_1_CONSOLE_GETCHAR:
> -        ret = qemu_chr_fe_read_all(serial_hd(0)->be, &ch, sizeof(ch));
> -        if (ret == sizeof(ch)) {
> +        if (qemu_chr_fe_read_all(serial_hd(0)->be, &ch, sizeof(ch)) == 
> sizeof(ch)) {
>              run->riscv_sbi.ret[0] = ch;
>          } else {
> -            run->riscv_sbi.ret[0] = -1;
> +            run->riscv_sbi.ret[0] = SBI_ERR_FAILURE;

I'm not sure I follow. This seems like a failure but we report success
to the caller of this function?

Can you expand the commit message to explain why we want this change

Alistair

>          }
> -        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;
> +    return 0;
>  }
>
>  int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
> 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
>
>