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

[Aleksei Filippov <alexei.filippov@syntacore.com>]

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
>>>