Re: [PATCH v2 1/6] x86/tdx: Add TDREPORT TDX Module call support

[Hans de Goede]

Hi,

On 7/8/21 4:07 PM, Kuppuswamy, Sathyanarayanan wrote:
> 
> 
> On 7/8/21 1:16 AM, Xiaoyao Li wrote:
>>
>> Sorry I guess I didn't state it clearly during internal review.
>>
>> I suggest something like this
>>
>> if (ret != TDCALL_SUCCESS) {
>>      if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
>>          return -EINVAL;
>>      else if (TDCALL_RETURN_CODE(ret) == TDCALL_OPERAND_BUSY)
>>          return -EBUSY;
>>      else
>>          return -EFAULT; //I'm not sure if -EFAULT is proper.
>> }
> 
> As per current spec, TDCALL_INVALID_OPERAND, TDCALL_OPERAND_BUSY and
> 0 are the only possible return values. So I have checked for failure case
> in if condition and returned success by default. Any reason for specifically
> checking for success code ?

Yes, new error codes might be introduced and you might forget to
update this (or other) checks.

Checking for errors really MUST always be done by checking for
ret != success (typically ret != 0 or ret < 0).

Only checking for known error codes means that if somehow an
unknown error code gets thrown this gets treated as success,
which is not acceptable behavior.

Regards,

Hans