Re: [XEN PATCH for-4.14] tools/xen-ucode: fix error code propagation of microcode load operation

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

On 12/06/2020 17:53, Ian Jackson wrote:
> Igor Druzhinin writes ("[PATCH] tools/xen-ucode: fix error code propagation 
> of microcode load operation"):
>> Otherwise it's impossible to know the reason for a fault or blob rejection
>> inside the automation.
> ...
>>          fprintf(stderr, "Failed to update microcode. (err: %s)\n",
>>                  strerror(errno));
> 
> This part is fine.
> 
>> +        ret = errno;
>>      xc_interface_close(xch);
> ...
>>      }
>>      close(fd);
>>  
>> -    return 0;
>> +    return ret;
> 
> Unfortunately I don't think this is right.  errno might not fit into a
> return value.

errno codes that Xen return are all lower than 127. It fits perfectly fine.

> Returning nonzero on microcode loading error would
> definitely be right, but ...
> 
> ... oh I have just read the rest of this file.
> 
> I think what is missing here is simply `return errno' (and the braces)
> There is no need to call xc_interface_close, or munmap, if we are
> about to exit.

Probably but that is identical to what was suggested.
Cleaning resource is just a nice thing to do although unnecessary.
Can change to just "return errno" if that's what you'd prefer.

> I think fixing the lost error return is 4.14 material, so I have
> added that to the subject line.
> 
> Paul, would you Release-ack a patch that replaced every `return errno'
> with (say) exit(12) ? 

That would again conceal real return code from automation.

Igor