Re: [Qemu-devel] [PATCH v2] numa: clarify error message when node index is out of range in -numa dist, ...

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> On 05/15/2018 10:26 AM, Andrew Jones wrote:
>> On Tue, May 15, 2018 at 04:48:33PM +0200, Igor Mammedov wrote:
>>> When using following CLI:
>>>    -numa dist,src=128,dst=1,val=20
>>> user gets a rather confusing error message:
>>>     "Invalid node 128, max possible could be 128"
>>>
>>> Where 128 is number of nodes that QEMU supports (MAX_NODES),
>>> while src/dst is an index up to that limit, so it should be
>>> MAX_NODES - 1 in error message.
>>> Make error message to explicitly state valid range for node
>>> index to be more clear.
>>>
>>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>>> Reviewed-by: Andrew Jones <drjones@redhat.com>
>>> ---
>
>>>       if (src >= MAX_NODES || dst >= MAX_NODES) {
>>>           error_setg(errp,
>>> -                   "Invalid node %d, max possible could be %d",
>>> -                   MAX(src, dst), MAX_NODES);
>>> +                   "Invalid node %d, The valid node range is [0 - %d]",
>>                                        ^ should be a '.'
>>
>> And maybe need a '.' at the end of the second sentence too, as it's not
>> an error phrase, but a real sentence.
>>
>>> +                   MAX(src, dst), MAX_NODES - 1);
>>>          return;
>>>      }
>
> Actually, error_setg() is documented as taking a single phrase (no '.'
> included), and that if you need a second sentence, it's better to use
> error_append_hint().

Correct.  Providing help on valid values is exactly what
error_append_hint() is for.

>                       Maybe Markus has an opinion on the best way to
> word this error message.

Yes: "Parameter 'src' expects an integer between 0 and 127"

Referring to an erroneous key=value by value is not nice.  What if the
value occurs in multiple places, and is valid in at least one?  key is
there, it's unique[*], so use it.


[*] Except in the few places that use repeated keys to form lists.  Ugh.