Re: [PATCH] exec: Remove the duplicated check in parse_cpu_option()

[Gavin Shan <gshan@redhat.com>]

On 12/8/19 3:51 AM, Greg Kurz wrote:
> On Sat, 7 Dec 2019 23:56:55 +1100
> Gavin Shan <gshan@redhat.com> wrote:
> 
>> On 12/7/19 3:58 AM, Greg Kurz wrote:
>>> On Fri,  6 Dec 2019 17:33:37 +1100
>>> Gavin Shan <gshan@redhat.com> wrote:
>>>
>>>> The @cpu_option shouldn't be NULL, otherwise assertion from g_strsplit()
>>>> should be raised as below message indicates. So it's meaningless to validate
>>>> @model_pices[0] in parse_cpu_option() as it shouldn't be NULL either.
>>>>
>>>>      qemu-system-aarch64: GLib: g_strsplit: assertion 'string != NULL' failed
>>>>
>>>> This just removes the check and unused message.
>>>>
>>>
>>> Hrm... the check isn't about @cpu_option being NULL. It is about filtering out
>>> invalid syntaxes like:
>>>
>>> -cpu ''
>>>
>>> or
>>>
>>> -cpu ,some-prop
>>>
>>
>> Greg, Thanks for your review on this trivial patch.
>>
>> @cpu_option[0] is NULL when we have "-cpu ''". We run into assertion raised
>> by subsequent cpu_class_by_name(). However, @cpu_option[0] isn't NULL with
>> something like "-cpu ,xxx", but the CPU model specific class can't be found
>> at last.
>>
> 
> You're right, the case with a leading ',' is caught by the other check.
> 
>> So the validation mostly relies on cpu_class_by_name() if I'm correct. It's
>> fine to remove the check. However, it provides explicit error message, which
>> isn't bad though:
>>
>>      error_report("-cpu option cannot be empty");
>>
> 
> It's definitely not fine to remove an error message that clearly explains
> to the user what he has done wrong in favor of QEMU aborting and printing
> something cryptic like:
> 
>      cpu_class_by_name: Assertion `cpu_model && cc->class_by_name' failed.
> 
> Assertions are for bugs, not for bad command line usage.
> 

Yes, Agree as explained previously. The explicit message is a bonus at least.
So please ignore this trivial patch and sorry for the noise.

>>>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>>>> ---
>>>>    exec.c | 5 -----
>>>>    1 file changed, 5 deletions(-)
>>>>
>>>> diff --git a/exec.c b/exec.c
>>>> index ffdb518535..3cff459e43 100644
>>>> --- a/exec.c
>>>> +++ b/exec.c
>>>> @@ -963,11 +963,6 @@ const char *parse_cpu_option(const char *cpu_option)
>>>>        const char *cpu_type;
>>>>    
>>>>        model_pieces = g_strsplit(cpu_option, ",", 2);
>>>> -    if (!model_pieces[0]) {
>>>> -        error_report("-cpu option cannot be empty");
>>>> -        exit(1);
>>>> -    }
>>>> -
>>>>        oc = cpu_class_by_name(CPU_RESOLVING_TYPE, model_pieces[0]);
>>>>        if (oc == NULL) {
>>>>            error_report("unable to find CPU model '%s'", model_pieces[0]);
>>>

Regards,
Gavin