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

[Gavin Shan]

On 12/8/19 3:51 AM, Greg Kurz wrote:
> On Sat, 7 Dec 2019 23:56:55 +1100
> Gavin Shan <address@hidden> wrote:
>
> > On 12/7/19 3:58 AM, Greg Kurz wrote:
> > > On Fri,  6 Dec 2019 17:33:37 +1100
> > > Gavin Shan <address@hidden> 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 <address@hidden>
> > > > ---
> > > >    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