Re: [Qemu-devel] [PATCH v2 1/2] vl: don't use RUN_STATE_PRECONFIG as initial state

[Igor Mammedov]

On Tue, 5 Jun 2018 09:01:09 -0300
Eduardo Habkost <address@hidden> wrote:

> On Tue, Jun 05, 2018 at 10:37:55AM +0200, Igor Mammedov wrote:
> > On Mon, 4 Jun 2018 21:56:47 -0300
> > Eduardo Habkost <address@hidden> wrote:  
> > > On Mon, Jun 04, 2018 at 04:21:47PM +0200, Michal Privoznik wrote:
> > > [...]  
> > > > > @@ -3572,7 +3570,12 @@ int main(int argc, char **argv, char **envp)
> > > > >                  }
> > > > >                  break;
> > > > >              case QEMU_OPTION_preconfig:
> > > > > -                preconfig_exit_requested = false;
> > > > > +                if (!runstate_check(RUN_STATE_NONE)) {
> > > > > +                    error_report("'--preconfig' and '--incoming' 
> > > > > options are "
> > > > > +                                 "mutually exclusive");
> > > > > +                    exit(EXIT_FAILURE);
> > > > > +                }
> > > > > +                runstate_set(RUN_STATE_PRECONFIG);    
> > > > 
> > > > Specifying --preconfig twice on the command line now fails with a very
> > > > cryptic message (there's no --incoming).
> > > >     
> > > > >                  break;
> > > > >              case QEMU_OPTION_enable_kvm:
> > > > >                  olist = qemu_find_opts("machine");
> > > > > @@ -3768,9 +3771,12 @@ int main(int argc, char **argv, char **envp)
> > > > >                  }
> > > > >                  break;
> > > > >              case QEMU_OPTION_incoming:
> > > > > -                if (!incoming) {
> > > > > -                    runstate_set(RUN_STATE_INMIGRATE);
> > > > > +                if (!runstate_check(RUN_STATE_NONE)) {
> > > > > +                    error_report("'--preconfig' and '--incoming' 
> > > > > options are "
> > > > > +                                 "mutually exclusive");
> > > > > +                    exit(EXIT_FAILURE);
> > > > >                  }
> > > > > +                runstate_set(RUN_STATE_INMIGRATE);    
> > > > 
> > > > Same here. Specifying --incoming twice fails with cryptic message. But
> > > > one can argue that specifying --incoming twice is wrong anyway.
> > > >     
> > > 
> > > Initially I was going to suggest simply not changing runstate
> > > during option parsing to avoid this kind of problem, but maybe
> > > this would be a nice way to implement the command-line parsing
> > > rules:  
> > Is there a big reason to try making early incoming transition hack nicer?
> > I'd rather leave it as it is for now and fix it properly later
> > (i.e. postponing the transition after machine_done point, which is on my
> > todo list).  
> 
> Yeah, I'm not sure we want go towards encoding more knowledge in
> the state machine, or keeping the system simple and encoding the
> rules in more straightforward code+variables inside main().
I've tried before to use code+variables for preconfig checks without
introducing a new runstate and it turned out difficult to manage
and the later changes often broke it. With new runstate end result
was much cleaner.

> 
> > > 
> > >     case QEMU_OPTION_preconfig:
> > >         /*
> > >          * A INCOMING -> PRECONFIG transition would call:
> > >          *   error_setg("--preconfig and --incoming options are mutually 
> > > exclusive");
> > >          */
> > >         try_runstate_set(RUN_STATE_PRECONFIG, &error_fatal);
> > >         break;
> > >     case QEMU_OPTION_incoming:
> > >         /*
> > >          * A PRECONFIG -> INCOMING transition would also call:
> > >          *   error_setg("--preconfig and --incoming options are mutually 
> > > exclusive");
> > >          *
> > >          * Maybe a INCOMING -> INCOMING transition could
> > >          * result in:
> > >          *   error_setg("--incoming can't be specified twice");
> > >          */
> > >         try_runstate_set(RUN_STATE_INMIGRATE, &error_fatal);
> > >         break;
> > > 
> > >   
> > > > >                  incoming = optarg;
> > > > >                  break;
> > > > >              case QEMU_OPTION_only_migratable:    
> > > > 
> > > > Michal
> > > >     
> > >   
> >   
>