Re: [Qemu-devel] [PATCH 06/10] target-i386: print obsolete warnings if +-features are used

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 7 Jun 2016 13:44:58 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 06/06/2016 17:16, Igor Mammedov wrote:
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> >  target-i386/cpu.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index f791a06..31e5e6f 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -1975,6 +1975,9 @@ static void x86_cpu_parse_featurestr(CPUState *cs, char *features,
> >                  error_propagate(errp, local_err);
> >                  return;
> >              }
> > +            fprintf(stderr,
> > +                "'+%s' is obsolete and will be removed in future, use '%s=on'",
> > +                featurestr + 1, featurestr + 1);  
> 
> Could you detect using +foo together with foo=off, and -foo together
> with foo=on?  Those are the really problematic cases, without them +foo
> and -foo can become synonyms for =on and =off.
That's (legacy)current semantic of -cpu +-foo where it overrides any foo=x,
potentially it's possible to track foo=x locally in parser
and then compare with +-foo both ways.
But all we can do currently is to print warning about such use case.

I think Eduardo's suggestion to just warn that +-foo is obsolete for now
and drop support for it in several releases is sufficient(good) enough.

> Paolo
> 
> >              continue;
> >          } else if (featurestr[0] == '-') {
> >              add_flagname_to_bitmaps(featurestr + 1, minus_features, &local_err);
> > @@ -1982,6 +1985,9 @@ static void x86_cpu_parse_featurestr(CPUState *cs, char *features,
> >                  error_propagate(errp, local_err);
> >                  return;
> >              }
> > +            fprintf(stderr,
> > +                "'-%s' is obsolete and will be removed in future, use '%s=off'",
> > +                featurestr + 1, featurestr + 1);
> >              continue;
> >          }
> >  
> >