Re: [PATCH v2 2/3] spapr: Use error_append_hint() in spapr_caps.c

[Greg Kurz <groug@kaod.org>]

On Thu, 11 Jun 2020 13:42:48 +0300
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> wrote:

> 11.06.2020 13:21, Vladimir Sementsov-Ogievskiy wrote:
> > 11.06.2020 13:13, Greg Kurz wrote:
> >> On Thu, 11 Jun 2020 11:50:57 +0200
> >> Laurent Vivier <lvivier@redhat.com> wrote:
> >>
> >>> On 11/06/2020 11:10, Greg Kurz wrote:
> >>>> We have a dedicated error API for hints. Use it instead of embedding
> >>>> the hint in the error message, as recommanded in the "qapi/error.h"
> >>>> header file.
> >>>>
> >>>> Since spapr_caps_apply() passes &error_fatal, all functions must
> >>>> also call the ERRP_AUTO_PROPAGATE() macro for error_append_hint()
> >>>> to be functional.
> >>>>
> >>>> While here, add some missing braces around one line statements that
> >>>> are part of the patch context. Also have cap_fwnmi_apply(), which
> >>>> already uses error_append_hint() to call ERRP_AUTO_PROPAGATE() as
> >>>> well.
> >>>>
> >>>> Signed-off-by: Greg Kurz <groug@kaod.org>
> >>>> ---
> >>>>   hw/ppc/spapr_caps.c |   95 +++++++++++++++++++++++++++++----------------------
> >>>>   1 file changed, 54 insertions(+), 41 deletions(-)
> >>>>
> >>>> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> >>>> index efdc0dbbcfc0..2cb7ba8f005a 100644
> >>>> --- a/hw/ppc/spapr_caps.c
> >>>> +++ b/hw/ppc/spapr_caps.c
> >>> ...
> >>>> @@ -248,6 +249,7 @@ SpaprCapPossible cap_cfpc_possible = {
> >>>>   static void cap_safe_cache_apply(SpaprMachineState *spapr, uint8_t val,
> >>>>                                    Error **errp)
> >>>>   {
> >>>> +    ERRP_AUTO_PROPAGATE();
> >>>>       Error *local_err = NULL;
> >>>
> >>> I think you should rename it, something like "local_warn" to not be
> >>> confused with the _auto_errp_prop.local_err...
> >>>
> >>> or don't use ERRP_AUTO_PROPAGE(), use the local_err instead and move the
> >>> warning inside the braces of the if.
> >>>
> >>> Same comment for cap_safe_bounds_check_apply() and
> >>> cap_safe_indirect_branch_apply()
> >>>
> >>
> >> Hmm... local_err isn't useful actually. It looks like we just want
> >> to call warn_report() directly instead of error_setg(&local_err)
> >> and warn_report_err(local_err). I'll post a v3.
> > 
> > something like this I think:
> > 
> > --- a/hw/ppc/spapr_caps.c
> > +++ b/hw/ppc/spapr_caps.c
> > @@ -250,24 +250,23 @@ static void cap_safe_cache_apply(SpaprMachineState *spapr, uint8_t val,
> >                                    Error **errp)
> >   {
> >       ERRP_AUTO_PROPAGATE();
> > -    Error *local_err = NULL;
> >       uint8_t kvm_val =  kvmppc_get_cap_safe_cache();
> > 
> >       if (tcg_enabled() && val) {
> >           /* TCG only supports broken, allow other values and print a warning */
> > -        error_setg(&local_err,
> > +        error_setg(errp,
> >                      "TCG doesn't support requested feature, cap-cfpc=%s",
> >                      cap_cfpc_possible.vals[val]);
> > +        if (*errp) {
> > +            warn_report_err(*errp);
> > +            *errp = NULL;
> > +        }
> 
> what a stupid code :) at least, if condition is always true.
> 
> this all should be substitute by just
> 
> 	warn_report("TCG doesn't support requested feature, cap-cfpc=%s", cap_cfpc_possible.vals[val]);
> 

Exactly ! :)

> 
> >       } else if (kvm_enabled() && (val > kvm_val)) {
> >           error_setg(errp,
> >                      "Requested safe cache capability level not supported by KVM");
> >           error_append_hint(errp, "Try appending -machine cap-cfpc=%s\n",
> >                             cap_cfpc_possible.vals[kvm_val]);
> >       }
> > -
> > -    if (local_err != NULL) {
> > -        warn_report_err(local_err);
> > -    }
> >   }
> > 
> > 
> > Or, we need to implement warn_report_errp() function, as I proposed in earlier version of auto-propagation series.
> > 
> > =====
> > 
> > side idea: what if we make Error to be some kind of enum of pointer-to-pointer and pointer-to-function?
> > 
> > Than, instead of passing pointers to error_abort and error_fatal as special casing, we'll pass pointers to functions,
> > which do appropriate handling of error. And we'll be able to pass warn_report function. Not about this patch set,
> > but seems interesting, isn't it?
> > 
> 
>