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

[Vladimir Sementsov-Ogievskiy]

11.06.2020 13:39, Greg Kurz wrote:
> On Thu, 11 Jun 2020 13:21:51 +0300
> Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> 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:
>
> Not even that... we have one path (KVM) that directly
> uses errp and the other path (TCG) that does:
>
> Error *local_err = NULL;
>
> error_setg(&local_err, ...);
>
> if (local_err) {
>      warn_report_err(local_err);
> }
>
> It really looks like we just want to call warn_report().

yes, I also came this)

> > --- 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;
> > +        }
> >        } 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?


--
Best regards,
Vladimir