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

[Greg Kurz <groug@kaod.org>]

On Wed, 10 Jun 2020 21:03:15 +0300
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> wrote:

> 10.06.2020 20:17, 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 |   93 +++++++++++++++++++++++++++++----------------------
> >   1 file changed, 52 insertions(+), 41 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> > index efdc0dbbcfc0..0c3d3b64a508 100644
> > --- a/hw/ppc/spapr_caps.c
> > +++ b/hw/ppc/spapr_caps.c
> > @@ -189,24 +189,24 @@ static void spapr_cap_set_pagesize(Object *obj, Visitor *v, const char *name,
> >   
> >   static void cap_htm_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       if (!val) {
> >           /* TODO: We don't support disabling htm yet */
> >           return;
> >       }
> >       if (tcg_enabled()) {
> > -        error_setg(errp,
> > -                   "No Transactional Memory support in TCG,"
> > -                   " try appending -machine cap-htm=off");
> > +        error_setg(errp, "No Transactional Memory support in TCG");
> > +        error_append_hint(errp, "Try appending -machine cap-htm=off\n");
> >       } else if (kvm_enabled() && !kvmppc_has_cap_htm()) {
> >           error_setg(errp,
> > -"KVM implementation does not support Transactional Memory,"
> > -                   " try appending -machine cap-htm=off"
> > -            );
> > +"KVM implementation does not support Transactional Memory");
> 
> Should be indented after opening '('
> 

Many error_setg() lines in this file follow the same style of tweaking
indentation to stay below the 80 character limit. I've just kept the
existing style.

> > +        error_append_hint(errp, "Try appending -machine cap-htm=off\n");
> >       }
> >   }
> >   
> >   static void cap_vsx_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> >       CPUPPCState *env = &cpu->env;
> >   
> > @@ -218,13 +218,14 @@ static void cap_vsx_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
> >        * rid of anything that doesn't do VMX */
> >       g_assert(env->insns_flags & PPC_ALTIVEC);
> >       if (!(env->insns_flags2 & PPC2_VSX)) {
> > -        error_setg(errp, "VSX support not available,"
> > -                   " try appending -machine cap-vsx=off");
> > +        error_setg(errp, "VSX support not available");
> > +        error_append_hint(errp, "Try appending -machine cap-vsx=off\n");
> >       }
> >   }
> >   
> >   static void cap_dfp_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> >       CPUPPCState *env = &cpu->env;
> >   
> > @@ -233,8 +234,8 @@ static void cap_dfp_apply(SpaprMachineState *spapr, uint8_t val, Error **errp)
> >           return;
> >       }
> >       if (!(env->insns_flags2 & PPC2_DFP)) {
> > -        error_setg(errp, "DFP support not available,"
> > -                   " try appending -machine cap-dfp=off");
> > +        error_setg(errp, "DFP support not available");
> > +        error_append_hint(errp, "Try appending -machine cap-dfp=off\n");
> >       }
> >   }
> >   
> > @@ -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;
> >       uint8_t kvm_val =  kvmppc_get_cap_safe_cache();
> >   
> > @@ -258,13 +260,14 @@ static void cap_safe_cache_apply(SpaprMachineState *spapr, uint8_t val,
> >                      cap_cfpc_possible.vals[val]);
> >       } else if (kvm_enabled() && (val > kvm_val)) {
> >           error_setg(errp,
> > -                   "Requested safe cache capability level not supported by kvm,"
> > -                   " try appending -machine cap-cfpc=%s",
> > -                   cap_cfpc_possible.vals[kvm_val]);
> > +"Requested safe cache capability level not supported by KVM");
> 
> Hmm you do this intentionally.. OK, than, it's a kind of taste.
> 

Yes, but as said above, there's precedence in this file.

I'm okay with fixing the indent. It is acceptable to have error_setg()
lines span over 80 characters for the sake of being able to grep error
strings in the code base.

> > +        error_append_hint(errp, "Try appending -machine cap-cfpc=%s\n",
> > +                          cap_cfpc_possible.vals[kvm_val]);
> >       }
> >   
> > -    if (local_err != NULL)
> > +    if (local_err != NULL) {
> >           warn_report_err(local_err);
> > +    }
> >   }
> >   
> >   SpaprCapPossible cap_sbbc_possible = {
> > @@ -277,6 +280,7 @@ SpaprCapPossible cap_sbbc_possible = {
> >   static void cap_safe_bounds_check_apply(SpaprMachineState *spapr, uint8_t val,
> >                                           Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       Error *local_err = NULL;
> >       uint8_t kvm_val =  kvmppc_get_cap_safe_bounds_check();
> >   
> > @@ -287,13 +291,14 @@ static void cap_safe_bounds_check_apply(SpaprMachineState *spapr, uint8_t val,
> >                      cap_sbbc_possible.vals[val]);
> >       } else if (kvm_enabled() && (val > kvm_val)) {
> >           error_setg(errp,
> > -"Requested safe bounds check capability level not supported by kvm,"
> > -                   " try appending -machine cap-sbbc=%s",
> > -                   cap_sbbc_possible.vals[kvm_val]);
> > +"Requested safe bounds check capability level not supported by KVM");
> > +        error_append_hint(errp, "Try appending -machine cap-sbbc=%s\n",
> > +                          cap_sbbc_possible.vals[kvm_val]);
> >       }
> >   
> > -    if (local_err != NULL)
> > +    if (local_err != NULL) {
> >           warn_report_err(local_err);
> > +    }
> >   }
> >   
> >   SpaprCapPossible cap_ibs_possible = {
> > @@ -309,6 +314,7 @@ SpaprCapPossible cap_ibs_possible = {
> >   static void cap_safe_indirect_branch_apply(SpaprMachineState *spapr,
> >                                              uint8_t val, Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       Error *local_err = NULL;
> >       uint8_t kvm_val = kvmppc_get_cap_safe_indirect_branch();
> >   
> > @@ -319,9 +325,9 @@ static void cap_safe_indirect_branch_apply(SpaprMachineState *spapr,
> >                      cap_ibs_possible.vals[val]);
> >       } else if (kvm_enabled() && (val > kvm_val)) {
> >           error_setg(errp,
> > -"Requested safe indirect branch capability level not supported by kvm,"
> > -                   " try appending -machine cap-ibs=%s",
> > -                   cap_ibs_possible.vals[kvm_val]);
> > +"Requested safe indirect branch capability level not supported by KVM");
> > +        error_append_hint(errp, "Try appending -machine cap-ibs=%s\n",
> > +                          cap_ibs_possible.vals[kvm_val]);
> >       }
> >   
> >       if (local_err != NULL) {
> > @@ -408,17 +414,17 @@ static void cap_nested_kvm_hv_apply(SpaprMachineState *spapr,
> 
> You forget to add ERRP_AUTO_PROPAGATE
> 

Oops, it's in the next patch... I've re-ordered the patches and
I simply forgot to move that hunk here. I will fix that in v2.

> >       }
> >   
> >       if (tcg_enabled()) {
> > -        error_setg(errp,
> > -                   "No Nested KVM-HV support in tcg,"
> > -                   " try appending -machine cap-nested-hv=off");
> > +        error_setg(errp, "No Nested KVM-HV support in TCG");
> > +        error_append_hint(errp, "Try appending -machine cap-nested-hv=off");
> 
> Hmm, didn't you forget '\n' ? You consistantly add it in previous hints. (I do think that it's strange that we should add it by hand, but it seems a common thing to add it)
> 

Oops indeed I forgot. Good catch ! :)

From the documentation of error_append_hint() in "qapi/error.h" :

 * May be called multiple times.  The resulting hint should end with a
 * newline.

> >       } else if (kvm_enabled()) {
> >           if (!kvmppc_has_cap_nested_kvm_hv()) {
> >               error_setg(errp,
> > -"KVM implementation does not support Nested KVM-HV,"
> > -                       " try appending -machine cap-nested-hv=off");
> > +"KVM implementation does not support Nested KVM-HV");
> > +            error_append_hint(errp, "Try appending -machine cap-nested-hv=off");
> 
> and here
> 

Oops

> >           } else if (kvmppc_set_cap_nested_kvm_hv(val) < 0) {
> > -                error_setg(errp,
> > -"Error enabling cap-nested-hv with KVM, try cap-nested-hv=off");
> > +                error_setg(errp, "Error enabling cap-nested-hv with KVM");
> > +                error_append_hint(errp,
> > +                                  "Try appending -machine cap-nested-hv=off");
> 
> and here
> 

Thanks for all the catches !

> >           }
> >       }
> >   }
> > @@ -426,6 +432,7 @@ static void cap_nested_kvm_hv_apply(SpaprMachineState *spapr,
> >   static void cap_large_decr_apply(SpaprMachineState *spapr,
> >                                    uint8_t val, Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> >       PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> >   
> > @@ -436,22 +443,23 @@ static void cap_large_decr_apply(SpaprMachineState *spapr,
> >       if (tcg_enabled()) {
> >           if (!ppc_check_compat(cpu, CPU_POWERPC_LOGICAL_3_00, 0,
> >                                 spapr->max_compat_pvr)) {
> > -            error_setg(errp,
> > -                "Large decrementer only supported on POWER9, try -cpu POWER9");
> > +            error_setg(errp, "Large decrementer only supported on POWER9");
> > +            error_append_hint(errp, "Try -cpu POWER9\n");
> >               return;
> >           }
> >       } else if (kvm_enabled()) {
> >           int kvm_nr_bits = kvmppc_get_cap_large_decr();
> >   
> >           if (!kvm_nr_bits) {
> > -            error_setg(errp,
> > -                       "No large decrementer support,"
> > -                        " try appending -machine cap-large-decr=off");
> > +            error_setg(errp, "No large decrementer support");
> > +            error_append_hint(errp,
> > +                              "Try appending -machine cap-large-decr=off\n");
> >           } else if (pcc->lrg_decr_bits != kvm_nr_bits) {
> >               error_setg(errp,
> > -"KVM large decrementer size (%d) differs to model (%d),"
> > -                " try appending -machine cap-large-decr=off",
> > -                kvm_nr_bits, pcc->lrg_decr_bits);
> > +                       "KVM large decrementer size (%d) differs to model (%d)",
> > +                       kvm_nr_bits, pcc->lrg_decr_bits);
> > +            error_append_hint(errp,
> > +                              "Try appending -machine cap-large-decr=off\n");
> >           }
> >       }
> >   }
> > @@ -460,14 +468,15 @@ static void cap_large_decr_cpu_apply(SpaprMachineState *spapr,
> >                                        PowerPCCPU *cpu,
> >                                        uint8_t val, Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       CPUPPCState *env = &cpu->env;
> >       target_ulong lpcr = env->spr[SPR_LPCR];
> >   
> >       if (kvm_enabled()) {
> >           if (kvmppc_enable_cap_large_decr(cpu, val)) {
> > -            error_setg(errp,
> > -                       "No large decrementer support,"
> > -                       " try appending -machine cap-large-decr=off");
> > +            error_setg(errp, "No large decrementer support");
> > +            error_append_hint(errp,
> > +                              "Try appending -machine cap-large-decr=off\n");
> >           }
> >       }
> >   
> > @@ -482,6 +491,7 @@ static void cap_large_decr_cpu_apply(SpaprMachineState *spapr,
> >   static void cap_ccf_assist_apply(SpaprMachineState *spapr, uint8_t val,
> >                                    Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       uint8_t kvm_val = kvmppc_get_cap_count_cache_flush_assist();
> >   
> >       if (tcg_enabled() && val) {
> > @@ -504,14 +514,15 @@ static void cap_ccf_assist_apply(SpaprMachineState *spapr, uint8_t val,
> >               return;
> >           }
> >           error_setg(errp,
> > -"Requested count cache flush assist capability level not supported by kvm,"
> > -                   " try appending -machine cap-ccf-assist=off");
> > +"Requested count cache flush assist capability level not supported by KVM");
> > +        error_append_hint(errp, "Try appending -machine cap-ccf-assist=off\n");
> >       }
> >   }
> >   
> >   static void cap_fwnmi_apply(SpaprMachineState *spapr, uint8_t val,
> >                                   Error **errp)
> >   {
> > +    ERRP_AUTO_PROPAGATE();
> >       if (!val) {
> >           return; /* Disabled by default */
> >       }
> > 
> > 
> 
>