diff mbox series

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

Message ID 159186660024.48605.6756496231687601694.stgit@bahia.lan (mailing list archive)
State New, archived
Headers show
Series spapr: Improve error reporting in spapr_caps.c | expand

Commit Message

Greg Kurz June 11, 2020, 9:10 a.m. UTC
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(-)

Comments

Vladimir Sementsov-Ogievskiy June 11, 2020, 9:47 a.m. UTC | #1
11.06.2020 12:10, 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>

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Laurent Vivier June 11, 2020, 9:50 a.m. UTC | #2
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()

>      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");
> +        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 = {

Thanks,
Laurent
Greg Kurz June 11, 2020, 10:13 a.m. UTC | #3
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.

> >      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");
> > +        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 = {
> 
> Thanks,
> Laurent
>
Vladimir Sementsov-Ogievskiy June 11, 2020, 10:21 a.m. UTC | #4
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;
+        }
      } 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?
Vladimir Sementsov-Ogievskiy June 11, 2020, 10:30 a.m. UTC | #5
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;
> +        }
>       } 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?

union I mean of course

> 
> 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?
>
Greg Kurz June 11, 2020, 10:39 a.m. UTC | #6
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().

> --- 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?
>
Vladimir Sementsov-Ogievskiy June 11, 2020, 10:42 a.m. UTC | #7
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]);


>       } 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?
>
Greg Kurz June 11, 2020, 10:44 a.m. UTC | #8
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?
> > 
> 
>
Vladimir Sementsov-Ogievskiy June 11, 2020, 10:44 a.m. UTC | #9
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?
>>
>
Vladimir Sementsov-Ogievskiy June 11, 2020, 10:48 a.m. UTC | #10
11.06.2020 13:44, Vladimir Sementsov-Ogievskiy wrote:
> 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?
>>>
>>
> 

Just for record: probably, we'll want at lest something like this (not needed in this series):

diff --git a/include/qapi/error.h b/include/qapi/error.h
index 30140d9bfe..25b5da0733 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -475,4 +475,10 @@ extern Error *error_abort;
   */
  extern Error *error_fatal;
  
+/*
+ * Special error destination to call warn_report_err.
+ * See error_setg() and error_propagate() for details.
+ */
+extern Error *error_warn_report;
+
  #endif
diff --git a/util/error.c b/util/error.c
index b6c89d1412..928eb4cc7a 100644
--- a/util/error.c
+++ b/util/error.c
@@ -27,8 +27,9 @@ struct Error
  
  Error *error_abort;
  Error *error_fatal;
+Error *error_warn_report;
  
-static void error_handle_fatal(Error **errp, Error *err)
+static bool error_handle_special(Error **errp, Error *err)
  {
      if (errp == &error_abort) {
          fprintf(stderr, "Unexpected error in %s() at %s:%d:\n",
@@ -43,6 +44,12 @@ static void error_handle_fatal(Error **errp, Error *err)
          error_report_err(err);
          exit(1);
      }
+    if (errp == &error_warn_report) {
+        warn_report_err(err);
+        return true;
+    }
+
+    return false;
  }
  
  static void error_setv(Error **errp,
@@ -70,8 +77,9 @@ static void error_setv(Error **errp,
      err->line = line;
      err->func = func;
  
-    error_handle_fatal(errp, err);
-    *errp = err;
+    if (!error_handle_special(errp, err)) {
+        *errp = err;
+    }
  
      errno = saved_errno;
  }
@@ -283,7 +291,9 @@ void error_propagate(Error **dst_errp, Error *local_err)
      if (!local_err) {
          return;
      }
-    error_handle_fatal(dst_errp, local_err);
+    if (error_handle_special(dst_errp, local_err)) {
+        return;
+    }
      if (dst_errp && !*dst_errp) {
          *dst_errp = local_err;
      } else {
Laurent Vivier June 11, 2020, 12:36 p.m. UTC | #11
On 11/06/2020 12:44, Greg Kurz wrote:
> 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 ! :)
> 

Yes, it seems appropriate.

Thanks,
Laurent
diff mbox series

Patch

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
@@ -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");
+        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");
+        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) {
@@ -402,23 +408,25 @@  static void cap_hpt_maxpagesize_cpu_apply(SpaprMachineState *spapr,
 static void cap_nested_kvm_hv_apply(SpaprMachineState *spapr,
                                     uint8_t val, Error **errp)
 {
+    ERRP_AUTO_PROPAGATE();
     if (!val) {
         /* capability disabled by default */
         return;
     }
 
     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\n");
     } 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\n");
         } 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\n");
         }
     }
 }
@@ -426,6 +434,7 @@  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 +445,23 @@  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 +470,15 @@  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 +493,7 @@  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 +516,15 @@  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 */
     }