Re: [Qemu-devel] [PATCH v2 2/4] spapr: fix error reporting in xics_system_init()

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, May 21, 2017 at 07:03:33PM +0200, Greg Kurz wrote:
> On Sat, 20 May 2017 16:45:09 +1000
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > On Fri, May 19, 2017 at 12:32:12PM +0200, Greg Kurz wrote:
> > > If the user explicitely asked for kernel-irqchip support and "xics-kvm"
> > > initialization fails, we shouldn't fallback to emulated "xics" as we
> > > do now. It is also awkward to print an error message when we have an
> > > errp pointer argument.
> > > 
> > > Let's use the errp argument to report the error and let the caller decide.
> > > This simplifies the code as we don't need a local Error * here.
> > > 
> > > Signed-off-by: Greg Kurz <groug@kaod.org>  
> > 
> > Concept looks good, but..
> > 
> > > ---
> > > v2: - total rewrite
> > > ---
> > >  hw/ppc/spapr.c |   13 ++++++-------
> > >  1 file changed, 6 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index 91f7434861a8..75e298b4c6be 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -128,18 +128,14 @@ static void xics_system_init(MachineState *machine, int nr_irqs, Error **errp)
> > >      sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
> > >  
> > >      if (kvm_enabled()) {
> > > -        Error *err = NULL;
> > > -
> > >          if (machine_kernel_irqchip_allowed(machine) &&
> > >              !xics_kvm_init(spapr, errp)) {
> > >              spapr->icp_type = TYPE_KVM_ICP;
> > > -            spapr->ics = spapr_ics_create(spapr, TYPE_ICS_KVM, nr_irqs, &err);
> > > +            spapr->ics = spapr_ics_create(spapr, TYPE_ICS_KVM, nr_irqs, errp);  
> > 
> > I believe there are reasons you're not supposed to just pass an errp
> > through to a subordinate function.  Instead you're supposed to have a
> > local Error * and use error_propagate().
> > 
> 
> You only need to have a local Error * if it is used to check the return status
> of the function (ie, you cannot check *errp because errp could be NULL) as
> described in error.h. This isn't the case here but...

Fair point; patch applied to ppc-for-2.10.

> 
> > >          }
> > >          if (machine_kernel_irqchip_required(machine) && !spapr->ics) {
> > > -            error_reportf_err(err,
> > > -                              "kernel_irqchip requested but unavailable: ");
> > > -        } else {
> > > -            error_free(err);
> > > +            error_prepend(errp, "kernel_irqchip requested but unavailable: ");
> > > +            return;
> > >          }
> > >      }
> > >  
> > > @@ -147,6 +143,9 @@ static void xics_system_init(MachineState *machine, int nr_irqs, Error **errp)
> > >          xics_spapr_init(spapr);
> > >          spapr->icp_type = TYPE_ICP;
> > >          spapr->ics = spapr_ics_create(spapr, TYPE_ICS_SIMPLE, nr_irqs, errp);
> > > +        if (!spapr->ics) {  
> > 
> > It would also be more standard to check the returned error, rather
> > than the other result.
> > 
> 
> ... if you prefer to use a local Error *, I'll gladly do that. :)
> 
> > > +            return;
> > > +        }
> > >      }
> > >  }
> > >  
> > >   
> > 
> 



-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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