Re: [Qemu-devel] [PATCH 02/11] pseries: Cleanup error handling of spapr_cpu_init()

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

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On Fri, Dec 11, 2015 at 07:54:48AM -0700, Eric Blake wrote:
> On 12/10/2015 05:11 PM, David Gibson wrote:
> > Currently spapr_cpu_init() is hardcoded to handle any errors as fatal.
> > That works for now, since it's only called from initial setup where an
> > error here means we really can't proceed.
> > 
> > However, we'll want to handle this more flexibly for cpu hotplug in future
> > so generalize this using the error reporting infrastructure.  While we're
> > at it make a small cleanup in a related part of ppc_spapr_init() to use
> > the error infrastructure instead of an old-style explicit fprintf / exit.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/ppc/spapr.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> > @@ -1633,7 +1634,7 @@ static void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu)
> >      }
> >  
> >      if (cpu->max_compat) {
> > -        ppc_set_compat(cpu, cpu->max_compat, &error_fatal);
> > +        ppc_set_compat(cpu, cpu->max_compat, errp);
> >      }
> >  
> >      xics_cpu_setup(spapr->icp, cpu);
> 
> Pre-patch: you can't reach the xics_cpu_setup() call on error.
> 
> Post-patch: depending on what the caller passed in, you can fall through
> to xics_cpu_setup() with a potentially incomplete cpu.
> 
> I think a more robust solution is probably along the lines of:
> 
> Error *err = NULL;
> if (cpu->max_compat) {
>     ppc_set_compat(cpu, cpu->max_compat, &err);
>     if (err) {
>         error_propagate(errp, err);
>         return;
>     }
> }
> xics_cpu_setup(spapr_icp, cpu);

Yes, good point.  I _think_ xics_cpu_setup() would be safe to call
even if ppc_set_compat() fails, but checking for the error immediately
is safer indeed.  I'll adjust in the next spin.

-- 
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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