Re: [PATCH for-6.0 5/9] spapr: Simplify error path of spapr_core_plug()

[Greg Kurz <groug@kaod.org>]

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On Mon, 23 Nov 2020 16:13:18 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Sat, Nov 21, 2020 at 12:42:04AM +0100, Greg Kurz wrote:
> > spapr_core_pre_plug() already guarantees that the slot for the given core
> > ID is available. It is thus safe to assume that spapr_find_cpu_slot()
> > returns a slot during plug. Turn the error path into an assertion.
> > It is also safe to assume that no device is attached to the corresponding
> > DRC and that spapr_drc_attach() shouldn't fail.
> > 
> > Pass &error_abort to spapr_drc_attach() and simplify error handling.
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>
> 
> Applied to ppc-for-6.0, thanks.
> 

This patch depends on the previous one.

> > ---
> >  hw/ppc/spapr.c | 21 ++++++++++-----------
> >  1 file changed, 10 insertions(+), 11 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index da7586f548df..cfca033c7b14 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -3739,8 +3739,7 @@ int spapr_core_dt_populate(SpaprDrc *drc, SpaprMachineState *spapr,
> >      return 0;
> >  }
> >  
> > -static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> > -                            Error **errp)

../../hw/ppc/spapr.c: In function ‘spapr_core_plug’:
../../hw/ppc/spapr.c:3802:32: error: ‘errp’ undeclared (first use in this function); did you mean ‘errno’?
                                errp) < 0) {
                                ^~~~
                                errno
../../hw/ppc/spapr.c:3802:32: note: each undeclared identifier is reported only once for each function it appears in

Please either drop it from ppc-for-6.0 or possibly adapt spapr_core_plug()
to handle errors from ppc_set_compat().

<my 2 cents>
Since I can't see how this could fail for a hotplugged CPU if it
succeeded for the boot CPU, I'd pass &error_abort despite this
being a hotplug path.
</my 2 cents>

> > +static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev)
> >  {
> >      SpaprMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
> >      MachineClass *mc = MACHINE_GET_CLASS(spapr);
> > @@ -3755,20 +3754,20 @@ static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >      int i;
> >  
> >      core_slot = spapr_find_cpu_slot(MACHINE(hotplug_dev), cc->core_id, &index);
> > -    if (!core_slot) {
> > -        error_setg(errp, "Unable to find CPU core with core-id: %d",
> > -                   cc->core_id);
> > -        return;
> > -    }
> > +    g_assert(core_slot); /* Already checked in spapr_core_pre_plug() */
> > +
> >      drc = spapr_drc_by_id(TYPE_SPAPR_DRC_CPU,
> >                            spapr_vcpu_id(spapr, cc->core_id));
> >  
> >      g_assert(drc || !mc->has_hotpluggable_cpus);
> >  
> >      if (drc) {
> > -        if (!spapr_drc_attach(drc, dev, errp)) {
> > -            return;
> > -        }
> > +        /*
> > +         * spapr_core_pre_plug() already buys us this is a brand new
> > +         * core being plugged into a free slot. Nothing should already
> > +         * be attached to the corresponding DRC.
> > +         */
> > +        spapr_drc_attach(drc, dev, &error_abort);
> >  
> >          if (hotplugged) {
> >              /*
> > @@ -3981,7 +3980,7 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
> >      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> >          spapr_memory_plug(hotplug_dev, dev);
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
> > -        spapr_core_plug(hotplug_dev, dev, errp);
> > +        spapr_core_plug(hotplug_dev, dev);
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_PCI_HOST_BRIDGE)) {
> >          spapr_phb_plug(hotplug_dev, dev, errp);
> >      } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_TPM_PROXY)) {
> 


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