Re: [Qemu-devel] [PATCH] spapr_pci: fail gracefully with non-pseries machine types

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

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On Wed, Oct 11, 2017 at 09:29:08AM +0200, Greg Kurz wrote:
> On Sat, 7 Oct 2017 16:19:25 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > On Fri, Oct 06, 2017 at 05:09:04PM +0200, Greg Kurz wrote:
> > > QEMU currently crashes when the user tries to add a spapr-pci-host-bridge
> > > on a non-pseries machine:
> > > 
> > > $ qemu-system-ppc64 -M ppce500 -device spapr-pci-host-bridge,index=1
> > > hw/ppc/spapr_pci.c:1535:spapr_phb_realize:
> > > Object 0x1003dacae60 is not an instance of type spapr-machine
> > > Aborted (core dumped)
> > > 
> > > The same thing happens with the deprecated but still available child type
> > > spapr-pci-vfio-host-bridge.
> > > 
> > > Fix both by checking the machine type with object_dynamic_cast().
> > > 
> > > Signed-off-by: Greg Kurz <groug@kaod.org>  
> > 
> > 
> > 
> > > ---
> > >  hw/ppc/spapr_pci.c |    8 +++++++-
> > >  1 file changed, 7 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > > index 5049ced4e8b4..9e85106f51f8 100644
> > > --- a/hw/ppc/spapr_pci.c
> > > +++ b/hw/ppc/spapr_pci.c
> > > @@ -1507,7 +1507,7 @@ static void spapr_pci_unplug_request(HotplugHandler *plug_handler,
> > >  
> > >  static void spapr_phb_realize(DeviceState *dev, Error **errp)
> > >  {
> > > -    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> > > +    sPAPRMachineState *spapr;
> > >      SysBusDevice *s = SYS_BUS_DEVICE(dev);
> > >      sPAPRPHBState *sphb = SPAPR_PCI_HOST_BRIDGE(s);
> > >      PCIHostState *phb = PCI_HOST_BRIDGE(s);
> > > @@ -1519,6 +1519,12 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
> > >      const unsigned windows_supported =
> > >          sphb->ddw_enabled ? SPAPR_PCI_DMA_MAX_WINDOWS : 1;
> > >  
> > > +    spapr = (sPAPRMachineState *) qdev_get_machine();
> > > +    if (!object_dynamic_cast((Object *) spapr, TYPE_SPAPR_MACHINE)) {
> > > +        error_setg(errp, TYPE_SPAPR_PCI_HOST_BRIDGE " needs a pseries machine");
> > > +        return;
> > > +    }  
> > 
> > This is slightly clunky.  You could instead use OBJECT_CHECK in the
> > initializer, then just if (!spapr) here.
> > 
> 
> The negative review on v2 seem to indicate we have an agreement on using
> object_dynamic_cast() explicitly. So we have two possibilities, either
> the "clunky" v1, or possibly:
> 
> -    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> +    /* We don't use SPAPR_MACHINE() in order to exit gracefully if the user
> +     * tries to add a PHB to a non-pseries machine.
> +     */
> +    sPAPRMachineState *spapr =
> +        (sPAPRMachineState *) object_dynamic_cast(qdev_get_machine(),
> +                                                  TYPE_SPAPR_MACHINE);
>      SysBusDevice *s = SYS_BUS_DEVICE(dev);
>      sPAPRPHBState *sphb = SPAPR_PCI_HOST_BRIDGE(s);
>      PCIHostState *phb = PCI_HOST_BRIDGE(s);
>      char *namebuf;
>      int i;
>      PCIBus *bus;
>      uint64_t msi_window_size = 4096;
>      sPAPRTCETable *tcet;
>      const unsigned windows_supported =
>          sphb->ddw_enabled ? SPAPR_PCI_DMA_MAX_WINDOWS : 1;
>  
> +    if (!spapr) {
> +        error_setg(errp, TYPE_SPAPR_PCI_HOST_BRIDGE " needs a pseries machine");
> +        return;
> +    }
> +
> 
> Which one do you prefer ? I'll also change spapr_cpu_core_realize()
> if needed.

Second one looks good to me.

> 
> > > +
> > >      if (sphb->index != (uint32_t)-1) {
> > >          sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
> > >          Error *local_err = NULL;
> > >   
> > 
> > 
> 



-- 
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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