Re: [Qemu-ppc] [RFC for-2.10 2/3] pci: Allow host bridges to override PCI/PCIe hybrid device behaviour

[David Gibson]

On Wed, Apr 26, 2017 at 06:29:05PM +0300, Michael S. Tsirkin wrote:
> On Tue, Mar 28, 2017 at 01:16:50PM +1100, David Gibson wrote:
> > Currently PCI/PCIe hybrid devices - that is, devices which can appear as
> > either plain PCI or PCIe depending on where they're attached - will only
> > appear in PCIe mode if they're attached to a PCIe bus via a root port or
> > downstream port.
> > 
> > This is correct for "standard" PCIe setups, but there are some platforms
> > which need different behaviour (notably "pseries" whose paravirtualized
> > PCI host bridges have some idiosyncracies).
> > 
> > This patch allows the host bridge to override the normal behaviour.
> > 
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> >  hw/pci/pci.c              | 11 +++++++++--
> >  include/hw/pci/pci_host.h |  1 +
> >  2 files changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index 779787b..ac68065 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -392,9 +392,16 @@ bool pci_bus_is_root(PCIBus *bus)
> >  
> >  bool pci_allow_hybrid_pcie(PCIDevice *pci_dev)
> >  {
> > -    PCIBus *bus = pci_dev->bus;
> > +    PCIHostState *host_bridge = 
> > PCI_HOST_BRIDGE(pci_device_root_bus(pci_dev)->qbus.parent);
> > +    PCIHostBridgeClass *hc = PCI_HOST_BRIDGE_GET_CLASS(host_bridge);
> > +
> > +    if (hc->allow_hybrid_pcie) {
> > +        return hc->allow_hybrid_pcie(host_bridge, pci_dev);
> > +    } else {
> > +        PCIBus *bus = pci_dev->bus;
> >  
> > -    return pci_bus_is_express(bus) && !pci_bus_is_root(bus);
> > +        return pci_bus_is_express(bus) && !pci_bus_is_root(bus);
> > +    }
> >  }
> >  
> >  void pci_bus_new_inplace(PCIBus *bus, size_t bus_size, DeviceState *parent,
> 
> I think I'd prefer adding some flags in PCIBus

I'm not really sure what you have in mind from that.  Remember that we
need to be able to set this based on machine type for backwards
compatibility.

>  While we are at it,
> is_root can become a flag too.

Seems a bit odd to me, since it can be derived from the existing
information.

> 
> > diff --git a/include/hw/pci/pci_host.h b/include/hw/pci/pci_host.h
> > index ba31595..ad03cca 100644
> > --- a/include/hw/pci/pci_host.h
> > +++ b/include/hw/pci/pci_host.h
> > @@ -54,6 +54,7 @@ typedef struct PCIHostBridgeClass {
> >      SysBusDeviceClass parent_class;
> >  
> >      const char *(*root_bus_path)(PCIHostState *, PCIBus *);
> > +    bool (*allow_hybrid_pcie)(PCIHostState *, PCIDevice *);
> >  } PCIHostBridgeClass;
> >  
> >  /* common internal helpers for PCI/PCIe hosts, cut off overflows */
> 

-- 
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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