On Tue, Apr 18, 2017 at 12:21:51PM +1000, David Gibson wrote: > On Mon, Apr 17, 2017 at 03:30:46PM -0300, Eduardo Habkost 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 <da...@gibson.dropbear.id.au> > > > --- > > > 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) > > > > Why are we asking the device about allowing hybrid pcie, and not > > the bus itself? Shouldn't we be able to query this before the > > device is plugged, and before pci_dev->bus is even set? > > > > In other words, why pci_allow_hyberid_pcie() and > > pci_device_get_bus() get a PCIDevice* argument instead of a > > PCIBus* argument? > > Ah good point. I made it a PCIDevice simply for convenience, but > you're right we should be able to query before the device is plugged.
Understood. > > > > > > { > > > - PCIBus *bus = pci_dev->bus; > > > + PCIHostState *host_bridge = > > > PCI_HOST_BRIDGE(pci_device_root_bus(pci_dev)->qbus.parent); > > > > There's something I don't understand completely: what exactly > > guarantees that pci_device_root_bus(...)->qbus.parent is always > > going to be a PCI_HOST_BRIDGE? > > Well, by definition whatever is above the root bus isn't PCI, which > pretty much means it has to be a PCI host bridge. A machine could > break this assumption, but I think that would be a bug. We use this > same pattern to find a PCI device's (or bus's) host bridge in other > places - there doesn't appear to be another way. After taking a better look at the way PCI buses are created, I agree it's OK. Maybe a PCIHostState *pci_host_bridge(PCIBus *bus) helper would be useful? Anyway, both pci_bus_root_bus() and pci_host_bridge() could be implemented as follow-ups if you prefer, so: Reviewed-by: Eduardo Habkost <ehabk...@redhat.com> But I still have another suggestion: > > > > + 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); Maybe it's a matter of personal taste, but instead of requiring an explicit check for NULL hc->allow_hybrid_pcie, why not set a default hc->allow_hybrid_pcie() implementation on TYPE_PCI_HOST_BRIDGE that returns (pci_bus_is_express(bus) && !pci_bus_is_root(bus))? -- Eduardo