Re: [Qemu-devel] [Qemu-ppc] [RFC PATCH qemu] spapr_pci: Create PCI-express root bus by default

[Alexey Kardashevskiy <aik@ozlabs.ru>]

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On 31/10/16 13:53, David Gibson wrote:
> On Fri, Oct 28, 2016 at 12:07:12PM +0200, Greg Kurz wrote:
>> On Fri, 28 Oct 2016 18:56:40 +1100
>> Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
>>
>>> At the moment sPAPR PHB creates a root buf of TYPE_PCI_BUS type.
>>> This means that vfio-pci devices attached to it (and this is
>>> a default behaviour) hide PCIe extended capabilities as
>>> the bus does not pass a pci_bus_is_express(pdev->bus) check.
>>>
>>> This changes adds a default PCI bus type property to sPAPR PHB
>>> and uses TYPE_PCIE_BUS if none passed; older machines get TYPE_PCI_BUS
>>> for backward compatibility as a bus type is used in the bus name
>>> so the root bus name becomes "pcie.0" instead of "pci.0".
>>>
>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>> ---
>>>
>>> What can possibly go wrong with such change of a name?
>>> From devices prospective, I cannot see any.
>>>
>>> libvirt might get upset as "pci.0" will not be available,
>>> will it make sense to create pcie.0 as a root bus and always
>>> add a PCIe->PCI bridge and name its bus "pci.0"?
>>>
>>> Or create root bus from TYPE_PCIE_BUS and force name to "pci.0"?
>>> pci_register_bus() can do this.
>>>
>>>
>>> ---
>>>  hw/ppc/spapr.c              | 5 +++++
>>>  hw/ppc/spapr_pci.c          | 5 ++++-
>>>  include/hw/pci-host/spapr.h | 1 +
>>>  3 files changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>>> index 0b3820b..a268511 100644
>>> --- a/hw/ppc/spapr.c
>>> +++ b/hw/ppc/spapr.c
>>> @@ -2541,6 +2541,11 @@ DEFINE_SPAPR_MACHINE(2_8, "2.8", true);
>>>          .driver   = TYPE_SPAPR_PCI_HOST_BRIDGE,     \
>>>          .property = "mem64_win_size",               \
>>>          .value    = "0",                            \
>>> +    },                                              \
>>> +    {                                               \
>>> +        .driver   = TYPE_SPAPR_PCI_HOST_BRIDGE,     \
>>> +        .property = "root_bus_type",                \
>>> +        .value    = TYPE_PCI_BUS,                   \
>>>      },
>>>  
>>>  static void phb_placement_2_7(sPAPRMachineState *spapr, uint32_t index,
>>> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
>>> index 7cde30e..2fa1f22 100644
>>> --- a/hw/ppc/spapr_pci.c
>>> +++ b/hw/ppc/spapr_pci.c
>>> @@ -1434,7 +1434,9 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
>>>      bus = pci_register_bus(dev, NULL,
>>>                             pci_spapr_set_irq, pci_spapr_map_irq, sphb,
>>>                             &sphb->memspace, &sphb->iospace,
>>> -                           PCI_DEVFN(0, 0), PCI_NUM_PINS, TYPE_PCI_BUS);
>>> +                           PCI_DEVFN(0, 0), PCI_NUM_PINS,
>>> +                           sphb->root_bus_type ? sphb->root_bus_type :
>>> +                           TYPE_PCIE_BUS);
>>
>> Shouldn't we ensure that sphb->root_bus_type is either TYPE_PCIE_BUS or
>> TYPE_PCI_BUS ?
> 
> Yes, I think so.  In fact, I think it would be better to make the
> property a boolean that just selects PCI-E, rather than this which
> exposes qemu (semi-)internal type names on the comamnd line.


Sure, a "pcie-root" boolean property should do.

However this is not my main concern, I rather wonder if we have to have
pci.0 when we pick PCIe for the root.



>> Otherwise, if we pass something like:
>>
>> -global spapr-pci-host-bridge.root_bus_type=pcie
>>
>> we get the following not really explicit error:
>>
>> ERROR:/home/greg/Work/qemu/qemu-spapr/qom/object.c:474:object_new_with_type: assertion failed: (type != NULL)
>>
>>>      phb->bus = bus;
>>>      qbus_set_hotplug_handler(BUS(phb->bus), DEVICE(sphb), NULL);
>>>  
>>> @@ -1590,6 +1592,7 @@ static Property spapr_phb_properties[] = {
>>>      DEFINE_PROP_UINT64("pgsz", sPAPRPHBState, page_size_mask,
>>>                         (1ULL << 12) | (1ULL << 16)),
>>>      DEFINE_PROP_UINT32("numa_node", sPAPRPHBState, numa_node, -1),
>>> +    DEFINE_PROP_STRING("root_bus_type", sPAPRPHBState, root_bus_type),
>>>      DEFINE_PROP_END_OF_LIST(),
>>>  };
>>>  
>>> diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
>>> index b92c1b5..a4ee873 100644
>>> --- a/include/hw/pci-host/spapr.h
>>> +++ b/include/hw/pci-host/spapr.h
>>> @@ -79,6 +79,7 @@ struct sPAPRPHBState {
>>>      uint64_t dma64_win_addr;
>>>  
>>>      uint32_t numa_node;
>>> +    char *root_bus_type;
>>>  };
>>>  
>>>  #define SPAPR_PCI_MEM_WIN_BUS_OFFSET 0x80000000ULL
>>
> 


-- 
Alexey


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