Re: [Qemu-devel] [PATCH v6 7/7] hw/pci-bridge: format SeaBIOS-compliant OFW device node for PXB

[Laszlo Ersek]

On 06/17/15 23:49, Michael S. Tsirkin wrote:
> On Wed, Jun 17, 2015 at 09:35:20PM +0200, Laszlo Ersek wrote:
>> On 06/17/15 21:21, Michael S. Tsirkin wrote:
>>> On Wed, Jun 17, 2015 at 02:45:05PM +0200, Laszlo Ersek wrote:
>>>> SeaBIOS expects OpenFirmware device paths in the "bootorder" fw_cfg file
>>>> to follow the pattern
>>>>
>>>>   /address@hidden/address@hidden/...
>>>>
>>>> for devices that live behind an extra root bus. The extra root bus in
>>>> question is the N'th among the extra root bridges. (In other words, N
>>>> gives the position of the affected extra root bus relative to the other
>>>> extra root buses, in bus_nr order.) N starts at 1, and is formatted in
>>>> hex.
>>>>
>>>> The "address@hidden" node text is hardcoded in SeaBIOS (see the macro
>>>> FW_PCI_DOMAIN).
>>>>
>>>> Cc: Kevin O'Connor <address@hidden>
>>>> Cc: Marcel Apfelbaum <address@hidden>
>>>> Cc: Michael S. Tsirkin <address@hidden>
>>>> Signed-off-by: Laszlo Ersek <address@hidden>
>>>> Tested-by: Marcel Apfelbaum <address@hidden>
>>>> Reviewed-by: Marcel Apfelbaum <address@hidden>
>>>> ---
>>>>
>>>> Notes:
>>>>     v6:
>>>>     - no changes
>>>>     
>>>>     v5:
>>>>     - constify parameter and local variables of 
>>>> pxb_host_ofw_unit_address(),
>>>>       in accord with the previous patch
>>>>     
>>>>     v4:
>>>>     - new in v4
>>>>
>>>>  hw/pci-bridge/pci_expander_bridge.c | 39 
>>>> ++++++++++++++++++++++++++++++++++++-
>>>>  1 file changed, 38 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/hw/pci-bridge/pci_expander_bridge.c 
>>>> b/hw/pci-bridge/pci_expander_bridge.c
>>>> index 4398d98..37574ec 100644
>>>> --- a/hw/pci-bridge/pci_expander_bridge.c
>>>> +++ b/hw/pci-bridge/pci_expander_bridge.c
>>>> @@ -42,6 +42,8 @@ typedef struct PXBDev {
>>>>      uint16_t numa_node;
>>>>  } PXBDev;
>>>>  
>>>> +static GList *pxb_dev_list;
>>>> +
>>>>  #define TYPE_PXB_HOST "pxb-host"
>>>>  
>>>>  static int pxb_bus_num(PCIBus *bus)
>>>
>>>
>>> So this trick breaks if we ever do have multiple roots, with expanders
>>> under each.
>>
>> Assuming I understand what you mean by "multiple roots", I guess the
>> trick could be extended to maintain a separate list of expanders for
>> each root.
> 
> You don't need an extra list: expander are already linked
> under root.
> 
>>> I guess you could go to parent bus, scan child devices of parent and
>>> count TYPE_PXB_DEVICE devices there.
>>>
>>>
>>> BTW does this work if we have pci bridges under the default root in
>>> addition to PXBs?
>>
>> I have no clue how to configure that on the QEMU command line, sorry.
> 
> Simple -device pvi-bridge-device,chassis_nr=XXX,id=foo then attach
> devices there.
> 
>>> Does seabios know to skip regular bridges when it's
>>> counting roots?
>>
>> Something for Kevin to answer :)
>>
>> The initial scan in OVMF doesn't look for regular bridges specifically.
>> When a device in 0x00..0x1f, function 0, responds from a bus in
>> 0x01..0xff, that bus is considered a live extra root bus.
> 
> Do you do it before or after configuring bridges under root bus 0?

Before.

The driver that scans the roots and produces
EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL instances is OVMF's own (cloned and
modified from another platform's similar driver). The driver that
configures bridges and does the rest of the enumeration is the generic
PCI bus driver that OVMF only includes without modifications. That
driver depends on the EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL instances produced
by the former.

Thanks
Laszlo

> If after, then it's a bug - you will discover regular bridges this way.
> 
> 
>> The bridges
>> that hang off the expanders come to life much later, when the generic
>> edk2 PCI bus driver enumerates devices (on the root buses that the OVMF
>> PCI host bridge / root bridge driver produced). No clue about regular
>> bridges.
>>
>> Thanks
>> Laszlo
>>
>>>> @@ -88,12 +90,29 @@ static const char *pxb_host_root_bus_path(PCIHostState 
>>>> *host_bridge,
>>>>      return bus->bus_path;
>>>>  }
>>>>  
>>>> +static char *pxb_host_ofw_unit_address(const SysBusDevice *dev)
>>>> +{
>>>> +    const PCIHostState *host = PCI_HOST_BRIDGE(dev);
>>>> +    const PCIBus *bus;
>>>> +    const PXBDev *pxb;
>>>> +    int position;
>>>> +
>>>> +    bus = host->bus;
>>>> +    pxb = PXB_DEV(bus->parent_dev);
>>>> +    position = g_list_index(pxb_dev_list, pxb);
>>>> +    assert(position >= 0);
>>>> +
>>>> +    return g_strdup_printf("%x/address@hidden", position + 1);
>>>> +}
>>>> +
>>>>  static void pxb_host_class_init(ObjectClass *class, void *data)
>>>>  {
>>>>      DeviceClass *dc = DEVICE_CLASS(class);
>>>> +    SysBusDeviceClass *sbc = SYS_BUS_DEVICE_CLASS(class);
>>>>      PCIHostBridgeClass *hc = PCI_HOST_BRIDGE_CLASS(class);
>>>>  
>>>> -    dc->fw_name = "pci";
>>>> +    dc->fw_name = "pci-root";
>>>> +    sbc->explicit_ofw_unit_address = pxb_host_ofw_unit_address;
>>>>      hc->root_bus_path = pxb_host_root_bus_path;
>>>>  }
>>>>  
>>>> @@ -148,6 +167,15 @@ static int pxb_map_irq_fn(PCIDevice *pci_dev, int pin)
>>>>      return pin - PCI_SLOT(pxb->devfn);
>>>>  }
>>>>  
>>>> +static gint pxb_compare(gconstpointer a, gconstpointer b)
>>>> +{
>>>> +    const PXBDev *pxb_a = a, *pxb_b = b;
>>>> +
>>>> +    return pxb_a->bus_nr < pxb_b->bus_nr ? -1 :
>>>> +           pxb_a->bus_nr > pxb_b->bus_nr ?  1 :
>>>> +           0;
>>>> +}
>>>> +
>>>>  static int pxb_dev_initfn(PCIDevice *dev)
>>>>  {
>>>>      PXBDev *pxb = PXB_DEV(dev);
>>>> @@ -191,9 +219,17 @@ static int pxb_dev_initfn(PCIDevice *dev)
>>>>                                 PCI_STATUS_66MHZ | PCI_STATUS_FAST_BACK);
>>>>      pci_config_set_class(dev->config, PCI_CLASS_BRIDGE_HOST);
>>>>  
>>>> +    pxb_dev_list = g_list_insert_sorted(pxb_dev_list, pxb, pxb_compare);
>>>>      return 0;
>>>>  }
>>>>  
>>>> +static void pxb_dev_exitfn(PCIDevice *pci_dev)
>>>> +{
>>>> +    PXBDev *pxb = PXB_DEV(pci_dev);
>>>> +
>>>> +    pxb_dev_list = g_list_remove(pxb_dev_list, pxb);
>>>> +}
>>>> +
>>>>  static Property pxb_dev_properties[] = {
>>>>      /* Note: 0 is not a legal a PXB bus number. */
>>>>      DEFINE_PROP_UINT8("bus_nr", PXBDev, bus_nr, 0),
>>>> @@ -207,6 +243,7 @@ static void pxb_dev_class_init(ObjectClass *klass, 
>>>> void *data)
>>>>      PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
>>>>  
>>>>      k->init = pxb_dev_initfn;
>>>> +    k->exit = pxb_dev_exitfn;
>>>>      k->vendor_id = PCI_VENDOR_ID_REDHAT;
>>>>      k->device_id = PCI_DEVICE_ID_REDHAT_PXB;
>>>>      k->class_id = PCI_CLASS_BRIDGE_HOST;
>>>> -- 
>>>> 1.8.3.1