[Qemu-devel] [PATCH v3 6/6] hw/pci-bridge: set explicit OFW unit address for TYPE_PXB_HOST

[Laszlo Ersek <lersek@redhat.com>]

The PXB implementation doesn't allow firmware (SeaBIOS or OVMF) to boot
off devices behind the PXB. This happens because the
sysbus_get_fw_dev_path() function in "hw/core/sysbus.c" doesn't have
enough information to format a unique identifier for the PXB in question,
and consequently the OpenFirmware device path passed down to the guest
firmware in the "bootorder" fw_cfg file is unusable for identifying the
boot device.

For example, the command line fragment

  -device pxb,id=bridge1,bus_nr=4 \
  \
  -netdev user,id=netdev0 \
  -device e1000,netdev=netdev0,bus=bridge1,addr=2,bootindex=0

results in the following "bootorder" entry:

  /pci/pci-bridge@0/ethernet@2/ethernet-phy@0

The initial "pci" node is formatted by sysbus_get_fw_dev_path(), and the
resultant OpenFirmware device path is independent of bus_nr=4 -- and
therefore it is useless for identifying the device.

In this patch we change the fw_name device class member of TYPE_PXB_HOST
from "pci" to "pci-root", and set each instance's explicit OFW unit
address to the PXB bus number. The same command line fragment results in
the following OpenFirmware device path in the "bootorder" fw_cfg file:

  /pci-root@4/pci-bridge@0/ethernet@2/ethernet-phy@0

The original, initial "/pci" fragment has been replaced with
"/pci-root@4", which (a) looks better, (b) provides all the necessary
information.

Cc: Markus Armbruster <armbru@redhat.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v3:
    - using new sysbus device property, not inserting additional bus

 hw/pci-bridge/pci_expander_bridge.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
index c7a085d..d468670 100644
--- a/hw/pci-bridge/pci_expander_bridge.c
+++ b/hw/pci-bridge/pci_expander_bridge.c
@@ -93,7 +93,7 @@ static void pxb_host_class_init(ObjectClass *class, void *data)
     DeviceClass *dc = DEVICE_CLASS(class);
     PCIHostBridgeClass *hc = PCI_HOST_BRIDGE_CLASS(class);
 
-    dc->fw_name = "pci";
+    dc->fw_name = "pci-root";
     hc->root_bus_path = pxb_host_root_bus_path;
 }
 
@@ -152,6 +152,7 @@ static int pxb_dev_initfn(PCIDevice *dev)
 {
     PXBDev *pxb = PXB_DEV(dev);
     DeviceState *ds, *bds;
+    char *bus_nr_str;
     PCIBus *bus;
     const char *dev_name = NULL;
 
@@ -166,6 +167,10 @@ static int pxb_dev_initfn(PCIDevice *dev)
     }
 
     ds = qdev_create(NULL, TYPE_PXB_HOST);
+    bus_nr_str = g_strdup_printf("%x", pxb->bus_nr);
+    qdev_prop_set_string(ds, "explicit_ofw_unit_address", bus_nr_str);
+    g_free(bus_nr_str);
+
     bus = pci_bus_new(ds, "pxb-internal", NULL, NULL, 0, TYPE_PXB_BUS);
 
     bus->parent_dev = dev;
-- 
1.8.3.1