[Qemu-devel] [PATCH v2 4/4] hw/pci-bridge: push down PXB in qtree in order to format PXB bus numer

[Laszlo Ersek]

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/address@hidden/address@hidden/address@hidden

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 insert a dummy bus between the main sysbus and the
TYPE_PXB_HOST device. Formatting child addresses is a bus class level
responsibility, which is exactly what we'll use here.

After the patch, the same command line fragment results in the following
OpenFirmware device path in the "bootorder" fw_cfg file:

  /extra-pci-roots/address@hidden/address@hidden/address@hidden/address@hidden

The original, initial "/pci" fragment has been replaced with
"/extra-pci-roots/address@hidden", which (a) looks better, (b) provides all the
necessary information. sysbus_get_fw_dev_path() formats the first node
("extra-pci-roots") as always, and the new function
extra_pci_roots_bus_get_fw_dev_path() formats the second one
("address@hidden").

Here's the comparison ("diff -u -b -U28") between the "info qtree"
outputs, before and after (the hpet device is the first common line):

> --- qtree.before        2015-06-10 18:16:44.903359633 +0200
> +++ qtree.after 2015-06-10 18:19:01.904139538 +0200
> @@ -1,30 +1,33 @@
>  bus: main-system-bus
>    type System
> +  dev: extra-pci-roots, id ""
> +    bus: extra-pci-roots-bus.0
> +      type extra-pci-roots-bus
>    dev: pxb-host, id ""
>      bus: pxb-internal
>        type pxb-bus
>        dev: pci-basic-bridge, id "bridge1"
>          chassis_nr = 4 (0x4)
>          addr = 00.0
>          romfile = ""
>          rombar = 1 (0x1)
>          multifunction = false
>          command_serr_enable = true
>          class PCI bridge, addr 04:00.0, pci id 1b36:000a (sub 0000:0000)
>          bus: bridge1
>            type PCI
>            dev: e1000, id ""
>              mac = "52:54:00:12:34:56"
>              vlan = <null>
>              netdev = "netdev0"
>              autonegotiation = true
>              mitigation = true
>              addr = 02.0
>              romfile = ""
>              rombar = 1 (0x1)
>              multifunction = false
>              command_serr_enable = true
>              class Ethernet controller, addr 05:02.0, pci id 8086:100e (sub 
> 1af4:1100)
>              bar 0: mem at 0x88100000 [0x8811ffff]
>              bar 1: i/o at 0xd000 [0xd03f]
>    dev: hpet, id ""

Cc: Markus Armbruster <address@hidden>
Cc: Marcel Apfelbaum <address@hidden>
Cc: Michael S. Tsirkin <address@hidden>
Signed-off-by: Laszlo Ersek <address@hidden>
---

Notes:
    v2:
    - new in v2, addressing the "bootorder" fw_cfg issue discussed earlier
    - Cc'd Markus, because I probably butchered a handful of QOM rules in
      this patch :)

 hw/pci-bridge/pci_expander_bridge.c | 45 +++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/hw/pci-bridge/pci_expander_bridge.c 
b/hw/pci-bridge/pci_expander_bridge.c
index c7a085d..30e93d6 100644
--- a/hw/pci-bridge/pci_expander_bridge.c
+++ b/hw/pci-bridge/pci_expander_bridge.c
@@ -19,6 +19,15 @@
 #include "qemu/error-report.h"
 #include "sysemu/numa.h"
 
+/*
+ * We'll insert a dummy bus between the main sysbus and TYPE_PXB_HOST, because
+ * the main sysbus doesn't know how to format the bus number of the extra root
+ * bus in sysbus_get_fw_dev_path(). We'll use this dummy bus just for
+ * formatting that.
+ */
+#define TYPE_EXTRA_PCI_ROOTS_DEV "extra-pci-roots"
+#define TYPE_EXTRA_PCI_ROOTS_BUS "extra-pci-roots-bus"
+
 #define TYPE_PXB_BUS "pxb-bus"
 #define PXB_BUS(obj) OBJECT_CHECK(PXBBus, (obj), TYPE_PXB_BUS)
 
@@ -93,7 +102,8 @@ 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 = "pxbhost";
+    dc->bus_type = TYPE_EXTRA_PCI_ROOTS_BUS;
     hc->root_bus_path = pxb_host_root_bus_path;
 }
 
@@ -151,6 +161,8 @@ static int pxb_map_irq_fn(PCIDevice *pci_dev, int pin)
 static int pxb_dev_initfn(PCIDevice *dev)
 {
     PXBDev *pxb = PXB_DEV(dev);
+    DeviceState *extra_pci_roots_dev;
+    BusState *extra_pci_roots_bus;
     DeviceState *ds, *bds;
     PCIBus *bus;
     const char *dev_name = NULL;
@@ -165,7 +177,10 @@ static int pxb_dev_initfn(PCIDevice *dev)
         dev_name = dev->qdev.id;
     }
 
-    ds = qdev_create(NULL, TYPE_PXB_HOST);
+    extra_pci_roots_dev = qdev_create(NULL, TYPE_EXTRA_PCI_ROOTS_DEV);
+    extra_pci_roots_bus = qbus_create(TYPE_EXTRA_PCI_ROOTS_BUS,
+                                      extra_pci_roots_dev, NULL);
+    ds = qdev_create(extra_pci_roots_bus, TYPE_PXB_HOST);
     bus = pci_bus_new(ds, "pxb-internal", NULL, NULL, 0, TYPE_PXB_BUS);
 
     bus->parent_dev = dev;
@@ -221,11 +236,37 @@ static const TypeInfo pxb_dev_info = {
     .class_init    = pxb_dev_class_init,
 };
 
+static char *extra_pci_roots_bus_get_fw_dev_path(DeviceState *dev)
+{
+    return g_strdup_printf("address@hidden", qdev_fw_name(dev),
+                           pxb_bus_num(PCI_HOST_BRIDGE(dev)->bus));
+}
+
+static void extra_pci_roots_bus_class_init(ObjectClass *klass, void *data)
+{
+    BusClass *k = BUS_CLASS(klass);
+
+    k->get_fw_dev_path = extra_pci_roots_bus_get_fw_dev_path;
+}
+
+static const TypeInfo extra_pci_roots_bus_info = {
+    .name = TYPE_EXTRA_PCI_ROOTS_BUS,
+    .parent = TYPE_BUS,
+    .class_init = extra_pci_roots_bus_class_init,
+};
+
+static const TypeInfo extra_pci_roots_bus_dev_info = {
+    .name = TYPE_EXTRA_PCI_ROOTS_DEV,
+    .parent = TYPE_SYS_BUS_DEVICE,
+};
+
 static void pxb_register_types(void)
 {
     type_register_static(&pxb_bus_info);
     type_register_static(&pxb_host_info);
     type_register_static(&pxb_dev_info);
+    type_register_static(&extra_pci_roots_bus_info);
+    type_register_static(&extra_pci_roots_bus_dev_info);
 }
 
 type_init(pxb_register_types)
-- 
1.8.3.1