pseries: Remove "busname" property for PCI host bridge

Currently the "spapr-pci-host-bridge" device has a "busname" property which
can be used to override the default assignment of qbus names for the bus
subordinate to the PHB.  We use that for the default primary PCI bus, to
make libvirt happy, which expects there to be a bus named simply "pci".
The default qdev core logic would name the bus "pci.0", and the pseries
code would otherwise name it "pci@800000020000000" which is the name it
is given in the device tree based on its BUID.

The "busname" property is rather clunky though, so this patch simplifies
things by just using a special case hack for the default PHB, setting
busname to "pci" when index=0.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>

hw/ppc/spapr.c

@@ -856,7 +856,7 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
     /* Set up PCI */
     spapr_pci_rtas_init();
 
-    phb = spapr_create_phb(spapr, 0, "pci");
+    phb = spapr_create_phb(spapr, 0);
 
     for (i = 0; i < nb_nics; i++) {
         NICInfo *nd = &nd_table[i];

hw/spapr_pci.c

@@ -518,6 +518,7 @@ static int spapr_phb_init(SysBusDevice *s)
 {
     sPAPRPHBState *sphb = SPAPR_PCI_HOST_BRIDGE(s);
     PCIHostState *phb = PCI_HOST_BRIDGE(s);
+    const char *busname;
     char *namebuf;
     int i;
     PCIBus *bus;
@@ -575,9 +576,6 @@ static int spapr_phb_init(SysBusDevice *s)
     }
 
     sphb->dtbusname = g_strdup_printf("pci@%" PRIx64, sphb->buid);
-    if (!sphb->busname) {
-        sphb->busname = sphb->dtbusname;
-    }
 
     namebuf = alloca(strlen(sphb->dtbusname) + 32);
 
@@ -621,7 +619,26 @@ static int spapr_phb_init(SysBusDevice *s)
                                     &sphb->msiwindow);
     }
 
-    bus = pci_register_bus(DEVICE(s), sphb->busname,
+    /*
+     * Selecting a busname is more complex than you'd think, due to
+     * interacting constraints.  If the user has specified an id
+     * explicitly for the phb , then we want to use the qdev default
+     * of naming the bus based on the bridge device (so the user can
+     * then assign devices to it in the way they expect).  For the
+     * first / default PCI bus (index=0) we want to use just "pci"
+     * because libvirt expects there to be a bus called, simply,
+     * "pci".  Otherwise, we use the same name as in the device tree,
+     * since it's unique by construction, and makes the guest visible
+     * BUID clear.
+     */
+    if (s->qdev.id) {
+        busname = NULL;
+    } else if (sphb->index == 0) {
+        busname = "pci";
+    } else {
+        busname = sphb->dtbusname;
+    }
+    bus = pci_register_bus(DEVICE(s), busname,
                            pci_spapr_set_irq, pci_spapr_map_irq, sphb,
                            &sphb->memspace, &sphb->iospace,
                            PCI_DEVFN(0, 0), PCI_NUM_PINS);
@@ -663,7 +680,6 @@ static void spapr_phb_reset(DeviceState *qdev)
 }
 
 static Property spapr_phb_properties[] = {
-    DEFINE_PROP_STRING("busname", sPAPRPHBState, busname),
     DEFINE_PROP_INT32("index", sPAPRPHBState, index, -1),
     DEFINE_PROP_HEX64("buid", sPAPRPHBState, buid, -1),
     DEFINE_PROP_HEX32("liobn", sPAPRPHBState, dma_liobn, -1),
@@ -694,14 +710,12 @@ static const TypeInfo spapr_phb_info = {
     .class_init    = spapr_phb_class_init,
 };
 
-PCIHostState *spapr_create_phb(sPAPREnvironment *spapr, int index,
-                               const char *busname)
+PCIHostState *spapr_create_phb(sPAPREnvironment *spapr, int index)
 {
     DeviceState *dev;
 
     dev = qdev_create(NULL, TYPE_SPAPR_PCI_HOST_BRIDGE);
     qdev_prop_set_uint32(dev, "index", index);
-    qdev_prop_set_string(dev, "busname", busname);
     qdev_init_nofail(dev);
 
     return PCI_HOST_BRIDGE(dev);

hw/spapr_pci.h

@@ -39,7 +39,6 @@ typedef struct sPAPRPHBState {
 
     int32_t index;
     uint64_t buid;
-    char *busname;
     char *dtbusname;
 
     MemoryRegion memspace, iospace;
@@ -82,8 +81,7 @@ static inline qemu_irq spapr_phb_lsi_qirq(struct sPAPRPHBState *phb, int pin)
     return xics_get_qirq(spapr->icp, phb->lsi_table[pin].irq);
 }
 
-PCIHostState *spapr_create_phb(sPAPREnvironment *spapr, int index,
-                               const char *busname);
+PCIHostState *spapr_create_phb(sPAPREnvironment *spapr, int index);
 
 int spapr_populate_pci_dt(sPAPRPHBState *phb,
                           uint32_t xics_phandle,