diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 03e3803..f6e9c2a 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2370,6 +2370,39 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
     return head;
 }
 
+static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
+                                uint64_t *buid, hwaddr *pio, hwaddr *pio_size,
+                                hwaddr *mmio, hwaddr *mmio_size,
+                                unsigned n_dma, uint32_t *liobns, Error **errp)
+{
+    const uint64_t base_buid = 0x800000020000000ULL;
+    const hwaddr phb0_base = 0x10000000000ULL; /* 1 TiB */
+    const hwaddr phb_spacing = 0x1000000000ULL; /* 64 GiB */
+    const hwaddr mmio_offset = 0xa0000000; /* 2 GiB + 512 MiB */
+    const hwaddr pio_offset = 0x80000000; /* 2 GiB */
+    const uint32_t max_index = 255;
+
+    hwaddr phb_base;
+    int i;
+
+    if (index > max_index) {
+        error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
+                   max_index);
+        return;
+    }
+
+    *buid = base_buid + index;
+    for (i = 0; i < n_dma; ++i) {
+        liobns[i] = SPAPR_PCI_LIOBN(index, i);
+    }
+
+    phb_base = phb0_base + index * phb_spacing;
+    *pio = phb_base + pio_offset;
+    *pio_size = SPAPR_PCI_IO_WIN_SIZE;
+    *mmio = phb_base + mmio_offset;
+    *mmio_size = SPAPR_PCI_MMIO_WIN_SIZE;
+}
+
 static void spapr_machine_class_init(ObjectClass *oc, void *data)
 {
     MachineClass *mc = MACHINE_CLASS(oc);
@@ -2406,6 +2439,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
     fwc->get_dev_path = spapr_get_fw_dev_path;
     nc->nmi_monitor_handler = spapr_nmi;
+    smc->phb_placement = spapr_phb_placement;
 }
 
 static const TypeInfo spapr_machine_info = {
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 4f00865..c0fc964 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1311,7 +1311,8 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
         sphb->ddw_enabled ? SPAPR_PCI_DMA_MAX_WINDOWS : 1;
 
     if (sphb->index != (uint32_t)-1) {
-        hwaddr windows_base;
+        sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
+        Error *local_err = NULL;
 
         if ((sphb->buid != (uint64_t)-1) || (sphb->dma_liobn[0] != (uint32_t)-1)
             || (sphb->dma_liobn[1] != (uint32_t)-1 && windows_supported == 2)
@@ -1322,21 +1323,14 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
             return;
         }
 
-        if (sphb->index > SPAPR_PCI_MAX_INDEX) {
-            error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
-                       SPAPR_PCI_MAX_INDEX);
+        smc->phb_placement(spapr, sphb->index,
+                           &sphb->buid, &sphb->io_win_addr, &sphb->io_win_size,
+                           &sphb->mem_win_addr, &sphb->mem_win_size,
+                           windows_supported, sphb->dma_liobn, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
             return;
         }
-
-        sphb->buid = SPAPR_PCI_BASE_BUID + sphb->index;
-        for (i = 0; i < windows_supported; ++i) {
-            sphb->dma_liobn[i] = SPAPR_PCI_LIOBN(sphb->index, i);
-        }
-
-        windows_base = SPAPR_PCI_WINDOW_BASE
-            + sphb->index * SPAPR_PCI_WINDOW_SPACING;
-        sphb->mem_win_addr = windows_base + SPAPR_PCI_MMIO_WIN_OFF;
-        sphb->io_win_addr = windows_base + SPAPR_PCI_IO_WIN_OFF;
     }
 
     if (sphb->buid == (uint64_t)-1) {
diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
index 30dbd46..8c9ebfd 100644
--- a/include/hw/pci-host/spapr.h
+++ b/include/hw/pci-host/spapr.h
@@ -79,18 +79,9 @@ struct sPAPRPHBState {
     uint32_t numa_node;
 };
 
-#define SPAPR_PCI_MAX_INDEX          255
-
-#define SPAPR_PCI_BASE_BUID          0x800000020000000ULL
-
 #define SPAPR_PCI_MEM_WIN_BUS_OFFSET 0x80000000ULL
 
-#define SPAPR_PCI_WINDOW_BASE        0x10000000000ULL
-#define SPAPR_PCI_WINDOW_SPACING     0x1000000000ULL
-#define SPAPR_PCI_MMIO_WIN_OFF       0xA0000000
-#define SPAPR_PCI_MMIO_WIN_SIZE      (SPAPR_PCI_WINDOW_SPACING - \
-                                     SPAPR_PCI_MEM_WIN_BUS_OFFSET)
-#define SPAPR_PCI_IO_WIN_OFF         0x80000000
+#define SPAPR_PCI_MMIO_WIN_SIZE      0xf80000000
 #define SPAPR_PCI_IO_WIN_SIZE        0x10000
 
 #define SPAPR_PCI_MSI_WINDOW         0x40000000000ULL
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 39dadaa..9e1c5a5 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -40,6 +40,10 @@ struct sPAPRMachineClass {
     bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
     bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
     const char *tcg_default_cpu; /* which (TCG) CPU to simulate by default */
+    void (*phb_placement)(sPAPRMachineState *spapr, uint32_t index,
+                          uint64_t *buid, hwaddr *pio, hwaddr *pio_size,
+                          hwaddr *mmio, hwaddr *mmio_size,
+                          unsigned n_dma, uint32_t *liobns, Error **errp);
 };
 
 /**
