ppc/pnv: move PHB4 XSCOM init to phb4_realize()

The 'stack->phb_regs_mr' PHB4 passthrough XSCOM initialization relies on
'stack->phb' being not NULL. Moving 'stack->phb_regs_mr' region_init()
and add_subregion() to phb4_realize() time is a natural thing to do
since it's strictly PHB related.

The remaining XSCOM initialization is also related to 'stack->phb' but
in a different manner. For instance, 'stack->nest_regs_mr'
MemoryRegionOps, 'pnv_pec_stk_nest_xscom_ops', uses
pnv_pec_stk_nest_xscom_write() as a write callback. When trying to write
the PEC_NEST_STK_BAR_EN reg, pnv_pec_stk_update_map() is called. Inside
this function, pnv_phb4_update_regions() is called twice. This function
uses 'stack->phb' to manipulate memory regions of the phb.

This is not a problem now but, when enabling user creatable phb4s, a
stack that doesn't have an associated phb (i.e. stack->phb = NULL) it
will cause a SIGINT during boot in pnv_phb4_update_regions().

All this can be avoided if all XSCOM realize is moved to phb4_realize(),
when we have certainty about the existence of 'stack->phb'. A lot of
code was moved from pnv_phb4_pec.c to pnv_phb4.c due to static constant
and variables being used but the cleaner logic is worth the trouble.

Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20220111131027.599784-3-danielhb413@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

2 files changed, 304 insertions, 292 deletions

diff --git a/hw/pci-host/pnv_phb4.c b/hw/pci-host/pnv_phb4.c
index 2223b985b2..8ef58bf2de 100644
--- a/hw/pci-host/pnv_phb4.c
+++ b/hw/pci-host/pnv_phb4.c
@@ -29,6 +29,10 @@
     qemu_log_mask(LOG_GUEST_ERROR, "phb4[%d:%d]: " fmt "\n",            \
                   (phb)->chip_id, (phb)->phb_id, ## __VA_ARGS__)
 
+#define phb_pec_error(pec, fmt, ...)                                    \
+    qemu_log_mask(LOG_GUEST_ERROR, "phb4_pec[%d:%d]: " fmt "\n",        \
+                  (pec)->chip_id, (pec)->index, ## __VA_ARGS__)
+
 /*
  * QEMU version of the GETFIELD/SETFIELD macros
  *
@@ -854,6 +858,258 @@ const MemoryRegionOps pnv_phb4_xscom_ops = {
     .endianness = DEVICE_BIG_ENDIAN,
 };
 
+static uint64_t pnv_pec_stk_nest_xscom_read(void *opaque, hwaddr addr,
+                                            unsigned size)
+{
+    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
+    uint32_t reg = addr >> 3;
+
+    /* TODO: add list of allowed registers and error out if not */
+    return stack->nest_regs[reg];
+}
+
+static void pnv_pec_stk_update_map(PnvPhb4PecStack *stack)
+{
+    PnvPhb4PecState *pec = stack->pec;
+    MemoryRegion *sysmem = get_system_memory();
+    uint64_t bar_en = stack->nest_regs[PEC_NEST_STK_BAR_EN];
+    uint64_t bar, mask, size;
+    char name[64];
+
+    /*
+     * NOTE: This will really not work well if those are remapped
+     * after the PHB has created its sub regions. We could do better
+     * if we had a way to resize regions but we don't really care
+     * that much in practice as the stuff below really only happens
+     * once early during boot
+     */
+
+    /* Handle unmaps */
+    if (memory_region_is_mapped(&stack->mmbar0) &&
+        !(bar_en & PEC_NEST_STK_BAR_EN_MMIO0)) {
+        memory_region_del_subregion(sysmem, &stack->mmbar0);
+    }
+    if (memory_region_is_mapped(&stack->mmbar1) &&
+        !(bar_en & PEC_NEST_STK_BAR_EN_MMIO1)) {
+        memory_region_del_subregion(sysmem, &stack->mmbar1);
+    }
+    if (memory_region_is_mapped(&stack->phbbar) &&
+        !(bar_en & PEC_NEST_STK_BAR_EN_PHB)) {
+        memory_region_del_subregion(sysmem, &stack->phbbar);
+    }
+    if (memory_region_is_mapped(&stack->intbar) &&
+        !(bar_en & PEC_NEST_STK_BAR_EN_INT)) {
+        memory_region_del_subregion(sysmem, &stack->intbar);
+    }
+
+    /* Update PHB */
+    pnv_phb4_update_regions(stack);
+
+    /* Handle maps */
+    if (!memory_region_is_mapped(&stack->mmbar0) &&
+        (bar_en & PEC_NEST_STK_BAR_EN_MMIO0)) {
+        bar = stack->nest_regs[PEC_NEST_STK_MMIO_BAR0] >> 8;
+        mask = stack->nest_regs[PEC_NEST_STK_MMIO_BAR0_MASK];
+        size = ((~mask) >> 8) + 1;
+        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-mmio0",
+                 pec->chip_id, pec->index, stack->stack_no);
+        memory_region_init(&stack->mmbar0, OBJECT(stack), name, size);
+        memory_region_add_subregion(sysmem, bar, &stack->mmbar0);
+        stack->mmio0_base = bar;
+        stack->mmio0_size = size;
+    }
+    if (!memory_region_is_mapped(&stack->mmbar1) &&
+        (bar_en & PEC_NEST_STK_BAR_EN_MMIO1)) {
+        bar = stack->nest_regs[PEC_NEST_STK_MMIO_BAR1] >> 8;
+        mask = stack->nest_regs[PEC_NEST_STK_MMIO_BAR1_MASK];
+        size = ((~mask) >> 8) + 1;
+        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-mmio1",
+                 pec->chip_id, pec->index, stack->stack_no);
+        memory_region_init(&stack->mmbar1, OBJECT(stack), name, size);
+        memory_region_add_subregion(sysmem, bar, &stack->mmbar1);
+        stack->mmio1_base = bar;
+        stack->mmio1_size = size;
+    }
+    if (!memory_region_is_mapped(&stack->phbbar) &&
+        (bar_en & PEC_NEST_STK_BAR_EN_PHB)) {
+        bar = stack->nest_regs[PEC_NEST_STK_PHB_REGS_BAR] >> 8;
+        size = PNV_PHB4_NUM_REGS << 3;
+        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-phb",
+                 pec->chip_id, pec->index, stack->stack_no);
+        memory_region_init(&stack->phbbar, OBJECT(stack), name, size);
+        memory_region_add_subregion(sysmem, bar, &stack->phbbar);
+    }
+    if (!memory_region_is_mapped(&stack->intbar) &&
+        (bar_en & PEC_NEST_STK_BAR_EN_INT)) {
+        bar = stack->nest_regs[PEC_NEST_STK_INT_BAR] >> 8;
+        size = PNV_PHB4_MAX_INTs << 16;
+        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-int",
+                 stack->pec->chip_id, stack->pec->index, stack->stack_no);
+        memory_region_init(&stack->intbar, OBJECT(stack), name, size);
+        memory_region_add_subregion(sysmem, bar, &stack->intbar);
+    }
+
+    /* Update PHB */
+    pnv_phb4_update_regions(stack);
+}
+
+static void pnv_pec_stk_nest_xscom_write(void *opaque, hwaddr addr,
+                                         uint64_t val, unsigned size)
+{
+    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
+    PnvPhb4PecState *pec = stack->pec;
+    uint32_t reg = addr >> 3;
+
+    switch (reg) {
+    case PEC_NEST_STK_PCI_NEST_FIR:
+        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR] = val;
+        break;
+    case PEC_NEST_STK_PCI_NEST_FIR_CLR:
+        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR] &= val;
+        break;
+    case PEC_NEST_STK_PCI_NEST_FIR_SET:
+        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR] |= val;
+        break;
+    case PEC_NEST_STK_PCI_NEST_FIR_MSK:
+        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR_MSK] = val;
+        break;
+    case PEC_NEST_STK_PCI_NEST_FIR_MSKC:
+        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR_MSK] &= val;
+        break;
+    case PEC_NEST_STK_PCI_NEST_FIR_MSKS:
+        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR_MSK] |= val;
+        break;
+    case PEC_NEST_STK_PCI_NEST_FIR_ACT0:
+    case PEC_NEST_STK_PCI_NEST_FIR_ACT1:
+        stack->nest_regs[reg] = val;
+        break;
+    case PEC_NEST_STK_PCI_NEST_FIR_WOF:
+        stack->nest_regs[reg] = 0;
+        break;
+    case PEC_NEST_STK_ERR_REPORT_0:
+    case PEC_NEST_STK_ERR_REPORT_1:
+    case PEC_NEST_STK_PBCQ_GNRL_STATUS:
+        /* Flag error ? */
+        break;
+    case PEC_NEST_STK_PBCQ_MODE:
+        stack->nest_regs[reg] = val & 0xff00000000000000ull;
+        break;
+    case PEC_NEST_STK_MMIO_BAR0:
+    case PEC_NEST_STK_MMIO_BAR0_MASK:
+    case PEC_NEST_STK_MMIO_BAR1:
+    case PEC_NEST_STK_MMIO_BAR1_MASK:
+        if (stack->nest_regs[PEC_NEST_STK_BAR_EN] &
+            (PEC_NEST_STK_BAR_EN_MMIO0 |
+             PEC_NEST_STK_BAR_EN_MMIO1)) {
+            phb_pec_error(pec, "Changing enabled BAR unsupported\n");
+        }
+        stack->nest_regs[reg] = val & 0xffffffffff000000ull;
+        break;
+    case PEC_NEST_STK_PHB_REGS_BAR:
+        if (stack->nest_regs[PEC_NEST_STK_BAR_EN] & PEC_NEST_STK_BAR_EN_PHB) {
+            phb_pec_error(pec, "Changing enabled BAR unsupported\n");
+        }
+        stack->nest_regs[reg] = val & 0xffffffffffc00000ull;
+        break;
+    case PEC_NEST_STK_INT_BAR:
+        if (stack->nest_regs[PEC_NEST_STK_BAR_EN] & PEC_NEST_STK_BAR_EN_INT) {
+            phb_pec_error(pec, "Changing enabled BAR unsupported\n");
+        }
+        stack->nest_regs[reg] = val & 0xfffffff000000000ull;
+        break;
+    case PEC_NEST_STK_BAR_EN:
+        stack->nest_regs[reg] = val & 0xf000000000000000ull;
+        pnv_pec_stk_update_map(stack);
+        break;
+    case PEC_NEST_STK_DATA_FRZ_TYPE:
+    case PEC_NEST_STK_PBCQ_TUN_BAR:
+        /* Not used for now */
+        stack->nest_regs[reg] = val;
+        break;
+    default:
+        qemu_log_mask(LOG_UNIMP, "phb4_pec: nest_xscom_write 0x%"HWADDR_PRIx
+                      "=%"PRIx64"\n", addr, val);
+    }
+}
+
+static const MemoryRegionOps pnv_pec_stk_nest_xscom_ops = {
+    .read = pnv_pec_stk_nest_xscom_read,
+    .write = pnv_pec_stk_nest_xscom_write,
+    .valid.min_access_size = 8,
+    .valid.max_access_size = 8,
+    .impl.min_access_size = 8,
+    .impl.max_access_size = 8,
+    .endianness = DEVICE_BIG_ENDIAN,
+};
+
+static uint64_t pnv_pec_stk_pci_xscom_read(void *opaque, hwaddr addr,
+                                           unsigned size)
+{
+    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
+    uint32_t reg = addr >> 3;
+
+    /* TODO: add list of allowed registers and error out if not */
+    return stack->pci_regs[reg];
+}
+
+static void pnv_pec_stk_pci_xscom_write(void *opaque, hwaddr addr,
+                                        uint64_t val, unsigned size)
+{
+    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
+    uint32_t reg = addr >> 3;
+
+    switch (reg) {
+    case PEC_PCI_STK_PCI_FIR:
+        stack->nest_regs[reg] = val;
+        break;
+    case PEC_PCI_STK_PCI_FIR_CLR:
+        stack->nest_regs[PEC_PCI_STK_PCI_FIR] &= val;
+        break;
+    case PEC_PCI_STK_PCI_FIR_SET:
+        stack->nest_regs[PEC_PCI_STK_PCI_FIR] |= val;
+        break;
+    case PEC_PCI_STK_PCI_FIR_MSK:
+        stack->nest_regs[reg] = val;
+        break;
+    case PEC_PCI_STK_PCI_FIR_MSKC:
+        stack->nest_regs[PEC_PCI_STK_PCI_FIR_MSK] &= val;
+        break;
+    case PEC_PCI_STK_PCI_FIR_MSKS:
+        stack->nest_regs[PEC_PCI_STK_PCI_FIR_MSK] |= val;
+        break;
+    case PEC_PCI_STK_PCI_FIR_ACT0:
+    case PEC_PCI_STK_PCI_FIR_ACT1:
+        stack->nest_regs[reg] = val;
+        break;
+    case PEC_PCI_STK_PCI_FIR_WOF:
+        stack->nest_regs[reg] = 0;
+        break;
+    case PEC_PCI_STK_ETU_RESET:
+        stack->nest_regs[reg] = val & 0x8000000000000000ull;
+        /* TODO: Implement reset */
+        break;
+    case PEC_PCI_STK_PBAIB_ERR_REPORT:
+        break;
+    case PEC_PCI_STK_PBAIB_TX_CMD_CRED:
+    case PEC_PCI_STK_PBAIB_TX_DAT_CRED:
+        stack->nest_regs[reg] = val;
+        break;
+    default:
+        qemu_log_mask(LOG_UNIMP, "phb4_pec_stk: pci_xscom_write 0x%"HWADDR_PRIx
+                      "=%"PRIx64"\n", addr, val);
+    }
+}
+
+static const MemoryRegionOps pnv_pec_stk_pci_xscom_ops = {
+    .read = pnv_pec_stk_pci_xscom_read,
+    .write = pnv_pec_stk_pci_xscom_write,
+    .valid.min_access_size = 8,
+    .valid.max_access_size = 8,
+    .impl.min_access_size = 8,
+    .impl.max_access_size = 8,
+    .endianness = DEVICE_BIG_ENDIAN,
+};
+
 static int pnv_phb4_map_irq(PCIDevice *pci_dev, int irq_num)
 {
     /* Check that out properly ... */
@@ -1175,6 +1431,52 @@ static AddressSpace *pnv_phb4_dma_iommu(PCIBus *bus, void *opaque, int devfn)
     return &ds->dma_as;
 }
 
+static void pnv_phb4_xscom_realize(PnvPHB4 *phb)
+{
+    PnvPhb4PecStack *stack = phb->stack;
+    PnvPhb4PecState *pec = stack->pec;
+    PnvPhb4PecClass *pecc = PNV_PHB4_PEC_GET_CLASS(pec);
+    uint32_t pec_nest_base;
+    uint32_t pec_pci_base;
+    char name[64];
+
+    assert(pec);
+
+    /* Initialize the XSCOM regions for the stack registers */
+    snprintf(name, sizeof(name), "xscom-pec-%d.%d-nest-stack-%d",
+             pec->chip_id, pec->index, stack->stack_no);
+    pnv_xscom_region_init(&stack->nest_regs_mr, OBJECT(stack),
+                          &pnv_pec_stk_nest_xscom_ops, stack, name,
+                          PHB4_PEC_NEST_STK_REGS_COUNT);
+
+    snprintf(name, sizeof(name), "xscom-pec-%d.%d-pci-stack-%d",
+             pec->chip_id, pec->index, stack->stack_no);
+    pnv_xscom_region_init(&stack->pci_regs_mr, OBJECT(stack),
+                          &pnv_pec_stk_pci_xscom_ops, stack, name,
+                          PHB4_PEC_PCI_STK_REGS_COUNT);
+
+    /* PHB pass-through */
+    snprintf(name, sizeof(name), "xscom-pec-%d.%d-pci-stack-%d-phb",
+             pec->chip_id, pec->index, stack->stack_no);
+    pnv_xscom_region_init(&stack->phb_regs_mr, OBJECT(phb),
+                          &pnv_phb4_xscom_ops, phb, name, 0x40);
+
+    pec_nest_base = pecc->xscom_nest_base(pec);
+    pec_pci_base = pecc->xscom_pci_base(pec);
+
+    /* Populate the XSCOM address space. */
+    pnv_xscom_add_subregion(pec->chip,
+                            pec_nest_base + 0x40 * (stack->stack_no + 1),
+                            &stack->nest_regs_mr);
+    pnv_xscom_add_subregion(pec->chip,
+                            pec_pci_base + 0x40 * (stack->stack_no + 1),
+                            &stack->pci_regs_mr);
+    pnv_xscom_add_subregion(pec->chip,
+                            pec_pci_base + PNV9_XSCOM_PEC_PCI_STK0 +
+                            0x40 * stack->stack_no,
+                            &stack->phb_regs_mr);
+}
+
 static void pnv_phb4_instance_init(Object *obj)
 {
     PnvPHB4 *phb = PNV_PHB4(obj);
@@ -1247,6 +1549,8 @@ static void pnv_phb4_realize(DeviceState *dev, Error **errp)
     pnv_phb4_update_xsrc(phb);
 
     phb->qirqs = qemu_allocate_irqs(xive_source_set_irq, xsrc, xsrc->nr_irqs);
+
+    pnv_phb4_xscom_realize(phb);
 }
 
 static const char *pnv_phb4_root_bus_path(PCIHostState *host_bridge,
diff --git a/hw/pci-host/pnv_phb4_pec.c b/hw/pci-host/pnv_phb4_pec.c
index f8038dff17..bf0fdf33fd 100644
--- a/hw/pci-host/pnv_phb4_pec.c
+++ b/hw/pci-host/pnv_phb4_pec.c
@@ -111,258 +111,6 @@ static const MemoryRegionOps pnv_pec_pci_xscom_ops = {
     .endianness = DEVICE_BIG_ENDIAN,
 };
 
-static uint64_t pnv_pec_stk_nest_xscom_read(void *opaque, hwaddr addr,
-                                            unsigned size)
-{
-    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
-    uint32_t reg = addr >> 3;
-
-    /* TODO: add list of allowed registers and error out if not */
-    return stack->nest_regs[reg];
-}
-
-static void pnv_pec_stk_update_map(PnvPhb4PecStack *stack)
-{
-    PnvPhb4PecState *pec = stack->pec;
-    MemoryRegion *sysmem = get_system_memory();
-    uint64_t bar_en = stack->nest_regs[PEC_NEST_STK_BAR_EN];
-    uint64_t bar, mask, size;
-    char name[64];
-
-    /*
-     * NOTE: This will really not work well if those are remapped
-     * after the PHB has created its sub regions. We could do better
-     * if we had a way to resize regions but we don't really care
-     * that much in practice as the stuff below really only happens
-     * once early during boot
-     */
-
-    /* Handle unmaps */
-    if (memory_region_is_mapped(&stack->mmbar0) &&
-        !(bar_en & PEC_NEST_STK_BAR_EN_MMIO0)) {
-        memory_region_del_subregion(sysmem, &stack->mmbar0);
-    }
-    if (memory_region_is_mapped(&stack->mmbar1) &&
-        !(bar_en & PEC_NEST_STK_BAR_EN_MMIO1)) {
-        memory_region_del_subregion(sysmem, &stack->mmbar1);
-    }
-    if (memory_region_is_mapped(&stack->phbbar) &&
-        !(bar_en & PEC_NEST_STK_BAR_EN_PHB)) {
-        memory_region_del_subregion(sysmem, &stack->phbbar);
-    }
-    if (memory_region_is_mapped(&stack->intbar) &&
-        !(bar_en & PEC_NEST_STK_BAR_EN_INT)) {
-        memory_region_del_subregion(sysmem, &stack->intbar);
-    }
-
-    /* Update PHB */
-    pnv_phb4_update_regions(stack);
-
-    /* Handle maps */
-    if (!memory_region_is_mapped(&stack->mmbar0) &&
-        (bar_en & PEC_NEST_STK_BAR_EN_MMIO0)) {
-        bar = stack->nest_regs[PEC_NEST_STK_MMIO_BAR0] >> 8;
-        mask = stack->nest_regs[PEC_NEST_STK_MMIO_BAR0_MASK];
-        size = ((~mask) >> 8) + 1;
-        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-mmio0",
-                 pec->chip_id, pec->index, stack->stack_no);
-        memory_region_init(&stack->mmbar0, OBJECT(stack), name, size);
-        memory_region_add_subregion(sysmem, bar, &stack->mmbar0);
-        stack->mmio0_base = bar;
-        stack->mmio0_size = size;
-    }
-    if (!memory_region_is_mapped(&stack->mmbar1) &&
-        (bar_en & PEC_NEST_STK_BAR_EN_MMIO1)) {
-        bar = stack->nest_regs[PEC_NEST_STK_MMIO_BAR1] >> 8;
-        mask = stack->nest_regs[PEC_NEST_STK_MMIO_BAR1_MASK];
-        size = ((~mask) >> 8) + 1;
-        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-mmio1",
-                 pec->chip_id, pec->index, stack->stack_no);
-        memory_region_init(&stack->mmbar1, OBJECT(stack), name, size);
-        memory_region_add_subregion(sysmem, bar, &stack->mmbar1);
-        stack->mmio1_base = bar;
-        stack->mmio1_size = size;
-    }
-    if (!memory_region_is_mapped(&stack->phbbar) &&
-        (bar_en & PEC_NEST_STK_BAR_EN_PHB)) {
-        bar = stack->nest_regs[PEC_NEST_STK_PHB_REGS_BAR] >> 8;
-        size = PNV_PHB4_NUM_REGS << 3;
-        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-phb",
-                 pec->chip_id, pec->index, stack->stack_no);
-        memory_region_init(&stack->phbbar, OBJECT(stack), name, size);
-        memory_region_add_subregion(sysmem, bar, &stack->phbbar);
-    }
-    if (!memory_region_is_mapped(&stack->intbar) &&
-        (bar_en & PEC_NEST_STK_BAR_EN_INT)) {
-        bar = stack->nest_regs[PEC_NEST_STK_INT_BAR] >> 8;
-        size = PNV_PHB4_MAX_INTs << 16;
-        snprintf(name, sizeof(name), "pec-%d.%d-stack-%d-int",
-                 stack->pec->chip_id, stack->pec->index, stack->stack_no);
-        memory_region_init(&stack->intbar, OBJECT(stack), name, size);
-        memory_region_add_subregion(sysmem, bar, &stack->intbar);
-    }
-
-    /* Update PHB */
-    pnv_phb4_update_regions(stack);
-}
-
-static void pnv_pec_stk_nest_xscom_write(void *opaque, hwaddr addr,
-                                         uint64_t val, unsigned size)
-{
-    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
-    PnvPhb4PecState *pec = stack->pec;
-    uint32_t reg = addr >> 3;
-
-    switch (reg) {
-    case PEC_NEST_STK_PCI_NEST_FIR:
-        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR] = val;
-        break;
-    case PEC_NEST_STK_PCI_NEST_FIR_CLR:
-        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR] &= val;
-        break;
-    case PEC_NEST_STK_PCI_NEST_FIR_SET:
-        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR] |= val;
-        break;
-    case PEC_NEST_STK_PCI_NEST_FIR_MSK:
-        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR_MSK] = val;
-        break;
-    case PEC_NEST_STK_PCI_NEST_FIR_MSKC:
-        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR_MSK] &= val;
-        break;
-    case PEC_NEST_STK_PCI_NEST_FIR_MSKS:
-        stack->nest_regs[PEC_NEST_STK_PCI_NEST_FIR_MSK] |= val;
-        break;
-    case PEC_NEST_STK_PCI_NEST_FIR_ACT0:
-    case PEC_NEST_STK_PCI_NEST_FIR_ACT1:
-        stack->nest_regs[reg] = val;
-        break;
-    case PEC_NEST_STK_PCI_NEST_FIR_WOF:
-        stack->nest_regs[reg] = 0;
-        break;
-    case PEC_NEST_STK_ERR_REPORT_0:
-    case PEC_NEST_STK_ERR_REPORT_1:
-    case PEC_NEST_STK_PBCQ_GNRL_STATUS:
-        /* Flag error ? */
-        break;
-    case PEC_NEST_STK_PBCQ_MODE:
-        stack->nest_regs[reg] = val & 0xff00000000000000ull;
-        break;
-    case PEC_NEST_STK_MMIO_BAR0:
-    case PEC_NEST_STK_MMIO_BAR0_MASK:
-    case PEC_NEST_STK_MMIO_BAR1:
-    case PEC_NEST_STK_MMIO_BAR1_MASK:
-        if (stack->nest_regs[PEC_NEST_STK_BAR_EN] &
-            (PEC_NEST_STK_BAR_EN_MMIO0 |
-             PEC_NEST_STK_BAR_EN_MMIO1)) {
-            phb_pec_error(pec, "Changing enabled BAR unsupported\n");
-        }
-        stack->nest_regs[reg] = val & 0xffffffffff000000ull;
-        break;
-    case PEC_NEST_STK_PHB_REGS_BAR:
-        if (stack->nest_regs[PEC_NEST_STK_BAR_EN] & PEC_NEST_STK_BAR_EN_PHB) {
-            phb_pec_error(pec, "Changing enabled BAR unsupported\n");
-        }
-        stack->nest_regs[reg] = val & 0xffffffffffc00000ull;
-        break;
-    case PEC_NEST_STK_INT_BAR:
-        if (stack->nest_regs[PEC_NEST_STK_BAR_EN] & PEC_NEST_STK_BAR_EN_INT) {
-            phb_pec_error(pec, "Changing enabled BAR unsupported\n");
-        }
-        stack->nest_regs[reg] = val & 0xfffffff000000000ull;
-        break;
-    case PEC_NEST_STK_BAR_EN:
-        stack->nest_regs[reg] = val & 0xf000000000000000ull;
-        pnv_pec_stk_update_map(stack);
-        break;
-    case PEC_NEST_STK_DATA_FRZ_TYPE:
-    case PEC_NEST_STK_PBCQ_TUN_BAR:
-        /* Not used for now */
-        stack->nest_regs[reg] = val;
-        break;
-    default:
-        qemu_log_mask(LOG_UNIMP, "phb4_pec: nest_xscom_write 0x%"HWADDR_PRIx
-                      "=%"PRIx64"\n", addr, val);
-    }
-}
-
-static const MemoryRegionOps pnv_pec_stk_nest_xscom_ops = {
-    .read = pnv_pec_stk_nest_xscom_read,
-    .write = pnv_pec_stk_nest_xscom_write,
-    .valid.min_access_size = 8,
-    .valid.max_access_size = 8,
-    .impl.min_access_size = 8,
-    .impl.max_access_size = 8,
-    .endianness = DEVICE_BIG_ENDIAN,
-};
-
-static uint64_t pnv_pec_stk_pci_xscom_read(void *opaque, hwaddr addr,
-                                           unsigned size)
-{
-    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
-    uint32_t reg = addr >> 3;
-
-    /* TODO: add list of allowed registers and error out if not */
-    return stack->pci_regs[reg];
-}
-
-static void pnv_pec_stk_pci_xscom_write(void *opaque, hwaddr addr,
-                                        uint64_t val, unsigned size)
-{
-    PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(opaque);
-    uint32_t reg = addr >> 3;
-
-    switch (reg) {
-    case PEC_PCI_STK_PCI_FIR:
-        stack->nest_regs[reg] = val;
-        break;
-    case PEC_PCI_STK_PCI_FIR_CLR:
-        stack->nest_regs[PEC_PCI_STK_PCI_FIR] &= val;
-        break;
-    case PEC_PCI_STK_PCI_FIR_SET:
-        stack->nest_regs[PEC_PCI_STK_PCI_FIR] |= val;
-        break;
-    case PEC_PCI_STK_PCI_FIR_MSK:
-        stack->nest_regs[reg] = val;
-        break;
-    case PEC_PCI_STK_PCI_FIR_MSKC:
-        stack->nest_regs[PEC_PCI_STK_PCI_FIR_MSK] &= val;
-        break;
-    case PEC_PCI_STK_PCI_FIR_MSKS:
-        stack->nest_regs[PEC_PCI_STK_PCI_FIR_MSK] |= val;
-        break;
-    case PEC_PCI_STK_PCI_FIR_ACT0:
-    case PEC_PCI_STK_PCI_FIR_ACT1:
-        stack->nest_regs[reg] = val;
-        break;
-    case PEC_PCI_STK_PCI_FIR_WOF:
-        stack->nest_regs[reg] = 0;
-        break;
-    case PEC_PCI_STK_ETU_RESET:
-        stack->nest_regs[reg] = val & 0x8000000000000000ull;
-        /* TODO: Implement reset */
-        break;
-    case PEC_PCI_STK_PBAIB_ERR_REPORT:
-        break;
-    case PEC_PCI_STK_PBAIB_TX_CMD_CRED:
-    case PEC_PCI_STK_PBAIB_TX_DAT_CRED:
-        stack->nest_regs[reg] = val;
-        break;
-    default:
-        qemu_log_mask(LOG_UNIMP, "phb4_pec_stk: pci_xscom_write 0x%"HWADDR_PRIx
-                      "=%"PRIx64"\n", addr, val);
-    }
-}
-
-static const MemoryRegionOps pnv_pec_stk_pci_xscom_ops = {
-    .read = pnv_pec_stk_pci_xscom_read,
-    .write = pnv_pec_stk_pci_xscom_write,
-    .valid.min_access_size = 8,
-    .valid.max_access_size = 8,
-    .impl.min_access_size = 8,
-    .impl.max_access_size = 8,
-    .endianness = DEVICE_BIG_ENDIAN,
-};
-
 static void pnv_pec_instance_init(Object *obj)
 {
     PnvPhb4PecState *pec = PNV_PHB4_PEC(obj);
@@ -539,32 +287,7 @@ static void pnv_pec_stk_realize(DeviceState *dev, Error **errp)
     PnvPhb4PecStack *stack = PNV_PHB4_PEC_STACK(dev);
     PnvPhb4PecState *pec = stack->pec;
     PnvPhb4PecClass *pecc = PNV_PHB4_PEC_GET_CLASS(pec);
-    PnvChip *chip = pec->chip;
     int phb_id = pnv_phb4_pec_get_phb_id(pec, stack->stack_no);
-    uint32_t pec_nest_base;
-    uint32_t pec_pci_base;
-    char name[64];
-
-    assert(pec);
-
-    /* Initialize the XSCOM regions for the stack registers */
-    snprintf(name, sizeof(name), "xscom-pec-%d.%d-nest-stack-%d",
-             pec->chip_id, pec->index, stack->stack_no);
-    pnv_xscom_region_init(&stack->nest_regs_mr, OBJECT(stack),
-                          &pnv_pec_stk_nest_xscom_ops, stack, name,
-                          PHB4_PEC_NEST_STK_REGS_COUNT);
-
-    snprintf(name, sizeof(name), "xscom-pec-%d.%d-pci-stack-%d",
-             pec->chip_id, pec->index, stack->stack_no);
-    pnv_xscom_region_init(&stack->pci_regs_mr, OBJECT(stack),
-                          &pnv_pec_stk_pci_xscom_ops, stack, name,
-                          PHB4_PEC_PCI_STK_REGS_COUNT);
-
-    /* PHB pass-through */
-    snprintf(name, sizeof(name), "xscom-pec-%d.%d-pci-stack-%d-phb",
-             pec->chip_id, pec->index, stack->stack_no);
-    pnv_xscom_region_init(&stack->phb_regs_mr, OBJECT(&stack->phb),
-                          &pnv_phb4_xscom_ops, &stack->phb, name, 0x40);
 
     object_property_set_int(OBJECT(&stack->phb), "chip-id", pec->chip_id,
                             &error_fatal);
@@ -577,21 +300,6 @@ static void pnv_pec_stk_realize(DeviceState *dev, Error **errp)
     if (!sysbus_realize(SYS_BUS_DEVICE(&stack->phb), errp)) {
         return;
     }
-
-    pec_nest_base = pecc->xscom_nest_base(pec);
-    pec_pci_base = pecc->xscom_pci_base(pec);
-
-    /* Populate the XSCOM address space. */
-    pnv_xscom_add_subregion(chip,
-                            pec_nest_base + 0x40 * (stack->stack_no + 1),
-                            &stack->nest_regs_mr);
-    pnv_xscom_add_subregion(chip,
-                            pec_pci_base + 0x40 * (stack->stack_no + 1),
-                            &stack->pci_regs_mr);
-    pnv_xscom_add_subregion(chip,
-                            pec_pci_base + PNV9_XSCOM_PEC_PCI_STK0 +
-                            0x40 * stack->stack_no,
-                            &stack->phb_regs_mr);
 }
 
 static Property pnv_pec_stk_properties[] = {