diff --git a/hw/pci-host/pnv_phb4.c b/hw/pci-host/pnv_phb4.c
index a81763f34c..4e3a6b37f9 100644
--- a/hw/pci-host/pnv_phb4.c
+++ b/hw/pci-host/pnv_phb4.c
@@ -683,8 +683,41 @@ static void pnv_phb4_reg_write(void *opaque, hwaddr off, uint64_t val,
         return;
     }
 
-    /* Handle masking */
+    /* Handle RO, W1C, WxC and masking */
     switch (off) {
+    /* W1C: Write-1-to-Clear registers */
+    case PHB_TXE_ERR_STATUS:
+    case PHB_RXE_ARB_ERR_STATUS:
+    case PHB_RXE_MRG_ERR_STATUS:
+    case PHB_RXE_TCE_ERR_STATUS:
+    case PHB_ERR_STATUS:
+    case PHB_REGB_ERR_STATUS:
+    case PHB_PCIE_DLP_ERRLOG1:
+    case PHB_PCIE_DLP_ERRLOG2:
+    case PHB_PCIE_DLP_ERR_STATUS:
+    case PHB_PBL_ERR_STATUS:
+        phb->regs[off >> 3] &= ~val;
+        return;
+
+    /* WxC: Clear register on any write */
+    case PHB_PBL_ERR1_STATUS:
+    case PHB_PBL_ERR_LOG_0 ... PHB_PBL_ERR_LOG_1:
+    case PHB_REGB_ERR1_STATUS:
+    case PHB_REGB_ERR_LOG_0 ... PHB_REGB_ERR_LOG_1:
+    case PHB_TXE_ERR1_STATUS:
+    case PHB_TXE_ERR_LOG_0 ... PHB_TXE_ERR_LOG_1:
+    case PHB_RXE_ARB_ERR1_STATUS:
+    case PHB_RXE_ARB_ERR_LOG_0 ... PHB_RXE_ARB_ERR_LOG_1:
+    case PHB_RXE_MRG_ERR1_STATUS:
+    case PHB_RXE_MRG_ERR_LOG_0 ... PHB_RXE_MRG_ERR_LOG_1:
+    case PHB_RXE_TCE_ERR1_STATUS:
+    case PHB_RXE_TCE_ERR_LOG_0 ... PHB_RXE_TCE_ERR_LOG_1:
+    case PHB_ERR1_STATUS:
+    case PHB_ERR_LOG_0 ... PHB_ERR_LOG_1:
+        phb->regs[off >> 3] = 0;
+        return;
+
+    /* Write value updated by masks */
     case PHB_LSI_SOURCE_ID:
         val &= PHB_LSI_SRC_ID;
         break;
@@ -723,7 +756,6 @@ static void pnv_phb4_reg_write(void *opaque, hwaddr off, uint64_t val,
     case PHB_LEM_WOF:
         val = 0;
         break;
-    /* TODO: More regs ..., maybe create a table with masks... */
 
     /* Read only registers */
     case PHB_CPU_LOADSTORE_STATUS:
@@ -732,6 +764,12 @@ static void pnv_phb4_reg_write(void *opaque, hwaddr off, uint64_t val,
     case PHB_PHB4_TCE_CAP:
     case PHB_PHB4_IRQ_CAP:
     case PHB_PHB4_EEH_CAP:
+    case PHB_VERSION:
+    case PHB_DMA_CHAN_STATUS:
+    case PHB_TCE_TAG_STATUS:
+    case PHB_PBL_BUF_STATUS:
+    case PHB_PCIE_BNR:
+    case PHB_PCIE_PHY_RXEQ_STAT_G3_00_03 ... PHB_PCIE_PHY_RXEQ_STAT_G5_12_15:
         return;
     }
 
@@ -752,6 +790,7 @@ static void pnv_phb4_reg_write(void *opaque, hwaddr off, uint64_t val,
             pnv_phb4_update_all_msi_regions(phb);
         }
         break;
+
     case PHB_M32_START_ADDR:
     case PHB_M64_UPPER_BITS:
         if (changed) {
@@ -797,27 +836,63 @@ static void pnv_phb4_reg_write(void *opaque, hwaddr off, uint64_t val,
         break;
 
     /* Silent simple writes */
-    case PHB_ASN_CMPM:
-    case PHB_CONFIG_ADDRESS:
-    case PHB_IODA_ADDR:
-    case PHB_TCE_KILL:
-    case PHB_TCE_SPEC_CTL:
-    case PHB_PEST_BAR:
-    case PHB_PELTV_BAR:
+    /* PHB Fundamental register set A */
+    case PHB_CONFIG_DATA ... PHB_LOCK1:
     case PHB_RTT_BAR:
-    case PHB_LEM_FIR_ACCUM:
-    case PHB_LEM_ERROR_MASK:
-    case PHB_LEM_ACTION0:
-    case PHB_LEM_ACTION1:
-    case PHB_TCE_TAG_ENABLE:
+    case PHB_PELTV_BAR:
+    case PHB_PEST_BAR:
+    case PHB_CAPI_CMPM ... PHB_M64_AOMASK:
+    case PHB_NXLATE_PREFIX ... PHB_DMA_SYNC:
+    case PHB_TCE_KILL ... PHB_IODA_ADDR:
+    case PHB_PAPR_ERR_INJ_CTL ... PHB_PAPR_ERR_INJ_MASK:
     case PHB_INT_NOTIFY_ADDR:
     case PHB_INT_NOTIFY_INDEX:
-    case PHB_DMA_SYNC:
-       break;
+    /* Fundamental register set B */
+    case PHB_AIB_FENCE_CTRL ... PHB_Q_DMA_R:
+    /* FIR & Error registers */
+    case PHB_LEM_FIR_ACCUM:
+    case PHB_LEM_ERROR_MASK:
+    case PHB_LEM_ACTION0 ... PHB_LEM_WOF:
+    case PHB_ERR_INJECT ... PHB_ERR_AIB_FENCE_ENABLE:
+    case PHB_ERR_STATUS_MASK ... PHB_ERR1_STATUS_MASK:
+    case PHB_TXE_ERR_INJECT ... PHB_TXE_ERR_AIB_FENCE_ENABLE:
+    case PHB_TXE_ERR_STATUS_MASK ... PHB_TXE_ERR1_STATUS_MASK:
+    case PHB_RXE_ARB_ERR_INJECT ... PHB_RXE_ARB_ERR_AIB_FENCE_ENABLE:
+    case PHB_RXE_ARB_ERR_STATUS_MASK ... PHB_RXE_ARB_ERR1_STATUS_MASK:
+    case PHB_RXE_MRG_ERR_INJECT ... PHB_RXE_MRG_ERR_AIB_FENCE_ENABLE:
+    case PHB_RXE_MRG_ERR_STATUS_MASK ... PHB_RXE_MRG_ERR1_STATUS_MASK:
+    case PHB_RXE_TCE_ERR_INJECT ... PHB_RXE_TCE_ERR_AIB_FENCE_ENABLE:
+    case PHB_RXE_TCE_ERR_STATUS_MASK ... PHB_RXE_TCE_ERR1_STATUS_MASK:
+    /* Performance monitor & Debug registers */
+    case PHB_TRACE_CONTROL ... PHB_PERFMON_CTR1:
+    /* REGB Registers */
+    /* PBL core */
+    case PHB_PBL_CONTROL:
+    case PHB_PBL_TIMEOUT_CTRL:
+    case PHB_PBL_NPTAG_ENABLE:
+    case PHB_PBL_SYS_LINK_INIT:
+    case PHB_PBL_ERR_INF_ENABLE ... PHB_PBL_ERR_FAT_ENABLE:
+    case PHB_PBL_ERR_STATUS_MASK ... PHB_PBL_ERR1_STATUS_MASK:
+    /* PCI-E stack */
+    case PHB_PCIE_SCR:
+    case PHB_PCIE_DLP_STR ... PHB_PCIE_HOTPLUG_STATUS:
+    case PHB_PCIE_LMR ... PHB_PCIE_DLP_LSR:
+    case PHB_PCIE_DLP_RXMGN:
+    case PHB_PCIE_DLP_LANEZEROCTL ... PHB_PCIE_DLP_TRCRDDATA:
+    case PHB_PCIE_DLP_ERR_COUNTERS:
+    case PHB_PCIE_DLP_EIC ...   PHB_PCIE_LANE_EQ_CNTL23:
+    case PHB_PCIE_TRACE_CTRL:
+    case PHB_PCIE_MISC_STRAP ... PHB_PCIE_PHY_EQ_CTL:
+    /* Error registers */
+    case PHB_REGB_ERR_INJECT:
+    case PHB_REGB_ERR_INF_ENABLE ... PHB_REGB_ERR_FAT_ENABLE:
+    case PHB_REGB_ERR_STATUS_MASK ... PHB_REGB_ERR1_STATUS_MASK:
+        break;
 
     /* Noise on anything else */
     default:
-        qemu_log_mask(LOG_UNIMP, "phb4: reg_write 0x%"PRIx64"=%"PRIx64"\n",
+        qemu_log_mask(LOG_UNIMP,
+                      "phb4: unimplemented reg_write 0x%"PRIx64"=%"PRIx64"\n",
                       off, val);
     }
 }
@@ -905,36 +980,75 @@ static uint64_t pnv_phb4_reg_read(void *opaque, hwaddr off, unsigned size)
         return val;
 
     /* Silent simple reads */
+    /* PHB Fundamental register set A */
     case PHB_LSI_SOURCE_ID:
+    case PHB_DMA_CHAN_STATUS:
     case PHB_CPU_LOADSTORE_STATUS:
-    case PHB_ASN_CMPM:
+    case PHB_CONFIG_DATA ... PHB_LOCK1:
     case PHB_PHB4_CONFIG:
+    case PHB_RTT_BAR:
+    case PHB_PELTV_BAR:
     case PHB_M32_START_ADDR:
-    case PHB_CONFIG_ADDRESS:
-    case PHB_IODA_ADDR:
-    case PHB_RTC_INVALIDATE:
-    case PHB_TCE_KILL:
-    case PHB_TCE_SPEC_CTL:
     case PHB_PEST_BAR:
-    case PHB_PELTV_BAR:
-    case PHB_RTT_BAR:
+    case PHB_CAPI_CMPM:
+    case PHB_M64_AOMASK:
     case PHB_M64_UPPER_BITS:
-    case PHB_CTRLR:
-    case PHB_LEM_FIR_ACCUM:
-    case PHB_LEM_ERROR_MASK:
-    case PHB_LEM_ACTION0:
-    case PHB_LEM_ACTION1:
-    case PHB_TCE_TAG_ENABLE:
+    case PHB_NXLATE_PREFIX:
+    case PHB_RTC_INVALIDATE ... PHB_IODA_ADDR:
+    case PHB_PAPR_ERR_INJ_CTL ... PHB_ETU_ERR_SUMMARY:
     case PHB_INT_NOTIFY_ADDR:
     case PHB_INT_NOTIFY_INDEX:
-    case PHB_Q_DMA_R:
-    case PHB_ETU_ERR_SUMMARY:
-        break;
-
-    /* Noise on anything else */
+    /* Fundamental register set B */
+    case PHB_CTRLR:
+    case PHB_AIB_FENCE_CTRL ... PHB_Q_DMA_R:
+    case PHB_TCE_TAG_STATUS:
+    /* FIR & Error registers */
+    case PHB_LEM_FIR_ACCUM ... PHB_LEM_ERROR_MASK:
+    case PHB_LEM_ACTION0 ... PHB_LEM_WOF:
+    case PHB_ERR_STATUS ... PHB_ERR_AIB_FENCE_ENABLE:
+    case PHB_ERR_LOG_0 ... PHB_ERR1_STATUS_MASK:
+    case PHB_TXE_ERR_STATUS ... PHB_TXE_ERR_AIB_FENCE_ENABLE:
+    case PHB_TXE_ERR_LOG_0 ... PHB_TXE_ERR1_STATUS_MASK:
+    case PHB_RXE_ARB_ERR_STATUS ... PHB_RXE_ARB_ERR_AIB_FENCE_ENABLE:
+    case PHB_RXE_ARB_ERR_LOG_0 ... PHB_RXE_ARB_ERR1_STATUS_MASK:
+    case PHB_RXE_MRG_ERR_STATUS ... PHB_RXE_MRG_ERR_AIB_FENCE_ENABLE:
+    case PHB_RXE_MRG_ERR_LOG_0 ... PHB_RXE_MRG_ERR1_STATUS_MASK:
+    case PHB_RXE_TCE_ERR_STATUS ... PHB_RXE_TCE_ERR_AIB_FENCE_ENABLE:
+    case PHB_RXE_TCE_ERR_LOG_0 ... PHB_RXE_TCE_ERR1_STATUS_MASK:
+    /* Performance monitor & Debug registers */
+    case PHB_TRACE_CONTROL ... PHB_PERFMON_CTR1:
+    /* REGB Registers */
+    /* PBL core */
+    case PHB_PBL_CONTROL:
+    case PHB_PBL_TIMEOUT_CTRL:
+    case PHB_PBL_NPTAG_ENABLE:
+    case PHB_PBL_SYS_LINK_INIT:
+    case PHB_PBL_BUF_STATUS:
+    case PHB_PBL_ERR_STATUS ... PHB_PBL_ERR_INJECT:
+    case PHB_PBL_ERR_INF_ENABLE ... PHB_PBL_ERR_FAT_ENABLE:
+    case PHB_PBL_ERR_LOG_0 ... PHB_PBL_ERR1_STATUS_MASK:
+    /* PCI-E stack */
+    case PHB_PCIE_BNR ... PHB_PCIE_DLP_STR:
+    case PHB_PCIE_DLP_LANE_PWR:
+    case PHB_PCIE_DLP_LSR:
+    case PHB_PCIE_DLP_RXMGN:
+    case PHB_PCIE_DLP_LANEZEROCTL ... PHB_PCIE_DLP_CTL:
+    case PHB_PCIE_DLP_TRCRDDATA:
+    case PHB_PCIE_DLP_ERRLOG1 ... PHB_PCIE_DLP_ERR_COUNTERS:
+    case PHB_PCIE_DLP_EIC ...   PHB_PCIE_LANE_EQ_CNTL23:
+    case PHB_PCIE_TRACE_CTRL:
+    case PHB_PCIE_MISC_STRAP ... PHB_PCIE_PHY_RXEQ_STAT_G5_12_15:
+    /* Error registers */
+    case PHB_REGB_ERR_STATUS ... PHB_REGB_ERR_INJECT:
+    case PHB_REGB_ERR_INF_ENABLE ... PHB_REGB_ERR_FAT_ENABLE:
+    case PHB_REGB_ERR_LOG_0 ... PHB_REGB_ERR1_STATUS_MASK:
+        break;
+
+    /* Noise on unimplemented read, return all 1's */
     default:
-        qemu_log_mask(LOG_UNIMP, "phb4: reg_read 0x%"PRIx64"=%"PRIx64"\n",
-                      off, val);
+        qemu_log_mask(LOG_UNIMP, "phb4: unimplemented reg_read 0x%"PRIx64"\n",
+                      off);
+        val = ~0ull;
     }
     return val;
 }
diff --git a/include/hw/pci-host/pnv_phb4_regs.h b/include/hw/pci-host/pnv_phb4_regs.h
index 391d6a89ea..c1d5a83271 100644
--- a/include/hw/pci-host/pnv_phb4_regs.h
+++ b/include/hw/pci-host/pnv_phb4_regs.h
@@ -372,6 +372,7 @@
 #define P32_CAP                                 0x228
 #define P32_CTL                                 0x22C
 #define P32_STAT                                0x230
+
 /* PHB4 REGB registers */
 
 /* PBL core */
@@ -406,6 +407,7 @@
 #define   PHB_PCIE_CRESET_PERST_N       PPC_BIT(3)
 #define   PHB_PCIE_CRESET_PIPE_N        PPC_BIT(4)
 #define   PHB_PCIE_CRESET_REFCLK_N      PPC_BIT(8)
+#define PHB_PCIE_DLP_STR                0x1A18
 #define PHB_PCIE_HOTPLUG_STATUS         0x1A20
 #define   PHB_PCIE_HPSTAT_SIMDIAG       PPC_BIT(3)
 #define   PHB_PCIE_HPSTAT_RESAMPLE      PPC_BIT(9)
@@ -416,6 +418,7 @@
 #define   PHB_PCIE_LMR_RETRAINLINK      PPC_BIT(1)
 #define   PHB_PCIE_LMR_LINKACTIVE       PPC_BIT(8)
 
+#define PHB_PCIE_DLP_LANE_PWR           0x1A38
 #define PHB_PCIE_DLP_TRAIN_CTL          0x1A40
 #define   PHB_PCIE_DLP_LINK_WIDTH       PPC_BITMASK(30, 35)
 #define   PHB_PCIE_DLP_LINK_SPEED       PPC_BITMASK(36, 39)
@@ -435,18 +438,21 @@
 #define   PHB_PCIE_DLP_DL_PGRESET       PPC_BIT(22)
 #define   PHB_PCIE_DLP_TRAINING         PPC_BIT(20)
 #define   PHB_PCIE_DLP_INBAND_PRESENCE  PPC_BIT(19)
-
+#define PHB_PCIE_DLP_LSR                0x1A48
+#define PHB_PCIE_DLP_RXMGN              0x1A50
+#define PHB_PCIE_DLP_LANEZEROCTL        0x1A70
 #define PHB_PCIE_DLP_CTL                0x1A78
 #define   PHB_PCIE_DLP_CTL_BYPASS_PH2   PPC_BIT(4)
 #define   PHB_PCIE_DLP_CTL_BYPASS_PH3   PPC_BIT(5)
-
 #define PHB_PCIE_DLP_TRWCTL             0x1A80
 #define   PHB_PCIE_DLP_TRWCTL_EN        PPC_BIT(0)
 #define   PHB_PCIE_DLP_TRWCTL_WREN      PPC_BIT(1)
+#define PHB_PCIE_DLP_TRCRDDATA          0x1A88
 #define PHB_PCIE_DLP_ERRLOG1            0x1AA0
 #define PHB_PCIE_DLP_ERRLOG2            0x1AA8
 #define PHB_PCIE_DLP_ERR_STATUS         0x1AB0
 #define PHB_PCIE_DLP_ERR_COUNTERS       0x1AB8
+#define PHB_PCIE_DLP_EIC                0x1AC8
 
 #define PHB_PCIE_LANE_EQ_CNTL0          0x1AD0
 #define PHB_PCIE_LANE_EQ_CNTL1          0x1AD8
@@ -458,6 +464,7 @@
 #define PHB_PCIE_LANE_EQ_CNTL23         0x1B08 /* DD1 only */
 #define PHB_PCIE_TRACE_CTRL             0x1B20
 #define PHB_PCIE_MISC_STRAP             0x1B30
+#define PHB_PCIE_PHY_EQ_CTL             0x1B38
 #define PHB_PCIE_PHY_RXEQ_STAT_G3_00_03 0x1B40
 #define PHB_PCIE_PHY_RXEQ_STAT_G5_12_15 0x1B98
 
@@ -591,5 +598,4 @@
 
 #define IODA3_PEST1_FAIL_ADDR           PPC_BITMASK(3, 63)
 
-
 #endif /* PCI_HOST_PNV_PHB4_REGS_H */
diff --git a/tests/qtest/pnv-phb4-test.c b/tests/qtest/pnv-phb4-test.c
index 0c8e58dd5f..96d1bd6724 100644
--- a/tests/qtest/pnv-phb4-test.c
+++ b/tests/qtest/pnv-phb4-test.c
@@ -139,6 +139,12 @@ static void phb4_writeonly_read_test(QTestState *qts)
     g_assert_cmpuint(val, ==, 0x0);
 }
 
+/* Check that reading an unimplemented address 0x0 returns -1 */
+static void phb4_unimplemented_read_test(QTestState *qts)
+{
+    g_assert_cmpint(pnv_phb4_xscom_read(qts, 0x0), ==, -1);
+}
+
 static void test_phb4(void)
 {
     QTestState *qts = NULL;
@@ -157,6 +163,9 @@ static void test_phb4(void)
     /* Check write-only logic */
     phb4_writeonly_read_test(qts);
 
+    /* Check unimplemented register read */
+    phb4_unimplemented_read_test(qts);
+
     qtest_quit(qts);
 }
 
