diff --git a/OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.c b/OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.c
index 58938b5d8b..c20f299304 100644
--- a/OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.c
+++ b/OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.c
@@ -23,7 +23,6 @@
 //
 #define PMBA_RTE      BIT0
 #define PIIX4_PMIOSE  BIT0
-#define Q35_ACPI_EN   BIT7
 
 //
 // Offset in the Power Management Base Address to the ACPI Timer
@@ -64,9 +63,9 @@ AcpiTimerLibConstructor (
       AcpiEnBit  = PIIX4_PMIOSE;
       break;
     case INTEL_Q35_MCH_DEVICE_ID:
-      Pmba       = POWER_MGMT_REGISTER_Q35 (0x40);
-      AcpiCtlReg = POWER_MGMT_REGISTER_Q35 (0x44); // ACPI_CNTL
-      AcpiEnBit  = Q35_ACPI_EN;
+      Pmba       = POWER_MGMT_REGISTER_Q35 (ICH9_PMBASE);
+      AcpiCtlReg = POWER_MGMT_REGISTER_Q35 (ICH9_ACPI_CNTL);
+      AcpiEnBit  = ICH9_ACPI_CNTL_ACPI_EN;
       break;
     default:
       DEBUG ((EFI_D_ERROR, "%a: Unknown Host Bridge Device ID: 0x%04x\n",
diff --git a/OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.c b/OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.c
index c9601d8e97..55f3572eef 100644
--- a/OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.c
+++ b/OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.c
@@ -24,7 +24,6 @@
 //
 #define PMBA_RTE      BIT0
 #define PIIX4_PMIOSE  BIT0
-#define Q35_ACPI_EN   BIT7
 
 //
 // Offset in the Power Management Base Address to the ACPI Timer
@@ -62,9 +61,9 @@ AcpiTimerLibConstructor (
       AcpiEnBit  = PIIX4_PMIOSE;
       break;
     case INTEL_Q35_MCH_DEVICE_ID:
-      Pmba       = POWER_MGMT_REGISTER_Q35 (0x40);
-      AcpiCtlReg = POWER_MGMT_REGISTER_Q35 (0x44); // ACPI_CNTL
-      AcpiEnBit  = Q35_ACPI_EN;
+      Pmba       = POWER_MGMT_REGISTER_Q35 (ICH9_PMBASE);
+      AcpiCtlReg = POWER_MGMT_REGISTER_Q35 (ICH9_ACPI_CNTL);
+      AcpiEnBit  = ICH9_ACPI_CNTL_ACPI_EN;
       break;
     default:
       DEBUG ((EFI_D_ERROR, "%a: Unknown Host Bridge Device ID: 0x%04x\n",
@@ -118,7 +117,7 @@ InternalAcpiGetTimerTick (
       Pmba = POWER_MGMT_REGISTER_PIIX4 (0x40);
       break;
     case INTEL_Q35_MCH_DEVICE_ID:
-      Pmba = POWER_MGMT_REGISTER_Q35 (0x40);
+      Pmba = POWER_MGMT_REGISTER_Q35 (ICH9_PMBASE);
       break;
     default:
       DEBUG ((EFI_D_ERROR, "%a: Unknown Host Bridge Device ID: 0x%04x\n",
diff --git a/OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c b/OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
index 2be0793057..649b5c9a4d 100644
--- a/OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
+++ b/OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
@@ -64,7 +64,7 @@ AcpiTimerLibConstructor (
       Pmba = POWER_MGMT_REGISTER_PIIX4 (0x40);
       break;
     case INTEL_Q35_MCH_DEVICE_ID:
-      Pmba = POWER_MGMT_REGISTER_Q35 (0x40);
+      Pmba = POWER_MGMT_REGISTER_Q35 (ICH9_PMBASE);
       break;
     default:
       DEBUG ((EFI_D_ERROR, "%a: Unknown Host Bridge Device ID: 0x%04x\n",
diff --git a/OvmfPkg/Library/PlatformBdsLib/BdsPlatform.c b/OvmfPkg/Library/PlatformBdsLib/BdsPlatform.c
index 1e87820e93..2521ea4e6a 100644
--- a/OvmfPkg/Library/PlatformBdsLib/BdsPlatform.c
+++ b/OvmfPkg/Library/PlatformBdsLib/BdsPlatform.c
@@ -870,7 +870,7 @@ PciAcpiInitialization (
       PciWrite8 (PCI_LIB_ADDRESS (0, 1, 0, 0x63), 0x0a); // D
       break;
     case INTEL_Q35_MCH_DEVICE_ID:
-      Pmba = POWER_MGMT_REGISTER_Q35 (0x40);
+      Pmba = POWER_MGMT_REGISTER_Q35 (ICH9_PMBASE);
       //
       // 00:1f.0 LPC Bridge (Q35) LNK routing targets
       //
diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index 5ce0a9099a..4ce358ccbc 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -258,9 +258,9 @@ MiscInitialization (
       break;
     case INTEL_Q35_MCH_DEVICE_ID:
       PmCmd      = POWER_MGMT_REGISTER_Q35 (PCI_COMMAND_OFFSET);
-      Pmba       = POWER_MGMT_REGISTER_Q35 (0x40);
-      AcpiCtlReg = POWER_MGMT_REGISTER_Q35 (0x44); // ACPI_CNTL
-      AcpiEnBit  = BIT7; // Q35_ACPI_EN
+      Pmba       = POWER_MGMT_REGISTER_Q35 (ICH9_PMBASE);
+      AcpiCtlReg = POWER_MGMT_REGISTER_Q35 (ICH9_ACPI_CNTL);
+      AcpiEnBit  = ICH9_ACPI_CNTL_ACPI_EN;
       break;
     default:
       DEBUG ((EFI_D_ERROR, "%a: Unknown Host Bridge Device ID: 0x%04x\n",