diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 57034c784f..4c5b6511cb 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -276,3 +276,8 @@
   #  runtime OS from tampering with firmware structures (special memory ranges
   #  used by OVMF, the varstore pflash chip, LockBox etc).
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire|FALSE|BOOLEAN|0x1e
+
+  ## Informs modules (including pre-DXE-phase modules) whether the platform
+  #  firmware contains a CSM (Compatibility Support Module).
+  #
+  gUefiOvmfPkgTokenSpaceGuid.PcdCsmEnable|FALSE|BOOLEAN|0x35
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 43ff519336..19728f20b3 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -428,6 +428,9 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdInstallAcpiSdtProtocol|TRUE
+!ifdef $(CSM_ENABLE)
+  gUefiOvmfPkgTokenSpaceGuid.PcdCsmEnable|TRUE
+!endif
 !if $(SMM_REQUIRE) == TRUE
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire|TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmEnableBspElection|FALSE
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 5b3e217e92..3c0c229e3a 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -433,6 +433,9 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdInstallAcpiSdtProtocol|TRUE
+!ifdef $(CSM_ENABLE)
+  gUefiOvmfPkgTokenSpaceGuid.PcdCsmEnable|TRUE
+!endif
 !if $(SMM_REQUIRE) == TRUE
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire|TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmEnableBspElection|FALSE
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index a378d0a449..f6c1d8d228 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -433,6 +433,9 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdInstallAcpiSdtProtocol|TRUE
+!ifdef $(CSM_ENABLE)
+  gUefiOvmfPkgTokenSpaceGuid.PcdCsmEnable|TRUE
+!endif
 !if $(SMM_REQUIRE) == TRUE
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire|TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmEnableBspElection|FALSE
diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc
index 1b18f1769b..5751ff1f03 100644
--- a/OvmfPkg/OvmfXen.dsc
+++ b/OvmfPkg/OvmfXen.dsc
@@ -361,6 +361,9 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdInstallAcpiSdtProtocol|TRUE
+!ifdef $(CSM_ENABLE)
+  gUefiOvmfPkgTokenSpaceGuid.PcdCsmEnable|TRUE
+!endif
 
 [PcdsFixedAtBuild]
   gEfiMdeModulePkgTokenSpaceGuid.PcdStatusCodeMemorySize|1