diff --git a/OvmfPkg/SmmAccess/SmmAccessPei.c b/OvmfPkg/SmmAccess/SmmAccessPei.c
index a3631a1b9d..21119f80ee 100644
--- a/OvmfPkg/SmmAccess/SmmAccessPei.c
+++ b/OvmfPkg/SmmAccess/SmmAccessPei.c
@@ -330,7 +330,8 @@ SmmAccessPeiEntryPoint (
   EsmramcVal &= ~(UINT32)MCH_ESMRAMC_TSEG_MASK;
   EsmramcVal |= mQ35TsegMbytes == 8 ? MCH_ESMRAMC_TSEG_8MB :
                 mQ35TsegMbytes == 2 ? MCH_ESMRAMC_TSEG_2MB :
-                MCH_ESMRAMC_TSEG_1MB;
+                mQ35TsegMbytes == 1 ? MCH_ESMRAMC_TSEG_1MB :
+                MCH_ESMRAMC_TSEG_EXT;
   EsmramcVal |= MCH_ESMRAMC_T_EN;
   PciWrite8 (DRAMC_REGISTER_Q35 (MCH_ESMRAMC), EsmramcVal);
 
diff --git a/OvmfPkg/SmmAccess/SmramInternal.c b/OvmfPkg/SmmAccess/SmramInternal.c
index 9918a45148..18c42d2904 100644
--- a/OvmfPkg/SmmAccess/SmramInternal.c
+++ b/OvmfPkg/SmmAccess/SmramInternal.c
@@ -198,7 +198,9 @@ SmramAccessGetCapabilities (
   SmramMap[DescIdxMain].PhysicalSize =
     (TsegSizeBits == MCH_ESMRAMC_TSEG_8MB ? SIZE_8MB :
      TsegSizeBits == MCH_ESMRAMC_TSEG_2MB ? SIZE_2MB :
-     SIZE_1MB) - SmramMap[DescIdxSmmS3ResumeState].PhysicalSize;
+     TsegSizeBits == MCH_ESMRAMC_TSEG_1MB ? SIZE_1MB :
+     mQ35TsegMbytes * SIZE_1MB) -
+    SmramMap[DescIdxSmmS3ResumeState].PhysicalSize;
   SmramMap[DescIdxMain].RegionState = CommonRegionState;
 
   return EFI_SUCCESS;