From: Laszlo Ersek <[email protected]>

On X64, the reset vector code in
"OvmfPkg/ResetVector/Ia32/PageTables64.asm" identity maps the first 4GB of
RAM for PEI, consuming six frames starting at 8MB.

This range is declared by the PcdOvmfSecPageTablesBase/Size PCDs.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <[email protected]>
[[email protected]: Move to MemDetect.c; use PCDs]
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <[email protected]>
---
 OvmfPkg/PlatformPei/MemDetect.c     | 14 ++++++++++++++
 OvmfPkg/PlatformPei/PlatformPei.inf |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index a298d62..091f012 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -187,6 +187,20 @@ MemDetect (
       PcdGet32 (PcdOvmfSecPeiTempRamSize),
       EfiACPIMemoryNVS
       );
+
+#ifdef MDE_CPU_X64
+    //
+    // Reserve the initial page tables built by the reset vector code.
+    //
+    // Since this memory range will be used by the Reset Vector on S3
+    // resume, it must be reserved as ACPI NVS.
+    //
+    BuildMemoryAllocationHob (
+      (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSecPageTablesBase),
+      (UINT64)(UINTN) PcdGet32 (PcdOvmfSecPageTablesSize),
+      EfiACPIMemoryNVS
+      );
+#endif
   }
 
   return LowerMemorySize;
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf 
b/OvmfPkg/PlatformPei/PlatformPei.inf
index b4e8327..d62863c 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -67,6 +67,8 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdS3AcpiReservedMemoryBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesSize
   gEfiIntelFrameworkModulePkgTokenSpaceGuid.PcdS3AcpiReservedMemorySize
   gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
-- 
1.8.5.2


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