[PATCH 10/10] OvmfPkg/Sec: Fill Temp Ram after TemporaryRamMigration

[Jordan Justen <jordan.l.justen@intel.com>]

On some platforms, the TemporaryRamMigration PPI may cause Temporary
RAM to become inaccessible after the RAM is migrated. To emulate this
in OVMF, we should initialize memory to a bad state to make sure it
isn't accidentally being used after TemporaryRamMigration is called.

I tested IA32 booting to shell and X64 booting to OS with this change.
With X64 I also tested S3 suspend/resume.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien.grall@linaro.org>
---
 OvmfPkg/Sec/SecMain.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 86c22a2ac9..72946e0eab 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -948,6 +948,14 @@ TemporaryRamMigration (
     LongJump (&JumpBuffer, (UINTN)-1);
   }
 
+  //
+  // Initialize Temporary RAM to a bad value to make sure it will not
+  // be used after migration.
+  //
+  SetMem32 (
+    (VOID*)(UINTN)TemporaryMemoryBase, CopySize,
+    PcdGet32 (PcdInitValueInTempStack));
+
   SaveAndSetDebugTimerInterrupt (OldStatus);
 
   return EFI_SUCCESS;
-- 
2.20.0.rc1