From ffee5bbcf23c264483b9d4091d96c3c8421fd2a7 Mon Sep 17 00:00:00 2001
From: Hendrik Borghorst <hborghor@amazon.de>
Date: Fri, 16 Oct 2020 10:05:08 +0200
Subject: [PATCH] uefi: Wipe emulated NvVariable memory on allocation

EDK2 implements an emulation of non-volatile memory by keeping the data
persistent over reboots. For now we don't want to persist data and
provide a solution that is inline with the in-memory store of the .metal
instances.

This way we don't have to return EFI_UNSUPPORTED on SetVariable runtime
service. This turned out to cause problems with Linux distribution's
update routings (efibootmgr failing).

Signed-off-by: Hendrik Borghorst <hborghor@amazon.de>
Reviewed-by: Evgeny Iakovlev <eyakovl@amazon.de>
Reviewed-by: Alexander Graf (AWS) <graf@amazon.de>

diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index b1f8140d60..5f10976144 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -219,6 +219,7 @@ ReserveEmuVariableNvStore (
 {
   EFI_PHYSICAL_ADDRESS  VariableStore;
   RETURN_STATUS         PcdStatus;
+  UINT32                VarStoreSize;
 
   VariableStore = (EFI_PHYSICAL_ADDRESS)(UINTN)PlatformReserveEmuVariableNvStore ();
   PcdStatus     = PcdSet64S (PcdEmuVariableNvStoreReserved, VariableStore);
@@ -227,6 +228,12 @@ ReserveEmuVariableNvStore (
   PlatformInitEmuVariableNvStore ((VOID *)(UINTN)VariableStore);
  #endif
 
+  VarStoreSize = 2 * PcdGet32 (PcdFlashNvStorageFtwSpareSize);
+
+  // Clean variable space for now, as we don't want to persist variables over reboot
+  if ((VOID *)(UINTN)VariableStore != NULL)
+    SetMem((VOID *)(UINTN)VariableStore, VarStoreSize, 0x0);
+
   ASSERT_RETURN_ERROR (PcdStatus);
 }