From 89f7626324077b308f831b678f617aa174b65c14 Mon Sep 17 00:00:00 2001
From: Hendrik Borghorst <hborghor@amazon.de>
Date: Wed, 30 Jun 2021 16:42:01 +0200
Subject: [PATCH] x86: Use simple emulated variable store instead of RAM
 persistent

The ovmf package provides a variable store that is emulating a
flash-based persistence storage for UEFI variable inside the RAM. On
reboot the RAM is persisted so that variables are not reset.

Nitro has no need for that feature and manually wiped the emulated
store on reboot with a previous commit enabling us, to keep certain
variables in the future. The feature was never used.

Now that we are offering the persistent variable soon over Nitro
itself we can just use the RAM-based variable store that has no
persistence. The same store is already used for ARM instances.

Testing done:
- Boot Ubuntu Groovy instance
- Boot Windows 2016 and 2019
- Remove all boot entries in Ubuntu with efibootmgr and reboot
successfully.

- Boot with old Fvb-variable store, remove all variables in guest, LU to
new Nitro with new var store, reboot guest, check variables are
repopulated: Works
- Boot with new variable store, remove all variables in guest, LU to old
Fvb-based variable store, reboot guest, check variables are repopulated:
Works

Signed-off-by: Hendrik Borghorst <hborghor@amazon.de>
Signed-off-by: Sabin Rapan <sabrapan@amazon.com>
Signed-off-by: Costin Lupu <lvpv@amazon.com>
Reviewed-by: Adamos Ttofari <attofari@amazon.de>
Reviewed-by: Evgeny Iakovlev <eyakovl@amazon.de>
Reviewed-by: Lav Joshi <lavjoshi@amazon.de>

diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 190505ba3a..c26832dd43 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -630,6 +630,7 @@
 [PcdsDynamicDefault]
   # only set when
   #   ($(SMM_REQUIRE) == FALSE)
+  gEfiMdeModulePkgTokenSpaceGuid.PcdEmuVariableNvModeEnable|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdEmuVariableNvStoreReserved|0
 
 !if $(SMM_REQUIRE) == FALSE
@@ -1094,12 +1095,6 @@
   !if $(EXTERNAL_VARIABLE_STORE) == TRUE
     nitro/ExtVarStore/ExtVarStore.inf
   !endif
-  OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
-  OvmfPkg/EmuVariableFvbRuntimeDxe/Fvb.inf {
-    <LibraryClasses>
-      PlatformFvbLib|OvmfPkg/Library/EmuVariableFvbLib/EmuVariableFvbLib.inf
-  }
-  MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
   MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf {
     <LibraryClasses>
       NULL|MdeModulePkg/Library/VarCheckUefiLib/VarCheckUefiLib.inf
diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index 5fcf7e9c51..1c59d58970 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -404,10 +404,8 @@ INF  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe.inf
 !if $(EXTERNAL_VARIABLE_STORE) == TRUE
   INF nitro/ExtVarStore/ExtVarStore.inf
 !endif
-INF  OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
-INF  OvmfPkg/EmuVariableFvbRuntimeDxe/Fvb.inf
-INF  MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteDxe.inf
-INF  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf
+# Nitro: We use the Xen VariableRuntimeDxe.inf to eliminate flash
+INF MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf
 !endif
 
 #