The kvmtool option '--flash <flash filename>' is used to launch
a guests VM with a CFI flash device that maps the flash file
specified at the command line.
However, kvmtool allows guest VMs to be launched without a CFI
flash device. In such scenarios the firmware can utilize the
emulated variable storage for UEFI variables. To support this
the PCD gEfiMdeModulePkgTokenSpaceGuid.PcdEmuVariableNvModeEnable
must be set to TRUE.

Therefore, update the NorFlashKvmtoolLib to fallback to variable
emulation if a CFI device is not detected. Also improve the error
logging.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
---
 ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtool.c      | 38 +++++++++++++++++---
 ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtoolLib.inf |  3 +-
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtool.c b/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtool.c
index 43f5858644b1f47ada17e00fba55a670ab5862bd..2beeefdd272d6f8841f7d0b972394739b745982e 100644
--- a/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtool.c
+++ b/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtool.c
@@ -1,7 +1,7 @@
 /** @file
    An instance of the NorFlashPlatformLib for Kvmtool platform.
 
- Copyright (c) 2020, ARM Ltd. All rights reserved.<BR>
+ Copyright (c) 2020 - 2023, Arm Ltd. All rights reserved.<BR>
 
  SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -228,7 +228,7 @@ NorFlashPlatformLibConstructor (
   CONST CHAR8   *Label;
   UINT32        LabelLen;
 
-  if (mNorFlashDeviceCount != 0) {
+  if ((mNorFlashDeviceCount != 0) || PcdGetBool (PcdEmuVariableNvModeEnable)) {
     return EFI_SUCCESS;
   }
 
@@ -337,9 +337,39 @@ NorFlashPlatformLibConstructor (
     }
 
     if (mNorFlashDevices[UefiVarStoreIndex].DeviceBaseAddress != 0) {
-      return SetupVariableStore (&mNorFlashDevices[UefiVarStoreIndex]);
+      Status = SetupVariableStore (&mNorFlashDevices[UefiVarStoreIndex]);
+      if (EFI_ERROR (Status)) {
+        DEBUG ((
+          DEBUG_ERROR,
+          "ERROR: Failed to setup variable store, Status = %r\n",
+          Status
+          ));
+        ASSERT (0);
+      }
+    } else {
+      DEBUG ((
+        DEBUG_ERROR,
+        "ERROR: Invalid Flash device Base address\n"
+        ));
+      ASSERT (0);
+      Status = EFI_NOT_FOUND;
+    }
+  } else {
+    // No Flash device found fallback to Runtime Variable Emulation.
+    DEBUG ((
+      DEBUG_INFO,
+      "INFO: No Flash device found fallback to Runtime Variable Emulation.\n"
+      ));
+    Status = PcdSetBoolS (PcdEmuVariableNvModeEnable, TRUE);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "ERROR: Failed to set PcdEmuVariableNvModeEnable, Status = %r\n",
+        Status
+        ));
+      ASSERT (0);
     }
   }
 
-  return EFI_NOT_FOUND;
+  return Status;
 }
diff --git a/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtoolLib.inf b/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtoolLib.inf
index b5f35d4782896761e7975a6e5c196ff0fab0d6db..fba1245e41ec4b146db79a821b8343247377af41 100644
--- a/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtoolLib.inf
+++ b/ArmVirtPkg/Library/NorFlashKvmtoolLib/NorFlashKvmtoolLib.inf
@@ -1,7 +1,7 @@
 ## @file
 #  Nor Flash library for Kvmtool.
 #
-#  Copyright (c) 2020, ARM Ltd. All rights reserved.<BR>
+#  Copyright (c) 2020 - 2023, Arm Ltd. All rights reserved.<BR>
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
 ##
@@ -39,6 +39,7 @@ [Pcd]
   gArmTokenSpaceGuid.PcdFvBaseAddress
   gArmTokenSpaceGuid.PcdFvSize
 
+  gEfiMdeModulePkgTokenSpaceGuid.PcdEmuVariableNvModeEnable
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingBase
-- 
'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'



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