Re: [PATCH v1] MinPlatformPkg: Fix SetLargeVariable fail issue

["Nate DeSimone" <nathaniel.l.desimone@intel.com>]

Great catch Xiaoqiang!

Only issue I see is that for 100% correctness we will need to add a check to see if we are past ExitBootServices(). 

This issue is if we are in OS runtime and we try to overwrite an existing variable when there isn't enough space to do so without a reclaim... the current value of the large variable will be deleted and it will be impossible to store the new value until after a platform reset.

To do this check you will need to add an AtOsRuntime() API to the VariableWriteLib implemented in MinPlatformPkg/Library/DxeRuntimeVariableWriteLib and MinPlatformPkg/Library/SmmVariableWriteLib to check for OS runtime. The DXE implementation can just be a passthrough to EfiAtRuntime() in MdePkg/Library/UefiRuntimeLib. But the SMM one will need to add a notification callback for gEdkiiSmmExitBootServicesProtocolGuid and set a global variable to indicate whether that event has been triggered yet. Because UefiRuntimeLib can only be used by DXE_RUNTIME drivers, you will need to make a separate version of this library for boot time only DXE_DRIVERs that has an implementation of AtOsRuntime() that always returns FALSE.

-----Original Message-----
From: Zhang, Xiaoqiang <xiaoqiang.zhang@intel.com> 
Sent: Monday, May 8, 2023 10:39 PM
To: devel@edk2.groups.io
Cc: Zhang, Xiaoqiang <xiaoqiang.zhang@intel.com>; Chiu, Chasel <chasel.chiu@intel.com>; Desimone, Nathaniel L <nathaniel.l.desimone@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>; Dong, Eric <eric.dong@intel.com>
Subject: [PATCH v1] MinPlatformPkg: Fix SetLargeVariable fail issue

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4454

On Server platform, when the large variable "FspNvsBuffer" is already in the UEFI variable store and the remaining variable storage space is less than the large variable size. And also not in OS runtime then we need to add the size of the current data that will end up being replaced by the new data to the remaining space before we decide that there is not enough space to store the large variable.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Eric Dong <eric.dong@intel.com>

Signed-off-by: Xiaoqiang Zhang <xiaoqiang.zhang@intel.com>
---
 Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/LargeVariableWriteLib.c       | 10 +++++++++-
 Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/BaseLargeVariableWriteLib.inf |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/LargeVariableWriteLib.c b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/LargeVariableWriteLib.c
index de23ae6160..da820f65b9 100644
--- a/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/LargeVariableWriteLib.c
+++ b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/LargeVa
+++ riableWriteLib.c
@@ -22,7 +22,7 @@
 #include <Library/PrintLib.h>
 #include <Library/VariableReadLib.h>
 #include <Library/VariableWriteLib.h>
-
+#include <Library/LargeVariableReadLib.h>
 #include "LargeVariableCommon.h"
 
 /**
@@ -270,6 +270,7 @@ SetLargeVariable (
   UINT8         *OffsetPtr;
   UINTN         BytesRemaining;
   UINTN         SizeToSave;
+  UINTN         BufferSize = 0;
 
   //
   // Check input parameters.
@@ -365,6 +366,13 @@ SetLargeVariable (
     // Non-Volatile storage to store the data.
     //
     RemainingVariableStorage = GetRemainingVariableStorageSpace ();
+    //
+    // Check if current variable already existed in NV storage variable space
+    //
+    Status = GetLargeVariable (VariableName, VendorGuid, &BufferSize, NULL);
+    if ((Status == EFI_BUFFER_TOO_SMALL) && (BufferSize != 0)) {
+      RemainingVariableStorage = RemainingVariableStorage + BufferSize;
+    }
     if (DataSize > RemainingVariableStorage) {
       DEBUG ((DEBUG_ERROR, "SetLargeVariable: Not enough NV storage space to store the data\n"));
       Status = EFI_OUT_OF_RESOURCES;
diff --git a/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/BaseLargeVariableWriteLib.inf b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/BaseLargeVariableWriteLib.inf
index 2493a94596..cbc2a5d93a 100644
--- a/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/BaseLargeVariableWriteLib.inf
+++ b/Platform/Intel/MinPlatformPkg/Library/BaseLargeVariableLib/BaseLar
+++ geVariableWriteLib.inf
@@ -49,3 +49,4 @@
   PrintLib
   VariableReadLib
   VariableWriteLib
+  LargeVariableReadLib
--
2.39.1.windows.1