ReBarDxe: Add CMOS reset detection

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2022 xCuri0
+Copyright (c) 2022-2023 xCuri0
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -22,7 +22,7 @@ Run ReBarState (found in Releases) and set the Resizable BAR size. **If Resizabl
 
 If you have any issues after enabling Resizable BAR see [Common Issues (and fixes)](https://github.com/xCuri0/ReBarUEFI/wiki/Common-issues-(and-fixes))
 
-**Some firmware don't clear NVRAM variables (ReBarState) when the CMOS is cleared. This can be a problem as CMOS clear will reset BIOS settings (4G/CSM) while keeping ReBarState enabled requiring you to boot with iGPU/non-rebar GPU to disable ReBarState. To mitigate this issue see wiki page [Enabling 4G Decode and CSM Off by default](https://github.com/xCuri0/ReBarUEFI/wiki/Enabling-4G-Decode-and-CSM-Off-by-default). If it can be figured out how to detect boot failures then this won't be required**
+You won't have any issues with clearing CMOS like on earlier builds, there is now CMOS reset detection by checking system date.
 
 ### AliExpress X99 Tutorial by Miyconst
 [![Resizable BAR on LGA 2011-3 X99](http://img.youtube.com/vi/vcJDWMpxpjE/0.jpg)](http://www.youtube.com/watch?v=vcJDWMpxpjEE "Resizable BAR on LGA 2011-3 X99")

ReBarDxe/ReBar.c

@@ -1,5 +1,5 @@
 /*
-Copyright (c) 2022 xCuri0 <[email protected]>
+Copyright (c) 2022-2023 xCuri0 <[email protected]>
 SPDX-License-Identifier: MIT
 */
 #include <Uefi.h>
@@ -24,6 +24,9 @@ SPDX-License-Identifier: MIT
 // for quirk
 #define PCI_VENDOR_ID_ATI 0x1002
 
+// if system time is before this year then CMOS reset will be detected and rebar will be disabled.
+#define BUILD_YEAR 2023
+
 // a3c5b77a-c88f-4a93-bf1c-4a92a32c65ce
 static GUID reBarStateGuid = { 0xa3c5b77a, 0xc88f, 0x4a93, {0xbf, 0x1c, 0x4a, 0x92, 0xa3, 0x2c, 0x65, 0xce}};
 
@@ -286,6 +289,7 @@ EFI_STATUS EFIAPI rebarInit(
     UINTN bufferSize = 1;
     EFI_STATUS status;
     UINT32 attributes;
+    EFI_TIME time;
 
     DEBUG((DEBUG_INFO, "ReBarDXE: Loaded\n"));
 
@@ -301,6 +305,21 @@ EFI_STATUS EFIAPI rebarInit(
     if (reBarState)
     {
         DEBUG((DEBUG_INFO, "ReBarDXE: Enabled, maximum BAR size 2^%u MB\n", reBarState));
+
+        // Detect CMOS reset by checking if year before BUILD_YEAR
+        status = gRT->GetTime (&time, NULL);
+        if (time.Year < BUILD_YEAR) {
+            reBarState = 0;
+            bufferSize = 1;
+            attributes = EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS;
+
+            status = gRT->SetVariable(L"ReBarState", &reBarStateGuid,
+                attributes,
+                bufferSize, &reBarState);
+
+            return EFI_SUCCESS;
+        }
+
         // For overriding PciHostBridgeResourceAllocationProtocol
         pciHostBridgeResourceAllocationProtocolHook();
     }

ReBarState/ReBarState.cpp

@@ -163,7 +163,7 @@ int main()
 		std::cout << "ReBarState variable doesn't exist / Disabled. Enter a value to create it\n";
 	}
 
-	std::cout << "\nVerify that 4G Decoding is enabled otherwise system will not POST with GPU. There is also a possibility of BIOS not supporting large BARs even with 4G decoding enabled.\n";
+	std::cout << "\nVerify that 4G Decoding is enabled otherwise system will not POST with GPU. If your ReBarState value keeps getting reset then check your system time.\n";
 	std::cout << "\nIt is recommended to first try smaller sizes above 256MB in case BIOS doesn't support large BARs.\n";
 	std::cout << "\nEnter ReBarState Value\n      0: Disabled \nAbove 0: Maximum BAR size set to 2^x MB \n     32: Unlimited BAR size\n\n";