Support nested boot.

For example: Ventoy-->rEFInd.iso-->Ventoy-->Windows.iso

EDK2/edk2_mod/edk2-edk2-stable201911/MdeModulePkg/Application/Ventoy/Ventoy.c

@@ -363,10 +363,22 @@ EFI_HANDLE EFIAPI ventoy_get_parent_handle(IN EFI_DEVICE_PATH_PROTOCOL *pDevPath
     return Handle;
 }
 
+STATIC ventoy_ram_disk g_backup_ramdisk_param;
+STATIC ventoy_os_param g_backup_os_param_var;
+
+
 EFI_STATUS EFIAPI ventoy_save_ramdisk_param(VOID)
 {
+    UINTN DataSize;
     EFI_STATUS Status = EFI_SUCCESS;
     EFI_GUID VarGuid = VENTOY_GUID;
+
+    DataSize = sizeof(g_backup_ramdisk_param);
+    Status = gRT->GetVariable(L"VentoyRamDisk", &VarGuid, NULL, &DataSize, &g_backup_ramdisk_param);
+    if (!EFI_ERROR(Status))
+    {
+        debug("find previous ramdisk variable <%llu>", g_backup_ramdisk_param.DiskSize);
+    }
     
     Status = gRT->SetVariable(L"VentoyRamDisk", &VarGuid, 
                   EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
@@ -380,21 +392,38 @@ EFI_STATUS EFIAPI ventoy_delete_ramdisk_param(VOID)
 {
     EFI_STATUS Status = EFI_SUCCESS;
     EFI_GUID VarGuid = VENTOY_GUID;
-    
-    Status = gRT->SetVariable(L"VentoyRamDisk", &VarGuid, 
+
+    if (g_backup_ramdisk_param.DiskSize > 0 && g_backup_ramdisk_param.PhyAddr > 0)
+    {
+        Status = gRT->SetVariable(L"VentoyRamDisk", &VarGuid, 
+                  EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                  sizeof(g_backup_ramdisk_param), &g_backup_ramdisk_param);
+        debug("resotre ramdisk variable %r", Status);
+    }
+    else
+    {
+        Status = gRT->SetVariable(L"VentoyRamDisk", &VarGuid, 
                   EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
                   0, NULL);
-    debug("delete efi variable %r", Status);
+        debug("delete ramdisk variable %r", Status);
+    }
 
     return Status;
 }
 
-
 EFI_STATUS EFIAPI ventoy_save_variable(VOID)
 {
+    UINTN DataSize;
     EFI_STATUS Status = EFI_SUCCESS;
     EFI_GUID VarGuid = VENTOY_GUID;
-    
+
+    DataSize = sizeof(g_backup_os_param_var);
+    Status = gRT->GetVariable(L"VentoyOsParam", &VarGuid, NULL, &DataSize, &g_backup_os_param_var);
+    if (!EFI_ERROR(Status))
+    {
+        debug("find previous efi variable <%a>", g_backup_os_param_var.vtoy_img_path);
+    }
+
     Status = gRT->SetVariable(L"VentoyOsParam", &VarGuid, 
                   EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
                   sizeof(g_chain->os_param), &(g_chain->os_param));
@@ -407,11 +436,21 @@ EFI_STATUS EFIAPI ventoy_delete_variable(VOID)
 {
     EFI_STATUS Status = EFI_SUCCESS;
     EFI_GUID VarGuid = VENTOY_GUID;
-    
-    Status = gRT->SetVariable(L"VentoyOsParam", &VarGuid, 
+
+    if (0 == CompareMem(&(g_backup_os_param_var.guid), &VarGuid, sizeof(EFI_GUID)))
+    {
+        Status = gRT->SetVariable(L"VentoyOsParam", &VarGuid, 
+                  EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                  sizeof(g_backup_os_param_var), &(g_backup_os_param_var));
+        debug("restore efi variable %r", Status);
+    }
+    else
+    {
+        Status = gRT->SetVariable(L"VentoyOsParam", &VarGuid, 
                   EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
                   0, NULL);
-    debug("delete efi variable %r", Status);
+        debug("delete efi variable %r", Status);
+    }
 
     return Status;
 }

EDK2/edk2_mod/edk2-edk2-stable201911/MdeModulePkg/Application/Ventoy/Ventoy.h

@@ -169,7 +169,6 @@ typedef struct ventoy_virt_chunk
 	{ 0x37b87ac6, 0xc180, 0x4583, { 0xa7, 0x05, 0x41, 0x4d, 0xa8, 0xf7, 0x7e, 0xd2 }}
 
 
-#define VTOY_BLOCK_DEVICE_PATH_NAME  L"ventoy"
 
 #if   defined (MDE_CPU_IA32)
   #define VENTOY_UEFI_DESC   L"IA32 UEFI"

EDK2/edk2_mod/edk2-edk2-stable201911/MdeModulePkg/Application/Ventoy/VentoyProtocol.c

@@ -624,26 +624,77 @@ EFI_STATUS EFIAPI ventoy_block_io_flush(IN EFI_BLOCK_IO_PROTOCOL *This)
 	return EFI_SUCCESS;
 }
 
+STATIC UINTN ventoy_get_current_device_path_id(VOID)
+{
+    UINTN i = 0;
+    UINTN Count = 0;
+    UINTN NameLen = 0;
+    UINTN MaxId = 0;
+    UINTN CurId = 0;
+    BOOLEAN Find = FALSE;
+    EFI_HANDLE *Handles = NULL;
+    EFI_STATUS Status = EFI_SUCCESS;
+    EFI_DEVICE_PATH_PROTOCOL *DevicePath = NULL;
+    VENDOR_DEVICE_PATH *venPath = NULL;
+    
+    NameLen = StrSize(L"ventoy_xxx");
+    
+    Status = gBS->LocateHandleBuffer(ByProtocol, &gEfiDevicePathProtocolGuid, 
+                                     NULL, &Count, &Handles);
+    if (EFI_ERROR(Status))
+    {
+        return 0;
+    }
+
+    for (i = 0; i < Count; i++)
+    {
+        Status = gBS->HandleProtocol(Handles[i], &gEfiDevicePathProtocolGuid, (VOID **)&DevicePath);
+        if (EFI_ERROR(Status))
+        {
+            continue;
+        }
+
+        if (DevicePath->Type == HARDWARE_DEVICE_PATH && DevicePath->SubType == HW_VENDOR_DP)
+        {
+            venPath = (VENDOR_DEVICE_PATH *)DevicePath;
+            if (CompareGuid(&venPath->Guid, &gVtoyBlockDevicePathGuid))
+            {
+                CurId = StrDecimalToUintn((CHAR16 *)(venPath + 1) + StrLen(L"ventoy_"));
+                MaxId = MAX(MaxId, CurId);
+                Find = TRUE;
+            }
+        }
+    }
+
+    FreePool(Handles);
+
+    return Find ? (MaxId + 1) : 0;
+}
 
 EFI_STATUS EFIAPI ventoy_fill_device_path(VOID)
 {
+    UINTN CurVtoyDpId = 0;
     UINTN NameLen = 0;
     UINT8 TmpBuf[128] = {0};
     VENDOR_DEVICE_PATH *venPath = NULL;
+    CHAR16 VtoyDpName[32];
+
+    CurVtoyDpId = ventoy_get_current_device_path_id();
+    UnicodeSPrintAsciiFormat(VtoyDpName, sizeof(VtoyDpName), "ventoy_%03lu", CurVtoyDpId);
 
     venPath = (VENDOR_DEVICE_PATH *)TmpBuf;
-    NameLen = StrSize(VTOY_BLOCK_DEVICE_PATH_NAME);
+    NameLen = StrSize(VtoyDpName);
     venPath->Header.Type = HARDWARE_DEVICE_PATH;
     venPath->Header.SubType = HW_VENDOR_DP;
     venPath->Header.Length[0] = sizeof(VENDOR_DEVICE_PATH) + NameLen;
     venPath->Header.Length[1] = 0;
     CopyMem(&venPath->Guid, &gVtoyBlockDevicePathGuid, sizeof(EFI_GUID));
-    CopyMem(venPath + 1, VTOY_BLOCK_DEVICE_PATH_NAME, NameLen);
+    CopyMem(venPath + 1, VtoyDpName, NameLen);
     
     gBlockData.Path = AppendDevicePathNode(NULL, (EFI_DEVICE_PATH_PROTOCOL *)TmpBuf);
     gBlockData.DevicePathCompareLen = sizeof(VENDOR_DEVICE_PATH) + NameLen;
 
-    debug("gBlockData.Path=<%s>\n", ConvertDevicePathToText(gBlockData.Path, FALSE, FALSE));
+    debug("gBlockData.Path=<%lu><%s>\n", CurVtoyDpId, ConvertDevicePathToText(gBlockData.Path, FALSE, FALSE));
 
     return EFI_SUCCESS;
 }