UEFI grT->GetVariable() returning Not Found Status

[PopoviciPaul]

Hi. I made an app with EDK2 in which I am trying to read a UEFI variable which I'm setting from Ubuntu OS on a QEMU environment.

This is the code:

EFI_STATUS
EFIAPI
UefiMain(
    IN EFI_HANDLE ImageHandle,
    IN EFI_SYSTEM_TABLE *SystemTable
) {
    EFI_STATUS Status;
    UINT8 CheckValue;
    UINTN DataSize = sizeof(CheckValue);
    UINT32 Attributes;  

    Status = gRT->GetVariable(
        L"my_variable",
        &MyGuid,
        &Attributes,    
        &DataSize,
        &CheckValue
    );
if (EFI_ERROR(Status)) {
        Print(L"Error: variable not found. Returning\n");
        return EFI_SUCCESS;
    }

    if (CheckValue != 100) {
        Print(L"Variable is not set to 100. Returning\n");
        return EFI_SUCCESS;
    }

And the value is beiing set like this from Ubuntu OS on QEMU with this script:

#!/bin/bash

VAR_NAME="my_variable"
GUID="12345678-1234-1234-1234-123456789abc"
DATA_FILE="/tmp/check_data"

echo -ne '\x07\x00\x00\x00\x64' > "$DATA_FILE"

sudo efivar --name "${GUID}-${VAR_NAME}" --write --data "$DATA_FILE"

rm "$DATA_FILE"

As you can see from the script I am trying to set the variable to 100(0x64). I also have another similar script for setting it to 0. At boottime when UEFI shell comes up I read the value with dmpstore command and I confirm that it's value is 0x64(100). However when the application tries to read it with GetVariable() as in the above example it doesn't find it as if the variable would not exist(Not found status).
My variable which I set from ubuntu has following propreties: Non-Volatile, Boot Service Access, Runtime service Access. So the way I see it it should be accessible for the app.
I am reading through UEFI specs but I have not figured out what the issue is. Please help me fix this if possible. Thanks.

[AndrewFalanga]

I cannot say with certainty what the problem might be. I would check the following

• Ensure that the variable truly is written with the non-volatile NV attribute when you make it. Your example seems to assume it will be assigned, but this may not be the case.
• Be sure you have a backing store for the non volatile variables to stay. (if you're immediately restarting the vm, as in rebooting from the OS, this is less likely to be the case)