Acer Aspire E5 EFI Vars Write Protected

Discussion in 'BIOS Mods' started by austinghoward, May 25, 2018.

  1. austinghoward

    austinghoward MDL Novice

    May 25, 2018
    Hello all! I've been scouring the internet over the last couple of weeks looking into how to turn on hardware virtualization for my Acer Aspire E5-553G. As with many other Acer laptops this one comes with the Insyde H20, I believe the setup utility calls it v5.0, but dmidecode lists it as v 1.13.

    Anyway I have Arch linux installed on it and that boots fine from EFI, and auto mounts the efivarfs to `/sys/firmware/efi/efivars`. Through various sources, I've uncovered that the variable resides at address 0xee and needs to be flipped to 0x1. Easy enough, copy the `/sys/firmware/efi/efivars/Setup-a04a27f4-df00-4d42-b552-39511302113d`, modify the appropriate byte and write the file back, right? This is where I ran into some issues, after modifying the file, I can't write it back. I get the following error:

    cp: error writing '/sys/firmware/efi/efivars/Setup-a04a27f4-df00-4d42-b552-39511302113d': Read-only file system

    So I check the mount listing to make sure it's not mounted readonly and I find this:

    efivarfs on /sys/firmware/efi/efivars type efivarfs (rw,relatime)

    That looks fine to me. A little digging on the arch wiki and I find mention of rebooting with the kernel option `efi_no_storage_paranoia`. Tried this, and it seems to make no difference.

    I went back to the drawing board and decided to compile a UEFI bootable image from the grub sources with a custom command built-in to write to the Setup UEFI variables. After some googling and coding the module, I have bootable image, reboot to it and it fails writing to the variable as well. The error code that it returns indicates that the variable is write-protected as well.

    At this point I'm stumped. Surely this area is not write-protected in the hardware somehow, right? Is there something I am missing that I should have performed prior to writing the variable that may have "unlocked" write mode for that memory?

    Thanks for any tips!