OVMF: NV Variable Store Layout of Larger Build Targets

["Devon Bautista" <dbautista@newmexicoconsortium.org>]

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Hello All,

I am currently working with the Linuxboot developers to improve testing 
kernel + initramfs pairs in firmware using OVMF.

The current maximum image size of an OVMF image is 4MB, which is 
insufficient for storing even a minimal and compressed kernel and 
initramfs. To get around this, we've been maintaining our own fork of 
EDK2 that adds 8MiB and 16MiB OVMF build targets that have enough room 
in the DXE volume to store a reasonably-sized kernel and initramfs. 
However, it would be convenient if upstream EDK2 supported these larger 
OVMF targets.

In discussing this with the previous OVMF maintainer Laszlo Ersek here 
<https://edk2.groups.io/g/devel/message/75794>, it was brought up that:

  * The trend of the ever-growing DXE-phase warrants a larger firmware
    volume size
  * 8MiB and 16MiB image sizes seem to be justified because of this QEMU
    commit
    <https://github.com/qemu/qemu/commit/0657c657eb37bb48bfd9fe3ae8a323ae3455f47b>

However, as Laszlo mentioned, introducing a larger volume size is 
compatibility breaking, and so seizing the opportunity to come up with a 
larger non-volatile variable store layout is necessary.

That said, I would like to use this thread to discuss among hardware 
vendors an optimal variable store layout for these larger image sizes.

Best,
Devon


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