OVMF dynamic NVRAM size discovering

[Denis Plotnikov <dplotnikov@virtuozzo.com>]

Hello!

I'd like to ask whether it's a good idea or not to make the omfv
discover the variable image size in the runtime.

We have a setting in our product to use separate pflash images for OVMF
code and variables parts in QEMU/KVM based virtual machines.
Currently, we use a 2M code image but want to switch to using a 4M ones
to extend the variable values storage, because of Windows certification
requirements.

We think of adding an ability to OVFM to discover the size of the 
variable part
dynamically.

It could work like the following:
1. teach qemu to provide the size of pflash0 and pflash1 via fw_cfg
2. modify OVMF in order to discover the variable size part dynamically 
via fw_cfg and adjust the OVMF's inner parameters accordingly

We have some concerns about our understanding of OVMF and would like to 
ask to
evaluate the approach suggested.
Is it feasible? Do we miss something?

-- 
Best,
Denis