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Aditya reports [0] that his recent MacbookPro crashes in the firmware
when using the variable services at runtime. The culprit appears to be a
call to QueryVariableInfo(), which we did not use to call on Apple x86
machines in the past as they only upgraded from EFI v1.10 to EFI v2.40
firmware fairly recently, and QueryVariableInfo() (along with
UpdateCapsule() et al) was added in EFI v2.00.

The only runtime service introduced in EFI v2.00 that we actually use in
Linux is QueryVariableInfo(), as the capsule based ones are optional,
generally not used at runtime (all the LVFS/fwupd firmware update
infrastructure uses helper EFI programs that invoke capsule update at
boot time, not runtime), and not implemented by Apple machines in the
first place. QueryVariableInfo() is used to 'safely' set variables,
i.e., only when there is enough space. This prevents machines with buggy
firmwares from corrupting their NVRAMs when they run out of space.

Gi...