If a system does not support setting the platform profile (i.e., does
not have the file /sys/firmware/acpi/platform_profile), then everything
that interacts with it is skipped to prevent errors. This situation is
more common than I expected.[1]
[1] https://github.com/FeralInteractive/gamemode/issues/524
This reduces duplication of the split lock mitigation path.
Additionally, it allows extending the functionality of procsysctl into
also getting the split lock mitigation state.
The platform profile lives in /sys/firmware/acpi/platform_profile. The
desiredprof and defaultprof options correspond to the values for the
platform profile set when gamescope begins and ends, respectively.
HACK: The platform profile may restrict what values the governor can
take, so we choose to set the governor before the platform profile in
order to store the correct default governor, and restore the platform
profile before the governor. This is done to maximize correctness after
restoration, but it can cause issues if the previous platform profile
restricts the governor.
TODO: Save all the state we care about before any of it is changed. In
thsi case, we should set (and restore) the platform profile before the
governor.
