RE: [PATCH] x86/mce: drop cpu_missing since we have more capable mce_missing_cpus

["Luck, Tony" <tony.luck@intel.com>]

> what do we do with the sysfs knob? It probably is an ABI:
>
> /sys/devices/system/machinecheck/machinecheck1/tolerant
> /sys/devices/system/machinecheck/machinecheck2/tolerant

$ git grep tolerant -- Documentation/ABI/
$

An undocumented ABI! Well, not documented with all the other sysfs bits.

It does appear in:
Documentation/x86/x86_64/machinecheck.rst

Of course, like a lot of documentation, it isn't accurate. It wasn't
updated to describe what happens with recoverable errors.
Final paragraph says:

        Note this only makes a difference if the CPU allows recovery
        from a machine check exception. Current x86 CPUs generally do not.

Recovery was first introduced in the Nehalem generation which ark.intel.com
says was launched in Q1'2010. So over a decade.

Choices:
1) Leave the file there, but remove the code that uses the value
2) Delete the file too

Option 1 doesn't break any scripts that look for the file, but may make
people shout louder when they find it no longer does anything.

Option 2 is the more honest approach.


-Tony