Re: GPZv4

[Thomas Gleixner <tglx@linutronix.de>]

On Tue, 17 Apr 2018, speck for Jon Masters wrote:
> So we need to close on the following urgently:
>
> 1). What are we going to refer to this as?
> 	- MDD
> 	- SSB
> 	- something else?
> 
> In the case of "MDD" it's x86 specific and "enabling" it means you
> disable a feature (MD). To me, that seems to be inverted logic. You
> would set it to "on", "off", or "kernel" (MD only in userspace).

No it's not inverted logic. It's the same logic as kpti= and spectre_v2=
and we are not going to make this one the other way round just because.

So we need a acronym for it, which fits the problem. Either use the code
name for this thing like we did with spectre or 'mdd' which describes it
really well.

> 2). We need a prctl option for a task to request behavior for SSB. One
> option could be a new PR_SET_MITIGATION where we then have minor
> parameters for additional mitigations that are required later.

And we need ponies.....

Seriously. We do the simple 'xxx=' command line option now and have that
ready ASAP in case the embargo ends early.

The prctl is an optimization which can be done afterwards and we first need
to agree whether we want it at all. I'm not too fond of yet another
conditional branch in the entry/exit code. The code patching there is
already bad enough. If we keep up adding this crap at that rate then we
have sooner than later more NOOPs and conditionals than actual code.

Thanks,

	tglx