Re: [RFC PATCH v2 6/6] x86/entry/pti: don't switch PGD on when pti_disable is set

[Ingo Molnar]

* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> > Oh, and yes, I think the npti flag should also break ptrace(). I do agree with 
> > Andy that it's a "capability", although I do not think it should actually be 
> > implemented as one.
> 
> For all that Linux capabilities are crap, nopti walks like one and quacks like 
> one.  It needs to affect ptrace() permissions, it needs a way to disable it 
> systemwide, it needs LSM integration, etc.  Using CAP_DISABLE_PTI gives us all 
> of this without tons of churn, auditing, and a whole new configuration thingy 
> for each LSM.  And I avoids permanently polluting ptrace checks, the LSM 
> interface, etc for what is, essentially, a performance hack to work around a 
> blatant error in the design of some CPUs.
> 
> Plus, with ambient caps, we already did the nasty part of the with and finished 
> all the relevant bikeshedding.
> 
> So I'd rather just hold my nose and add the new capability bit.

Those all seem pretty valid arguments to me.

Thanks,

	Ingo