Re: [PATCH RFC V3 4/9] x86/pks: Preserve the PKRS MSR on context switch

[Ira Weiny]

On Mon, Oct 19, 2020 at 11:37:14AM +0200, Peter Zijlstra wrote:
> On Fri, Oct 16, 2020 at 10:14:10PM -0700, Ira Weiny wrote:
> > > so it either needs to
> > > explicitly do so, or have an assertion that preemption is indeed
> > > disabled.
> > 
> > However, I don't think I understand clearly.  Doesn't [get|put]_cpu_ptr()
> > handle the preempt_disable() for us? 
> 
> It does.
> 
> > Is it not sufficient to rely on that?
> 
> It is.
> 
> > Dave's comment seems to be the opposite where we need to eliminate preempt
> > disable before calling write_pkrs().
> > 
> > FWIW I think I'm mistaken in my response to Dave regarding the
> > preempt_disable() in pks_update_protection().
> 
> Dave's concern is that we're calling with with preemption already
> disabled so disabling it again is superfluous.

Ok, thanks, and after getting my head straight I think I agree with him, and
you.

Thanks I've reworked the code to removed the superfluous calls.  Sorry about
being so dense...  :-D

Ira