Re: [PATCH] powerpc/64s: use ibm,tlbiel-congruence-classes-(hash|radix) dt property

[Nicholas Piggin <npiggin@gmail.com>]

On Mon, 24 Apr 2017 10:13:23 +1000
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Sun, 2017-04-23 at 19:57 +1000, Nicholas Piggin wrote:
> > On Sun, 23 Apr 2017 10:39:11 +1000
> > Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> >   
> > > On Sun, 2017-04-23 at 09:14 +1000, Nicholas Piggin wrote:  
> > > > I think we were going to take another look at moving the setup
> > > > code
> > > > later, but I think that might wait until 4.13.    
> > > 
> > > Except without that we won't boot a post-P9 CPU right ? So we'll
> > > end up
> > > having to chase distros to backport it :-( Oh well...  
> > 
> > Okay, well what if we just move the TLB flushing to somewhere like
> > early_init_mmu(_secondary) for power CPUs first?
> > 
> > Non-local tlbie does not seem to have this requirement, so would it
> > make it more robust just to execute that once during boot with the
> > primary thread?  
> 
> I wouldn't do a broadcast before we have LPCR setup... but for no
> obvious reason. Also I'm not sure our boot time cleanup does things
> properly vs hash & radix. I think we really need 2 passes.
> 
> Oh well..
> 
> My main worry is the fact that on future chip we won't be setting up
> LPCR properly. We should at least assume an unknown chip is P9, is that
> what you do with your cpu-features patches ?

cpu-features patches set up LPCR based on ISAv3 compatible MMU property
(among other things). In case that does not match, we currently don't do
anything graceful.

Actually those patches I think are missing the TLB flush though, which
I will add as a per-cpu local flush in the MMU setup path.