[RFC PATCH 3/8] powerpc/64s: put the per-cpu data_offset in r14

[Nicholas Piggin]

On Wed, 20 Dec 2017 18:53:24 +0100
Gabriel Paubert <paubert at iram.es> wrote:

> On Thu, Dec 21, 2017 at 12:52:01AM +1000, Nicholas Piggin wrote:
> > Shifted left by 16 bits, so the low 16 bits of r14 remain available.
> > This allows per-cpu pointers to be dereferenced with a single extra
> > shift whereas previously it was a load and add.
> > ---
> >  arch/powerpc/include/asm/paca.h   |  5 +++++
> >  arch/powerpc/include/asm/percpu.h |  2 +-
> >  arch/powerpc/kernel/entry_64.S    |  5 -----
> >  arch/powerpc/kernel/head_64.S     |  5 +----
> >  arch/powerpc/kernel/setup_64.c    | 11 +++++++++--
> >  5 files changed, 16 insertions(+), 12 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> > index cd6a9a010895..4dd4ac69e84f 100644
> > --- a/arch/powerpc/include/asm/paca.h
> > +++ b/arch/powerpc/include/asm/paca.h
> > @@ -35,6 +35,11 @@
> >  
> >  register struct paca_struct *local_paca asm("r13");
> >  #ifdef CONFIG_PPC_BOOK3S
> > +/*
> > + * The top 32-bits of r14 is used as the per-cpu offset, shifted by PAGE_SHIFT.  
> 
> Top 32, really? It's 48 in later comments.

Yep, I used 32 to start with but it wasn't enough. Will fix.

Thanks,
Nick