Subject: Re: [PATCH 1/2] powerpc: add Book E support to 64-bit hibernation

From: Scott Wood <[email-masked]>
Date: Mon, 17 Jun 2013 19:22:03 -0500

On 06/17/2013 07:17:30 PM, Benjamin Herrenschmidt wrote:
> On Mon, 2013-06-17 at 19:01 -0500, Scott Wood wrote:
> > I really doubt the exception scratch registers need to be saved --
> > we're not trying to restore into the middle of an exception
> > prolog/epilog.
> >
> > book3s has the PACA as well and they don't save it.  Don't we rely =20
> on
> > things like boot-time memory allocations happening in the same place
> > when we resume?  extlb is part of the PACA, so the same applies.
>=20
> I doubt we seriously tested hibernation :-) The PACA SPR should
> definitely be saved/restored.

OK.  It's not obvious to me how much the entire mechanism depends on =20
things like boot time allocations being the same each time -- if we do =20
depend on that in general, then the PACA shouldn't change on a =20
particular CPU, right?

Is it possible to restore on a different CPU than we saved on?  If so, =20
could restoring the PACA leave us pointing to a different CPU's PACA?

-Scott=