Re: [PATCH v1 05/10] powerpc/mm: Do early ioremaps from top to bottom on PPC64 too.

[Christoph Hellwig]

On Wed, Aug 14, 2019 at 08:10:59AM +0200, Christophe Leroy wrote:
> > Note that while a few other architectures have a magic hack like powerpc
> > to make ioremap work before vmalloc, the normal practice would be
> > to explicitly use early_ioremap.  I guess your change is fine for now,
> > but it might make sense convert powerpc to the explicit early_ioremap
> > scheme as well.
> > 
> 
> I've been looking into early_ioremap(), but IIUC early_ioremap() is for
> ephemeral mappings only, it expects all early mappings to be gone at the end
> of init.

Yes.

> PPC installs definitive early mappings (for instance for PCI). How does that
> have to be handled ?

Good question, and no good answer.  I've just been looking at a generic
ioremap for simple architectures, and been finding all kinds of crap
and inconsistencies, and this is one of the things I noticed.