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

On Wed, Aug 14, 2019 at 08:10:59AM +0200, Christophe Leroy wrote:

quoted

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.