Subject: Re: [PATCH] powerpc 8xx: Loading kernels over 8Mbytes without CONFIG_PIN_TLB

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sun, 08 Dec 2013 07:58:34 +1100

On Sat, 2013-12-07 at 10:39 +0100, christophe leroy wrote:
> Function setup_initial_memory_limit() in mm/init_32.c defines the
> limits 
> based on the parameters given by the bootloader.
> As far as I know, the 8xx doesn't do speculative access just because
> an area is loaded in a TLB Entry.

Speculative accesses are ... speculative :-) The address used for such
an access can be anything really. So yes, architecturally, powerpc
processors can access *anything* speculatively just because there's a
valid non-garded translation.

Whether the 8xx does it at all, I don't know. 44x originally did but
that was so buggy that we had to force G on all mappings (until later
versions of the core just burned the feature out). Pretty much all other
powerpc's do it.

Cheers,
Ben.