[PATCH 3/8] pseries: phyp dump: reserve-release proof-of-concept

[Paul Mackerras]

Manish Ahuja writes:

> Initial patch for reserving memory in early boot, and freeing it later.
> If the previous boot had ended with a crash, the reserved memory would contain
> a copy of the crashed kernel data.

The main problem I see here is that if this option is turned on, the
kernel now has only 256MB of memory from early boot until
subsys_initcalls are done -- on any machine, and whether or not there
is actually a dump.  That means, for instance, that a machine running
bare-metal (such as a G5) might not be able to allocate the hash table
for the MMU.  Also, any allocations made during that time won't be
able to be node-local.

So it will be necessary to read the flattened device tree early on to
see whether or not there is a dump, so that we don't reserve most of
memory in the cases where there isn't a dump.

Paul.