pseries: savevm support for pseries machine

pseries: savevm support for pseries machine

This adds the necessary pieces to implement savevm / migration for the
pseries machine.  The most complex part here is migrating the hash
table - for the paravirtualized pseries machine the guest's hash page
table is not stored within guest memory, but externally and the guest
accesses it via hypercalls.

This patch uses a hypervisor reserved bit of the HPTE as a dirty bit
(tracking changes to the HPTE itself, not the page it references).
This is used to implement a live migration style incremental save and
restore of the hash table contents.

Normally a hash table is 16MB but it can get bigger depending on how
much RAM the guest has. Due to its nature, updates to it are random so
the live migration style is used for it.

In addition it adds VMStateDescription information to save and restore
the (few) remaining pieces of state information needed by the pseries
machine.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1374175984-8930-9-git-send-email-aliguori@us.ibm.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>