[RFCv2 7/9] pseries: Add support for hash table resizing

[Paul Mackerras]

On Fri, Jan 29, 2016 at 04:24:01PM +1100, David Gibson wrote:
> This adds support for using experimental hypercalls to change the size
> of the main hash page table while running as a PAPR guest.  For now these
> hypercalls are only in experimental qemu versions.
> 
> The interface is two part: first H_RESIZE_HPT_PREPARE is used to allocate
> and prepare the new hash table.  This may be slow, but can be done
> asynchronously.  Then, H_RESIZE_HPT_COMMIT is used to switch to the new
> hash table.  This requires that no CPUs be concurrently updating the HPT,
> and so must be run under stop_machine().
> 
> This also adds a debugfs file which can be used to manually control
> HPT resizing or testing purposes.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Reviewed-by: Paul Mackerras <paulus at samba.org>