Re: [RFC 0/3] Prototype PAPR hash page table resizing (guest side)

[Anshuman Khandual <khandual@linux.vnet.ibm.com>]

On 12/24/2015 04:08 PM, David Gibson wrote:
> On Thu, Dec 24, 2015 at 02:52:53PM +0530, Anshuman Khandual wrote:
>> > On 12/22/2015 10:44 AM, David Gibson wrote:
>>> > > I've discussed with Paul and Ben previously the possibility of
>>> > > extending PAPR to allow changing the size of a running guest's hash
>>> > > page table (HPT).  This would allow for much more flexible memory
>>> > > hotplug, since the HPT wouldn't have to be sized in advance for the
>>> > > maximum possible memory size of the guest.
>> > 
>> > Does it include reducing the size of HPT as well ?
> It does, but that could fail with H_PTEG_FULL if there's a collision
> between bolted entries in the reduced table.

So in the case when we request for a reduced size HPT table, as mentioned
in the second implementation method, will we allocate the required smaller
HPT table to shadow the original or we just reduce the original HPT in
size without allocating a new one ?