ZONE_DEVICE and pmem API support for powerpc

[Dan Williams]

On Tue, Apr 11, 2017 at 10:42 AM, Oliver O'Halloran <oohall at gmail.com> wrote:
> Hi all,
>
> This series adds support for ZONE_DEVICE and the pmem api on powerpc. Namely,
> support for altmaps and the various bits and pieces required for DAX PMD faults.
> The first two patches touch generic mm/ code, but otherwise this is fairly well
> contained in arch/powerpc.
>
> If the nvdimm folks could sanity check this series I'd appreciate it.

Quick feedback: I'm in the process of cleaning up and resubmitting my
patch set to push the pmem api down into the driver directly.

    https://lwn.net/Articles/713064/

I'm also reworking memory hotplug to allow sub-section allocations
which has collided with Michal Hocko's hotplug reworks. It will be
good to have some more eyes on that work to understand the cross-arch
implications.

    https://lkml.org/lkml/2017/3/19/146

> Series is based on next-20170411, but it should apply elsewhere with minor
> fixups to arch_{add|remove}_memory due to conflicts with HMM.  For those
> interested in testing this, there is a driver and matching firmware that carves
> out some system memory for use as an emulated Con Tutto memory card.
>
> Driver: https://github.com/oohal/linux/tree/contutto-next
> Firmware: https://github.com/oohal/skiboot/tree/fake-contutto
>
> Edit core/init.c:686 to control the amount of memory borrowed for the emulated
> device.  I'm keeping the driver out of tree for a until 4.13 since I plan on
> reworking the firmware interface anyway and There's at least one showstopper
> bug.

Is this memory card I/O-cache coherent? I.e. existing dma mapping api
can hand out mappings to it? Just trying to figure out if this the
existing pmem-definition of ZONE_DEVICE or a new one.