Re: [PATCH v3 5/5] mm: enable CONFIG_MOVABLE_NODE on powerpc

From: Reza Arbab
Date: Mon Sep 26 2016 - 20:19:42 EST

On Tue, Sep 27, 2016 at 07:15:41AM +1000, Benjamin Herrenschmidt wrote:
What is that business with a command line argument ? Do that mean that
we'll need some magic command line argument to properly handle LPC memory
on CAPI devices or GPUs ? If yes that's bad ... kernel arguments should
be a last resort.

Well, movable_node is just a boolean, meaning "allow nodes which contain only movable memory". It's _not_ like "movable_node=10,13-15,17", if that's what you were thinking.

We should have all the information we need from the device-tree.

Note also that we shouldn't need to create those nodes at boot time,
we need to add the ability to create the whole thing at runtime, we may know
that there's an NPU with an LPC window in the system but we won't know if it's
used until it is and for CAPI we just simply don't know until some PCI device
gets turned into CAPI mode and starts claiming LPC memory...

Yes, this is what is planned for, if I'm understanding you correctly.

In the dt, the PCI device node has a phandle pointing to the memory node. The memory node describes the window into which we can hotplug at runtime.

Reza Arbab