Re: [PATCH 03/11] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()

[Andy Lutomirski]

On Mon, Sep 21, 2015 at 11:23 PM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> So when memory hotplug removes a piece of physical memory from pagetable
> mappings, it also frees the underlying PGD entry.
>
> This complicates PGD management, so don't do this. We can keep the
> PGD mapped and the PUD table all clear - it's only a single 4K page
> per 512 GB of memory hotplugged.

Ressurecting an ancient thread: I want this particular change to make
it (much) easier to make vmapped stacks work correctly.  Could it be
applied by itself?

--Andy