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

Ingo Molnar
2016-03-10T09:56:17Z

* Andy Lutomirski <luto@amacapital.net> wrote:

> On Fri, Feb 12, 2016 at 11:04 AM, Andy Lutomirski <luto@amacapital.net> wrote:
> > On Mon, Sep 21, 2015 at 11:23 PM, Ingo Molnar <mingo@kernel.org> 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?
> >
>
> It's incomplete. pageattr.c has another instance of the same thing.
> I'll see if I can make it work, but I may end up doing something a
> little different.

If so then mind picking up (and fixing ;-) tip:WIP.x86/mm in its entirety? It's
well tested so shouldn't have too many easy to hit bugs. Feel free to rebase and
restructure it, it's a WIP tree.

I keep getting distracted with other things but I'd hate if this got dropped on
the floor.

Thanks,

Ingo