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

[Andy Lutomirski]

On Fri, Feb 12, 2016 at 11:04 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> 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?
>

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.

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC