Re: [PATCHv3 1/2] mm/memblock: extend the limit inferior of bottom-up after parsing hotplug attr

[Pingfan Liu]

I send out a series [RFC PATCH 0/4] x86_64/mm: remove bottom-up
allocation style by pushing forward the parsing of mem hotplug info (
https://lore.kernel.org/lkml/1546849485-27933-1-git-send-email-kernelfans@xxxxxxxxx/T/#t).
Please give comment if you are interested.

Thanks,
Pingfan

On Fri, Jan 4, 2019 at 2:47 AM Tejun Heo <tj@xxxxxxxxxx> wrote:
>
> Hello,
>
> On Wed, Jan 02, 2019 at 07:05:38PM +0200, Mike Rapoport wrote:
> > I agree that currently the bottom-up allocation after the kernel text has
> > issues with KASLR. But this issues are not necessarily related to the
> > memory hotplug. Even with a single memory node, a bottom-up allocation will
> > fail if KASLR would put the kernel near the end of node0.
> >
> > What I am trying to understand is whether there is a fundamental reason to
> > prevent allocations from [0, kernel_start)?
> >
> > Maybe Tejun can recall why he suggested to start bottom-up allocations from
> > kernel_end.
>
> That's from 79442ed189ac ("mm/memblock.c: introduce bottom-up
> allocation mode").  I wasn't involved in that patch, so no idea why
> the restrictions were added, but FWIW it doesn't seem necessary to me.
>
> Thanks.
>
> --
> tejun