Re: [PATCH v2 0/2] mm: Memory offlining + page isolation cleanups

[David Hildenbrand]

On 22.10.19 10:08, Michal Hocko wrote:
> On Tue 22-10-19 08:52:28, David Hildenbrand wrote:
> > On 21.10.19 19:23, David Hildenbrand wrote:
> > > Two cleanups that popped up while working on (and discussing) virtio-mem:
> > >    https://lkml.org/lkml/2019/9/19/463
> > >
> > > Tested with DIMMs on x86.
> > >
> > > As discussed with michal in v1, I'll soon look into removing the use
> > > of PG_reserved during memory onlining completely - most probably
> > > disallowing to offline memory blocks with holes, cleaning up the
> > > onlining+offlining code.
> >
> > BTW, I remember that ZONE_DEVICE pages are still required to be set
> > PG_reserved. That has to be sorted out first.
>
> Do they?

Yes, especially KVM code :/

> > I remember that somebody was
> > working on it a while ago but didn't hear about that again. Will look into
> > that as well - should be as easy as adding a zone check (if there isn't a
> > pfn_to_online_page() check already). But of course, there might be special
> > cases ....
>
> I remember Alexander didn't want to change the PageReserved handling
> because he was worried about unforeseeable side effects. I have a vague
> recollection he (or maybe Dan) has promissed some follow up clean ups
> which didn't seem to materialize.

I'm looking into it right now, especially the KVM part.

--

Thanks,

David / dhildenb