Re: [PATCH v2 0/5] Allocate memmap from hotadded memory

Michal Hocko
2019-08-01T07:40:12Z

On Thu 01-08-19 09:31:09, David Hildenbrand wrote:
> On 01.08.19 09:26, David Hildenbrand wrote:
[...]
> > I am not sure about the implications of having
> > pfn_valid()/pfn_present()/pfn_online() return true but accessing it
> > results in crashes. (suspend, kdump, whatever other technology touches
> > online memory)
>
> (oneidea: we could of course go ahead and mark the pages PG_offline
> before unmapping the pfn range to work around these issues)

PG_reserved and an elevated reference count should be enough to drive
any pfn walker out. Pfn walkers shouldn't touch any page unless they
know and recognize their type.
--
Michal Hocko
SUSE Labs