Re: [PATCH v17 08/10] PM: hibernate: disable when there are active secretmem users

[David Hildenbrand]

On 08.02.21 11:51, Michal Hocko wrote:
> On Mon 08-02-21 11:32:11, David Hildenbrand wrote:
> > On 08.02.21 11:18, Michal Hocko wrote:
> > > On Mon 08-02-21 10:49:18, Mike Rapoport wrote:
> > > > From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > > >
> > > > It is unsafe to allow saving of secretmem areas to the hibernation
> > > > snapshot as they would be visible after the resume and this essentially
> > > > will defeat the purpose of secret memory mappings.
> > > >
> > > > Prevent hibernation whenever there are active secret memory users.
> > >
> > > Does this feature need any special handling? As it is effectivelly
> > > unevictable memory then it should behave the same as other mlock, ramfs
> > > which should already disable hibernation as those cannot be swapped out,
> > > no?
> >
> > Why should unevictable memory not go to swap when hibernating? We're merely
> > dumping all of our system RAM (including any unmovable allocations) to swap
> > storage and the system is essentially completely halted.
> My understanding is that mlock is never really made visible via swap
> storage.

"Using swap storage for hibernation" and "swapping at runtime" are two 
different things. I might be wrong, though.

--
Thanks,

David / dhildenb