[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 at linux.ibm.com>
>>>>
>>>> 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