# Re: \[PATCH v1 5/7\] mm: introduce page\_offline\_(begin\|end\|freeze\|unfreeze) to synchronize setting PageOffline()

- From: David Hildenbrand \<hidden\>
- Date: 2021-05-03 08:11:36 
- List: linux-mm
- Page: https://ratatoskr.run/linux-mm/2021/05/205156
- Thread: https://ratatoskr.run/linux-hyperv/2021/04/204966/t.md

```text
On 02.05.21 08:33, Mike Rapoport wrote:
> On Thu, Apr 29, 2021 at 02:25:17PM +0200, David Hildenbrand wrote:
>> A driver might set a page logically offline -- PageOffline() -- and
>> turn the page inaccessible in the hypervisor; after that, access to page
>> content can be fatal. One example is virtio-mem; while unplugged memory
>> -- marked as PageOffline() can currently be read in the hypervisor, this
>> will no longer be the case in the future; for example, when having
>> a virtio-mem device backed by huge pages in the hypervisor.
>>
>> Some special PFN walkers -- i.e., /proc/kcore -- read content of random
>> pages after checking PageOffline(); however, these PFN walkers can race
>> with drivers that set PageOffline().
>>
>> Let's introduce page_offline_(begin|end|freeze|unfreeze) for
>
> Bikeshed: freeze|thaw?
>

Sure :)


-- 
Thanks,

David / dhildenb


```