On 16.10.19 16:09, Michal Hocko wrote:
On Wed 16-10-19 15:55:00, David Hildenbrand wrote:
On 16.10.19 15:45, Michal Hocko wrote:
[...]
There is state stored in the struct page. In other words this shouldn't
be really different from HWPoison pages. I cannot find the code that is
doing that and maybe we don't handle that. But we cannot simply online
hwpoisoned page. Offlining the range will not make a broken memory OK
all of the sudden. And your usecase sounds similar to me.
Sorry to say, but whenever we online memory the memmap is overwritten,
because there is no way you could tell it contains garbage or not. You have
to assume it is garbage. (my recent patch even poisons the memmap when
offlining, which helped to find a lot of these "garbage memmap" BUGs)
online_pages()
...
move_pfn_range_to_zone(zone, pfn, nr_pages, NULL);
...
memmap_init_zone()
-> memmap initialized
So yes, offlining memory with HWPoison and re-onlining it effectively drops
HWPoison markers. On the next access, you will trigger a new HWPoison.
Right you are! I need to sit on this much more and think about it with a
clean head.
Sure, take your time and let me know if you need any details on how
virtio-mem works, how it uses these interfaces, and how the mm internals
it uses play along.
Thanks Michal!
--
Thanks,
David / dhildenb
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