Re: [Bug 206401] kernel panic on Hyper-V after 5 minutes due to memory hot-add

[David Hildenbrand <david@redhat.com>]

On 18.02.20 10:19, kkabe@vega.pgw.jp wrote:
> mhocko@kernel.org sed in <20200218084700.GD21113@dhcp22.suse.cz>
> 
>>> On Tue 18-02-20 15:24:48, kkabe@vega.pgw.jp wrote:
>>> [...]
>>>> Tried out the above patch.
>>>> It seems to be working; no panic, total memory has increased and
>>>> the hot-added memory is added as HIGHMEM.
>>>
>>> I was about to post a patch to mark hotplug broken on 32b but it seems
>>> you do care about this setup. Could you describe your usecase please?
> 
> My usecase is testing out the kernel on Hyper-V before loading it on
> real i686 machine. Hyper-V machine is faster to skim out other bugs.
> So memory hot-add is not a must requirement for me,
> but having hot-add may be handy to see the application memory requirement.
> (as in the anaconda test revealed)
> 
> If we're disabling it, we have to announce it somewhere;
> where is appropriate? `modinfo hv_balloon`'s "hot_add" description?
> 

I'd really vote to just disable that. Basic testing of kernels can be
done without memory hotadd. If I am not wrong, doing a "online_movable"
or "online_kernel" from user space could still make us trigger crashes
and would have to be fenced.

-- 
Thanks,

David / dhildenb