Re: [Xen-devel] [PATCH RFC 7/8] mm: allow to control onlining/offlining of memory by a driver

[David Hildenbrand <david@xxxxxxxxxx>]

On 13.04.2018 17:59, Michal Hocko wrote:
> On Fri 13-04-18 15:33:28, David Hildenbrand wrote:
>> Some devices (esp. paravirtualized) might want to control
>> - when to online/offline a memory block
>> - how to online memory (MOVABLE/NORMAL)
>> - in which granularity to online/offline memory
>>
>> So let's add a new flag "driver_managed" and disallow to change the
>> state by user space. Device onlining/offlining will still work, however
>> the memory will not be actually onlined/offlined. That has to be handled
>> by the device driver that owns the memory.
> 
> Is there any reason to create the memblock sysfs interface to this
> memory at all? ZONE_DEVICE mem hotplug users currently do not do that
> and manage the memory themselves. It seems you want to achieve the same
> thing, no?
> 

Yes, I think so, namely kdump. We have to retrigger kexec() whenever a
memory block is added/removed. udev events are sent for that reason when
a memory block is created/deleted. And I think this is not done for
ZONE_DEVICE devices, or am I wrong?

-- 

Thanks,

David / dhildenb

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