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Re: [Xen-devel] [PATCH RFC] mm/memory_hotplug: Introduce memory block types

On 04/10/2018 19:50, Michal Suchánek wrote:
> On Thu, 4 Oct 2018 17:45:13 +0200
> David Hildenbrand <david@xxxxxxxxxx> wrote:
>> On 04/10/2018 17:28, Michal Suchánek wrote:
>>> The state of the art is to determine what to do with hotplugged
>>> memory in userspace based on platform and virtualization type.  
>> Exactly.
>>> Changing the default to depend on the driver that added the memory
>>> rather than platform type should solve the issue of VMs growing
>>> different types of memory device emulation.  
>> Yes, my original proposal (this patch) was to handle it in the kernel
>> for known types. But as we learned, there might be some use cases that
>> might still require to make a decision in user space.
>> So providing the user space either with some type hint (auto-online
>> vs. standby) or the driver that added it (system vs. hyper-v ...)
>> would solve the issue.
> Is that not available in the udev event?

Not that I am aware. Memory blocks "devices" have no drivers.

ls -la /sys/devices/system/memory/memory0/subsystem/drivers
total 0

(add_memory()/add_memory_resource() creates the memory block devices
when called from a driver)

> Thanks
> Michal



David / dhildenb

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