Re: [PATCH v4 0/8] Introduce the microvm machine type

[David Hildenbrand]

On 25.09.19 11:12, Gerd Hoffmann wrote:
>   Hi,
> 
>> If you want to add hotplug to microvm, you can reuse the existing code
>> for CPU and memory hotplug controllers, and write drivers for them in
>> Linux's drivers/platform.  The drivers would basically do what the ACPI
>> AML tells the interpreter to do.
> 
> How would the linux kernel detect those devices?
> 
> I guess that wouldn't be ACPI, seems everyone wants avoid it[1].
> 
> So device tree on x86?  Something else?
> 
> cheers,
>   Gerd
> 
> [1] Not clear to me why, some minimal ACPI tables listing our
>     devices (isa-serial, fw_cfg, ...) doesn't look unreasonable
>     to me.  We could also make virtio-mmio discoverable that way.
>     Also we could do acpi cpu hotplug without having to write those
>     linux platform drivers.  We would need a sysbus-acpi device though,
>     but given that most acpi code is already separated out so piix and
>     q35 can share it it should not be that hard to wire up.
> 

Just to make one thing clear, the same could be used for DIMM based
memory hotplug, too. virtio-mem is not simply exposing DIMMs to a guest
using virtio. It's even designed to co-exist with DIMM based memory hotplug.

-- 

Thanks,

David / dhildenb