[Qemu-devel] Thoughts about introducing virtio-cpu

[Boeuf, Sebastien]

Hi everyone,

I have recently learned about the on-going work from David Hildenbrand
about virtio-mem, with a strong focus on proposing a unified solution
for every architecture, which is the point of using paravirtualization
here.
This proposes a standardized way across different hypervisors to manage
the guest RAM available, which at the same time will allow for a clean
memory hot(un)plug support.

Based on this, I was thinking that once this will be ready, and
assuming you manage your devices through a PCI bus, the last bit to get
rid of ACPI dependency would be about CPU. We could standardize the way
vCPUs are created and managed by each hypervisors by introducing
virtio-cpu. And the same way I mentioned architecture agnostic and
clean hotplug for virtio-mem, I would expect this new virtio device to
target the same goals.

The end goal is to propose an approach where hypervisors could be
unified across architectures, which would be convenient to support CPU
hotplug features, without being forced to use ACPI only for this
purpose.

I am really looking for community's feedback here, as I would like to
understand if there are some technical reasons why this approach would
not be feasible/acceptable. Also, please let me know if there is
already some on-going work, I'd be happy to participate!

Thanks,
Sebastien