virtio: support virtio-mem on x86-64 as tech-preview
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2014492
Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=41597605
Depends: https://bugzilla.redhat.com/show_bug.cgi?id=2023396
Tested: I did a simple virtio-mem smoke test: started a VM with one virtio-mem device, configured differing memory onlining policies and resized the VM. Further, I tested /proc/kcore and kdump to make sure we're not touching hotunplugged device memory but including hotplugged device memory in the dumps.
virtio-mem is a mechanism to resize VM memory at runtime by hotplugging and hotunplugging memory to be used as system RAM as triggered by the hypervisor: paravirtualized memory hot(un)plug.
More details about the project can be found at: https://virtio-mem.gitlab.io
Everything is in place to support virtio-mem on x86-64 as tech-preview in RHEL9. Let's backport the final pieces from v5.16-rc1 and enable it as tech-preview.
Signed-off-by: David Hildenbrand david@redhat.com