Goal

As I user, I want to automatically configure virtual disks for my VMs with block limits that match the host storage so that performance isn't negatively impacted by a mismatch.

To help with this, QEMU will offer a way to use the backend block limits to configure device properties. This may be through "auto" values on the individual properties, an extended "backing-defaults" properties or otherwise (see RHEL-110007).

In order to keep live migration working, libvirt can only launch new VMs with automatically detected values; it will have to configure the migration destination explicitly with the same values that were auto-detected when the VM was launched.

Acceptance criteria

TBD