Goal

• Add libvirt domain XML to set the rotational attribute on virtio-blk devices

Acceptance criteria

• When the XML attribute is not set, use QEMU's default. Verify that /sys/block/vda/queue/rotational is "1" inside the guest.
• When the XML attribute is set to "on", verify that /sys/block/vda/queue/rotational is "1" inside the guest
• When the XML attribute is set to "off", verify that /sys/block/vda/queue/rotational is "0" inside the guest
• Note that performance depends on the workload, so there is no expectation that a value of "on" or "off" is faster. Treat this feature as functional, not a performance optimization.